Weight estimation in native cross bred Assamese goats

In the Assam region, village goats serve a vital role in smallholder productions systems. Accurate bodyweight measurements are not always feasible in smallholder systems for animal husbandry, and so proxy measures may be more useful. However, bodyweight proxies are not equally informative at all life stages of the goat, and are not all equally obtainable. In this study we recorded health measures on 149 indigenous Assamese village goats including bodyweight, body length (poll to tail head), chest girth, body condition score on a 5-point thin to fat scale (BCS), and conjunctival eye colour (FAMACHA©) score. Goats in the region were thin (median score = 2), and anaemic with 82% of goats scoring a >4 on the FAMACHA scale (mean score 3.98 ± 0.69). Adult goats measured 68.0cm ±7.12 and weight 16kg ± 4.36, and kids measured 42.6cm ± 9.86 and weighed 4.19kg ±2.62. A series of linear regressions were created to predict bodyweight, and models which had clinical relevance were tested using K-folding (resampling the data k-times so all data points have both been included and excluded from the models). A quadratic regression model of girth2, body length and pregnancy status had the lowest Root Mean Square Error (RMSE) and had significant predictive ability on bodyweight (F4,143=881.6, p<0.001). However a simpler linear model of girth and age had an acceptable RMSE and retained highly significant predictive ability on bodyweight (F2,146=758.8, p<0.001) while minimising prediction error for small goats where dosages should be more specific. We discuss the importance of selecting clinically relevant and pragmatic models in smallholder settings.