Goat Nutrition in Australia – a review

Summary

The foundations of profitable animal production systems include market demand, processing facilities, genetic potential for growth and production and a sound knowledge of the nutritional requirements of livestock which underpin cost-efficient productivity. The diversity of genotypes in the Australian goat population and the starkly contrasting environments where goats exist or are farmed increases the complexity of their nutrient requirements. Much of the research into goat nutrition has been undertaken in tropical environments and the relevance of this to Australian conditions and goat populations remains unclear.
The Australian rangeland goat appears well adapted to its environment whereas Boer goats, imported for their superior growth potential, appear less well suited to either rangeland or intensive production systems.
The purpose of this review was to thoroughly investigate the gaps in nutritional information to support future investment decisions by Meat & Livestock Australia to underpin the growth of the goat industry. The terms of reference were as follows:Clarify the nutritional requirements for goats
Determine how and why publications vary widely in their recommendations
Determine the variation in nutrient requirements between rangeland, Boer, Boer-cross, dairy and fleece-producing goats and their progeny
Investigate the alignment between the recommendations and animals response to a range of feeding regimes and practises

This review has provided confirmation that the guidelines for the nutrient requirements of goats vary widely and that there remains a diversity of opinion as to which is the correct source of information. NRC (2007) has published the most comprehensive set of recommendations following an extensive review of published research from 1981 to 2006 however these guidelines require validation under a range of environmental conditions.
Satisfaction of daily nutrient demand is assumed to be reliant on dry matter intake however no allowance has been made for when intake is restricted for any reason; this is of particular importance for goats where the phenomenon of “winter stasis” has been identified as an important factor limiting productivity. Their unique oral structure and inherent ability of goats to select the most nutritious components of plant material ensures their survival in rangeland areas when sufficient feed is available however pastoralists may benefit from education programs directed at the identification of key indicator species to assist in early destocking decisions. Depot nutrition is becoming increasingly important and it is clear that producers would benefit from some education about nutritional management of goats under confined conditions.
The recommendations for daily energy requirements of goats in the literature vary predominantly in line with the key differences between NRC (1981) and NRC (2007) such that the former attributed an activity allowance for ME m and the latter did not. It appears the main reason for this change is based on the presumption that goats will have access to grazing and hence nutrient intake while walking. NRC (2007) acknowledges that these recommendations require field evaluation. Once validation has been undertaken, producers will benefit from the development of a set of simple set of guidelines for their genotype and a concurrent education program of implementation.
It is well understood that the protein requirements of goats increases with an increasing level of productivity such that the protein requirements of lactating goats of any genotype are likely to be higher than that required for maintenance. As pasture species mature, protein concentration declines however the change in nutritive value of some perennial shrubs such as the saltbushes, appears more random. Of greater interest is the ability of goats to adapt to pasture species that provide excessively high protein concentrations in winter and spring; Boer and Boer-cross goats in medium to high rainfall environments exhibit severe symptoms of lameness and scouring under these conditions and appear to have low resistance to internal parasites. It should be noted that within these environments there are many animals that are not affected providing a positive outlook for genetic selection.
Although the majority of goats producers and their advisors are of the opinion that goats require a diet that is high in fibre there is a plethora of evidence demonstrating a similar preference for a highly digestible diet to sheep where it is available. It is the opinion of this author that the degree of environmental adaptation may determine a goat’s preference for fibre such that within a rangeland environment where selectivity is high, goats may be eating a more digestible diet than is immediately apparent. As for all ruminants, a minimum level of effective dietary fibre is required to maintain a neutral pH in the rumen to facilitate digestion.
The mineral nutrition of goats particularly under intensive farming regimes requires urgent attention; the requirements of goats for key nutrients such as copper appear significantly different to sheep and it may be that acute mineral deficiencies are partially responsible for the productivity constraints of intensively farmed goats.
As goats have prolific reproductive capacity, it is likely that the application of the current nutritional strategies for ewes may be of benefit to does; these include stimulation of ovulation rates with a sudden increase in the plane of nutrition pre joining and particular emphasis on late pregnancy nutrition to increase kid survival. These intensive strategies are unlikely to be of practical benefit in an extensive pastoral environment and there may be differences in the cost-effective responses between genotypes.
Although the optimum weight and age for weaning has yet to be determined, it is apparent that Boer and Boer cross kids have similar growth potential to lambs when fed a high quality diet and that their requirement for protein may be less than that of lambs. Where it is cost-efficient to do so, kids respond well to lot feeding providing they have prior introduction to the feedlot diet pre-weaning.
Optimisation of transitional feeding of goats in depots prior to transport is impeded by the lack of time to adapt to a change in feed such that the focus is one of weight loss minimisation rather than weight gain or productivity. As the pregnancy status of these goats is unknown and nutritional requirements increase significantly as pregnancy advances it is clear that a maintenance diet may not always be appropriate. The cost-efficiency of improved feeding strategies was outside the terms of reference of this review but needs to be determined; depot managers would benefit greatly from improved nutritional information.
At the end of each chapter of this review recommendations for further research have been suggested for consideration. Validation of the most relevant nutrient requirements for goats would provide the industry with a platform on which to expand with a higher degree of confidence than currently exists.