Summer-autumn ill-thrift in Tasmanian Beef herds.

Summary

This report presents the outcomes of the project Summer-autumn ill-thrift in Tasmanian beef herds (B.SBP.0109) funded by Meat and Livestock Australia (MLA) and undertaken by Macquarie Franklin. The project consisted of a literature review and a beef industry producer survey to determine the severity and possible causes of ill-thrift during the autumn period. The relationship between management practices and autumn ill-thrift was also explored. 
​The impact of autumn ill-thrift in cattle in Tasmania is estimated to cost the industry around $3-11m annually (based on the estimates presented in this report) depending on the length of the period over which it occurs each season. If the problem is applicable to all of southern Australia then this figure could be in the order of $25-100m annually (again, based on the estimates presented in this report). In Tasmania many producers have reported anecdotal evidence of cattle underperforming during the late autumn period. The literature review showed that ill-thrift during autumn is a real phenomenon which has been widely documented and researched both in Australia and overseas. While to some extent the causes of ill-thrift are multifactorial, the literature review highlights key factors which have been linked with ill-thrift (mycotoxins, pasture quality and internal parasites). 
Results of the producer survey strongly supported the literature review findings regarding the link between autumn ill-thrift and mycotoxins. It also showed that beef production in Tasmania is largely from perennial rye grass pastures and is therefore likely to be highly vulnerable to negative impacts on productivity caused by ill-thrift. Further, many producers appear unaware of the condition or its impacts. Mycotoxins are therefore likely to be a major contributor to ill-thrift in cattle over the autumn period and further research is recommended to investigate mycotoxin impacts on cattle liveweight gains. Seasonal changes in pasture quality (e.g. low soluble carbohydrate content in autumn herbage) directly affect liveweight gain of cattle. 
Based on the results of two earlier trials, it is probable that the lower than expected liveweight gain over the autumn period seen in Tasmania is at least partly attributed to the poor quality of perennial ryegrass at this time of year. Educating beef producers about the variation in nutritive values of pasture during the year and the impact of best practice grazing techniques (e.g. minimising dead matter and maintaining healthy levels of post grazing residual mass) could help improve liveweight gain of cattle over autumn.