Body measurements of bucks of three goat breeds in Ethiopia and their correlation to breed, age and testicular measurements

Abstract

Body size and testicular measurements have been found to be important parameters for evaluating breeding soundness. Therefore a study was performed on Afar ( n = 180), Boran ( n = 180) and Woito-Guji ( n = 180) male goats to record the normal testicular characteristics and evaluate the effect of breed, age and body condition on these testicular measurements. A predictive model for each of the testicular measurements was developed, using live body measurements. Breed and age of the bucks had a significant effect ( P < 0.05) on the body condition score (BCS), body weight (BW), scrotal circumference (SC), testicular measurements (testicular diameter, testicular length, testicular volume and testicular weight) and epididymal weight. The Afar breed consistently recorded the lowest mean BCS, BW and SC in all age categories. BCS showed a significant but low correlation with age, BW, SC and the testicular measurements ( P < 0.01). Body weight however recorded an intermediate correlation with SC ( r = 0.58; P < 0.01), while SC was highly correlated to testicular diameter ( r = 0.69), testicular volume ( r = 0.74) and testicular weight ( r = 0.74). Moderate to strong correlations were recorded between the testicular measurements, and epididymal weight. In the univariable linear regression model, all live body attributes used (breed, age, BCS, BW and SC), were found to be independently related to the testicular and epididymal parameters. However, in the multivariable linear regression, with the exception of age, all other independent predictors were found to be linearly related to one or more of the testicular and epididymal measurements. Scrotal circumference was eventually the only live body measurement to be used in the final model to predict all the testicular and epididymal measurements in the bucks. Examples of predicted testicular and epididymal measurements using the final model are reported. In conclusion, the Boran bucks were found to have superior body and reproduction traits and SC, which is easily measured in the live animal and predicted to be the best indicator of testicular and epididymal measurements. These findings, especially of the prediction models developed, could be useful in the selection of bucks for breeding purposes.