Use of heart girth to predict body weight of working oxen in the Ethiopianhighlands

Few studies have been conducted in sub-Saharan Africa where multiple record ings of heart girth and body weight were made for the same cattle populatio n. In this study, monthly measurements were taken of working oxen on 24 sma llholder farms in the Ethiopian highlands for 1 year. The overall yearly me an body weight of oxen across working and nonworking periods was 281+/-37 k g. No significant differences in mean monthly body weights were observed. e xcept for December and January compared to August (297+/-36 and 296+/-37, a nd 271+/-35 kg, respectively, P < 0.05) and December versus April 272+/-35 kg (P < 0.05). Simple linear regression equations derived from body weight and heart girth measurements were significantly different between months. N evertheless, separate monthly equations and a single equation for the year explained variation in body weight about the same. The monthly equations pr edicted 83 to 95% of oxen weights to within +/- 10% of weighbridge values, while the equation for the entire year predicted 87%. The R-2 values for th e monthly equations ranged from 0.63 to 0.87 and the R-2 value for the enti re year was 0.75. The single equation for the year predicted body weight of oxen as a group to within +/-27 kg of mean monthly weighbridge values, whe reas for a single animal the predicted body weight was +/-37 kg of the actu al weight (C.I. 95%). The single equation can be used to monitor mean body weight of the oxen population equally well across working and nonworking pe riods of the year. (C) 2001 Elsevier Science B.V. All rights reserved.