Evaluation of the efficacy of Grofactor, a beta-adrenergic agonist based on zilpaterol hydrochloride, using feedlot finishing bulls1

Abstract

Beta-adrenergic agonists (β-AA) have been shown to positively impact finishing performance and some carcass traits of feedlot cattle. Our objective was to evaluate the efficacy of a β-AA on the basis of zilpaterol hydrochloride (Grofactor, Laboratorios Virbac México, Guadalajara, Mexico) on growth and DMI, carcass characteristics, and meat quality of finishing bulls. Forty-five bulls (75% 25% ) initially weighing 448.7 ± 2.58 kg were blocked by BW and randomly assigned to 1 of 3 diets, using pens of 3 animals, in a randomized complete block design: 1) daily feeding without β-AA in the basal diet (Control), 2) daily feeding with 0.15 mg/kg BW of Grofactor added to the basal diet (ZHG), or 3) daily feeding with 0.15 mg/kg BW of Zilmax (MSD Salud Animal México, Mexico City, Mexico) added to the basal diet (ZHZ). The duration of the feeding period was 30 d with a subsequent 4-d withdrawal period. Compared with Control bulls, the group fed ZHG had a 12% better ( < 0.025) G:F ratio, and their final BW ( 0.094) and ADG ( 0.084) tended to be enhanced. Feedlot performance of ZHG and ZHZ bulls was similar, although the DMI was ∼4% lower ( 0.05) in ZHG bulls vs. the ZHZ and Control groups. The HCW ( 0.001) and dressing percentage ( 0.015) were higher by 20 kg and 3%, respectively, in ZHG bulls vs. Control bulls. The KPH fat was lower ( 0.007) in bulls fed ZHG than in nonsupplemented bulls, but other carcass characteristics were not different in the ZHG and ZHZ bulls, and noncarcass components were not affected by ZHG or ZHZ supplementation. At 48 h postmortem, ZHG bulls had lower ( 0.007) water holding capacity and trended toward ( 0.06) increased chroma and reduced pH ( 0.09) compared to Control bulls. However, compared to ZHZ bulls, ZHG bulls had higher ( 0.02) chroma and a trend ( 0.08) toward increased hue angle. At 14 d postmortem, meat quality variables did not differ between the 3 groups of bulls. Supplementation of ZH Grofactor improved feedlot performance and some carcass characteristics of finishing bulls without affecting meat quality. The effects of Grofactor on feedlot performance, carcass traits, and meat quality were similar to those of Zilmax.

Non-inferiority trial of two commercial zilpaterol HCl brands in <em>Bos indicus</em> cattle under humid tropical conditions

“…42 These values are similar to those obtained in this trial for Bos indicus (i.e., final weight increments of 7.75 kg at a dose of 6 mg of generic ZH/kg feed). The mean final weight reported by Avendaño et al using a generic ZH, was higher than the one achieved here 21 ; however, the weight gain reported by these authors was similar to the corresponding value obtained during this trial (e.g., 77.80 vs. 53.16, respectively).…”

“…One exception is an essay that estimated carcass quality when using a generic ZH brand (Grofactor® Virbac, Mexico) 21 ; however, as environmental conditions are key factors for the well-being and fattening efficiency of bulls, that study failed to disclose details on the cattle housing such as shade surface or how the feed was served. Consequently, this is the first carefully structured trial to compare productive variables from a non-inferiority perspective, conducted under humid tropical conditions in cattle with a marked Bos indicus genotype.…”

“…Upon selection, all bulls were treated with 200 µg/kg SC of ivermectin (Dectiver®, Lapisa, Mexico) and vaccinated against clostridial diseases (Ultrabac/Somubac®; Zoetis, Mexico). As in other related studies, 20,21 an anabolic combination was implanted (i.e. Synovex-plus®; MSD) containing 200 mg of trenbolone acetate and 28 mg of oestradiol benzoate.…”

“…After a thorough literature review, only two trials could be compared with the one described here. One occurred in Baja California, Mexico, which is a geographical area characterized by high environmental temperatures (annual mean of 25.3 °C with a range of 5 °C to 45 °C) 18 and a BWh region (i.e., dry climate, with the driest season during winter and an average annual temperature higher than 18 °C), 21 corresponding to a desert-like scenario. When the study was conducted, the temperature oscillated approximately 20.3 °C with 57.6 % humidity, 19 and zebu-type cattle were tested as well as 75/25 % Bos indicus/Bos taurus bulls.…”

Suplementación de clorhidrato de zilpaterol en corderos finalizados con dieta sin fibra de forraje

“…El agonista adrenérgico β2 (AA β2) clorhidrato de zilpaterol (CZ) es un promotor de crecimiento que resulta efectivo para mejorar el comportamiento productivo y las características de la canal de importancia económica cuando se ofrece entre 4 y 5 semanas antes del sacrificio a corderos finalizados en corral (3)(4)(5)(6) , no así en pastoreo (7) . Este AA β2 funciona como promotor de crecimiento porque redistribuye sustrato energético del tejido graso y algunos órganos hacia la formación de masa muscular (hipertrofia) (4,8,9) . Cabe mencionar que la efectividad del CZ como promotor de crecimiento en corderos de engorda se ha demostrado ofreciendo dietas formuladas tanto con grano y forraje para favorecer el correcto funcionamiento ruminal.…”