Residual Feed Intake and the Cow Herd

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Residual Feed Intake and the Cow Herd

• A. M. Meyer1, R. L. Kallenbach2, M. S. Kerley1
• University of Missouri, Columbia
• 1 Division of Animal Sciences
• 2 Division of Plant Sciences
• 2007 NBCEC Brown Bagger Series

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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
RFI Determination
Experiment 2
Experiment 1
1st Calving Season
2nd Calving Season
Summer 2005
Summer 2006
Fall 2005
Winter/ Spring 2007
Fall 2006
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
a.b P lt 0.01
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Forage Dry Matter Intake- Exp. 1
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High RFI
Low RFI
P 0.23
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Pasture Carrying Capacity- Exp. 1
a.b P lt 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 (n4 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
a.b P lt 0.0001
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Forage Dry Matter Intake for Cow-calf Pairs- Exp.
2
11
High RFI
Low RFI
P 0.12
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Total Dry Matter Intake for Cow-calf Pairs- Exp. 2
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3.3 kg soyhulls/ pair
High RFI
Low RFI
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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
  lt 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 lt 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 lt 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

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Questions?

• Thank you.