lessons from studies in genetics of heat...

Lessons from studies in genetics of heat stress

Ignacy Misztal

University of Georgia

ADSA Resilience Symposium 2016

Animal Breeding and Climate Change

• Remarkable success of breeding – Kg milk 1944-2007: 23% feed, 35% water, 37% CO2

(Capper et al., 2009) – Broiler 1957-2001: grows 3 times faster using 33%

feed (Havenstein et al., 2003) – … – > 50% gain via genetics (Shook, 2006; Havenstein et

al., 2003).

• Challenge of climate change • Do we need a special breeding for resilience?


Selection as optimization

• Domestication

• Intensive selection

• Gains for preferred traits

• Correlated losses for other traits

• Effect of losses reduced/eliminated by management

• Very poor fitness of domesticated animals have when released back into the wild (Frankham, 2008).


Climate change

• Greater variations

• Hotter

• Extensive literature on heat stress/tolerance

• Heat tolerance as proxy for resilience

• Can one select for heat tolerance?


Challenge of heat stress

• Perceived reduction of heat tolerance in hot areas

• Little observable heat stress with DHI data (e.g., Wright et al., 2015)

• Mainstream selection in Holsteins in milder/colder climates

• Selection against heat tolerance? – If so, can one select for heat tolerance?


Assumption for heat stress model P

rod

uct

ion

/Rep

rod

uct

ion

Temperature humidity index (THI)

cow 2

cow 3

cow 1

Breeding value: BV = a + f(THI)*v

a – regular breeding value v – heat-tolerance breeding value

f(THI) – function of temperature humidity index

Ravagnolo et

al., 2001

Effect of THI on daily milk production

48

49

50

51

52

53

54

55

56

57

58

59

55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85

slope= -0.46

lb

THI

0.52

0.54

0.56

0.58

0.6

0.62

0.64

0.66

0.68

0.7

0.72

50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84

THI

NR

45

Effect of THI on Non-return rate at 45 days

Genetics results

• Heat stress begins at about 72F THI (22C at 100% humidity)

• Genetic variability for heat tolerance present but not big

• Relationship between regular and heat tolerance genetics antagonistic at ~ -0.4


Heat stress across USA

Variation in heat tolerance across USA

Genetic evaluation for heat stress with national data

Do colder regions contribute information about heat stress?

Profile of heat tolerant bull

Can one identify heat-tolerant sires?

What are they?

Bohmanova et al. (2005 and 2006)

Differences between most 100 and least

100 heat tolerant sires

Milk -1100kg

Fat% +0.2%

Pro% +0.1%

Dairy Form -1.4

Udder +0.7

Longevity +0.90

Fertility +1.6

Index +36

• Selection for fluid milk

detrimental to heat stress

• Low accuracy of active

sires for heat stress

Heat stress in later parities (Aguilar

et al., 2009)

US test days

3-trait RR and RPT models

Heat stress effect

Estimation of parameters

National evaluation

Variances for three-parity test-day repeatability

model

Milk

1 2 3

5.6 7.5 6.5

4.0 7.0 9.0

-0.46 -0.38 -0.47

Fat (kg*100)

1 2 3

74 94 109

37 75 142

-0.39 -0.39 -0.30

Protein (kg*100)

1 2 3

43 57 52.2

22 48 108

-0.43 -0.36 -0.50

Genetic variance for heat stress increases up to 5 times


Genetic trends of daily milk yield for

3 parities – regular effect

First Second Third


Genetic trends for heat stress effect

at 5.5o C over the threshold

First Second Third

• Improvement higher than deterioration

• Test days capture fraction of heat stress information (Freitas et al., 2005)


K. Tokuhisa*, S. Tsuruta, and I. Misztal University of Georgia, Athens

# 709


Mortality in SouthEast

0.10%

0.20%

0.30%

0.40%

0.50%

0.60%

0.70%

0.80%

0.90%

1 2 3 4 5 6 7 8 9 10 11 12

Mo

rta

lity

Month

SE Mortality (1-3rd parities) 1999-2008

1st parity

2nd parity

3rd parity

Tokuhisa et al. (2011)


Is cost of heat stress higher than it seems?

• Low survival in SouthEast from parity to parity

• Due to increasing heat stress with parities?

• Selection for survival but not for mortality

• Available data only from better farms


Days open in Thai crosses

Boonkum et al., 2011

Small effect for milk


Iranian Holsteins

35

40

45

50

55

Jan

Feb

Mar

ch

Ap

r

May Jun

Jul

Au

g

Sep

Oct

No

v

Dec

Mokhtar et al, 2012

Small effect for milk

Co

nce

pti

on

rat

e


THI

Heat production

Rectal temperature

Milk

Fertility

Mortality/ Morbidity

Profile of a “heat-tolerant cow”

Partially based on Dikmen et al. (2012)

• What is a heat tolerant cow? • Milk as long as

possible?

• Reduces production when dangerous?

• Reduces production early to maintain reproduction

• Thresholds management specific

• Match genotype to environment


Genetics of growth in pigs under different

heat loads (Zumbach et al., 2007)

• Pigs in NC or TX exposed to heat stress

• Heat stress affect growth

• How to model heat stress for growth?


Theoretical and realized heat loads

80

82

84

86

88

90

92

94

96

98

2005

/05

2005

/06

2005

/07

2005

/08

2005

/09

2005

/10

2005

/11

2005

/12

2006

/01

2006

/02

2006

/03

2006

/04

2006

/05

2006

/06

2006

/07

2006

/08

2006

/09

2006

/10

2006

/11

2006

/12

Year-Month of slaughter

Ca

rca

ss

we

igh

t (k

g)

10

12

14

16

18

20

22

24

26

28

30

-He

at

Lo

ad

*0.1

5+

24

CW H

Zumbach et al., 2007 ADSA Resilience Symposium

2016

Variances during cold and hot periods

Genetic

Litter

Error

h2

rhot,cold

Hot

28

17.0

55

0.28

0.42

Cold

14

19.2

66

0.14

ADSA Resilience Symposium

2016

Heat stress in purebred and crossbred pigs

9kg 2 kg

Crossbred Purebred

Better environment almost eliminates heat stress

Fragomeni et al., 2016)


Beef

• Annual economic losses from heat stress (St-Pierre et al., 2003)

– $87 million for beef cows

– $282 million for finishing cattle

• Limited quantifiable heat stress for Angus in US (Bradford et al., 2016)

– Adaptation of beef industry for local condition

• Timing of breeding

• Crossbreeding


-0.2

0

0.2

0.4

0.6

0.8

1

2001 2003 2005 2007 2009 2011 2013

Ge

net

ic S

D u

nit

s

Birth year

THI ≤ 75 THI = 80 THI = 85

WW Direct Genetic Trend for Angus in Southeast

Bradford et al., 2016

No heat stress

High heat stress


Is beef resilient

• Research by Don Spiers (Missouri)

– 3 days in heat chamber without water

– Removing hair by torches


QTL for heat stress

• Slick hair gene (Olsen et al., 2010)

• Gene for spring shedding in beef?

• Markers for rectal temperature (Dikmen et al., 2013) – Max 0.44% for 1 Mbase region

• Studies in AZ (Collier et al., 2012) – 500 SNP from microarray studies

– 500 SNP from GWAS

– 5 in common


ssGBLUP for Heat Stress in

Holsteins (Aguilar, 2011)

• Multiple-Trait Test-Day model, heat stress

as random regression • ~ 90 millions records, ~ 9 millions pedigrees

• ~ 3,800 genotyped bulls

Regular effect -first parity Heat stress effect – first parity


2016


2016

Example – Intensive selection for

growth in broiler chicken

• Unlimited appetite / obesity artificial lightning

• Different maturity rate of males and females separation of sexes

• Poor survival of males male supplementation

• Increased susceptibility to diseases antibiotics

• Low hatchability alternate heating/cooling of incubators

• …

Selection for main traits with improved management for secondary traits

Eitan and Soller, 2014 ADSA Resilience Symposium

2016

Resilience and management intensity R

esili

ence

Management intensity

Beef

Dairy

Pigs

Chicken

Energy distribution Pigs and selection for RFI (Dekkers, 2015)


Heat tolerant lines?

• Needs several generations of selection

• Market for heat tolerant animals small

• Improved management simpler

• Selection and production environments

• Interbull and dairy cattle


Conclusions

• Selection as optimization –winner and

loser traits

• Management compensates for “losers”

– Capabilities different by species

• Optimal management for each

environment

• Current selection OK if selection and

production environments similar


2016

lessons from studies in genetics of heat...

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