Optimising reproduction in the Dorper ewe through nutrition

Summary

This study comprised two experiments aimed at increasing the reproductive performance of Dorper ewes.  

Experiment 1 investigated the effect of ewe liveweight at joining, liveweight change and supplementary feeding with lupins on fertility and conception rate of Dorpers.  

Experiment 2 was aimed at optimising lamb birthweight for high lamb survival and assessed the impact of ewe liveweight profile over pregnancy and lactation on the birthweight and weaning weight of the lamb.  

Experiment 1 found that fertility (ewes pregnant/ewes mated) and conception rate (lambs scanned/ewes mated) increased with increased liveweight at joining and liveweight change pre and early joining.  Providing a 200g/h/d lupin supplement for 3 weeks (2 weeks prior to joining and during the first week of joining) increased fertility by 7% and increased conception rate by around 18%.  A higher supplementation rate of 500g/h/d for 2 weeks also increased fertility but did not increase conception and also caused the ewes to lose weight.  

Experiment 2 found that the optimal birthweight of Doper lambs are 4-6 kg for high survival rates (90%).  Birthweight of lambs can be predicted by ewe liveweight at joining, ewe weight change during pregnancy, sex and birth-type of the lamb (single or twin).  Weaning weight is also influenced by these factors as well as the weight change of the ewe during lactation. These effects are similar to those seen in Merinos.  

Producers can use these relationships to determine cost-effective feeding strategies for their Dorper ewes to maximise reproductive rates.