Evaluation of crossbred goat genotypes for growth, carcass and meat quality characteristics

Dhanda, Jagvinder Singh. (2001). Evaluation of crossbred goat genotypes for growth, carcass and meat quality characteristics PhD Thesis, School of Animal Studies, The University of Queensland.

       
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Author Dhanda, Jagvinder Singh.
Thesis Title Evaluation of crossbred goat genotypes for growth, carcass and meat quality characteristics
School, Centre or Institute School of Animal Studies
Institution The University of Queensland
Publication date 2001
Thesis type PhD Thesis
Total pages 289
Language eng
Subjects 830304 Goats
Formatted abstract
• Australia is the largest exporter of the goat meat in the world. Traditionally, the goat meat industry in Australia has relied mainly on harvesting the feral goat population. As a result, the quantity and quality of goat meat produced have been unreliable and inconsistent. With this in view, efforts have been made in the last few years to develop a sustainable goat meat industry in Australia. Thus, a large cooperative meat goat project funded by Meat and Livestock Australia (MLA) and Rural Industries Research and Development Corporation (RIRDC) was started at Gatton College in 1996 to collect scientific information for the industry regarding suitability of different breed combinations in terms of growth, carcass and meat quality. The present study was a part of this ongoing project.

• Buck kids from six goat genotypes, Boer x Angora (BA), Boer x Feral (BF), Boer x Saanen (BS), Feral x Feral (FF), Saanen x Angora (SA) and Saanen x Feral (SF) were compared for their growth, carcass and meat quality characteristics. The present study was conducted on F₁ male kids from two kidding periods (Trial I and Trial II) i.e. January-March and October-November, 1997. There were not enough male kids born to choose from the BF genotype during the first kidding, so the BF kids were not included in Trial I of this study.

• Half (five from each genotype, 25 kids in Trial I and 30 kids in Trial II) of these kids were reared to a liveweight in the range of 14-22 kg, to produce Capretto carcasses. The other five kids from each genotype (25 kids in Trial I and 30 kids in Trial II) were castrated, weaned at 10-15 kg liveweight and reared to produce Chevon carcasses. These were slaughtered when they reached a liveweight in the range of 30- 35 kg. Kids from the Capretto group were reared on pasture with their mothers until slaughter. Chevon kids after weaning were raised on pasture with ad libitum access to concentrate pellets (18% CP and 12.3 MJ/kg ME, on an as-fed basis) till slaughter.

• BS kids had significantly (P ≤0,05) higher birth weights than FF kids. Due to their better average daily gain BS kids took less time to reach the required weight at slaughter compared to FF and BA kids for both Capretto and Chevon groups. The average daily gain (g/day) decreased in buck kids with increase in age/body weight i.e. from production of Capretto to Chevon carcasses. For the genotypes used in Trial I and II in the present study, Capretto kids reached the required slaughter weight in 77-102 days while Chevon kids took 219-282 days to attain the required slaughter weight.

• There were few differences between genotypes in terms of the percentage contribution of head and skin to the empty body weight, with BA kids having a higher percentage of skin compared to other genotypes in both groups. Saanen sired kids, i.e. SA and SF kids, had significantly greater amounts of internal fat compared to other genotypes. There was no consistent effect of age/carcass weight on the percentage of visceral organs to empty body weight for the different genotypes. However, the proportions of heart and liver in the empty body weight increased whereas the percentage of head and skin to empty body weight decreased significantly (P ≤ 0.05) with increasing age/carcass weight. Total internal fat deposition increased significantly from Capretto to Chevon group.

• The dressing percentage (based on empty body weight) of Capretto kids ranged from 50-54 percent, while Chevon kids dressed out in the range of 51-56 percent with few significant differences between genotypes. The carcasses from BS genotype were significantly longer compared to BA and FF genotypes. There were significant differences between genotypes for the eye muscle area and subcutaneous fat thickness measurements at 12/13th rib and rump sites. For both the groups, the correlation between the ultrasonic (measured on the live animal) and ruler measurement (measured on the cold carcass) for fat depth at the 12/13th rib was highly significant (r = 0.70-0.76) but for the rump site, the correlation between these two modes of measurement was relatively low (r = 0.29-0.49). For all genotypes the subcutaneous fat thickness increased significantly from Capretto to Chevon group.

• There were no significant differences between genotypes and between groups for the percent contribution of primal cuts to the carcass side weight; the percentage of primal cuts being neck (10-11%), flank (12-14%), ribs (22-26%), shoulder (18-21%) and long leg (33-35%). The overall composition of Capretto carcasses were 60-66 percent muscle, 8-12 percent fat and 24-27 percent bone while Chevon carcasses comprised of 60-69 percent muscle, 10-17 percent fat and 18-22 percent bone. There were significant differences for the percent muscle and fat (subcutaneous and intermuscular) and small differences in bone content between genotypes. BS carcasses from both the groups were leaner compared to other carcasses. Significant correlations were observed between the percentage of muscle, fat and bone in most of the primal cuts and that in the carcass side for both Capretto and Chevon groups. With increase in age/carcass weight, muscle and fat contents increased significantly while the bone content decreased significantly in the carcass.

• The ultimate pH of the longissimus muscle from both the groups was on the higher side (5.6-6.1) than that observed in other meat animals. There were some variations between genotypes in the percent cooking loss; FF genotype from the Capretto group and BA genotype from the Chevon group had higher cooking loss than other genotypes. There were significant differences between genotypes in terms of pigment concentration of the longissimus muscle, which increased significantly (P ≤ 0.01) from Capretto (1.5-2.3 mg/g) to Chevon (2.6-3.7 mg/g) carcasses. Genotype had an influence on the longissimus muscle colour coordinates (CIE L*, a*, b* values) however fat colour did not vary between genotypes. BS kids from the Capretto group had paler muscle colour. There was a positive correlation (r = 0.36-0.52) between muscle pigment concentration and muscle colour in both the groups. The muscle 'Colour became darker red and fat colour became more yellow with increase in age/carcass weight. Wamer-Bratzler shear force values of cooked meat samples did not differ significantly between genotypes however, these values increased significantly from Capretto (2.5-4.0 kg/cm²) to Chevon (4.2-6.3 kg/ cm²) group. In both the groups, based on the average score for tenderness, flavour, juiciness and overall acceptability, panellists found goat meat to be of an acceptable eating quality. There was no consistent effect of age/carcass weight on sensory scores for eating quality.

• There were no significant differences between genotypes for chemical composition of the longissimus muscle. The moisture content decreased and crude protein and fat contents increased significantly while the ash content remained unaffected with increase in age/carcass weight. The proportions of individual fatty acids in the adipose tissue differed significantly between genotypes for both Capretto and Chevon groups. With increase in age/carcass weight and resultant change in diet (from mainly milk in Capretto to predominantly pasture in Chevon kids), the saturated fatty acid concentration decreased and the unsaturated fatty acid concentration increased.

• Faster growth, desirable carcass characteristics and superior meat quality are some of the important criteria, which determine the selection of a particular genotype for meat production. Based on these growth, carcass and meat quality parameters, it can be concluded that BS kids performed better for the production of Capretto and Chevon carcasses than the kids from other genotypes used in the study.

Keyword Goats -- Australia.
Goat industry -- Australia.
Goats -- Australia -- Physiology.

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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