Energy requirements of early‐weaned Dorper cross‐bred female lambs

Abstract

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35kg were assessed in a comparative slaughter trial. Thirty-five Dorper×thin-tailed Han cross-bred female lambs weaned at ~50days of age (20.3±2.15kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed adlibitum was slaughtered when the lambs reached an average BW of 28.5kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: adlibitum or restricted to 70% or 40% of the adlibitum intake. All the lambs were slaughtered when the sheep fed adlibitum reached a BW of 35kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper×thin-tailed Han cross-bred female lambs (28.7±1.75kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3kJ/kg metabolic shrunk body weight (SBW0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18MJ/d for the lambs gaining 100-350g/d from 20 to 35kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.