resistance of purebred brahman, hereford, and brahman x
TRANSCRIPT
Louisiana State University Louisiana State University
LSU Digital Commons LSU Digital Commons
LSU Historical Dissertations and Theses Graduate School
1973
Resistance of Purebred Brahman, Hereford, and Brahman X Resistance of Purebred Brahman, Hereford, and Brahman X
Hereford Crossbred Cattle to the Lone Star Tick, Amblyomma Hereford Crossbred Cattle to the Lone Star Tick, Amblyomma
Americanum (L.). Americanum (L.).
Gene Ray Strother Louisiana State University and Agricultural & Mechanical College
Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses
Recommended Citation Recommended Citation Strother, Gene Ray, "Resistance of Purebred Brahman, Hereford, and Brahman X Hereford Crossbred Cattle to the Lone Star Tick, Amblyomma Americanum (L.)." (1973). LSU Historical Dissertations and Theses. 2430. https://digitalcommons.lsu.edu/gradschool_disstheses/2430
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Xerox University Microfilms300 North Zeeb RoadAnn Arbor, Michigan 48106
73-27,872
SIR0IHER, Gene Ray, 1937- RESISTANCE OF PUREBRED BRAEMAN, HEREFORD,AND BRAIMAN X HEREFORD CROSSBRED CATTLE TO THE LONE STAR TICK, AMBLYQMMA. AMERICANUM CL.)*
The Louisiana S tate U n iversity and A gricu ltural and Mechanical C ollege, Ph.D., 1973 Entomology
University Microfilms, A XEROX Company, Ann Arbor, Michigan
RESISTANCE OF PUREBRED BRAHMAN, HEREFORD, AND BRAHMAN X HEREFORD
CROSSBRED CATTLE TO THE LONE STAR TICK, AMBLYOMMA AMERICANUM (L .)
A D is s e r ta t io n
S ubm itted t o th e G raduate F a c u lty o f th e L o u is ia n a S ta te U n iv e rs ity and
A g r ic u l tu r a l and M echanical C o lle g e in p a r t i a l f u l f i l lm e n t o f th e
re q u ire m e n ts fo r th e degree o f D o c to r o f P h ilosophy
in
The D epartm ent o f Entomology
by
Gene Ray S tr o th e r B .S ., L o u is ia n a S ta te U n iv e r s i ty , 1961 M .S ., L o u is ia n a S ta te U n iv e r s i ty , 1970
May, 1973
ACKNOWLEDGEMENTSThe a u th o r w ish es to e x p re ss h i s g r a t i t u d e and in d e b te d n e s s to
h is m ajo r p r o f e s s o r , D r. Edward C. B u rn s , P ro fe s s o r o f Entomology who
c o n t r ib u te d tim e and many h e lp f u l s u g g e s tio n s d u rin g th e c o u rse of t h i s
i n v e s t i g a t i o n and th e p re p a ra t io n o f t h i s m a n u s c r ip t . He i s g r a t e f u l
f o r h e lp f u l a d v is e o f f e re d by th e members o f h is a d v iso ry com m ittee :
D r. L. D. Newsom, Boyd P ro fe s s o r and Head o f th e D epartm ent o f Entom ology;
D r. B. H. W ilson , P ro fe s s o r of Entom ology; D r. J . H. R o b e r ts , P ro fe s s o r
o f Entom ology and Zoology; Mr. E . H. F lo y d , P ro fe s s o r o f Entom ology;
D r. L. I . S m art, A sso c ia te P ro fe s s o r o f Anim al S c ie n c e ; and D r. K. C. Corkum,
A s s o c ia te P ro fe s s o r -of Zoology.
A p p re c ia tio n i s e x p re ssed to D r. W. A. Jo h n so n , P ro fe s s o r o f P o u ltry
S c ien ce and D r. L . I . S m art, A s s o c ia te P r o fe s s o r o f Animal S c ie n ce fo r
t h e i r a s s i s t a n c e in su p p ly in g th e c h ic k s and c a t t l e u sed in t h i s s tu d y .
In d e b te d n e ss i s e x p re sse d to D r. K enneth Koonce, A s s o c ia te P ro fe s s o r
o f E x p e rim en ta l S t a t i s t i c s , f o r h i s a s s i s t a n c e w ith s t a t i s t i c a l a n a ly s is
of th e d a ta .
The a u th o r w ish es to e x p re s s h i s a p p r e c ia t io n to : P . A. Suggs,
D an ie l M elancon, James Clower and C h a r le s R ich a rd so n fo r t h e i r c o n tr ib u t io n s
and a s s i s t a n c e .
G r a t i tu d e , a p p r e c ia t io n and s p e c i a l th an k s a r e e x p re sse d to th e
w r i t e r ' s w ife N e ll and to ou r c h i ld r e n f o r t h e i r i n s p i r a t i o n , a s s i s t a n c e ,
and p a t ie n c e d u rin g th e c o u rse o f t h i s r e s e a r c h and in th e p re p a ra t io n o f
t h i s m a n u sc r ip t . A p p re c ia tio n i s a l s o e x p re s se d to th e w r i t e r ' s m o th e r- in -
law , N adine W. C urry f o r h e r encouragem ent d u r in g t h i s s tu d y .
To th e s e and to a l l o th e r s who have h e lp e d and a s s i s t e d in some way
d u rin g th e c o u rse o f th e r e s e a rc h and p r e p a r a t io n o f t h i s m a n u sc r ip t , th e
a u th o r w ish es to e x p re ss h i s a p p r e c ia t io n .i i
TABLE OF CONTENTS
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF TABLES .
LIST OF FIGURES .
LIST OF PLATES .
ABSTRACT
INTRODUCTION
REVIEW OF LITERATURE
RESISTANCE WITHIN BREEDS
RESISTANCE BETWEEN BREEDS
METHODS AND MATERIALS
TICK REARING
CATTLE
TICK INFESTATION OF CATTLE
COLLECTION OF REPLETE FEMALE TICKS
STATISTICAL ANALYSIS
RESULTS AND DISCUSSION
CONCLUSIONS
REFERENCES CITED
APPENDIX
VITA
PAGEi i
i i i
i v
v
v i
v i i
I5
8
10
14
14
19
19
22
24
25
40
42
45
49
LIST OF TABLES
TABLE PAGEI . Number o f r e p l e t e fem ale lone s t a r t i c k s dropped from
t e s t c a t t l e fo l lo w in g th e I n f e s t a t i o n o f each an im al by 300 m ales and 300 fe m a le s . . . . . 26
I I . A n a ly s is o f v a r ia n c e o f numbers o f fem ale lone s t a rt i c k s fe e d in g to r e p l e t i o n on c a t t l e • 27
I I I . Average w e ig h t i n m il l ig ra m s o f fem ale lo n e s t a r t i c k s feed in g to r e p l e t i o n from each g roup o f t e s t c a t t l e fo llo w in g th e i n f e s t a t i o n o f each an im al by 300 m ales and 300 fe m a le s . . . . . . . 30
IV. A n a ly s is o f v a r ia n c e o f w e ig h ts o f fem ale lo n e s t a rt i c k s fe e d in g t o r e p l e t i o n on c a t t l e . . . 32
V. Mean t i c k w e ig h t , w e ig h t o f th e egg m ass , and p e rc e n t h a tch o f eggs from a sam ple com prised o f th e f i r s t 10 r e p l e t e fem ale lo n e s t a r t i c k s dropped from each an im al fo l lo w in g each i n f e s t a t i o n by 300 m ales and 300 fem ales p e r a n im a l. . . . . . . 35
V I. A n a ly s is o f v a r ia n c e o f p e rc e n t o f eggs h a tch e d from asample co m prised o f th e f i r s t 10 r e p l e t e fem ale lo n es t a r t i c k s d ropped from each an im al fo llo w in g each i n f e s t a t i o n by 300 m a les and 300 fem ales p e r an im al 36
V II. P e rcen t o f eggs h a tc h e d from a sam ple com prised o f thef i r s t 10 r e p l e t e fem ale lo n e s t a r t i c k s dropped fromeach an im a l fo llo w in g each i n f e s t a t i o n by 300 m ales and 300 fem a les p e r a n im a l . . . . . 38
APPENDIX TABLE
1. Average w e ig h t i n m il l ig ra m s o f r e p l e t e fem a les dropped from in d iv id u a l a n im a ls . . . . . . 46
2. Mean t i c k w e ig h t, egg m ass w e ig h t and p e rc e n t h a tc hfrom in d iv id u a l a n im a ls . . . . . . 47
3. R atio n s fe d s t e e r s d u r in g c o n fin em en t. . . . 48
iv
LIST OF FIGURES
PAGE1. A reas in th e U n ited S ta te s w here p o p u la t io n s o f th e
lo n e s t a r t i c k , Amhlvnrnma am ericam m ( L . ) i s o fp o s s ib le econom ic im p o rtan ce . . . . . 3
2 . A verage number o f r e p l e t e fem ale lo n e s t a r t i c k s dropped from each g roup o f t e s t c a t t l e fo llo w in g th r e e i n f e s t a t i o n sby 300 m a le s and 300 fem a les p e r an im a l . . . 29
3 . A verage w e ig h t in m il l ig ra m s o f r e p l e t e fem ale lone s t a r t i c k s dropped from each g roup o f t e s t c a t t l e fo llo w in g th e i n f e s t a t i o n o f each an im al by 300 m alesand 300 fe m a le s . . . . . . . . 33
v
LIST OF PLATESPAGE
I . The unfed lo n e s t a r t i c k , m ale , fem a le , nymphand l a r v a ...................................................................................................... 2
I I . H olding c r a t e s and c o l l e c t i n g t r a y s u sed in c o l l e c t i n gr e p le te fem ale lo n e s t a r t i c k s a s th e y dropped from th e s t e e r s ............................................................................................. 16
I I I . Method o f h o ld in g t i c k s . 17
IV. A pparatus (c o n v e r te d c h ic k r e a r in g b a t t e r y ) usedfo r c o l l e c t i n g th e im m ature form s o f th e lo n e s t a r t i c k from c h ic k s . * .......................................................................... 18
V. An i n f e s t a t i o n u n i t o f 300 m ale and 300 fem ale .lone s t a r t i c k s u sed to i n f e s t each s t e e r a t each i n f e s t a t i o n ................................................................. 20
VI. The p u reb red H e re fo rd ( to p ) , p u re b re d Brahman ( c e n te r ) ,and Brahman X H e re fo rd c ro s sb re d s t e e r s (b o tto m ), u sed to compare r e s i s t a n c e betw een th e b re e d s . . . . 21
V II . D e s s ic a to r j a r f o r h o ld in g r e p l e t e fem a les f o ro v ip o s i t io n and h a t c h a b i l i t y d a t a ..................................... 23
vi
ABSTRACT
The purpose o f t h i s in v e s t i g a t i o n was to d e te rm in e i f d i f f e r e n c e s
in r e s i s t a n c e to th e lo n e s t a r t i c k e x is t e d betw een Brahman and
European b re e d c a t t l e . P u reb red H e re fo rd , p u re b re d Brahman, and
Brahman X H ere fo rd c ro s sb re d s t e e r s w ere in f e s te d th r e e tim es w ith
300 male and 300 fem ale t i c k s p e r a n im a l.
Number and w eigh t o f r e p l e t e fem ale t i c k s dropped from each an im a l,
a s w e l l as th e p e rc e n t o f eggs h a tc h e d w ere u sed as c r i t e r i a o f r e s i s t a n c e .
The number o f fem ale t i c k s f e e d in g to r e p l e t i o n on an an im al was found
to be p o s i t iv e ly c o r r e la t e d w i th th e w e ig h t o f th e " re p le te t i c k s . A ll
t e s t c a t t l e a c q u ire d a h ig h l e v e l o f r e s i s t a n c e to th e lo n e s t a r t i c k
by th e t h i r d in f e s t a t i o n a s i n d ic a te d by s i g n i f i c a n t l y red u ced numbers
and w eigh ts o f r e p le t e fem a le t i c k s .
The av erag e number and w e ig h t o f engorged fem ale t i c k s p e r an im al
su g g e s t t h a t the Brahman X H e re fo rd c ro s s b re d s t e e r s w ere m ost r e s i s t a n t ;
th e p u reb red H erefo rd s t e e r s w ere l e a s t r e s i s t a n t , and p u re b re d Brahman
s t e e r s were in te rm e d ia te in r e s i s t a n c e . H a tc h a b i l i ty o f eggs from
fem a le t i c k s fed on p u re b re d Brahman s t e e r s was s i g n i f i c a n t l y low er th an
t h a t o f eggs l a id by r e p l e t e fe m a le s f e d on p u reb red H e re fo rd and
Brahman X H e re fo rd c ro s sb re d s t e e r s .
vii
INTRODUCTION
T ic k s have been a sco u rg e to c a t t l e from tim e im m em orial. One o f
th e g r e a t e s t d e te r r e n ts to im provem ent o f c a t t l e in th e s o u th e rn U n ited
S ta te s was Texas f e v e r , a d is e a s e t r a n s m i t t e d by th e Texas fe v e r t i c k
B o o p h ilu s a n n u la tu s (S a y ) . C a t t l e from im proved b reed s t h a t w ere
b ro u g h t in to th e a r e a soon c o n t r a c te d th e d is e a s e and d ie d . G re a t
s t r i d e s have bsen made in th e im provem ent o f c a t t l e in th e s o u th e rn
s t a t e s s in c e th e Texas fe v e r t i c k was e r a d ic a te d from th e U n ite d S ta te s
in th e l a t e 1 9 3 0 's .
At th e p re s e n t tim e th e lo n e s t a r t i c k , Amblvomma am ericanum ( L . ) ,
i s c o n s id e re d the m ost im p o rtan t t i c k in L o u is ia n a . I t i s r e f e r r e d to
a s th e lo n e s t a r t i c k b ecause o f a c o n sp icu o u s l i g h t sp o t on th e p o s te r io r
o f th e scutum of th e fem ale ( P l a t e 1 ) . T h is t i c k i s im p o r ta n t from th e
p u b l ic - h e a l th s ta n d p o in t s in c e i t i s c a p a b le of t r a n s m i t t in g tu la r e m ia ,
Rocky M ountain s p o t te d fe v e r and A m erican Q f e v e r . I t a l s o c a u se s t i c k
p a r a ly s i s in man and dog. The lo n e s t a r t i c k i s more w id e ly d i s t r i b u t e d
in th e U n ite d S ta te s than any o th e r Amblvomma s p e c ie s and re a c h e s p e s t i
fe ro u s p o p u la tio n s each y ear in u p la n d wooded p a s tu re s th ro u g h o u t i t s
ran g e w here c o n tr o l m easures a r e n o t p r a c t i c e d . D i s t r i b u t io n o f th e lone
s t a r t i c k in th e U n ite d S ta te s i s shown in F ig u re 1 . I t i s commonly
found i n up land b ru sh o r tim b e r la n d a r e a s from so u th w e s te rn Texas to
M is s o u r i , and eas tw ard to th e A t l a n t i c C o a s t . McCoy (1971) r e p o r te d
t h a t t h i s s p e c ie s was a b se n t from th e c o a s t a l m arshes and r a r e l y was
found in th e a l l u v i a l a re a s o f L o u is ia n a . R e s u lt o f h is w ork showed
t h a t t h i s t i c k was abundant in m ost o f th e up lan d re g io n s o f th e s t a t e .
2
P la te I . The un fed lo n e s t a r t i c k , m a le , fe m a le , nymph, and la r v a . (P ho tog raphed by B. H. W ilso n ) .
wmmmm
mm¥ v i!r
3
F ig u re 1 . A reas in th e U n ited S ta te s where p o p u la t io n s o f th e lo n e s t a r t i c k , Amblvomma americanum ( L .) , i s o f p o s s ib le econom ic im p o rtan ce .
MILES
4
R ecen t f in d in g ? (W ilson e t a l . 1972, H a ir and Howell 1970, an d p e rs o n a l
o b s e r v a t io n s ) , u s in g CO2 a s an a t t r a c t a n t and c o l l e c t i o n s o f a d u l t s
from h o sts d u r in g w in te r m onths, in d ic a te th a t th e lo n e s t a r t i c k i s
a c t i v e from m id -w in te r to e a r ly f a l l . The s p e c ie s i s a th r e e - h o s t
t i c k and h as a w ide ra n g e o f h o s t a n im a ls .
I n r e c e n t y e a r s r e s i s t a n c e o f t i c k s to in s e c t i c id e s h a s become o f
g r e a t c o n ce rn in c e r t a i n a re a s o f th e w o rld . R e s is ta n c e o f th e t i c k
to i n s e c t i c i d e s h as h e lp e d s t im u la te i n t e r e s t in n o n -c h e m ica l m ethods
o f p e s t c o n t r o l . R esearch in A u s t r a l i a in v o lv in g b o th s e l e c t i o n f o r
t i c k r e s i s t a n c e among B r i t i s h b re e d s and c ro s s b re e d in g w ith Zebu b reed s
h a s shown some p ro m isin g r e s u l t s w ith t i c k s o f th e genus B o o n h ilu s .
A lth o u g h i t i s g e n e r a l ly b e l ie v e d in . th e U n ited S ta te s t h a t
c a t t l e o f th e Brahman b re e d a r e more r e s i s t a n t to p a r a s i t e s th a n c a t t l e
o f th e B r i t i s h b re e d s , th e r e i s l i t t l e ev id en ce to s u b s t a n t i a t e t h i s
b e l i e f . S tu d ie s co n d u cted in o th e r c o u n tr ie s co n cern ed w ith r e s i s t a n c e
o f c a t t l e to t i c k s have been r e s t r i c t e d a lm o s t e x c lu s iv e ly to th e one-
h o s t t r o p i c a l c a t t l e t i c k , B oonh ilu s m ic ro p lu s ( C a n e s t r i n i ) .
The m ain o b je c t iv e o f t h i s s tu d y was to d e te rm in e i f a d i f f e r e n c e
in r e s i s t a n c e e x i s t e d betw een th e Brahman (Zebu) and B r i t i s h b re e d s o f
c a t t l e to th e lo n e s t a r t i c k .
Two ty p e s o f r e s i s t a n c e in c a t t l e to t i c k s w ere m easu red : (1 )
in n a te r e s i s t a n c e to an i n i t i a l i n f e s t a t i o n o f t i c k s ; and (2 ) th e
a b i l i t y o f c a t t l e to a c q u ir e r e s i s t a n c e fo llo w in g s u c c e s s iv e i n f e s t a t i o n s
o f t i c k s .
REVIEW OF LITERATURE
D if f e re n c e s in re sp o n se o f c a t t l e to t i c k i n f e s t a t i o n have been
r e l a t i v e l y w e ll docum ented s in c e th e e a r ly 1 9 0 0 's . As e a r l y a s 1908
H u ll o f A u s t r a l i a observed r e s i s t a n c e in in d iv id u a l a n im a ls o f th e
J e r s e y b re e d exposed to n a tu r a l i n f e s t a t i o n s o f B o o p h ilu s m ic ro p lu s
(Jo h n s to n and B a n c ro f t 1918). He was th e f i r s t p e rso n to d e s c r ib e
t i c k r e s i s t a n c e in c a t t l e and to a p p r e c ia te i t s im p o rta n c e . He n o ted
th a t in r e s i s t a n t cows few t i c k s m atured p e r seaso n and t h a t th e
t i c k s t h a t d id m atu re l a id eggs w ith low h a t c h a b i l i t y . F u r th e rm o re ,
he s t a t e d t h a t cows th a t p o s se sse d r e s i s t a n c e d id n o t r e q u i r e t r e a t
ment to p re v e n t t i c k s from co m p le tin g developm ent on them . Jo h n s to n
and B a n c ro f t (1 9 1 8 ), s tu d y in g th e same herd o f c a t t l e , co n firm ed th a t
c e r t a i n in d iv id u a ls w ere c o n s i s t e n t ly more r e s i s t a n t to t i c k s th a n
th e a v e ra g e . They re p o r te d t h a t by 1915 c a . h a l f o f th e h e rd was o f
th e t i c k r e s i s t a n t ty p e . They c o n c lu d ed , a f t e r t r a c in g p ro g en y o f
th e o r i g i n a l r e s i s t a n t cows, t h a t th e r e s i s t a n t c h a r a c t e r i s t i c was
h e r e d i t a r y . They gave th e fo llo w in g c r i t e r i a f o r th e a s se ssm e n t o f
r e s i s t a n c e in c a t t l e to t i c k s :
1. A f a i l u r e by t i c k s to com ple te developm ent on th e h o s t .
They n o te d t h a t on r e s i s t a n t a n im a ls t i c k s o f te n w ere u n a b le to m atu re
and d ie d a t ta c h e d to th e a n im a l.
2 . A ten d en cy tow ard v e ry l i g h t i n f e s t a t i o n in c e r t a i n in d iv id u a ls
when o th e r a n im a ls in th e h e rd w ere h e a v i ly i n f e s t e d .
3 . F a i lu r e o f fem ale t i c k s t o become engorged in num bers s im i la r
to th o s e on s u s c e p t ib le a n im a ls u n d er th e same c o n d i t io n s .
6
4 . F a i lu r e o f engorged t i c k s e i t h e r to la y a norm al number o f
eggs o r to la y eggs w ith norm al h a t c h a b i l i t y .
In a r e c e n t r e p o r t Hewetson (1972) gave th e fo llo w in g c r i t e r i a
fo r m easurem ent o f r e s i s t a n c e by c a t t l e to t i c k i n f e s t a t i o n :
1 . R e la t iv e num bers o f r e p le t e fem ale t i c k s d ropped .
2 . R e la t iv e w e ig h ts o f r e p l e t e fem ales d ro p p ed .
3 . R e la t iv e h a t c h a b i l i t y o f eg g s.
4 . R e la t iv e le n g th o f th e p a r a s i t i c l i f e c y c le o f t i c k s on th e
h o s t .
R iek (1962) f i r s t r e p o r te d t h a t th e w e ig h t o f t i c k s dropped by
p u re b re d Bos in d ic u s L in naeus was l e s s th a n th e w e ig h t o f th o se dropped
by Bos ta u ru s L in n a e u s . He a l s o p o in te d o u t t h a t th e w e ig h t o f t i c k s
dropped by c ro s s b re d s approached th e w e ig h t o f th o s e dropped by
p u re b re d B. t a u r u s . Heweton (1971) observed t h a t p u reb red and c ro ssb re d
Zebu (S ah iw a l) c a t t l e dropped t i c k s o f s im i la r s i z e (230 mg) when f i r s t
i n f e s t e d , b u t by th e tim e o f th e f o u r t h . i n f e s t a t i o n th e p u reb red s dropped
t i c k s s i g n i f i c a n t l y l i g h t e r in w e ig h t th a n th o se dropped by c ro s sb re d s .
R iek (1962) n o t o n ly observ ed th a t t i c k s d ropped by pu reb red B. ta u ru s
b re e d s w ere s i g n i f i c a n t l y h e a v ie r b u t a l s o found th a t th e y l a id a g r e a te r
w eig h t o f eggs th a n t i c k s dropped from p u reb red B. in d ic u s b re e d s . However,
he d id n o t f in d s i g n i f i c a n t d i f f e r e n c e s i n w e ig h t o f eggs p roduced , o r
th e num bers o f l a r v a e h a tch ed betw een t i c k s d ropped by th r e e - q u a r te r
Zebu X B r i t i s h and p u re b re d B r i t i s h c a t t l e .
The f a c t t h a t t i c k s on Zebu c a t t l e to o k lo n g e r to become r e p le te
th an th o se on B r i t i s h c a t t l e was r e p o r te d by R iek (1962) and Heweston
(1 9 7 1 ).
7
T rag e r (1 9 3 9 a), w orking w ith a r t i f i c i a l i n f e s t a t i o n s o f D erm acentor
v a r i a b l l l s (Say) on r a b b i t s , d e e r m ic e , and g u in e a p ig s , r e p o r te d th a t
r e s i s t a n c e cou ld be a c q u ire d in a n im a ls a f t e r exposu re to t i c k i n f e s t a
t i o n . He a ls o d em onstra ted t h a t r e s i s t a n c e co u ld be a r t i f i c i a l l y
produced in g u in ea p ig s by i n j e c t i o n o f e x t r a c t s from t i c k la rv a e
(T ra g e r 1939b). Loomis (1 9 6 1 ), i n w ork w ith s e v e r a l s p e c ie s in c lu d in g
th e lo n e s t a r t i c k , Amblvomma am ericanum . re p o r te d th a t t i c k s re fu se d
to a t t a c h on r a b b i t s a f t e r 4 o r 5 h eav y i n f e s t a t i o n s , and th a t r a b b i t s
e x h ib i te d an a c q u ire d im m unity . R iek (1962) d e s c r ib e d two ty p e s o f
r e s i s t a n c e in c a t t l e exposed to B. m ic r o p lu s : (1 ) a c q u ire d r e s is ta n c e
(im m u n o lo g ica lly developed) and (2 ) in n a te o r in h e r e n t r e s i s t a n c e
( g e n e t i c a l l y c o n t r o l l e d ) . He d e s c r ib e d a c q u ire d r e s i s t a n c e a s t h a t
r e s i s t a n c e w hich becomes o p e r a t iv e fo llo w in g a p rim ary ex p o su re to t i c k s
and r e p r e s e n ts th e h o s t 's re sp o n se to i n j e c t i o n s o f a n t ig e n s from th e
s a l i v a r y g lan d s o f th e t i c k d u r in g th e fe e d in g p ro c e s s . He s ta te d
t h a t in n a te r e s i s t a n c e , on th e o th e r han d , was g e n e t i c a l l y c o n tro l le d
and was more o r le s s s t a b l e , b e in g f u l l y o p e r a t iv e on th e f i r s t i n f e s t a
t io n o f an im a ls n o t p re v io u s ly exposed to t i c k s . However, Hewetson (1972)
p o in te d o u t th a t d e f in i t io n s p ro p o sed by R iek (1962) f o r in n a te and acq u ired
r e s i s t a n c e were n o t v a l id d e s c r ip t i o n s s in c e th e two were i n t e r r e l a t e d
and th e le v e l o f a cq u ired r e s i s t a n c e was i n h e r i t e d to a d e g re e .
B en n e tt and W harton (1968) o u t l in e d 4 f a c to r s t h a t th e y co n sid e red
was in v o lv ed i n r e s i s ta n c e o f c a t t l e to th e c a t t l e t i c k , B. m ic ro p lu s a s
fo llo w s :
1. Im m unological r e s i s t a n c e r e s u l t i n g i n a re sp o n se o f th e h o s t
to th e a n t ig e n ic s tim u lu s o f th e p a r a s i t e . They s t a t e d t h a t . i n j e c t i o n
8
o f s a l iv a r y f lu id from th e s a l i v a r y g la n d s o f th e t i c k p ro v id e s the
a n t ig e n ic s tim u lu s f o r th e re s p o n se o f th e h o s t . F av o rin g th e immuno
lo g ic a l n a tu re o f th e a n im a l 's d e fe n se r e a c t io n s a g a in s t t i c k s i s th e
d e f i n i t e s h i f t in th e b lood p i c tu r e ob serv ed a f t e r s e v e ra l i n f e s t a t i o n s
o f t i c k s (B alashov 1967). T here a r e m arked in c re a s e s in h is ta m in e
c o n te n ts , g lo b u lin f r a c t i o n s and a n a c c e le r a te d e ry th ro c y te sed im en ta
t i o n r a te in th e a n im a l 's b lo o d (R iek 1962; B alashov 1967; T a tc h e l l
1969 ).
2. B eh av io ra l c h a r a c t e r i s t i c s in f lu e n c e th e r e s i s t a n c e le v e l o f
c a t t l e , p a r t i c u l a r l y groom ing a c t i v i t i e s . .S now ball (1956) re p o r te d
t h a t B r i t i s h c a t t l e r e s t r i c t e d from groom ing produced a 2-3 fo ld in c re a s e
i n t i c k y ie ld , w h ile R iek (1962) r e p o r te d y ie ld in c r e a s e s o f c a . 1/3
in th e Shorthorn b reed o f c a t t l e and c a . 50% in Zebu c ro s sb re d c a t t l e
a f t e r grooming a c t i v i t i e s w ere r e s t r i c t e d .
3 . N u t r i t io n a l s t r e s s e x p re sse d a s m a ln u t r i t io n o r low ered c o n d i
t i o n caused by l a c t a t i o n c a n re d u c e th e r e s i s t a n c e l e v e l o f c a t t l e to
t i c k s . Wharton e t a l . (1970) r e p o r te d t h a t u n d er n u t r i t i o n a l s t r e s s
o r d u rin g l a c t a t i o n , a p ronounced re d u c t io n i n r e s i s t a n c e o f th e cow to
B. m ic ro p lu s o c c u rre d .
4 . P h y s ic a l f a c to r s su ch a s le n g th o f h a i r , c o lo r , and th ic k n e s s
o f s k in , m ight p o s s ib ly in f lu e n c e r e s i s t a n c e in c a t t l e to t i c k s . How
e v e r , no ev idence h a s been r e p o r te d showing t h a t th e s e f a c to r s a re
s i g n i f i c a n t (P a r r 1924, W ilk in so n 1955, R iek 1962).
R e s is ta n c e W ith in B reeds
Johnson and B an c ro ft (1918) co n firm ed H u l l 's c la im s th a t
9
in d iv id u a l an im a ls w ith in th e J e r s e y b re e d w ere c o n s i s t e n t ly more
r e s i s t a n t to t i c k s th an th e av erag e and Legg (1930) s t a t e d t h a t odd
an im a ls o f any b reed may be found c a r r y in g r e l a t i v e l y l i g h t i n f e s t a t i o n s
o f t i c k s , a lth o u g h exposed to o b v io u s ly h e a v i ly t i c k in f e s te d p a s tu r e .
He n o te d t h a t many in d iv id u a ls i n th e J e r s e y and F r e s ia n b re e d s were
a p p a r e n t ly c o n s id e ra b ly more r e s i s t a n t th a n o th e r an im a ls o f th e same
b reed exposed to th e same n a tu r a l i n f e s t a t i o n s o f th e c a t t l e t i c k ,
B. m ic ro p lu s . K e lly (1943) observed t h a t a s m a ll p e rc e n ta g e o f h a l f
b reed Zebu c a t t l e w ere c o n s id e ra b ly l e s s r e s i s t a n t th a n th e a v e ra g e .
Wide in d iv id u a l d i f f e r e n c e s o f t i c k r e s i s t a n c e to B. m ic ro p lu s were
re p o r te d by W ilk in so n (1955) in s e v e r a l B r i t i s h b re e d s o f c a t t l e .
W ilk in so n (1962) d em o n stra ted t h a t t i c k r e s i s t a n c e cou ld be s e le c te d
f o r in B r i t i s h b reed c a t t l e to th e d e g re e t h a t a c a r i c i d a l t re a tm e n t f o r
t i c k i n f e s t a t i o n cou ld be reduced by 83-100% w i th t i c k r e s i s t a n t c a t t l e .
F u rth e rm o re , t i c k numbers i n th e p a s tu r e s w here r e s i s t a n t c a t t l e w ere
g razed w ere reduced to a low le v e l .
S now ball (1956) showed th a t y i e l d o f r e p l e t e fem ales from in d iv id u a l
an im a ls v a r ie d from 0.1% to 32.0% when a n im a ls w ere in f e s te d w ith a
known number o f JB. m ic ro p lu s la rv a e . R iek (1962) r e p o r te d v a ry in g
d e g re e s o f t i c k r e s is ta n c e were o b se rv ed in p u re b re d B. t a u r u s , B.
in d ic u s , and i n th e c ro s sb re d c a t t l e . He n o te d t h a t some a n im a ls i n
each o f th e s e groups were r e s i s t a n t to th e e x t e n t t h a t v e ry few , i f
a n y , t i c k s w ere a b le to m atu re on them . W harton e t a l . (1969) found
t h a t Zebu X B r i t i s h c ro s sb re d c a t t l e e x h ib i te d a c o n s id e ra b le range in
t i c k r e s i s t a n c e , b o th from n a tu r a l and a r t i f i c i a l i n f e s t a t i o n s o f th e
10
cattle tick, B. microplus.
The d i f f e r e n c e s n o ted w i th in b reed s o f c a t t l e i n d i c a t e t h a t th e
c o n s id e ra b le g e n e t ic v a r i a t i o n o f t i c k r e s i s t a n c e w i th in b re e d s (40-50%
h e r i t a b i l i t y in B r i t i s h b reed c a t t l e and 82% h e r i t a b i l i t y i n F2 and F3
g e n e ra t io n s o f c ro s s e s w ith Zebu cows) make s e l e c t i o n w i th in b re e d s
fo r r e s i s t a n c e to B. m ic ro p lu s m ost a t t r a c t i v e (W harton e t a l . 1970,
Seifert 1971, and Hewetson 1972).
Resistance Between Breeds
The relatively high resistance of Zebu and Zebu-cross cattle to ticks was recognized in the United States by Nabours (1912) who stated that Brahman cattle (Zebu breed) were perfectly immune to attacks from
the Texas cattle tick, B. annulatus to the extent that ticks did not remain attached to them. Parr (1924) attributed the ability of Brahman cattle and their crosses to survive in Texas in the early 1 9 0 0 's to their resistance to ticks. Physical factors such as shortness of hair, thickness and toughness of the hide, and the waxy secretion from the skin have been credited for tick resistance in the Brahman breed. However, Parr
(1924) was unable to find significant differences in skin thickness between Brahman and British breeds of cattle. He also reported that tick infested pastures used for Brahman cattle became more or less free of ticks following 2 or 3 grazing seasons. Mitchell (cited by Parr 1924) considered the resistance displayed by Brahman cattle, to be a hereditary characteristic that could be transmitted even by one sixty-fourth of Brahman*
Legg (1930) and K e lly (1943) n o ted th e r e l a t i v e l y h ig h r e s i s t a n c e
e x h ib i te d by Zebu c a t t l e to n a tu r a l i n f e s t a t i o n s o f B. m ic ro p lu s . K e lly
11
(1943) s t a t e d t h a t " t i c k - r e p e l le n c y " was I n h e r i te d a lm o s t in d i r e c t p ro
p o r t io n to th e p e rc e n ta g e o f Zebu b lood p r e s e n t i n th e a n im a l.
R iek (1962) d e m o n stra ted w ith a r t i f i c i a l i n f e s t a t i o n s o f B. m ic ro p lu s
th e d i f f e r e n c e s i n t i c k r e s i s t a n c e betw een Zebu and B r i t i s h b re e d s . R e s u lts
o f h i s s tu d y showed t h a t 3 /4 Zebu X 1 /4 S h o rth o rn c ro s sb re d c a t t l e y ie ld e d
o n ly 3.4%, w h ile S h o rth o rn c a t t l e y ie ld e d 19.4% o f th e p o t e n t i a l number
o f engorged fem ales from i n f e s t a t i o n s o f 20,000 l a r v a e . O bserv ing
n a t u r a l i n f e s t a t i o n s o f B. m ic ro p lu s . F ra n c is and L i t t l e (1964) r e p o r te d
t h a t H ere fo rd c a t t l e c a r r i e d c a . 10 tim es a s many t i c k s a s D rough tm aster
c a t t l e (c a . 3 /8 Brahman and 5 /8 S h o r th o rn ) , even w i th a s p ra y program
t h a t p e rm itte d t i c k i n f e s t a t i o n to b u ild up o n ly to an econom ic th re s h o ld
l e v e l on th e H erefo rd c a t t l e . Four to f iv e sp ra y in g t r e a tm e n ts w ere
n e c e s sa ry f o r th e H ere fo rd c a t t l e , w h ile D ro u g h tm aster c a t t l e n e v e r
reach ed th e econom ic th re s h o ld le v e l o f i n f e s t a t i o n t h a t r e q u ire d
s p ra y in g . W harton e t a l . (1969) u s in g an a r b i t r a r i l y d e te rm in ed d ip p in g
th re s h o ld l e v e l o f 20 t i c k s (5mm. o r more in le n g th on th e r i g h t s i d e ) ,
a l s o found Zebu X B r i t i s h c ro s sb re d c a t t l e c a r r i e d few er t i c k s and
r e q u ir e d c o n s id e ra b ly l e s s d ip p in g th a n B r i t i s h b re e d c a t t l e when b o th
w ere exposed to th e same n a tu r a l i n f e s t a t i o n s o f B. m ic ro p lu s .
Jo h n sto n and Haydack (1969) r e p o r te d t h a t Brahman X B r i t i s h c r o s s
b red c a t t l e m a in ta in e d t h e i r B. m ic ro p lu s i n f e s t a t i o n a t a low le v e l
w ith o u t a c a r i c i d a l t r e a tm e n t and S e i f e r t (1971) found th a t Zebu c r o s s
b re e d s c a r r ie d an a v e ra g e o f 2 /5 th e number o f t i c k s c a r r i e d by B r i t i s h
c a t t l e .
Hewetson (1971) r e p o r te d t h a t Zebu X B r i t i s h c ro s sb re d c a t t l e
w ere a s r e s i s t a n t to B. m ic ro p lu s a s p u reb red Zebu on th e f i r s t i n f e s
t a t i o n . However, su b seq u en t to th e f i r s t i n f e s t a t i o n th e p u re b re d s
became more r e s i s t a n t th a n th e c ro s sb re d s d u r in g th e n e x t th r e e i n f e s
t a t i o n s . D if f e re n c e s betw een h a l f - b r e d , th r e e - e ig h th s , o r q u a r t e r -
b red Zebu b u l l s w ere n o t s i g n i f i c a n t when t e s t e d w ith a r t i f i c i a l
i n f e s t a t i o n o f B. m ic ro p lu s (H ew etson 1972).
The e f f e c t s o f t i c k i n f e s t a t i o n on grow th o f c a t t l e w ere m easured
by L a n c a s te r e t a l . (1955) Norman (1 9 5 7 ), F ra n c is (1 9 6 0 ), L i t t l e (1 9 6 3 ) ,
0 * K e lly and S e i f e r t (1 9 7 0 ), Seebeck e t a l . (1 9 7 1 ), S e i f e r t (1 9 7 1 ), and
T u rn e r and S h o rt (1 9 7 2 ). Only i n th e s tu d ie s o f S e i f e r t (1971) and
T u rn e r and S h o rt (1972) w ere co m parisons made betw een B r i t i s h b re e d s
and Zebu c a t t l e . T h e ir r e s u l t s i n d ic a te t h a t exposu re to m o d era te
l e v e l s o f i n f e s t a t i o n o f B. m ic ro p lu s to c a t t l e on p a s tu r e red u ced
w e ig h t g a in o f H ere fo rd X S h o rth o rn by 40-50 k g . /y e a r , b u t had n e g l i g i
b le e f f e c t s on Brahman c r o s s e s . Of th e above named r e p o r t s , o n ly th e
s tu d y o f L a n c a s te r e t a l . (1955) in v o lv e d th e lo n e s t a r t i c k . The r e s u l t s
o f t h i s s tu d y showed t h a t even when t i c k i n f e s t a t i o n was v e ry l i g h t ,
t r e a t e d s t e e r s g a in ed a n a v e rag e o f 9 pounds more p e r an im al th an
u n tr e a te d s t e e r s d u r in g a 9 0 -day p e r io d .
According to Bolte et al. (1 9 7 0 ), the lone star tick predisposes wildlife to secondary infections that often result in death of the animal. He reported that as much as 1 /3 of the fawn crop of whitetailed deer (Odocoileus virginianus) was lost to lone star tick induced pathological conditions at the Cookston Hills Wildlife Refuge in Oklahoma.
13
Loss was caused by nymphal and a d u l t fe e d in g t h a t r e s u l te d In g ro ss
t i s s u e damage and seco n d ary I n f e c t io n around th e eyes and head fo llo w ed
by b l in d n e s s .
METHODS AND MATERIALS
T ick R earing
The c u l tu r e o f lo n e s t a r t i c k s used i n t h i s s tu d y was e s ta b l i s h e d
from a c o l l e c t i o n made i n Ju n e , 1971. Nymphs w ere c o l le c te d from
wooded c a t t l e r e s t i n g a r e a s on th e C h ico t S to ck Farm n e a r H a ll Summit,
L o u is ia n a , th ro u g h th e use o f 8 week o ld c h ic k s and carbon d io x id e
l i b e r a t e d from d ry i c e . C hicks w ere p la c e d in d iv id u a l ly i n 12 x 14 x
16 i n . mesh w ire cag es and p o s i t io n e d 10-15 f e e t a p a r t i n a re a s w ith
h ig h nymphal p o p u la t io n s . Carbon d io x id e was u sed to s t im u la te th e
nymphs in th e im m ediate a re a o f th e c h ic k s and to a t t r a c t them from
th e su rro u n d in g a r e a . The b i r d s w ere moved p e r io d i c a l ly . A pprox im ate ly
4 h o u rs were r e q u ir e d f o r th e b i r d s to become h e a v i ly in f e s te d w ith
nymphs. A t th e end o f t h i s p e r io d , th e b i r d s w ere t r a n s f e r r e d to th e
la b o r a to r y and p la c e d in cages f o r c o l l e c t i n g r e p l e t e t i c k s a s th e y
dropped from th e c h ic k s . From th e i n i t i a l c o l l e c t i o n , la r g e numbers
o f t i c k s w ere m ass r e a re d fo r th e s tu d y u s in g c a t t l e a s h o s ts fo r
th e a d u l t t i c k s and 6 -8 week o ld c h ic k s a s h o s ts f o r th e im m ature fo rm s.
C a t t le w ere i n f e s t e d w ith a d u l t t i c k s by b ru sh in g th e t i c k s from
1 /2 p in t c a rd b o a rd i c e cream c a r to n s o n to th e t o p l in e o f th e an im als
w h ile th e y w ere r e s t r a i n e d in a c a t t l e w ork ing c h u te . The an im als
w ere co n fin ed i n d ry l o t s f o r f iv e days fo llo w in g i n f e s t a t i o n . They
w ere th e n p la c e d i n e le v a te d h o ld in g c r a te s ( 3% x 7 x 8 f e e t ) w ith
s l a t t e d f l o o r s . C o l le c t in g t r a y s (6 x 48 x 84 in c h e s ) c o n s tru c te d
w ith a 2 x 6 in c h p in e lum ber fram e and 1 /8 in c h g a lv a n iz e d hardw are
14
15
c lo th bottom s w ere used to c a tc h r e p l e t e fem ales a s th e y dropped from
th e c a t t l e . The h o ld in g c r a t e s w ere c o n s tru c te d from 2 x 6 In ch d re s se d
p in e lum ber and a r e shown In P la te 2 . R e p le te fem ales w ere p e r io d i c a l ly
hand p ick ed from th e bottom o f th e t r a y a s th e y dropped from th e c a t t l e .
S p l i t b u r la p sacks (36 x 42 i n . ) w ere p la c e d in th e bottom o f th e t r a y s
to c a tc h and f a c i l i t a t e rem oval o f w aste feed and m anure from th e t r a y s .
R ep le te fem ales w ere t r a n s f e r r e d to th e la b o r a to r y and c o n fin e d i n
h p in t card b o ard ic e cream c a r to n s w ith th e to p s covered w ith 90 mesh
p l a s t i c s c re e n . These w ere p la c e d s c r e e n down, o v e r m o is ten ed sand in
m e ta l boxes (14 x 24 x 36 in c h e s ) a s shown in p l a t e 3 . They w ere
m a in ta in e d under l a b o r a to r y c o n d i t io n s o f co n tin u o u s l i g h t p ro v id e d by
overhead f lu o r e s c e n t lamps and te m p e ra tu re c o n t r o l le d a t 26 + i°C .
This method and conditions described were used for holding all stages during development and in the unfed state before feeding.
C hicks (6 -8 weeks o ld ) se rv ed a s h o s ts f o r th e l a r v a l and nymphal
fe e d in g s ta g e s . U p rig h t m u l t i - l a y e r e d c h ic k r e a r in g b a t t e r i e s (30 x 48
x 84 in c h e s ) w ere c o n v e r te d f o r t i c k c o l l e c t i n g by rem oval o f a l l th e
low er cages and r e t e n t io n o f th e to p cag e . The m o d if ie d b a t t e r y se rv ed
a s an i n f e s t i n g and h o ld in g cage f o r th e b i r d s d u r in g engorgem ent and
d ro p p in g o f th e t i c k s . G a lv an ized m e ta l fu n n e ls (24 x 30 x 38 in c h e s )
equ ipped w ith 4 in c h o u t l e t s w ere p la c e d under th e to p c a g e s . A g raded
s e r i e s (d e c re a s in g in s iz e ) o f g a lv a n iz e d hardw are c lo th s c re e n s was
p la c e d in th e fu n n e ls to r e t a i n m anure and o th e r d e b r i s . C lean r e p l e t e
t i c k s w ere c o l le c te d a t th e bo ttom o f th e fu n n e ls in g la s s bow ls (3 x
9 in c h es ) p a r t i a l l y f i l l e d w ith w a te r . P la te 4 shows th e a p p a ra tu s
16
P la te I I . H olding c r a t e s and c o l l e c t i n g t r a y sused in c o l l e c t i n g r e p l e t e fem ale lo n e s t a r t i c k s as th e y d ropped from th e s t e e r s . (Photographed by B. H. W ilso n ) .
17
P la te I I I . Method o f h o ld in g t i c k s . (Photographed by W. H. L e g ra n d e ).
P la t e IV. A pparatus (c o n v e rte d c h ic k r e a r in g b a t te r y ) u sed f o r c o l l e c t i n g th e im m ature form s o f th e lo n e s t a r t i c k from c h ic k s . (Photographed by B. H. W ilso n ).
19
used f o r c o l l e c t in g th e Imm ature form s from c h ic k e n s .
C hicks w ere in f e s te d w ith t i c k s by e v e n ly b ru sh in g t i c k s from
h p in t c a rd b o ard ic e cream c a r to n s o n to th e f lo o r o f t i c k c o l l e c t i n g
cages covered w ith brown w rapping p a p e r . Ten b i rd s w ere th e n p la c e d
in each c o l l e c t i n g c ag e . Two h o u rs w ere a llo w ed f o r th e t i c k s to
c raw l from th e p ap er o n to th e b i r d s . The p a p e r was removed from'
th e c o l l e c t i n g cages a t th e end o f t h i s p e r io d .
A w a lk - in c o o le r , m a in ta in e d a t a te m p e ra tu re o f 36 + 2°F . was
used to red u ce t i c k a c t i v i t y w h ile s e p a r a t in g sex es and c o u n tin g
a d u l t t i c k s . T ick l o t s c o n ta in in g 300 m a les and 300 fem ales ( P la te 5)
w ere p re p a re d a s an i n f e s t a t i o n u n i t /a n im a l f o r e x p e r im e n ta l c a t t l e .
C a t t l e
Four p u reb red H e re fo rd , 4 p u re b re d Brahman, and 4 Brahman X
H ere fo rd c ro s sb re d s t e e r s a b o u t 1 y e a r o ld w ere used i n t h i s s tu d y .
The p u reb red s t e e r s w ere grown on th e LSU c a t t l e farm a t B aton Rouge,
L o u is ia n a . The Brahman X H ere fo rd c ro s s b re d s t e e r s w ere p u rch ased
f o r t h i s s tu d y from a s to c k farm a b o u t 50 m ile s n o rth w e s t o f B aton
R o u g e .’ The t e s t c a t t l e had no known h i s t o r y o f t i c k i n f e s t a t i o n ,
s in c e b o th a re a s were c o n s id e re d t i c k f r e e . The c ro s s b re d s t e e r s
w ere t r a n s f e r r e d to B&ton Rouge 90 days p r i o r to t i c k i n f e s t a t i o n
w here th e y w ere m a in ta in e d un d er th e same c o n d it io n s o f p a s tu r e and
feed a s th e p u re b re d c a t t l e . P la te 6 shows th e s t e e r s used i n t h i s
s tu d y .
T ick I n f e s t a t i o n o f C a t t le
The s t e e r s w ere in f e s t e d w ith a d u l t lo n e s t a r t i c k s a t 2 week
i n t e r v a l s f o r 3 c o n se c u tiv e i n f e s t a t i o n s d u r in g th e summer 1972. For
Plate V An i n f e s t a t i o n u n i t o f 300 m ale and 300 fem ale lo n e s t a r t i c k s u sed to i n f e s t each s t e e r a t each i n f e s t a t i o n . (Photographed by W. H. L e g ra n d e ) .
P la te V I. P u reb red H ere fo rd ( t o p ) , p u re b re d Brahman ( c e n t e r ) , and Brahman X H ere fo rd c ro s sb re d s t e e r s (b o tto m ), u sed to compare r e s i s t a n c e betw een th e b re e d s . (P hotographed by W. H. L eg ran d e).
22
each i n f e s t a t i o n th e s t e e r s w ere c o n fin e d i n c h u te s , h a l t e r e d and t i e d
w ith a s p a t i a l s e p a r a t io n o f a b o u t 4 f e e t . Each an im a l was In f e s te d
a lo n g th e to p l in e w ith 300 m ale and 300 fem ale t i c k s . They w ere k e p t
t i e d f o r a p e r io d o f 2 h o u rs im m ed ia te ly a f t e r i n f e s t a t i o n . The s t e e r s
w ere r e ta in e d i n a d ry l o t w i th g ra s s hay fe d on a f r e e - c h o ic e b a s is
and a g r a in r a t i o n ( i n g r e d i e n t s , Appendix T ab le 3) u n t i l th e y were
t r a n s f e r r e d to th e h o ld in g c r a t e s ( P la te 2 ) . The p e r io d betw een i n f e s
t a t i o n and lo a d in g i n t o th e h o ld in g c r a t e s was 7 days f o r th e i n i t i a l
i n f e s t a t i o n and 5 days f o r su b se q u e n t i n f e s t a t i o n s .
Collection of Replete Female TicksThe s t e e r s w ere p la c e d in th e h o ld in g c r a t e s , h a l t e r e d and snubbed
to th e f r o n t end o f th e h o ld in g c r a t e w ith a b o u t 2 f e e t o f ro p e to a llo w
l im ite d freedom o f movement d u rin g c o n fin em en t. They w ere h e ld in th e
c r a te s fo r 1 week d u r in g w hich tim e th e y w ere fed a h ig h b u lk g r a in
r a t i o n ( in g r e d ie n ts , A ppendix T ab le 3 ) . The t r a y s w ere c le a n e d and
in s p e c te d fo r r e p l e t e fem ale t i c k s tw ic e d a i l y .
R ep le te fem a les w ere t r a n s f e r r e d to th e l a b o r a to r y and w eighed
in d iv id u a l ly . The f i r s t 10 r e p l e t e fem ales c o l le c te d from each an im al
were r e ta in e d f o r egg la y in g and h a t c h a b i l i t y d a ta . These 10 fem ales
were p laced in d iv id u a l ly i n t o p l a s t i c j e l l y cups f o r o v ip o s i t io n . The
j e l l y cups c o n ta in in g th e fem a les w ere h e ld i n d e s s i c a to r j a r s th a t
c o n ta in e d a su p e r s a tu r a te d s o lu t io n o f p o ta ss iu m c h lo r id e ( P la t e 7 ) .
T h is s o lu t io n m a in ta in e d a r e l a t i v e h u m id ity in s id e th e d e s s i c a to r
o f 85% a t a te m p e ra tu re o f 80°F . A f te r o v ip o s i t io n was co m p le te , th e
egg m asses were w eighed and a sam ple o f 100 eggs was c o l l e c te d and
in c u b a te d . H a tc h a b i l i ty was c a lc u la te d by d e te rm in in g th e number o f eggs
P la te V II . D e s s ic a to r j a r f o r h o ld in g r e p l e t e fem ales f o r o v ip o s i t io n and h a t c h a b i l i t y d a ta . (P ho tographed by W. H. L eg ran d e ).
24
t h a t f a i l e d to h a tc h . |
A M e tt le r e l e c t r i c b a la n c e was used to w eigh r e p l e t e fem ale
t i c k s and egg m asse s .
S t a t i s t i c a l A n a ly s is
The analysis of variance and analysis of regression were used to determine the significance of differences among treatments.
One a b b r e v ia t io n and two sym bols w ere used w ith o u t e x p .lan a tio n in
some ta b le s o f r e s u l t s . The a b b r e v ia t io n , n s , i n d ic a te s t h a t th e
d i f f e r e n c e betw een means was n o t s i g n i f i c a n t a t th e 5 p e rc e n t l e v e l .
The s in g le a s t e r i s k (*) and d o u b le a s t e r i s k (**) in d ic a te s ig n i f ic a n c e
a t th e 5 p e rc e n t and 1 p e rc e n t l e v e l s , r e s p e c t iv e ly .
RESULTS AND DISCUSSION
R e s u lts o f a n a ly s i s o f r e g r e s s io n showed th a t th e r e l a t i o n s h i p
betw een th e number o f r e p l e t e lo n e s t a r fem ale t i c k s and th e w e ig h t
o f th e s e r e p l e t e fem a les was p o s i t i v e l y c o r r e la te d (P < 0 .0 1 ) w ith a
c o r r e l a t i o n c o e f f i c i e n t o f 0 .6 7 . T h is f in d in g a g re e s w ith r e s u l t s
r e p o r te d by o th e r r e s e a r c h e r s (R iek 1962, T a tc h e l l 1969, H ewetson 1 9 7 1 ).
They n o ted a low er number and a l i g h t e r mean w e ig h t o f r e p l e t e fem ale
t i c k s dropped from c a t t l e - t h a t w ere more r e s i s t a n t to B. m ic r o p lu s .
A verage num bers o f r e p l e t e fem a les dropped from H e re fo rd , Brahman,
and Brahman X H ere fo rd c ro s s b re d s t e e r s a t each i n f e s t a t i o n , a s w e ll
a s means f o r b re e d s and i n f e s t a t i o n s a r e shown i n T ab le I . The
d i f f e r e n c e betw een b re e d s ap p ro ach ed s t a t i s t i c a l s ig n i f ic a n c e
(P > 0 .0 5 < 0 .1 0 ) . D ata i n T ab le I show th e v a r i a t i o n w i th in b re e d s
t h a t a c c o u n ts f o r th e s e w id e ly s e p a ra te d means n o t b e in g s i g n i f i c a n t
a t th e 0 .0 5 l e v e l o f p r o b a b i l i t y . The mean y ie ld o f r e p l e t e fe m a le s
from p u re b re d H e re fo rd s t e e r s was 52% more th a n th e mean y ie ld from
p u reb red Brahman s t e e r s and 74% more th a n th e mean y ie ld from Brahman
X H erefo rd c ro s s b re d s t e e r s (T ab le I , T ab le I I ) . These d a ta i n d i c a t e
t h a t p u re b re d H ere fo rd s t e e r s w ere l e a s t r e s i s t a n t and t h a t Brahman X
H ere fo rd c ro s s e s w ere m ost r e s i s t a n t . P u reb red Brahman s t e e r s w ere
in te rm e d ia te i n y ie ld o f t i c k s when compared to th e p u reb red H e re fo rd
and th e c ro s s b re d s t e e r s . R e s u lts r e p o r te d by R iek (1962) in d ic a te d
a s im i l a r t r e n d w here c ro s s b re d Zebu s t e e r s y ie ld e d th e lo w e s t number
o f r e p l e t e fe m a le s , p u re b re d Zebu w ith a medium y ie ld , and B r i t i s h
25
26
Table I. Number of replete female lone star ticks dropped*from testc a t t l e fo llo w in g th e i n f e s t a t i o n o f each an im a l by 300 m ales and 300 fe m a le s p e r a n im a l.
Number of replete females dropped Animal First Second Third Breed
Breed___________ Number_________ Infestation Infestation Infestation MeanHereford 577 125 25 29
597 92 21 12598 85 8 4602 136 189 42
Mean 110 61 22 64
Brahman 830 111 22 3837 61 15 3842 40 68 7847 15 27 0
Mean 57 33 3 31
Crossbred 15 38 10 116 26 16 217 11 1 218 75 17 1 *
Mean 38 11 1 .5 17
Infestation 68 35 9 37Mean
27
Table II. Analysis of variance of numbers of female lone star ticks feeding to repletion on cattle.
Source of Variation
Degree of Freedom
MeanSquares
Total 35
Breed 2 7076.0 nsIndividual breed 9 1949.9Infestation 2 10522.5 **Breed X Infestation 4 736 .8 nsError 18 9 1 2 .1
28
c a t t l e y ie ld in g th e h ig h e s t number o f r e p l e t e B. m ic ro p lu s fem ale t i c k s .
Hewetson (1971) r e p o r te d no d i f f e r e n c e betw een p u reb red and c ro s s b re d
Zebu s t e e r s r e l a t i v e to th e number o f r e p le t e B. m ic ro p lu s fem ale t i c k s
d ropped a t th e f i r s t and second i n f e s t a t i o n s . However, he d id f in d a
s i g n i f i c a n t d i f f e r e n c e in th e number o f r e p le t e fem ales dropped betw een
th e two g roups a f t e r fo u r i n f e s t a t i o n s .
A ll th re e g roups o f t e s t c a t t l e in th e s tu d y a c q u ire d a h ig h l e v e l
o f r e s i s t a n c e to th e lo n e s t a r t i c k . The d a ta i n T ab le I I show t h a t a
h ig h ly s i g n i f i c a n t d i f f e r e n c e was found betw een i n f e s t a t i o n s . D ata in
T ab le I show th e av e rag e number o f r e p l e t e fem ales a t each i n f e s t a t i o n
f o r each b re e d , a s w e ll a s an o v e r a l l mean f o r each i n f e s t a t i o n . Y ie ld
o f r e p l e t e fem ales d e c lin e d 48.5% from th e f i r s t i n f e s t a t i o n to th e
second and 75.0% from th e second to th e t h i r d i n f e s t a t i o n . The y i e ld
o f r e p l e t e fem ales by b reed and i n f e s t a t i o n i s g r a p h ic a l ly p re s e n te d
i n F ig . 2 .
The av e rag e w e ig h ts o f r e p l e t e fem a les f o r b re e d s and i n f e s t a t i o n s
a r e p re s e n te d i n T ab le I I I . An a n a ly s i s o f v a r ia n c e o f th e s e d a ta show
th a t d i f f e r e n c e s in w e ig h t o f r e p l e t e fem ales betw een th e b re e d s w ere
n o t s i g n i f i c a n t . In c o n t r a s t , R iek (1962) re p o r te d t h a t r e p l e t e B.
m ic ro p lu s fem a les dropped by B. ta u r u s s t e e r s w ere s i g n i f i c a n t l y h e a v ie r
th a n r e p l e t e fem ale t i c k s dropped by B. in d ic u s s t e e r s . He a l s o
re p o r te d t h a t th e w e ig h t o f t i c k s dropped from Zebu c ro s sb re d s t e e r s
ten d ed to ap p ro ach th o se dropped from p u reb red B. ta u ru s s t e e r s w h ile
d a ta from t h i s i n v e s t i g a t i o n show w ide d i f f e r e n c e s betw een th e p u re b re d
H ere fo rd s t e e r s and th e c ro s sb re d s t e e r s (T ab le I I I ) .
Av.
no
. of
repl
ete
fem
ales
29
H ere fo rd □ - - -
Brahman A - - -
C ro ssb red © - -
Mean ( a l l c a t t l e )
120
110
100
80
60
30
20
10
02nd
I n f e s t a t i o n s
3 rd1 s t
— ra — A
— O
— ♦
F ig u re 2 . A verage number o f r e p l e t e fem ale lo n e s t a r t i c k s droppedfrom each group o f t e s t c a t t l e fo llo w in g th r e e i n f e s t a t i o n s by 300 m ales and 300 fem a les p e r a n im a l.
T ab le I I I . Average w e ig h t In m illig ra m s o f fem ale lone s t a r t i c k s fe e d in g to r e p l e t i o n from each group o f t e s t c a t t l e fo llo w in g th e i n f e s t a t i o n o f each an im al by 300 m ales and 300 fem a les .
F i r s t I n f e s t a t i o n Second I n f e s t a t i o n T h ird I n f e s t a t i o n BreedBreed__________No. t i c k s Av. Wt. No. t i c k s Av. Wt. No. T ick s Av. Wt.; Mean
H erefo rd 425 429.26 241 413.83 81 312.68 381.23
Brahman 222 387.61 129 293.74 13 271.13 313.99
C rossb red 146 344.36 44 321.73 6 242.29 317.97
I n f e s t a t i o nMean 401 .97 366.62 303.60 382.88
31
D ata from th e p re s e n t s tu d y show d i f f e r e n c e s i n w e ig h t o f r e p l e t e
fem ales betw een I n f e s t a t i o n s w ere h ig h ly s i g n i f i c a n t (T ab le IV ) .
D ata in T ab le I I I show t h a t a s r e s i s t a n c e d e v e lo p e d , t h e w e ig h t o f
r e p l e t e fem ales became p r o g r e s s iv e ly l e s s . I n c o n t r a s t , H ewetson
(1968) w ith B. m ic ro p lu s r e p o r te d t h a t a s r e s i s t a n c e dev elo p ed
a f t e r i n f e s t a t i o n s th e w e ig h t o f th e r e p l e t e fem ale t i c k s in c r e a s e d .
The s i g n i f i c a n t i n t e r a c t i o n betw een g ro u p s o f t e s t c a t t l e and
i n f e s t a t i o n s re g a rd in g a v e ra g e w e ig h t o f r e p l e t e fem ales (T ab le IV)
showed t h a t th e d i f f e r e n t g ro u p s o f s t e e r s e x h ib i te d d i f f e r e n t r a t e s
o f d e c l in e i n a v e rag e w e ig h t o f r e p l e t e fem a les betw een i n f e s t a t i o n s .
The d i f f e r e n c e s a r e a p p a re n t i n F ig . 3 . P u reb red H e re fo rd and Brahman
X H erefo rd c ro s sb re d s t e e r s responded i n a s im i la r m anner. Both
g roups showed a s l i g h t d e c l in e in w e ig h t o f r e p l e t e fem a les betw een
th e f i r s t and second i n f e s t a t i o n s . However, betw een th e second and
t h i r d i n f e s t a t i o n s th e a v e ra g e w e ig h t o f r e p l e t e fem a les from b o th
g ro u p s o f c a t t l e d e c lin e d s h a r p ly . C o n v e rse ly , w e ig h ts o f r e p l e t e
fem ale t i c k s dropped from Brahman s t e e r s e x h ib i te d a sh a rp d e c l in e
betw een th e f i r s t and second i n f e s t a t i o n s , b u t o n ly a s l i g h t d e c l in e
betw een th e second and th i r d i n f e s t a t i o n (F ig . 3 ) . Hewetson (1971)
o b serv ed th a t p u reb red and c ro s s b re d Zebu s t e e r s dropped r e p l e t e
B. m ic ro p lu s o f s im i la r s i z e (231 mg) when f i r s t i n f e s t e d ; how ever,
a s r e s i s t a n c e developed betw een i n f e s t a t i o n s , th e mean w e ig h t o f t i c k s
became p r o g r e s s iv e ly l e s s u n t i l a t a f o u r th i n f e s t a t i o n , t i c k s dropped
by th e p u re b re d Zebu s t e e r s w ere s i g n i f i c a n t l y l i g h t e r (159 mg) th a n
th o s e d ropped by th e c ro s sb re d Zebu s t e e r s (180 m g). D ata i n t h i s
32
T ab le IV. A n a ly s is o f v a r ia n c e o f w e ig h ts o f fem a le lo n e s t a r t i c k s fe e d in g to r e p le t io n on c a t t l e .
Source o f D egrees o f MeanV a r ia t io n Freedom Squares
T o ta l 1312
Breed 2 171390.46 ns
In d iv id u a l 9 191755.07
I n f e s t a t i o n 2 437621.12 **
Breed X i n f e s t a t i o n 4 64866.38 **
E r ro r 1295 24142.12
Means
33
H erefo rd D------ □
Brahman - A
C ro ssb red O O
Mean ( a l l b r e e d s ) # 1 ■ ♦450
425
400
375
350
325
a300
275
250
225
2nd 3 rd1 s t
I n f e s t a t i o n s
F ig u re 3 . A verage w e ig h t i n m il l ig ra m s o f r e p l e t e fem ale lo n e s t a r t i c k s dropped from each group o f t e s t c a t t l e fo llo w in g th e i n f e s t a t i o n o f each an im a l by 300 m ales and 300 fe m a le s .
34
s tu d y (T ab le IV) show no s i g n i f i c a n t d i f f e r e n c e s in th e w e ig h t o f r e p l e t e
fem ales betw een H erefo rd and c ro s s b re d s t e e r s .
The mean t i c k w e ig h ts , egg m ass w e ig h ts , and p e rc e n ta g e o f eggs
h a tch e d from sam ples ta k e n f o r h a t c h a b i l i t y a r e p re s e n te d in T ab le V.
The d i f f e r e n c e in p e rc e n ta g e o f eggs h a tc h e d from fem ales betw een groups
o f t e s t c a t t l e was h ig h ly s i g n i f i c a n t (T ab le V I ) . The mean p e rc e n ta g e
h a tc h o f eggs from r e p l e t e fem a les dropped by Brahman s t e e r s was 43%
le s s th a n th a t o f eggs from fem a les dropped by H e re fo rd s t e e r s and 50%
l e s s th a n t h a t o f eggs from fem ales dropped by th e Brahman X H erefo rd
c ro s sb re d s t e e r s . The d i f f e r e n c e betw een th e mean p e rc e n ta g e o f eggs
h a tch ed from r e p le te fem ales d ropped by p u re b re d H ere fo rd s t e e r s a s
compared to t h a t o f eggs from fem a les d ropped by Brahman X H erefo rd
c ro s sb re d s t e e r s was n o t s i g n i f i c a n t .
T ick w eig h t and egg m ass w e ig h t w ere h ig h ly c o r r e la t e d w ith a
c o r r e l a t i o n c o e f f i c i e n t o f 0 .8 7 . Snow and A r th u r (1966) w orking w ith
Hyalomma a n a to lic u m a n a to lic u m (Koch) and Sweatman (1967) w ork ing w ith
R h ip ic e p h a lu s san g u in eu s ( L a t r e i l l e ) a l s o r e p o r te d a h ig h c o r r e l a t i o n
betw een w e ig h t o f th e engorged fem ale and th e w e ig h t o f th e egg m ass.
A n a ly s is o f v a r ia n c e o f (d a ta on w e ig h t o f th e engorged fem ales and
w e ig h t o f th e egg m asses showed no s i g n i f i c a n t d i f f e r e n c e s betw een
b re e d s i n t h i s s tu d y . However, R iek (1962) r e p o r te d t h a t r e p l e t e
B. m ic ro p lu s fem ales dropped by p u re b re d B. ta u r u s b re e d s w ere s i g n i
f i c a n t l y h e a v ie r and la id a g r e a t e r w e ig h t o f eggs th a n t i c k s dropped
from p u re b re d B. in d ic u s c a t t l e , b u t he d id n o t f in d s i g n i f i c a n t
d i f f e r e n c e s betw een t i c k s d ropped from p u re b re d B. ta u ru s and 3 /4
35
Table V. Mean tick weight, weight of the egg mass, and percent hatch of eggs from a sample comprised of the first 10 replete female lone star ticks dropped from each animal following each Infestation by 300 males and 300 females per animal.
Breed of cattle
No. of ticks
Meanweight mg
Mean wt. of egg mass mg
Percenthatch
Hereford 114 3 93 .41 204.83 36 .30
Brahman 93 371 .99 185.87 20.67
Crossbred 77 334 .63 182.66 4 1 .2 4
Ten r e p l e t e fem ales w ere n o t dropped by a l l in d iv id u a ls from th e 2nd and 3rd i n f e s t a t i o n s . S e v e ra l r e p l e t e fem a les d ie d b e fo re o v ip o s i t io n began .
36
T ab le V I. A n a ly s is o f v a r ia n c e o f p e rc e n t o f eggs h a tc h e d from a sam ple com prised o f th e f i r s t 10 r e p l e t e fem ale lo n e s t a r t i c k s dropped from each an im al fo llo w in g each I n f e s t a t i o n by 300 m ales and 300 fem ales p e r a n im a l.
Source of Variation
Degree of Freedom
MeanSquares
Total 257
Breed 2 5657 .920**
Ind ividua1/breed 9 697.130
Infestation 2 1034.376 nsBreed x Infestation ' 4 1517.451 nsError 240 1016.307
Ten r e p l e t e fem a les w ere n o t d ropped by a l l I n d iv id u a ls from th e 2nd and 3rd I n f e s t a t i o n s . S e v e ra l r e p l e t e fem a les d ie d b e fo re o v ip o s i t io n b eg an .
37
Zebu X 1/4 Shorthorn crossbred steers In weight of rep le te females
dropped or weight of egg masses. Additional research using greater
numbers o f c a t t le Is needed to c la r ify th is point.
Even though th e r e was a s l i g h t In c re a s e I n p e rc e n t o f eggs
h a tc h e d betw een th e f i r s t and second I n f e s t a t i o n , th e d i f f e r e n c e
betw een I n f e s t a t i o n s was n o t s i g n i f i c a n t (T ab le V I, and T a b le V I I ) .
T h is I s i n ag reem ent w ith r e s u l t s r e p o r te d by Hewetson (1971) who
n o te d o n ly a s l i g h t d e c l in e i n h a t c h a b i l i t y o f eggs from m ic ro p lu s
fem a les dropped from p u re b re d and c ro s s b re d Zebu s t e e r s fo llo w in g
a t h i r d and f o u r th a r t i f i c i a l I n f e s t a t i o n .
T rends o b serv ed i n t h i s s tu d y on th e a v e rag e y i e ld and w e ig h t o f
r e p l e t e fem ale t i c k s i n d i c a t e t h a t Brahman i n a c ro s s b re e d in g p rogram
w ith B r i t i s h b re e d s o f c a t t l e may be e f f e c t i v e l y u t i l i z e d a s a non
c h em ica l ap p ro ach to t i c k C o n tro l i n a r e a s h e a v i ly i n f e s t e d w ith th e
lo n e s t a r t i c k . H ig h e r l e v e l s o f r e s i s t a n c e to t i c k i n f e s t a t i o n may
be g a in e d i n a b re e d in g program o f t h i s s o r t th a n any o th e r y e t
d e v is e d . In a d d i t io n t o th e im m edia te b e n e f i t s r e s u l t i n g from lo w er
p o p u la t io n s o f t i c k s en g o rg in g on c ro s s b re d a n im a ls , f u tu r e t i c k
p o p u la t io n s sh o u ld be re d u c e d . T h is r e d u c t io n would b e e f f e c t e d i n
two w ays: (1 ) red u ced number o f r e p l e t e fem a les d ropped t o r e i n f e s t
p a s tu r e la n d ; and (2) red u ced w e ig h .^ o f r e p l e t e fem a les r e s u l t i n g i n
few er eggs p e r fem ale d ro p p ed . The l a t t e r i s s u b s ta n t i a t e d by
th e w ork r e p o r te d by Snow and A r th u r (1966) who found t h a t th e
w e ig h t o f th e r e p l e t e fe m a le , Hyalomma a n a to lic u m a n a to lic u m i s
d i r e c t l y p r o p o r t io n a l to th e number o f eggs p roduced and t h a t o f
T ab le V II . P e rc e n t o f eggs h a tch ed from a sam ple com prised o f th e f i r s t 10 r e p l e t e fem alelo n e s t a r t i c k s dropped from each an im a l fo llo w in g each I n f e s t a t i o n by 300 m ales and 300 fem ales p e r a n im a l.
BreedF i r s t i n f e s t a t i o n Ho. t i c k s % h a tc h
Second i n f e s t a t i o n Ho., t i c k s % h a tc h
T h ird i n f e s t a t i o n Ho. t i c k s 7. h a tc h
BreedMean
H e re fo rd ' 37 28 .16 38 38 .16 25 4 5 .5 2 36 .30
Brahman 39 15.33 38 27.55 10 15.30 20 .67
C rossbred 37 43 .43 30 4 0 .4 7 4 26 .75 4 1 .2 4
I n f e s t a t i o nMean 113 28.73 106 35 .0 1 39 35 .83
aTen r e p l e t e fem ales w ere n o t dropped by a l l in d iv id u a ls from th e 2nd and 3rd i n f e s t a t i o n s . S e v e ra l r e p l e t e fem a les d ie d b e fo re o v ip o s i t io n began .
39
Drummond e t a l . (1971) In a s tu d y w ith th e lo n e s t a r t i c k found th a t th e
c o r r e l a t i o n betw een number o f eggs l a i d and w e ig h t o f th e r e p l e t e
fem ale was h ig h ly s i g n i f i c a n t . I n th e p re s e n t s tu d y , o b s e rv a t io n o f
th e a v e rag e w e ig h ts o f r e p l e t e fem ale t i c k s dropped from c ro s sb re d
s t e e r s shows t h a t th e se w e ig h ts w ere c o n s id e ra b ly l e s s th a n th e
a v e ra g e w e ig h ts o f r e p le t e fem a les dropped from p u reb red H erefo rd
s t e e r s . However, th e number o f eggs l a i d p e r egg mass was n o t
d e te rm in e d .
I n a d d i t io n to r e s i s t a n c e to th e lo n e s t a r t i c k in d ic a te d i n
t h i s s tu d y , Brahman c ro s sb re d c a t t l e have been r e p o r te d to be r e s i s t a n t
to h o r n f l i e s (T ugw ell and Burns 1 9 6 7 ), a s w e ll a s to g a s t r o i n t e s t i n a l
h e lm in th s (T u rn e r and S h o rt 19 7 2 ). Such f in d in g s s t r o n g ly su g g e s t t h a t
h o s t r e s i s t a n c e to p a r a s i t e s sh o u ld be c o n s id e re d i n l iv e s to c k b re e d in g
p ro g ram s.
CONCLUSIONS
1. I t a p p ea rs t h a t H ere fo rd X Brahman c ro s s b re d c a t t l e a r e more
r e s i s t a n t th an e i t h e r p u re b re d Brahman o r p u re b re d H e re fo rd c a t t l e
to th e lo n e s t a r t i c k . P u reb red H e re fo rd c a t t l e ap p ea r l e s s r e s i s t a n t
th a n p u re b re d Brahman c a t t l e to th e lo n e s t a r t i c k .
2 . Under f i e l d c o n d i t io n s in L o u is ia n a , p u re b re d Brahman c a t t l e
sh o u ld e f f e c t marked r e d u c t io n s o f th e lo n e s t a r t i c k on p a s tu r e s a s
a r e s u l t o f reduced egg h a t c h a b i l i t y .
3 . I t a p p e a rs re a s o n a b le to assum e t h a t B r i t i s h b re e d s a s w e l l
a s Brahman w i l l a c q u ire a h ig h l e v e l o f r e s i s t a n c e to th e lo n e s t a r
t i c k a f t e r s e v e ra l e x p o su res to them .
4 . A h ig h c o r r e l a t i o n betw een num bers and w e ig h ts o f r e p l e t e
fem a les in d ic a te t h a t th e s e c r i t e r i a a r e sound m easu res o f r e s i s t a n c e
in c a t t l e .
40
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APPENDIX
46
Table I. Average weight in milligrams of replete females dropped from individual animals.
Breed Animal Av. w e ig h t in m ill ig ra m s o f r e p l e t e fem ale
No. 1 s t i n f e s t a t i o n 2nd i n f e s t a t i o n 3 rd i n f e s t a t i o n
H erefo rd 577 404 .04 315.39 291 .36
597 454 .75 308.85 222 .18
598 369.91 338.73 360 .01
602 472 .12 441 .99 348 .76
Brahman 830 389 .67 276 .86 352 .33
837 337 .56 -308 .70 237 .37
842 428 .61 314.67 250 .79
847 466 .36 247 .18 -
C ro ssb red 15 341 .16 322 .70 303 .83
16 278 .45 319 .20 278 .34
17 222 .98 159.45 208 .82
18 389.02 333.08 175.58
47
T able 2 . Mean t i c k w e ig h t , egg mass w e ig h t.a n d p e rc e n t h a tc h from in d iv id u a l a n im a ls .
Breed Anim alno.
N o. o f t i c k s
Mean t i c k w e ig h t in mg.
Mean egg mass w e ig h t in mg.
P e rc e n tH atch
H erefo rd 577 30 378 .88 193.11 39 .14
597 30 371 .31 186.64 33 .41
598 24 350 .35 193 .00 35.62
602 30 464 .48 2 42 .50 37 .62
Brahman 830 23 345 .41 155.64 11 .19
837 23 381 .45 194.81 26 .14
842 27 3 66 .68 190.71 18.00
847 20 398.85 203 .25 28 .89
C rossbred 15 21 342 .59 196.95 4 7 .9 0
16 22 333 .98 184.81 37 .40
17 13 199.72 101.77 35.92
18 21 4 10 .87 216 .44 41 .63
48
T able 3 . R a t io n s fed s t e e r s d u rin g c o n fin e m en t.
A. G ra in r a t i o n fed s t e e r s w h ile c o n f in e d i n d ry l o t
7. in r a t i o n
3 5 .03 5 .010.0 10.07 .52 .5
f r e e c h o ic e
B. High b u lk g r a in r a t i o n fe d s t e e r s w h ile c o n f in e d i n th e c r a t e sd u r in g t i c k c o l l e c t i o n .
I n g r e d ie n t % in
c rack ed c o rn 2 0 .0r o l l e d o a t s 3 5 .0c o t to n eo.ed h u l l s 1 5 .0w heat V.ran 1 0 .0c o t to n seed m eal 1 0 .0b la c k s t r a p m o lasses 7 .5s a l t - m in e r a l mix 2 .5
I n g r e d ie n t
c ra ck e d c o rn r o l l e d o a t s w heat b ra n c o t to n seed m eal b la c k s t r a p m o lasses s a l t - m in e r a l mix
g r a s s hay
VITA
Gene Ray S t r o th e r was b o rn May 20, 1937, a t G lenm ora, L o u is ia n a .
He g ra d u a te d from P la ln v le w High S choo l, G lenm ora, L o u is ia n a In Ju n e ,
1955.
On August 31, 1957, he was married to Nell Curry of Hall Summit, Louisiana. He is the father of four children, Sherri Jean, Bradley
Winston, Mark Conly, and Jill Allison.He obtained a Bachelor of Science degree in Animal Science from
Louisiana State University in June, 1961.
He was employed by the Louisiana State Department of Agriculture as a Livestock Market News Reporter from July, 1961 until February,
1967.
He entered the United States Army Reserve in July, 1959, and was granted an honorable discharge in July, 1965.
He o b ta in e d a M aste r o f S cience d eg ree in Entom ology from
L o u is ia n a S ta te U n iv e r s i ty in J a n u a ry , 1970 and i s p r e s e n t ly a
c a n d id a te f o r th e D octor o f P h ilo so p h y d e g re e .
49
EXAMINATION AND THESIS REPORT
Candidate: Gene Ray S t r o th e r
Major Field: Entom ology
Title of Thesis: Resistance of Purebred Brahman, Hereford, and Brahman X HerefordCrossbred Cattle to the Lone Star Tick, Amblyomma americanum (L.)
Approved:
M a jo r P ro fesso r and C h a irm a n
D ^ a n 'o f th e G ra d u a te School
EXAMINING COMMITTEE:
r- / / i
Date of Examination:
April 16, 1973