Determination of the trace minerals requirements for maintenance and growth of 35-50 kg Dorper x Hu crossbred ram lambs

This study aimed at estimating the trace minerals net requirements for maintenance and growth of Dorper x Hu ram lambs using the comparative slaughter techniques in 35 lambs of 35-50 kg body weight (BW). Seven lambs were slaughtered at the initial BW (34.93 +/- 0.37 kg) to determine the basal whole-body composition. Another seven lambs were fed ad libitum (AL) and then slaughtered when it reached 41.73 +/- 0.53 kg BW. The remained 21 lambs were assigned into three treatment groups, seven animals each, and fed 100, 70 or 40% of AL intake, respectively, and were slaughtered when they reached a BW of 49.93 +/- 1.03 kg. The net requirements of maintenance were 5.1, 429.3, 94.0 and 48.8 mu g/kg empty BW (EBW) for Mn, Fe, Zn and Cu, respectively. The net requirements of growth at 35 kg BW were 0.86, 70.41, 33.46 and 4.31 mg/kg EBW for Mn, Fe, Zn and Cu, respectively. At a BW of 50 kg, the net growth requirements were 0.93, 68.40, 35.20 and 4.15 mg/kg EBW for Mn, Fe, Zn and Cu, respectively. Our data indicated that the Mn and Zn requirements increase, whereas those of Fe and Cu decrease when BW increases. In addition, the net Cu, Mn and Fe requirements for maintenance and Zn, Cu, Mn and Fe requirements for growth of Dorper x Hu hybrid ram lambs were higher than those reported in the NRC but Zn requirements for maintenance matched that of the NRC.