Residual Feed Intake and the Cow Herd A. M. Meyer 1 *, R. L. Kallenbach 2, M. S. Kerley 1 University of Missouri, Columbia 1 Division of Animal Sciences 2 Division of Plant Sciences 2007 NBCEC Brown Bagger Series

10/17/07NBCEC Brown Bagger SeriesAllison 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

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Previous RFI Research  Comprehensive research project at the Agricultural Research Centre at Trangie, New South Wales ( ) 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

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Current Research Objective: To determine the effect of residual feed intake rank on the grazed forage intake and performance of beef cows

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Research Timeline Summer 2005 RFI Determination Fall st Calving Season Winter/ Spring 2007 Fall 2006 Summer 2006 Experiment 1 2 nd Calving Season Experiment 2 Mid – late gestation Early gestation & Late lactation  DOB: Feb 26, Feb 20, 2004  Not all cows calved during first calving season

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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, ha)  Forage measurements Exclosures used to measure growth Rising plate meter readings and buffer areas used to keep similar forage availability among paddocks

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Cow Performance- Exp. 1 VariableLow RFIHigh RFISEMP RFI, kg/d b 5.04 a Initial BW, kg a b Initial BCS BW Change, kg BCS Change a.b P < 0.01

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 21% Forage Dry Matter Intake- Exp. 1 Low RFI High RFI P = 0.23

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Pasture Carrying Capacity- Exp. 1 VariableLow RFIHigh RFISEMP Area grazed, ha DM on offer, kg4215 b 4376 a a.b P < 0.10

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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, 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

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Cow and Calf Performance- Exp. 2 Variable Low RFIHigh RFISEMP Cows RFI b 5.13 a 0.26< Initial BW, kg Initial BCS BW Change, kg BCS Change Calves Age, d Initial BW, kg ADG, kg/d a.b P <

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Forage Dry Matter Intake for Cow-calf Pairs- Exp. 2 Low RFI High RFI P = %

10/17/07NBCEC Brown Bagger SeriesAllison Meyer Total Dry Matter Intake for Cow-calf Pairs- Exp. 2 9% Low RFI High RFI 3.3 kg soyhulls/ pair

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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 RFI post-weaning and RFI cow Phenotypic : Genetic: 0.98 (Arthur et al., 1999; Archer et al., 2002)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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 RFI postweaning and BW mature ± 0.26 (Herd and Bishop, 2000) (Archer et al., 2002)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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) (Nkrumah et al., in press)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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)

10/17/07NBCEC Brown Bagger SeriesAllison Meyer 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.