Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/21/2006
Publication Date: 9/1/2006
Citation: Ferrell, C.L., Berry, E.D., Freetly, H.C., Miller, D.N. 2006. Influence of genotype and diet on steer performance, manure odor, and carriage of pathogenic and other fecal bacteria. I. Animal performance. Journal of Animal Science. 84:2515-2522. Interpretive Summary: Differences in numerous traits among breed crosses were observed in this study. Those differences reflected, in part, lower feed intake, lower performance, and reduced carcass quality characteristics of Brahman as compared to MARC III steers. Many of these genotypic differences appeared to be negated by the high level of heterosis of the 1/2 Brahman steers. No evidence was observed to support suggestions that Brahman crossbred steers respond to varying diet quality differently than Bos taurus steers. Performance and feed utilization was reduced in steers grown on bromegrass hay but compensation was observed when they were switched to a high concentrate diet, as compared to those that were grown on a corn silage diet. However, when evaluated over the total system, compensatory responses were insufficient to totally overcome reduced performance during the growing period.
Technical Abstract: Objectives were to evaluate genotype and diet effects on steer performance during the growing period and subsequent responses to a high concentrate diet during the finishing period. Fifty-one steers [0 (15), 1/4 (20), 1/2 (7), and 3/4 Brahman (9) with the remaining proportion being MARC III] were allotted to eight pens. Beginning December 2, steers were individually fed chopped bromegrass hay (BG; N = 26; DM = 0.85, CP = 9.5%, ME = 2.19 Mcal/kg) or a corn silage-based diet (CS; N = 25; DM = 0.51, CP = 11.9%, ME = 2.75 Mcal/kg) for 119 d (PD 1). All steers were then fed a high corn diet (HC; DM = 0.79, CP = 11.7, ME = 3.08 Mcal/kg) to a target BW of 560 kg (PD 2; 176 d). Data were analyzed by ANOVA with genotype, diet (BG, CS), and the two-way interaction included. The interaction was not significant (P > 0.25). MARC III and 1/2 Braham steers weighed more (P < 0.01) than 1/4 or 3/4 Brahman steers initially, and at the end of PD 1, but final wt (559 kg) by design, did not differ due to genotype or diet. Weight of BG (325 kg) steers was less than CS (384 kg) steers at the end of PD 1. Steer ADG and intake of DM, CP, and ME were less (P < 0.05) for 1/4 and 3/4 Brahman than for 0 or 1/2 Brahman during PD 1, PD 2, and total, but efficiency did not differ among genotypes (P > 0.10). Carcass wt, marbling score, quality grade (P < 0.05), and kidney fat (P = 0.06) differed among genotypes. Other carcass traits did not differ significantly (P > 0.10) among genotypes. During PD 1, daily DMI (6.91 vs. 7.06 kg) was similar, but CP (0.66 vs. 0.84 kg) and ME (15.2 vs. 19.4 Mcal) intake of BG was less (P < 0.001) than CS. Values for DMI/gain (22.3 vs. 7.43 kg/kg), CP intake/gain (2.13 vs. 0.88 kg/kg), and ME intake/gain (48.8 vs. 20.4 Mcal/kg) were greater (P < 0.01) in BG than CS. Over the total study, ADG was lower (0.96 vs. 1.01 kg), and DMI (7.82 vs. 7.19 kg), DM intake/gain (8.21 vs. 7.10 kg/kg), and ME intake/gain (22.6 vs. 20.9 Mcal/kg) were greater (P < 0.05) in BG than in CS fed steers. Carcass weight, dressing percentage, adjusted backfat, and yield grade were greater (P < 0.04) for CS than for BG, but marbling, quality grade, and longissimus area did not differ. These data suggest differences exist among these genotypes in feed intake and performance, but little difference in efficiency was observed. Compensatory performance during finishing was insufficient to overcome reduced performance during the growing period in terms of overall feed efficiency of the system.