Browsing by Author "Diemont, Dirk Lusk Pierre"
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- ItemThe difference in energy metabolism between barrows and gilts and its effect on fat deposition and carcass quality(Stellenbosch : Stellenbosch University, 1992) Diemont, Dirk Lusk Pierre; Mellett, Mr. F. D.; Stellenbosch University. Faculty of AgriSciences. Department of Animal Science.ENGLISH ABSTRACT: In a 2x5 factorial experiment undertaken with 50 Large White x Landrace pigs, growth rate, FCR and commercial carcass yields were evaluated, while a chemical analysis of a sample slice between the 5th and 6th rib was performed. The experiment was divided into 5 groups, each containing 5 barrows and 5 gilts. Group 1 received the control ration with high energy (13,3 MJ ME/kg) and high protein (20,7%) without added fibre (in the form of saw dust). The energy and protein content decreased progressively for the 5 rations and the saw dust increased correspondingly. The pigs were fed ad lib with free access to water and were slaughtered at 86kg. Barrows were found to have significantly (P<0,05) heavier belly fat and skin masses than gilts, while the interaction between sex and nutrient density was almost at the significant level (P=0,05) with the P2 measurement. The differences between nutrient densities proved to be greater than the differences between sexes due to the low number of experimental animals used. Regression equations showed that the saw dust and protein content of the rations were more accurate predictors of the carcass yields, on-farm performance results and chemical analysis and linear measurements of the sample joint than the ME. Days to slaughter were predicted with R2-values of 29,7%; 30,0% and 21,6% when saw dust, protein and ME, respectively, were used as independent variables. Barrows tended to have higher R2-values than gilts with intermediate values for the sexes calculated together. The saw dust and protein content were the most accurate independent variables for both barrows and gilts when used in a multiple regression, while ME did not contribute usefully to the accuracy when combined in a multiple regression. When the chemical composition of the sample joint was used as the independent variable, the highest R2-value (36,1%) was obtained when the shoulder fat and skin mass was predicted by the % moisture. Of the linear measurements of the sample joint, eye muscle area was the most accurate predictor of the carcass yields (R2for loin spare rib = 29,0%). Due to a high correlation between linear measurements and chemical analysis results of the sample joint, linear measurements were used as independent variables to predict carcass yields. Eye muscle area achieved the highest R2-values (shoulder fat and skin = 27,6% and loin spare rib = 29,0%).