Energy requirements for maintenance and growth of early-weaned Dorper crossbred male lambs

This study aimed to investigate the net and metabolizable energy (NE and ME) requirements of Dorper crossbred lambs. Thirty-five Dorper×thin-tailed Han crossbred intact male lambs weaned at approximately 50 d of age (20.26±1.29 kg of BW), were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of 7 randomly selected lambs fed for ad libitum intake was slaughtered when the lambs reached an average BW of 28.2 kg. The remaining 21 lambs were alloted randomly to 3 levels of dry matter intake: ad libitum, or restricted to 70 or 40% of the ad libitum intake. All the lambs were slaughtered when the ad libitum fed sheep reached 35 kg of BW. Total body energy, crude protein, fat, ash, and moisture contents were determined. In a digestibility trial, fifteen Dorper×thin-tailed Han crossbred intact male lambs (32.38±2.23 kg of BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at 3 feed intake levels. The results showed that the maintenance requirements for NE and ME were 250.61 and 374.21 kJ/kg metabolic shrunk body weight (SBW0.75), respectively. The partial efficiency of energy use for maintenance was 0.67. Net energy requirements for growth ranged from 1.12 to 5.31 MJ/d, for the lambs gaining 100 to 350 g/d from 20 to 35 kg BW. Partial efficiency of ME for growth was 0.42. In conclusion, the current study suggested that the NE requirement for maintenance and growth of Dorper×thin-tailed Han early-weaned crossbred lambs were lower than those reported by existing AFRC and NRC nutritional systems.