Poster Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

Key considerations when lambing ewe lambs (hoggets) (#475)

Sara J Edwards 1 , Jennifer L Juengel 1
  1. Reproduction Team, AgResearch Ltd, Mosgiel, New Zealand

It is known that the fecundity of a ewe changes as she ages, with reproductive performance increasing sharply between lambing at one and two years of age, and a further smaller increase to three years of age. We demonstrated that this change in reproductive performance was primarily driven by the number of lambs born, as proportion of lambs weaned was relatively similar as the ewe ages. The weaning weight of the lamb born to the hogget was decreased, but this was primarily due to the later birth of the lambs due to the later breeding of the hogget. Thus two mechanisms to improve hogget lambing performance would be through breeding the hoggets earlier in the breeding season and through improving their ovulation rate. The effectiveness of breeding hoggets earlier in the breeding season is dependent on understanding the pattern of lambs attaining puberty. Therefore, the pattern of the age of which ewe lambs attained puberty over 5 years was analysed. These data showed that the peak period for attaining puberty occurred in mid-May, with approximately 65% of hoggets attaining puberty by the end of May. We have previously shown that introduction of the Inverdale gene would increase ovulation rate and number of lambs at d 35 of pregnancy in hoggets. However, whether a high level of higher-order multiple litters would be observed in these animals as young adults was unclear. Additional data analysis confirms that the introduction of the Inverdale gene increases the proportion of triplet or higher multiple litters in 2 year old dams to more than 40%. Taken together, these data suggest that there is scope for modifying the current best practice for lambing hoggets but this needs to occur within a farm system able to support higher performing hoggets.