Abstract
Part of this study involved establishing current heifer fertility levels on Northern Territory (NT) commercial cattle properties. Performance recording on 14 properties found that there is scope for large improvement on many stations. Modelling showed that realistic improvements in production have the potential to increase the annual gross margin of the NT cattle industry by $10.95 million. Some of the main findings of the performance recording were that pregnancy rates in 2 year old maiden heifers are generally adequate (>75%), but foetal and calf loss rates in first calf heifers are often high (>30%) and reconception rates are often low (<20%) associated with low liveweights.Significant relationships were found between liveweights (and P8 fat depth) and pregnancy rates for Brahman heifers in the NT for; (a) yearling mated heifers grazing improved pasture, (b) 2 year old maiden heifers grazing native pasture, and (c) lactating first calf heifers grazing native pasture.
Equations describing these relationships were used to produce tables which show the predicted pregnancy rates for different liveweights and fat depths in Brahman heifers in each of these situations. These tables will be useful management tools for cattle producers and advisors. They can be used in identifying target mating weights for different situations, budgeting calculations, and assessment of profitability of different scenarios etc.
Other significant findings of the study were that heifers of current NT commercial Brahman genotypes reach puberty too late to enable high pregnancy rates from yearling mating, and that feeding pre-partum protein supplements to first calf heifers is one method of increasing reconception rates in the Victoria River District.
This study has been successful in increasing the understanding of the relationship between mating liveweight (and fatness) and pregnancy rates in Brahman heifers and this knowledge can be applied to improve heifer performance in the NT.
| Date of Award | Apr 2011 |
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| Original language | English |
| Supervisor | Chris Austin (Supervisor) |