Effect of concentrate supplementation on nutrient intake and performance of lambs of two genotypes grazing a semiarid rangeland

Abstract

Nutrient intake and growth performance of 40 Malpura (M) and 32 Awassi×Malpura (AM) weaner (90 days old) lambs divided into four homogeneous groups were assessed. The groups grazed 8 h daily, receiving 10 g/kg (C10), 15 g/kg (C15), 20 g/kg (C20) and 25 g/kg (C25) body weight of concentrate. The pasture was dominated by Cenchrus ciliaris (33.7%) followed by Commelina forskalaei (11.4%), Elusine indica (9.1%), Erichola polystachya, Elusine aegyptica, Vigna sinesis, Sorghum halepense and other plant species. The biomass yield of C. ciliaris dominated pasture during the month of June was 2.084 t DM/ha. Daily dry matter intake (g/kg W 0.75) was increased ( P<0.01) along with the concentrate supplementation level averaging 70.7 (C10), 78.5 (C15), 82.8 (C20) and 94.9 (C25), respectively. Digestibility of dry matter, organic matter, crude protein and gross energy increased ( P<0.05) with the increase in supplementation level of dietary concentrate, while the digestibility of NDF, ADF and cellulose decreased ( P<0.05). Daily intake of digestible crude protein (DCP) and digestible energy (DE) per unit metabolic body weight differed between groups, decreasing from C25 to C10. Initial body weight of the lambs was similar in the four treatments and genetic groups while finishing body weights were higher ( P<0.01) in high concentrate supplemented groups (C25>C20>C15>C10). Furthermore, the finishing body weight was higher in crossbred AM (23.4 kg) than native Malpura (21.0 kg) lambs. On average the growing lambs under hot semiarid environment consumed 7.5 g DCP and 239.7 kcal DE/kg W 0.75 and had 115.7 g average daily gain. The results indicated that irrespective of the level of concentrate supplementation, the growth response and feed conversion efficiency was better in AM crosses than native Malpura lambs.