|BLACK, TERA - University Of Florida|
|BISCHOFF, KALYN - University Of Florida|
|MERCADANTE, VITOR - University Of Florida|
|MARQUEZINI, GUILHERME - University Of Florida|
|DILORENZO, NICOLAS - University Of Florida|
|Chase, Chadwick - Chad|
|MADDOCK, TRAVIS - University Of Florida|
|LAMB, GRAHAM - University Of Florida|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2013
Publication Date: 5/1/2013
Citation: Black, T.E., Bischoff, K.M., Mercadante, V.R., Marquezini, G.H., Dilorenzo, N., Chase, C.C., Coleman, S.W., Maddock, T.D., Lamb, G.C. 2013. Relationships among performance, residual feed intake, and temperament assessed in growing beef heifers and subsequently as 3-year-old, lactating beef cows. Journal of Animal Science. 91:2254-2263 doi: 10.2527/jas.2012-5242(05032013).
Interpretive Summary: As the cost of production within the beef industry continues to rise, producers are searching for methods to reduce input costs, while maintaining or increasing performance. Feed costs are directly associated with approximately two-thirds of total inputs, and mature cows consume the majority of the feed required to produce a finished beef carcass. Therefore, improving feed efficiency in the cow-calf unit is one way to mitigate production costs. Residual feed intake (RFI) is one phenotypic trait used to determine feed efficiency that measures variation in feed intake independent of BW, milk production, or growth rate. It is computed as the difference between an animal’s actual daily feed intake and its predicted daily feed intake for a given level of maintenance or production. Although it has been well established that RFI is a moderately heritable trait, there have been few published studies comparing an individual’s RFI between two different physiological states, such as growth and lactation. Several studies have investigated feed efficiency in young cattle, but few have determined how residual feed intake (RFI) may be related to subsequent mature animal performance. Scientists at ARS in Brooksville. FL along with colleagues at the University of Florida Agricultural Research and Education Center, Marianna, FL initiated research with objectives to determine whether RFI evaluated as heifers has an impact on subsequent RFI, overall performance, and temperament as mature cows, and to determine the correlation between RFI subsequently measured in growing heifers and RFI measured as mature, lactating cows. The cows were ranked by their RFI as heifers, but body weight, condition score, daily gain, milk production, backfat, ribeye area, and RFI as cows were similar among RFI groups. However, cows which were most efficient as heifers ate less as cows (similar as heifers since low RFI generally means low intake). Further, the rank correlation between efficiency as heifers and the same animals as cows was very low (r = 0.13). Feed efficiency was also not associated with temperament. We conclude that heifers with low RFI (efficient) eat less as cows while maintaining similar performance as heifers that are less efficient.
Technical Abstract: Seventy-four beef heifers were used to evaluate the relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-year-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets while individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70 d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and d 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.001) and was greatest (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Med, and lowest (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows which were most efficient as heifers (Low) had lower (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) than cows that ranked Med (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and d 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01), and positively associated with d 14 (r = 0.46; P = 0.001) and d 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers which were most efficient subsequently consumed less feed as lactating cows while maintaining similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer gains, tended to have reduced feed intakes, and produced more ECM.