Zilpaterol hydrochloride effects on performance, carcass traits, meat quality and gene expression in muscle and adipose tissues of finishing Nellore heifers

Abstract

The increasing demand for efficiency in animal production systems provides search for technologies that provide a more sustainable production. In this context, in order to increase the efficiency of production of beef cattle, the use of beta-agonists has been studied. Beta- agonists are organic molecules whose main effects are hypertrophy of muscle-tissues, and decrease in fat deposition, and that zilpaterol hydrochloride can be use. Thus, the aim of this research is to evaluate the effect of zilpaterol hydrochloride in finishing Nellore heifers in feedlot system on growth performance, feed efficiency, carcass traits, meat quality, parts yields in the boning, development of muscle tissue and fat, protein and energy metabolism, and gene expression of the enzymes calpain and calpastatin in the muscle, fatty acid synthase, acetyl-CoA carboxylase, lipoprotein lipase and carnitine palmitoyl transferase of adipose tissue. Seventy two Nellore heifers will used with approximately 270kg of initial weight and 18 months of age. The animals will be housed for 100 days, being 14 days of adaptation and 86 of experimental period. The diet will consist of a roughage:concentrate ratio of 35:65 with corn silage as the roughage and a corn, soybean meal-based concentrate. The experiment design will be of random blocks by initial body weight and two treatments, control diet (without zilpaterol hydrochloride) and diet with zilpaterol hydrochloride inclusion. The animal will be allocate are grouped into 18 pens according the experimental diets. Animal performance will be determined through periodic weightings of the animals, intake will be measured daily, blood samples will be collected for assessment of protein and energy metabolism. The carcass hot weight and carcass yield will be evaluated, Longissimus muscle and adipose tissue samples will collected to evaluate enzymes genes expression. 24 hours after slaughter half of the carcass will be boneless for parts yields. Longissimus muscle samples will collected to evaluate Longissimus muscle area, subcutaneous fat, color, weight loss cooking, shear force and sensory analysis. For the analysis weight loss cooking, shear force and sensory analysis the samples are vacuum packed and aged for 0, 7, 14 and 21 days. In addition section HH will be collected between 9th and 11th rib for proximate analysis of carcass.