The influence of supplementation with urea-molasses blocks on weight gain and nematode parasitism of dairy calves in central Kenya.

The effect of feeding urea-molasses blocks (UMB) on the growth and gastrointestinal nematode parasitism of dairy weaner calves grazing on the same pasture was investigated on a farm in Thika District, central Kenya. Twenty-six female calves, with an average age of 9 months, were initially treated orally with albendazole (10 mg/kg body weight) and assigned into two groups: animals in group I were fed urea-molasses blocks (UMB) prepared using a cold process and those in group II were the controls. The UMB were given in the evening, when the animals returned from grazing, and were consumed during the night at a rate of 550 g/head per day. Supplementation was undertaken on three occasions for three consecutive months, between July and August 1999, and between January and March and July and September 2000. The body weights of the calves and the faecal egg counts were measured monthly and larval cultures were performed on positive faecal samples from each group. Significant differences (p < 0.05) were found in the cumulative weight gains of the two groups of calves from September onwards. The UMB group averaged (+/- SD) 311.2 +/- 14.9 g/day over the study period, while the control group averaged 235.7 +/- 23.5 g/day; the UMB group also reached breeding weight earlier (p < 0.05) than the control group. There was no significant difference (p > 0.05) in the faecal egg counts between the groups, the predominant genera of gastrointestinal nematodes in faecal cultures being Haemonchus spp. and Trichostrongylus spp. Other nematodes were Cooperia spp., Bunostomum spp. and Oesophagostomum spp.