Date of this Version
Published in Livestock Production Science 69 (2001) 187–195.
Few studies have been conducted in sub-Saharan Africa where multiple recordings of heart girth and body weight were made for the same cattle population. In this study, monthly measurements were taken of working oxen on 24 smallholder farms in the Ethiopian highlands for 1 year. The overall yearly mean body weight of oxen across working and nonworking periods was 281 ± 37 kg. No significant differences in mean monthly body weights were observed, except for December and January compared to August (297 ± 36 and 296 ± 37, and 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. Nevertheless, separate monthly equations and a single equation for the year explained variation in body weight about the same. The monthly equations predicted 83 to 95% of oxen weights to within ±10% of weighbridge values, while the equation for the entire year predicted 87%. The R2 values for the monthly equations ranged from 0.63 to 0.87 and the R2 value for the entire 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, whereas for a single animal the predicted body weight was ± 37 kg of the actual 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 periods of the year.