Department of Animal Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
Directorate: Animal Sciences, Department of Agriculture, Western Cape Government, Private Bag X1, Elsenburg, 7607, South Africa.
Trop Anim Health Prod. 2023 Sep 26;55(5):325. doi: 10.1007/s11250-023-03732-y.
Producers require an accurate predictive tool that can determine the optimal point of slaughter based on fat depth. The modelling of fat deposition with a simple mathematical model could supply in this need. Dohne Merino and Merino ewes were crossed with Dorper, Dormer and Ile de France rams or rams of their own breeds to create two purebred (Dohne Merino and Merino) and six crossbred groups (Dohne x Dorper, Dohne x Dormer, Dohne x Ile de France, Merino x Dorper, Merino x Dormer and Merino x Ile de France) of offspring. Fat deposition of four lambs of each sex per genotypic group was monitored from 80 to 360 days using ultrasound, and the data subsequently fitted to various equations and evaluated for goodness of fit. A linear fitting of fat depth to age (R > 0.77) and live weight (R > 0.56) were deemed to provide the best fit. The slope parameters of the equations indicated that ewes deposited fat faster than rams and that Dorper crosses had the highest fat deposition rate. An attempt was also made to model loin muscle growth, but the model fit was judged to be unsatisfactory. The predictive models developed here are deemed suitable for inclusion in feedlot management systems to aid in the production of optimally classified lamb carcasses.
生产者需要一种准确的预测工具，能够根据脂肪深度确定最佳屠宰点。简单的数学模型可以模拟脂肪沉积，以满足这一需求。杜罗克美利奴羊和美利奴羊母羊与多伯羊、多默羊和伊夫雷亚杂交，或者与自己品种的公羊杂交，创造了两个纯种（杜罗克美利奴羊和美利奴羊）和六个杂交群体（杜罗克 x 多伯羊、杜罗克 x 多默羊、杜罗克 x 伊夫雷亚、美利奴 x 多伯羊、美利奴 x 多默羊和美利奴 x 伊夫雷亚）的后代。从 80 到 360 天，对每个基因型组的 4 只羔羊的每只羔羊的脂肪沉积进行超声监测，并将数据拟合到各种方程中，评估拟合优度。脂肪深度与年龄（R>0.77）和活重（R>0.56）的线性拟合被认为是最佳拟合。方程的斜率参数表明，母羊比公羊更快地沉积脂肪，多伯羊杂交种的脂肪沉积率最高。还尝试了对腰肉生长进行建模，但判断模型拟合不理想。这里开发的预测模型被认为适合纳入饲养管理系统，以帮助生产最佳分类的羔羊胴体。
