The impact of anthelmintic drugs on weight gain of smallholder goats in subtropical regions

Helminth infections are recognised as a major impediment to the productivity of goats in smallholder production systems. We used a multilevel framework to estimate the impact that administration of locally available anthelminthic drugs can have on the weight gains of goats in smallholder settings in India and Tanzania. We recruited 234 goats from 92 households from Odisha state in India and 253 goats from 15 households from Dodoma region in Tanzania. The goats were non-pregnant adult females, and from each household a minimum of two goats were recruited wherever possible. Each goat was randomly assigned to treatment with a locally available anthelminthic drug, or non-treatment. Each animal was tagged, weighed and had its body condition score (BCS) assessed. Animals were followed up after 28 and 56 days and re-weighed. To account for the local variations in exposure to helminths and for variations between households and herds, the data were analysed in a multilevel mixed model with herd in village as nested random effects. Over the 56 days of study, the non-treated goats in India had gained a mean of 30.64 grams per day (a daily gain of 0.23% baseline body weight) and in Tanzania 66.01 grams per day (0.33% baseline body weight). From the mixed model, the treated goats in India gained a mean of 25.22 grams per day more than non-treated goats, this is significantly greater than the weight gain in non-treated goats (p<0.001). In Tanzania treated goats gained a mean of 9.878 grams per day more than non-treated goats, which is also significantly greater than non-treated goats (p=0.007). Furthermore, in India and Tanzania, goats with a lighter weight at the baseline survey gained greater amounts of weight. In both studies the BCS of the treated goats improved by a greater amount than the non-treated goats. In this study we have demonstrated that in certain settings, the administration of anthelminthic drugs has a clear beneficial impact on goat weight. We speculate that the beneficial impacts vary with timing of administration, the drugs used and the helminth species challenge in the specific setting.