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

Abstract

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.

The Effects of Castration, Implant Protocol, and Supplementation of Bos indicus-Influenced Beef Cattle under Tropical Savanna Conditions on Growth Performance, Carcass Characteristics, and Meat Quality

“…Animals were immobilized in a squeeze chute, and surgical castration was performed quickly by an experienced veterinarian who supervised pre-and post-surgery treatments for preventing infections and speeding up the healing process. The ranch's protocol for disinfection procedures and veterinary treatment before and after castration was described by Huerta-Leidenz et al [28]. Castrated (steer) and intact (bull) calves were treated against ectoparasites and endoparasites with Ivermectin (1 mL/kg of BW; Ivermetopp Dorado, Topp Laboratories, Caracas, Venezuela) subcutaneously injected at the recommended dose according to their BW.…”

“…The carcass evaluation has been described in detail by Huerta-Leidenz et al [35] and Rodas-González et al [43]. After recording the hot carcass weight to estimate the hot carcass dressing yield (%), the following traits were evaluated 48 h postmortem in the chilled carcass: cold carcass weight to estimate cold carcass dressing yield (%), conformation profile score (1 = Very convex, 2 = Convex, 3 = Straight, 4 = Concave, 5 = Very concave; as detailed by Huerta-Leidenz et al [28], external fat finish (1 = Extremely abundant, 2 = Abundant, 3 = Medium, 4 = Slight, 5 = Scarce) [35], and adipose maturity (i.e., fat color, where, 1 = Ivory white, 2 = Creamy white, 3 = Light yellow, 4 = Intense yellow, 5 = Orange) according to Decreto Presidencial No. 1896 [3], ribeye area and adjusted fat thickness at the 12th-rib, degree of marbling, lean maturity (lean color and texture), and bone maturity (backbone ossification).…”

“…The excised steaks were vacuum packaged in a B620 Cryo-vac ® multilaminar shrink bag (Sealed Air Corp., Charlotte, NC, USA) using Koch-Ultravac ® packaging equipment (UltraSource LLC, Kansas City, KS, USA) and immediately frozen at −30 • C and stored at this temperature until further analyses. Culinary, sensory evaluation, and shear force protocols followed the American Meat Science Association (AMSA) guidelines [45] and have been described in detail in previous reports [28,43,46]. Briefly, cookery was performed in a Sunbeam-Oster ® open electric grill 1996 electric indoor grill (Sunbeam-Oster Co. Inc., Fort Lauderdale, FL, USA).…”

“…Beneficial effects of single or combined steroidal implants on steer growth performance have been unanimously reported under intensive feeding [21]. Positive growth performance responses of grazing steers to zeranol, a resorcylic acid lactone with estrogenic properties (ZER) or Trenbolone acetate + Estradiol (TBA/E2) implants have also been granted positive outcomes [14,[22][23][24][25][26][27][28]. However, the effects of implants on bull growth performance have been contradictory or inconsistent [14,23,[28][29][30].…”

“…Positive growth performance responses of grazing steers to zeranol, a resorcylic acid lactone with estrogenic properties (ZER) or Trenbolone acetate + Estradiol (TBA/E2) implants have also been granted positive outcomes [14,[22][23][24][25][26][27][28]. However, the effects of implants on bull growth performance have been contradictory or inconsistent [14,23,[28][29][30]. Potent implant combinations can have detrimental effects on steer carcass quality and beef palatability [31][32][33]; although, a meta-analysis conducted by Lean et al [34] demonstrated that multiple-implant protocols improved beef tenderness.…”