Effects of Sex Class, a Combined Androgen and Estrogen Implant, and Pasture Supplementation on Growth and Carcass Performance and Meat Quality of Zebu-Type Grass-Fed Cattle.

Nelson Huerta-Leidenz,Alexis Moya,Mindy M Brashears,Susmira Godoy,Markus F Miller,Nancy Jerez-Timaure,Jhones Onorino Sarturi

doi:10.3390/ani11123441

Abstract

Simple SummaryInadequate feeding and management practices of cattle breeders in the Apure’s savanna (Venezuela) impede the adoption of cow–calf-to-finish systems on their own ranches. This study evaluated the feasibility of finishing Zebu-type young cattle on savanna cultivated pastures with better growth and carcass traits and meat quality. Castration can be performed without detrimental consequences for cattle growth, eliciting a desirable response in live weight gain to the implant, while improving carcass finish, the yield of valuable cuts, and meat tenderness. The implant enhanced the rate of gain of steers only, with no beneficial effects on cut-out yields or adverse impacts on meat quality. The supplementation improved key performance traits, allowing cattle to be harvested at a younger age, which is clearly advantageous for rotating more animals per production cycle. Moreover, carcass quality was marginally improved, but tenderness was negatively affected. The data presented herein may be used as a benchmark for producers of similar cattle in tropical ecosystems throughout the world.Forty-seven Zebu calves were used to determine the effects of class (bull or steer), supplementation (SUPPL, a poultry litter-based supplement or mineral supplementation), and implant (20 mg estradiol combined with 120 mg of trenbolone acetate or no implant) on growth and carcass performance and beef eating quality. The average daily gain (ADG) of implanted cattle significantly increased for steers, but not for bulls. The SUPPL treatment increased ADG by 8.63% from day 0 to end, and shortened in 73.3 d the time to reach 480 kg BW (p < 0.01). Compared to bulls, the steer carcasses exhibited more desirable maturity and finish scores, thicker back fat (p < 0.05), and yielded greater (p < 0.01) percentages of high-value boneless subprimals (HVBLS) (+1.64%) and total cuts (1.35%). The SUPPL bulls dressed 2.63 and 1.63% greater than non-supplemented bulls and SUPPL steers, respectively (p < 0.05). Meat sensory quality was subtly affected (p < 0.05) by sex class or supplementation. The implant did not affect (p > 0.05) shear force or sensory ratings. The supplementation improved key growth performance traits while it adversely affected tenderness-related sensory traits. The implant enhanced the rate of gain of steers only, without improving cut-out yields or inducing adverse effects on palatability traits in both steers and bulls.

Highlights

Due to the harsh environmental conditions in neotropical savannas of South America, the profitable production of grass-fed Zebu-type cattle faces multiple challenges
No interactions (p > 0.05) between sex class × implant, sex class × supplementation, and supplementation × implant were observed for hip height, muscle score, frame-size score, BW, time to reach the endpoint, chronological age, adjusted final BW, and adjusted
An interaction between sex class × implant was observed (p = 0.01) for the interim ADG1 (d0 to d163) and ADG2 (d0 to end), in which implanted steers had 27.5% and 28.2% greater ADG1 and ADG2 compared to their non-implanted counterparts, while implants did not affect bulls (Figures 1 and 2)

Summary

Introduction

Due to the harsh environmental conditions in neotropical savannas of South America, the profitable production of grass-fed Zebu-type cattle faces multiple challenges. Most of the ranches are exclusively devoted to extensive cow–calf operations with low inputs This is not necessarily the situation of the grazing lowlands of Apure State, Venezuela, where a prominent hydraulic infrastructure has allowed flood control during the wet season, water supply for cattle and pasture irrigation during the dry season [1,2], and the introduction of new forage species, with better nutritional quality than the native savanna vegetation [3]. Under these improved savanna conditions, diligent ranchers are committed to adopting a grass-based beef cow–calf-to-finishing system to increase productivity. Detrimental effects of castration on growth traits and cutability have not been noted in grass-fed, tropically adapted cattle [4,7]

Methods

Results

Conclusion