Nutrient digestibility and feedlot performance of lambs fed diets varying protein and energy contents

Thirty-six Thalli male growing lambs were used in a completely randomized design with 2 x 2 factorial arrangement of treatments to evaluate the effect of varying levels of energy and protein on nutrient intake, digestibility, weight gain, and gain to feed ratio. Four experimental diets, i.e., low energy-low protein (LE-LP), low energy-high protein (LE-HP), high energy-low protein (HE-LP), and high energy-high protein (HE-HP) were formulated. The low- and high-energy diets contained 2.3 and 2.7 MJ/kg dry matter (DM) with 12% and 14% of crude protein. The lambs were fed ad libitum. Dietary energy and protein levels and their interactions influenced the nutrient intake. Maximum dry matter intake was noted in animals fed LE-HP diet followed by LE-LP, HE-HP, and HE-LP diets. Digestibility of DM and N increased (P < 0.01) and that of neutral detergent fiber decreased (P < 0.01) linearly with increasing levels of dietary energy and protein. Digestibility of N was only affected by protein level and interaction between energy and protein levels. Average daily gain was higher (P < 0.01) in lambs fed HE-HP diet followed by LE-HP, LE-LP, and HE-LP diets. Dietary energy and protein levels and their interaction had significant effect (P < 0.01) on gain to feed ratio.