Effects of feeding a multivalent polyclonal antibody preparation on feedlot performance, carcass characteristics, rumenitis, and blood gas profile
in Bos indicus biotype yearling bulls
ABSTRACT: The objective of this study was to evaluate effects of feeding monensin (MON) or a multivalent polyclonal antibody preparation (PAP) against several rumen microorganisms on feedlot performance, carcass characteristics, blood gas profile, and rumenitis of Bos indicus biotype (BT) yearling bulls. The study was designed as a completely randomized design with a 3 × 2 factorial arrangement, replicated 4 times, in which 32 yearling bulls of each of 3 BT evaluated (3-way-cross, TC; Canchim, CC; and Nellore, NE) were fed diets containing either MON at 300 mg∙d−1 or PAP at 10 mL∙d−1 across 3 different periods. No significant (P > 0.10) feed additive (FA) main effects were observed for any of the feedlot performance variables and carcass characteristics with the exception of dressing percentage. Yearling bulls receiving PAP had a decreased (P = 0.047) dressing percentage when compared with yearling bulls receiving MON. Significant (P < 0.05) BT main effects were observed for all feedlot performance variables and carcass characteristics with the exception of kidney-pelvic fat expressed in kilograms (P = 0.49) and LM lipids content (P = 0.45). Crossbred yearling bulls (TC and CC) had greater (P < 0.001) ADG, DMI in kilograms, DMI as % of BW, and improved (P = 0.001) G:F when compared with NE yearling bulls.
A tendency (P = 0.072) for a FA main effect was observed for rumenitis scores, in which yearling bulls receiving PAP had lesser rumenitis scores than those receiving MON. When the data were disposed as frequency percentage, 55.6% and 45.7% of the rumens from yearling bulls fed PAP and MON were scored between 0 and 1, respectively (0 = no lesions, 10 = severe lesions). Likewise, a significant BT main effect was observed (P = 0.008), where NE yearling bulls had greater rumenitis scores than those of crossbred yearling bulls (TC and CC). No significant FA main effects were observed (P > 0.10) for any of the fatty acids measured in the subcutaneous adipose tissue, with the exception that yearling bulls receiving MON had greater (P < 0.05) concentrations of palmitic acid (16:0), margaric acid (17:0), docosapentaenoic acid (22:5), and docosahexaenoic acid (22:6) than those yearling bulls receiving PAP. Feeding PAP tended to decrease incidence of rumen lesions and led to similar feedlot performance compared with feeding MON. Thus, PAP is a new technology that presents a possible alternative for ionophores.
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RESULTS
Feedlot Performance and Carcass Characteristics
Results of the feedlot performance and carcass characteristics are presented in Table 3. No significant (P > 0.10) FA main effects were observed for any of the feed- lot performance variables and carcass characteristics with the exception of dressing percentage. Yearling bulls receiving PAP had a decreased (P = 0.047) dressing percentage when compared with yearling bulls receiving MON. However, when evaluating pair-wise comparisons between FA at specific time points, there were notable differences (P = 0.001) for DMI expressed in kilograms (DMIKG) and as % of BW (DMIBW). Dry matter in-take expressed as % of BW was greater (P = 0.034) for yearling bulls fed PAP than for those fed MON in GRO period (2.32% vs. 2.21%), but no difference was observed (P = 0.98) between yearling bulls receiving PAP and MON during FNS period (2.05% vs. 2.04%). Likewise, the interaction in DMIKG followed the same pattern of response as in DMIBW; however, no differences were detected (P > 0.10) in GRO and FNS periods between yearling bulls fed PAP and MON (data not shown). Significant (P < 0.05) BT main effects were observed for all feedlot performance variables and carcass characteristics with the exception of kidney-pelvic fat expressed in kilograms (P = 0.49) and LM lipids content (P = 0.45).
Crossbred yearling bulls (TC and CC) had greater (P < 0.001) ADG, DMIKG, and DMIBW when compared with NE yearling bulls. In addition, a significant BT × period interaction was found (P = 0.001), where TC and CC yearling bulls had improved G:F when compared with NE yearling bulls during the FNS period (0.151, 0.148, and 0.111 for TC, CC, and NE, respectively); however, no differences between BT were in the GRO period (0.185, 0.183, and 0.169 for TC, CC, and NE, respectively). Regarding ultrasound and actual carcass characteristics, TC and CC yearling bulls had heavier (P = 0.001) HCW and larger (P = 0.001) initial and final LM area during total feeding period than NE yearling bulls. However, CC yearling bulls had greater (P = 0.049) LM area daily gain than TC yearling bulls, which had greater (P = 0.029) LM area daily gain than NE yearling bulls. Dressing percentage and amount of kidney-pelvic fat expressed as % of HCW were increased in NE yearling bulls (P = 0.019 and P = 0.043, respectively) when compared with TC yearling bulls, which did not differ from CC yearling bulls (P = 0.15 and P = 0.41 for dressing percentage and kidney-pelvic fat expressed as % of HCW, respectively). Yearling bulls of TC biotype presented greater (P = 0.001) initial and final 12th rib fat thickness than NE yearling bulls but did not differ from CC yearling bulls (P = 0.26). However, in terms of 12th rib fat daily gain, TC yearling bulls had a greater rate of subcutaneous adipose tissue accretion (P = 0.017) than NE yearling bulls and did not differ from CC yearling bulls (P = 0.16). A significant BT × FA interaction was observed (P = 0.043) for WBSF, in which steaks from CC and NE yearling bulls fed MON had increased shear force values (P = 0.001) than those from TC yearling bulls. However, when feeding PAP, no differences were observed (P = 0.15) between CC and TC yearling bulls, which still had decreased shear force values than NE yearling bulls (P = 0.002; Table 4).