Predicting empty body weight in growing goats: A meta-analytic approach

- Linear regression models to predict empty body weight in goats were proposed.
- The impact of sex, type of diet and genotype on empty body weight when estimated by body weight were depicted.
- Sex did not affect the relationship between empty body weight and body weight.
- Distinct models were proposed for suckling and post-weaning goats.
- For each tested genotype a specific model was recommended.

The objective of this study was to develop statistical models to predict empty body weight (EBW) by body weight (BW), testing the influence of sex (females, intact males or castrated males), type of diet (suckling or post-weaning), and genotype (Saanen, ½ Boer × ½ Saanen, ¾ Boer × ¼ Saanen, and Indigenous goats). Individual records of 311 goats combined from 10 studies, with BW ranging from 4.3 to 47.4 kg were used. The EBW was computed as the BW at slaughter minus the weight of the contents of the digestive tract, urinary bladder, and biliary vesicle. Linear regression analyses were performed to develop the models, considering sex, type of diet, and genotype as fixed effects and random effect of study. CONTRAST statements were used to conduct all pairwise comparisons of fixed effects and all the statistical analyses were performed using SAS. The present study revealed that sex did not affect both intercept (P = 0.53) and slope (P = 0.19). On the other hand, the EBW prediction was affected by type of diet (P < 0.01), and genotype (P = 0.02). Therefore, were proposed different equations to predict EBW from BW for suckling and post-weaning Saanen goats, where gastrointestinal tract content (g/kg EBW) in suckling goat kids increased as they grew, oppositely it remained slightly constant in post-weaning goats. The effect of genotype on the EBW:BW relationship was tested considering only post-weaning goats, and one equation was proposed for each genotype. In general, gastrointestinal tract content (g/kg EBW) decreased as goat kids grew in all genotypes but Indigenous goats. The results also highlighted different gastrointestinal relative capacity between genotypes. The development of these equations would enable producers and researchers to predict the animal EBW, and develop strategic plans in a goat herd.