Browsing by Author "Mulvaney, Fraser John"

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    The effect of nutrition during pregnancy on hogget reproduction : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University
    (Massey University, 2006) Mulvaney, Fraser John
    Mulvaney, F.J. (2006). The effect of nutrition during pregnancy on hogget reproduction. M.Sc. (Animal Science) Thesis, Massey University, Palmerston North. New Zealand. 59pp The reproduction rate of hoggets in New Zealand is much lower than that observed in adult ewes. New Zealand farmers have indicated this is a major limitation to the uptake of hogget breeding and lambing. A series of studies conducted during pregnancy in the U.K. under housed conditions, utilising a concentrate diet, reported rapidly grown hoggets had reduced placental and fetal development and lamb birth weight. It is, therefore, possible nutrition during pregnancy plays a role in the poor reproductive performance seen in New Zealand hoggets. This thesis investigates the impact of 'low', 'medium' and 'high' levels of feeding on pasture during pregnancy on hogget pregnancy rate, fetal loss, lamb birth weight and growth rate of resulting lambs. Two-hundred-and-forty hoggets that were mated (identified by crayon tupp mark) during a five day breeding period were randomly allocated one of three (n-80) nutritional regimes ('low', 'medium' and 'high'). The 'low' treatment group during the first 100 days of pregnancy were fed to maintain live weight. From day 100 until term, these hoggets were offered herbage to ensure a daily live weight change of 100 g/day. The 'medium' treated group were fed to ensure live weight change was 100 g/day throughout the entire pregnancy period, while the 'high' treated group were offered ad libitum, with the aim of achieving 200 g/day throughout the entire pregnancy period. The target live weight changes were achieved in the 'low', 'medium' and the 'high' hogget feeding treatment groups. Pregnancy rates at day 50 of pregnancy were significantly (P<0.05) higher in the 'medium' (66%) than the 'high' (46%) treated hoggets. At P87, pregnancy rate was significantly higher in the 'low' and the 'medium' treated hoggets than the 'high' treated hoggets with pregnancy rates of 58, 66 and 33%, respectively. This led to a significantly (P<0.05) reduced proportion of the hoggets lambing in 'low' and 'high' feeding treatment hoggets when compared to the 'medium' hogget feeding treatment. Lamb birth weight was reduced in lambs born to the 'low' (3.5±0.16 kg) treatment hoggets when compared to the 'medium' (4.0±0.19 kg) and the 'high' (4.0±0.19 kg) hogget treatment groups. A 'high' level of nutrition during pregnancy did not result in reduced lamb birth weight compared to the 'medium' level of nutrition. At L87, lambs bom to 'low' (18.1±1.01 kg) treated hoggets were significantly (P<0.05) lighter than lambs bom to 'medium' (20.6±0.76 kg) and 'high' (21.8±0.98 kg) treated hoggets. The numbers of lambs reared at L87 was 15,27 and 17 for 'low', 'medium' and 'high' treated hoggets, respectively. In conclusion, feeding hoggets at a 'low' and 'high' level of nutrition led to a substantially reduced number of lambs produced. In addition, lambs born to the 'low' fed hoggets were much lighter than lambs born to 'high' fed hoggets at L87. Therefore, this study indicates that farmers wishing to maximise reproductive performance of hoggets should feed hoggets to ensure live weight gain during pregnancy is above 60 g/day but below 200 g/day.
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    Investigating methods to improve the reproductive performance of hoggets : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Mulvaney, Fraser John
    The first two chapters identified that in comparison to mature multiparous ewes, fewer hoggets are bred, a greater proportion return to oestrus, have a lower proportion that ovulate and of those that do ovulate, the ovulation rate is lower, and there is a greater reproductive loss in early to mid pregnancy, fewer and lighter singleton counterparts lambs at birth, poorer mothering ability and lighter and fewer lambs at weaning. As a result of these findings, nutritional management experiments were designed to investigate the effects of nutrition on the reproductive performance of hoggets. The results indicate that offering ad-libitum levels of herbage prior to ram introduction can increase the proportion of hoggets bred which leads to a better pregnancy rate. However, ad-libitum levels herbage immediately after the completion of the breeding period could be associated with hoggets that were bred returning to oestrus. The efficiency of lamb production was reduced when the hoggets were offered ad-libitum levels of herbage during pregnancy. However. when twin-bearing hoggets were offered ad-libitum levels of nutrition from mid- to late- pregnancy the efficiency of lamb production was similar between nutritional levels. The twin-bearing hoggets may have both been offered a level of nutrition that did not lead to a sufficient nutritional intake restriction in the medium group to allow for hogget live weight differences to occur. Hoggets that were offered ad-libitum levels of nutrition during pregnancy were heavier than the hoggets offered medium levels of nutrition. Weaning single lambs born to hoggets at 10 weeks of age whilst weaning twin lambs at 9 weeks of age did not have an impact on hogget or lamb live weight compared to weaning at 13 or 14 weeks of age. This thesis has identified reproductive differences between hoggets and mature multiparous ewes and the impact of nutritional management on hogget reproductive performance and the effect of weaning age on lamb and hogget live weight. Implementing the results from the nutritional experiments into farm practice could improve hogget reproductive performance and help alleviate the issue of the negative impact of hogget breeding on subsequent breeding live weight, while also offering options to the farmer when planning the management of weaning lambs born to hoggets.