Although relatively little goat meat is eaten in Australia, goat meat is widely eaten and highly priced in many parts of the world, such as Southeast Asia, Middle East countries, Carribean, the United States of America and Canada. Goats are currently marketed based on liveweight, and because the global demand of goat meat (in these countries in particular) is higher than the goat population and supply, goats are mostly slaughtered as younger animals. In fact, the reason for slaughtering goats at a younger age or lighter weights is not about better quality or the nutritive value of the meat itself, but is about the number and availability of animals. This is a challenge for goat meat producers, but creates opportunities to promote bigger carcasses from older animals with specific meat quality and nutritive value characteristics. More importantly, because goats produce lean meat with the fat mostly deposited in the abdominal cavity, there is the possibility that bigger carcasses from older animals may not contain large amounts of fat. Therefore, this study was undertaken to examine the quality and nutritive value of meat from male Boer and Australian feral bucks slaughtered across a wide range of liveweights.
The study was conducted on the University of Queensland Gatton Campus, involving 60 Boer and 62 Australian feral goats. One group of kids from each breed was castrated (except kids at 5, 10 and 15 kg liveweight) and the other group was left as entire animals. A total of 3 to 5 animals in each breed and sex type (castrated and entire) were then slaughtered at one of 8 different slaughter weights from 5 to 105 kg liveweight for the Boer bucks and one of 8 different slaughter weights from 5 to 70 kg for the Australian feral bucks. The physical characteristics of fresh meat including muscle ultimate pH, muscle and fat colour, degree of marbling, muscle pigment concentration, cooking loss and shear force values of the meat were determined. Although both slaughter weight and castration (sex type) affected most of the quality characteristics of meat from Boer and Australian feral bucks, slaughter weight had a greater influence than castration. Although the results of the present study has shown that meat quality characteristics from Boer and Australian feral bucks decreased with increasing slaughter weights, it also indicated that Boer bucks should not be slaughtered at above 75 kg liveweight and for Australian feral bucks above 40 kg liveweight as they have poorer meat quality characteristics. In addition, Boer and feral bucks, when slaughtered at the same liveweight, had different meat quality characteristics.
In general, although castration of bucks increased relatively small amounts of intramuscular fat, longissimus thoracis and semimembranosus muscles taken from entire and castrated Boer and Australian feral bucks slaughtered across a wide range of liveweights contained very low intramuscular lilt. This indicates that entire and castrated mature Boer and feral bucks produce very lean meat which can be an ideal choice of red meat for health conscious consumers.
Meat from older goats, slaughtered at heavier liveweights, were less tender than meat taken from younger animals, slaughtered at lighter liveweights, and these results were reflected in the eating quality scores given by panellists, which were lower for the cooked meat taken from older animals. Thus, it can be presumed that meat taken from older goats (slaughter weight 45 kg and above) would be preferred less by consumers in terms of overall acceptance. Cooked meat from castrated bucks were preferred to cooked meat from entire animals. There were no significant differences between breeds in eating quality profiles of cooked meat when meat from animals, of the two breeds, were compared at the same liveweights.
Slaughter weight had the greatest influence on the fatty acid content of the muscles and adipose tissues from Boer and Australian feral bucks. Oleic, palmitic and stearic acids consistently comprised the largest amounts of fatty acids in muscle and adipose tissues from both entire and castrated animals over the range of slaughter weights studied. Importantly, the percentage of saturated fatty acids in longissimus thoracis muscle and subcutaneous and intermuscular fat decreased with increasing slaughter weight.
The average rate of changes in total cholesterol concentrations in longissimus thoracis, infraspinatus and biceps femoris muscles from Boer and Australian feral bucks were strongly influenced by slaughter weight. Remarkably, the pattern of total cholesterol concentrations decreased with increasing slaughter weight and this was consistent for the three muscles studied. Although the effect of castration was less consistent than the effect of slaughter weight, castration did change the pattern of total cholesterol concentrations in the three different muscles from Boer and Australian feral bucks. For example, the average total cholesterol concentrations in infraspinatus and biceps femoris muscles from castrated Boer bucks were lower than for these muscles from entire Boer bucks, while the average total cholesterol concentrations in biceps femoris muscles from castrated feral bucks were higher than for this muscle from entire feral bucks. As did the breed of goat when they slaughtered at the same liveweight. Notably, over the range of slaughter weights studied, longissimus thoracis muscles from both breeds had lower total cholesterol concentrations than infraspinatus and biceps femoris muscles.
Overall, this study has generated detailed information on the quality characteristics and nutritive value of meat from entire and castrated Boer and Australian feral bucks slaughtered across a wide range of liveweights. This information can be used to predict the quality characteristics and nutritive value of meat across a wide range of liveweights from these breeds of goats so that recommendations can be made to health conscious consumers.