Residual Feed Intake and the Cow

HerdA. M. Meyer1*, R. L. Kallenbach2, M. S. Kerley1

University of Missouri, Columbia1 Division of Animal Sciences

2 Division of Plant Sciences

2007 NBCEC Brown Bagger Series

10/17/07 NBCEC Brown Bagger Series Allison Meyer

Residual Feed Intake (RFI) RFI = actual intake – expected intake

-RFI → more efficient +RFI → less efficient

By definition, phenotypically independent of growth and mature size

Moderately heritable

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Previous RFI Research Comprehensive research project at the

Agricultural Research Centre at Trangie, New South Wales (1993-2000) Divergently selected for RFI Studied the impacts of RFI upon other traits

Research has also been established in US and Canada Greater availability of equipment and technology to

record individual feed intake and weights

Overall findings: Low RFI calves have lower feed intake yet similar performance to high RFI calves

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RFI and the Cow Herd Feed is the greatest non-fixed cost for beef cow-

calf producers 56-59% of total operating costs for US cow-calf

producers (USDA ERS, 2005)

Despite this, little research has been done to determine the impact of selection for RFI upon cow intake, performance, and profitability RFI determination limits numbers than can be used Difficulty of measuring pasture intake Production scenarios more difficult to control Unknown effects of changing diet and environment upon

RFI and intake

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Current Research

Objective:To determine the effect of residual feed intake rank on the grazed forage intake and performance of beef cows

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Establishment of Research Herd 42 purebred Hereford heifers, donated by

19 producers to the University of Missouri RFI determined feeding alfalfa-grass mixed hay

with GrowSafe feed intake system

Heifers were split into: Low RFI (highly efficient) Mid RFI High RFI (lowly efficient)

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Research Timeline

Summer 2005

RFI

Dete

rmin

atio

n

Fall 2005

1st C

alvi

ng

Seas

onWinter/ Spring 2007

Fall 2006

Summer 2006

Expe

rimen

t 12n

d Cal

ving

Se

ason

Expe

rimen

t 2

Mid – late gestation

Early gestation &

Late lactation DOB: Feb 26, 2001 - Feb 20, 2004

Not all cows calved during first calving season

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Experiment 1 84 d grazing trial

May 18 – Aug 9, 2006 Low RFI vs. High RFI cows Mid-late gestation

Non-endophyte infected tall-fescue based pasture Grazed continuously 4 paddocks (n = 7/rep, 1.8 - 2.4 ha)

Forage measurements Exclosures used to measure growth Rising plate meter readings and buffer areas

used to keep similar forage availability among paddocks

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Cow Performance- Exp. 1

Variable Low RFI High RFI SEM PRFI, kg/d -4.37b 5.04a 0.70 0.006Initial BW, kg 591.2a 565.0b 1.2 0.004Initial BCS 5.26 5.26 0.07 1.00BW Change, kg 19.5 22.1 3.4 0.68BCS Change 0.11 0.10 .05 0.86

a.b P < 0.01

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12.415.6

0

2.5

5

7.5

10

12.5

15

17.5

DMI,

kg/h

d/d

21%

Forage Dry Matter Intake- Exp. 1

Low RFI High RFI P = 0.23

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Pasture Carrying Capacity- Exp. 1

Variable Low RFI High RFI SEM PArea grazed, ha 1.71 1.82 0.05 0.35DM on offer, kg 4215b 4376a 11 0.06

a.b P < 0.10

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Experiment 2 60 d grazing trial

Feb 23 – April 23, 2007 Low RFI vs. High RFI pairs Late lactation

Stockpiled tall fescue and new spring growth Strip-grazed 3 paddocks each (n=4 pairs, 0.73-0.93 ha) Fed 3.3 kg soyhulls/pair

Forage measurements Pre- and post-grazed areas sampled ~14 d Forage growth was estimated using a growing degree

days calculation

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Cow and Calf Performance- Exp. 2

Variable Low RFI High RFI SEM PCows RFI -4.22b 5.13a 0.26 <0.000

1 Initial BW, kg 569.4 557.2 10.5 0.46 Initial BCS 4.85 4.98 0.14 0.55 BW Change, kg 18.4 26.6 10.0 0.59

BCS Change -0.04 0.15 0.08 0.19Calves Age, d 144 143 7 0.87 Initial BW, kg 140.7 131.5 6.0 0.34 ADG, kg/d 0.85 0.95 0.08 0.45

a.b P < 0.0001

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Forage Dry Matter Intake for Cow-calf Pairs- Exp. 2

12.5 14.1

0

2.5

5

7.5

10

12.5

15

17.5

DMI,

kg/h

d/d

Low RFI High RFI P = 0.12

11%

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15.8 17.4

0

2.5

5

7.5

10

12.5

15

17.5

20

DMI,

kg/h

d/d

Total Dry Matter Intake for Cow-calf Pairs- Exp. 2

9%

Low RFI High RFI

3.3 kg soyhulls/ pair

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Dry Matter Intake Current study

Exp. 1: Low RFI cows had 21% lower grazed forage DMI

Exp. 2: Low RFI pairs had 11% lower grazed forage DMI, 9% lower total DMI

Cows in the current studies appeared to remain in their RFI group

Correlation of RFIpost-weaning and RFIcow Phenotypic : 0.36 - 0.40 Genetic: 0.98 (Arthur et al., 1999; Archer et al., 2002)

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Dry Matter Intake Why difference between Exp. 1 and 2?

Calves in second study may have affected DMI difference, as they were of unknown RFI rank

Maintenance, gestation, and lactation may affect efficiency differently (Hughes and Pitchford, 2004)

Why lack of significance? Difficulty of measuring forage intake Low numbers used in current study

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Dry Matter Intake Herd et al. (1998): Compared grazed forage intake

of low and high RFI cows with calves using alkanes Small numerical difference in DMI

Arthur et al. (1999): Redetermination of RFI for 4 yr old open, non-lactating cows on pelleted, hay-based ration 4.5% decrease in DMI for low vs. high RFI cows (P < 0.05)

Growing cattle on concentrate diet RFI determined: Low RFI steers have 12-17% lower DMI

(Nkrumah et al., 2003; Kolath et al., 2006; Nkrumah et al., 2006; Castro Bulle et al., 2007) Divergently selected: Low RFI steers have 6-11% lower

DMI (Richardson et al., 1998; Arthur et al., 2001)

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Mature Size Current Study: Cows were managed together pre-

trials Exp. 1: Low RFI cows were heavier (P < 0.05) Exp. 2: No differences

Low RFI cows may have increased BW Significantly heavier (Herd et al., 1998) Numerically heavier at all time points during 4-yr study

(Arthur et al., 2005) No difference (Arthur et al., 1999)

Genetic correlation between RFIpostweaning and BWmature -0.09 ± 0.26 (Herd and Bishop, 2000) -0.22 (Archer et al., 2002)

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Performance Growth and body weight change

Current study: No difference in Exp. 1 or 2 Typical of results in cows (Arthur et al., 1999; Arthur et al., 2005)

and growing steers (Arthur et al., 2001a; Basarab et al., 2003; Kolath et al., 2006; Castro Bulle et al., 2007)

Pre-weaning calf gain Current Study: No difference No difference in ADG or weaning weight (Arthur et al., 2005) Milk production

No difference (Arthur et al., 1999; Arthur et al., 2005) Low RFI cows maintained 15% greater calf BW/cow DMI

(P = 0.07) (Herd et al., 1998)

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Body composition Current study:

Exp. 1: No differences Exp. 2: High RFI cows had numerically higher initial BCS

and positive BCS change Mature cows

No differences in rib/rump fat depth (Herd et al., 1998; Arthur et al., 1999)

High RFI cows had greater rib fat over 4 years, no effect upon reproduction (Arthur et al., 2005)

Growing steers High RFI steers had greater back fat thickness and/or

carcass fat (Richardson et al., 1998; Richardson et al., 2001; Basarab et al., 2003; Nkrumah et al., 2004)

Genetic correlation between RFI and rib fat 0.17 (Arthur et al., 2001) - 0.33 (Nkrumah et al., in press)

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Another question Reproduction

Very little data in beef cows No difference in pregnancy rate, calving rate, weaning

rate Low RFI cows had a later calving date (P < 0.10) and

greater percentage sired via natural service (Arthur et al., 2005)

Negative effect upon reproduction in litter bearing species (Pitchford, 2004)

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Conclusions Low RFI cows had numerically lower grazed

forage intakes than high RFI cows Low RFI cows may be heavier at maturity and

have less fat deposition than high RFI cows Further research is necessary to confirm these

differences and investigate other production parameters

► Selection for low RFI animals may decrease feed inputs necessary in cow-calf production Greatly aided by marker for RFI status

Questions?Thank you.