Residual Feed Intake
and the Cow Herd
A. M. Meyer1*, R. L. Kallenbach2, M. S. Kerley1
University of Missouri, Columbia
Division of Animal Sciences
2 Division of Plant Sciences
1
2007 NBCEC Brown Bagger Series
Residual Feed Intake (RFI)
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RFI = actual intake – expected intake
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-RFI → more efficient
+RFI → less efficient
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By definition, phenotypically independent of
growth and mature size
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Moderately heritable
10/17/07
NBCEC Brown Bagger Series
Allison Meyer
Previous RFI Research

Comprehensive research project at the Agricultural
Research Centre at Trangie, New South Wales (19932000)
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Research has also been established in US and Canada
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Divergently selected for RFI
Studied the impacts of RFI upon other traits
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
10/17/07
NBCEC Brown Bagger Series
Allison Meyer
RFI and the Cow Herd

Feed is the greatest non-fixed cost for beef cow-calf
producers

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56-59% of total operating costs for US cow-calf producers
ERS, 2005)
(USDA
Despite this, little research has been done to determine
the impact of selection for RFI upon cow intake,
performance, and profitability
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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
10/17/07
NBCEC Brown Bagger Series
Allison Meyer
Establishment of Research Herd

42 purebred Hereford heifers, donated by 19
producers to the University of Missouri
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RFI determined feeding alfalfa-grass mixed hay with
GrowSafe feed intake system

Heifers were split into:
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Low RFI (highly efficient)
Mid RFI
High RFI (lowly efficient)
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Research Timeline
Summer Fall
2005
2005
Summer Fall
2006 2006
Mid – late
gestation
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10/17/07
Winter/
Spring
2007
Early
gestation &
Late lactation
DOB: Feb 26, 2001 - Feb 20, 2004
Not all cows calved during first calving season
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Allison Meyer
Experiment 1
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84 d grazing trial
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Non-endophyte infected
tall-fescue based pasture
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May 18 – Aug 9, 2006
Low RFI vs. High RFI cows
Mid-late gestation
Grazed continuously
4 paddocks (n = 7/rep, 1.8 - 2.4 ha)
Forage measurements
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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
Low RFI
High RFI
SEM
P
RFI, kg/d
-4.37b
5.04a
0.70
0.006
Initial BW, kg
591.2a
565.0b
1.2
0.004
Initial BCS
5.26
5.26
0.07
1.00
BW Change, kg
19.5
22.1
3.4
0.68
BCS Change
0.11
0.10
.05
0.86
Variable
a.b
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P < 0.01
Allison Meyer
Forage Dry Matter Intake- Exp. 1
17.5
15
21%
DMI, kg/hd/d
12.5
10
15.6
7.5
5
12.4
2.5
0
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Low RFI
High RFI
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P = 0.23
Allison Meyer
Pasture Carrying CapacityExp. 1
Low RFI
High RFI
SEM
P
Area grazed, ha
1.71
1.82
0.05
0.35
DM on offer, kg
4215b
4376a
11
0.06
Variable
a.b
10/17/07
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P < 0.10
Allison Meyer
Experiment 2
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60 d grazing trial
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Stockpiled tall fescue
and new spring growth
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Feb 23 – April 23, 2007
Low RFI vs. High RFI pairs
Late lactation
Strip-grazed
3 paddocks each (n=4 pairs, 0.73-0.93 ha)
Fed 3.3 kg soyhulls/pair
Forage measurements
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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
Low RFI
High RFI
SEM
P
RFI
-4.22b
5.13a
0.26
<0.0001
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
0.19
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
Variable
Cows
Calves
Age, d
a.b
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P < 0.0001
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Forage Dry Matter Intake for
Cow-calf Pairs- Exp. 2
17.5
15
DMI, kg/hd/d
12.5
11%
10
7.5
12.5
14.1
5
2.5
0
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Low RFI
High RFI
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P = 0.12
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Total Dry Matter Intake for
Cow-calf Pairs- Exp. 2
20
17.5
9%
DMI, kg/hd/d
15
12.5
10
7.5
15.8
17.4
3.3 kg
soyhulls/
pair
5
2.5
0
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Low RFI
High RFI
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Dry Matter Intake
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Current study
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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
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Phenotypic : 0.36 - 0.40
Genetic: 0.98 (Arthur et al., 1999; Archer et al., 2002)
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Dry Matter Intake
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Why difference between Exp. 1 and 2?
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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?
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Difficulty of measuring forage intake
Low numbers used in current study
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Dry Matter Intake
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Herd et al. (1998): Compared grazed forage intake of low
and high RFI cows with calves using alkanes
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Arthur et al. (1999): Redetermination of RFI for 4 yr old
open, non-lactating cows on pelleted, hay-based ration
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Small numerical difference in DMI
4.5% decrease in DMI for low vs. high RFI cows (P < 0.05)
Growing cattle on concentrate diet
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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)
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Divergently selected: Low RFI steers have 6-11% lower DMI
(Richardson et al., 1998; Arthur et al., 2001)
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Mature Size
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Current Study: Cows were managed together pre-trials
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Exp. 1: Low RFI cows were heavier (P < 0.05)
Exp. 2: No differences
Low RFI cows may have increased BW
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Significantly heavier (Herd et al., 1998)
Numerically heavier at all time points during 4-yr study
(Arthur et al.,
2005)
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No difference
(Arthur et al., 1999)
Genetic correlation between RFIpostweaning and BWmature
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-0.09 ± 0.26 (Herd and Bishop, 2000)
-0.22 (Archer et al., 2002)
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Performance
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Growth and body weight change
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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)
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Pre-weaning calf gain
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Current Study: No difference
No difference in ADG or weaning weight
Milk production
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No difference
(Arthur et al., 2005)
(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
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Current study:
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Mature cows
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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
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Exp. 1: No differences
Exp. 2: High RFI cows had numerically higher initial BCS and
positive BCS change
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
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10/17/07
0.17 (Arthur et al., 2001) - 0.33 (Nkrumah et al., in press)
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Another question
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Reproduction
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Very little data in beef cows
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10/17/07
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
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Low RFI cows had numerically lower grazed forage
intakes than high RFI cows
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Low RFI cows may be heavier at maturity and have less
fat deposition than high RFI cows
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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
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10/17/07
Greatly aided by marker for RFI status
NBCEC Brown Bagger Series
Allison Meyer
Questions?
Thank you.