Nutrients intake and performance of lambs fed diets with two levels of crude protein and concentrate

Abstract Text: This study aimed to evaluate the dry matter (DMI), crude protein (CPI) and total digestible nutrients (TDNI) intake, the average daily gain (ADG), daily carcass gain in relation to body weight fasting (CG_BWF) and feed conversion (FC) of lambs fed diets containing two levels of concentrate (CONC) and two levels of crude protein (CP). Thirty-two intact Santa Ines x Texel lambs with an average body weight of 19 kg were used. They were distributed in a 2x2 factorial in a randomized block design with four treatments and eight replicates. The diets had 40 or 60% of CONC (plus corn silage as forage source) and 10.0 or 14.4% CP (high or low), in relation to the requirement of 12.5% CP according to the NRC (2007) for lambs with live weight of 20 kg and gains of 200 g/day. Feed was offered ad libitum to the animals at 8 h and 15 h. The offered and leftover feeds were weighed to estimate the daily DMI. The predetermined slaughter weight was 30 kg, when the animals were submitted to a solid fasting period of 16 hours, and weighed again to determine the slaughter weight. The durations of the confinement varied from 50 (14.25% CP and 60% CONC) to 106 (10% CP and 40% CONC) days. The data were subjected to analyses of variance and F test at a 10% probability using the statistical program SAEG 9.1. There was no interaction effect on intake of nutrients, but there were independent effects of CP and CONC levels. Higher nutrients intake were recorded for lambs fed the higher CONC or CP levels, whose CP intakes of DM, CP and TDN were, respectively, 972.8 and 821.68, 79.46 and 142.56, and 603.56 and 711.63 g/day. Only ADW was affected by the interaction CP x CONC, with values of 0.090 (10% CP and 40% CONC) to 0.200 kg/day (14.25% CP and 60% CONC). The CP levels affected CG_BWF (0.059 vs 0.106 kg) and FC (7.19 and 5.29) and CONC levels affected CG_BWF (0.066 and 0.098 kg) and FC (7.27 and 5.20). We concluded that diets with highest CP or concentrate levels resulted in greater nutrients intake and better animal performance.

Keywords: average daily gain, daily carcass gain, feed conversion