Impact of zilpaterol hydrochloride and soybean-oil supplementation on intramuscular fat, fatty acid profile and cholesterol concentration in the longissimus muscle of male hair lamb under moderate heat-stress conditions

Forty Dorper x Pelibuey crossbred male lambs (31.70 +/- 2.30 kg, 4 months of age) were used to evaluate the effect of zilpaterol hydrochloride (ZH; 0 or 10 mg/lamb daily) and soybean-oil (SBO, 0 or 60 g/kg DM) supplementation on intramuscular fat, fatty acid (FA) profiles and cholesterol concentration of their meat. After 34 days, the animals were slaughtered, and their longissimus thoracis muscle was collected. The climatic conditions were of moderate heat stress (average temperature 35.7 degrees C) during the study. Feedlot performance and carcass characteristics were not affected (P > 0.05) by ZH and SBO supplementation. The ZH treatment decreased the intramuscular fat content (by 30.4%), the amount of monounsaturated FA (by 3.5%) and the monounsaturated FA : saturated FA ratio (by 4.9%) compared with the control group. Supplementation with SBO decreased cis FA, C18: 1 n-9c and C20: 4 n-6, whereas the trans FA and cholesterol concentration increased. ZH use caused a decrease in body fat and intramuscular fat concentration. However, it caused a decrease in total monounsaturated fatty acids, which are among the healthiest fats in terms of the nutritional value of meat. Generally, principal changes in the lipid composition of hair lamb meat under heat-stress conditions were caused by SBO supplementation; however, they would have a minimal negative impact on human health.