Use of fat in diets of sheep in hot environments. I. Effects on performance, carcass characteristics and lipid composition of plasma

Abstract

This study was conducted to determine the effects on productivity, carcass traits and lipid composition of plasma of supplementing, with 5 or 10% animal fat, the diets of sheep reared in hot (38.1°C, 22.5% relative humidity) or cool (26.4°C, 32.8% relative humidity) environments as compared with a control diet with no fat added. Sheep diets supplemented with fat improved the average daily weight gain (ADG) in both environments, but the gain was more pronounced in the hot environment. ADG values of sheep in hot and cool environments were: (1) control: 141.2, 134.9; (2) 5% fat: 158.4, 177.1; (3) 10% fat: 183.3, 177.1. However, feed intake was reduced ( P ≤ 0.05) when fat was added to diets. Feed efficiency (FE) was improved ( P ≤ 0.05) with each increment of dietary fat fortification in both hot and cool environments; the respective values were (1) control: 9.46, 9.33; (2) 5% fat: 7.13, 7.06; (3) 10% fat: 6.59, 5.50. Increased dietary fat elevated ( P ≤ 0.05) cholesterol and phospholipid concentrations in the plasma of sheep in both environments but at a higher level in the cool environment. Plasma triglycerides were unaffected by different dietary and environmental treatments. Carcass composition, in terms of protein, fat and ash, was not significantly affected by dietary fat inclusion or by varying environmental conditions. Dressing percentage (and consequently carcass grade) were, however, adversely affected by increased dietary fat in both environments. The fatty-acid profile of carcass lipid was similar in all experimental sheep, except for palmitoleic acid, which was lower in sheep fed fat-supplemented diets and reared under a cool environment than those reared under a hot environment. The sensory evaluation indicated that meat of animals receiving fat-supplemented diets appeared to have a significantly better flavor than the control but similar degrees of tenderness, juiciness and overall acceptance in both environments. A preliminary economic assessment of adding fat to sheep diets indicated that such a practice was beneficial.