Determinants of Kid Mortality in Strains of Local Goats in a Research Herd in Morogoro, Tanzania

Abstract

Determinants of kid mortality were investigated amongst local strains of the Small East African goat bred, namely Kigoma, Mtwara and Dodoma, in retrospective and prospective studies. The strength of association and the role of chance were evaluated using mortality relative risk (RR) measures, 95% confidence intervals for the RRs and x2 test based p-values.

Retrospective results showed that birth weight modified the effect of strain on kid mortality. The Dodoma strain was superior to the other two strains (RR was 2.34 and 2.15) and the p - values were 0.0000 and 0.0003 for the Kigoma and Mtwara strains, respectively, in the group of kids with above average population birth weight (l.89 kg). However, no association was found between strain and kid mortality in the group whose birth weight was below the mean population birth weight. Kids with below average birth weight were 1.66 times more likely to die than heavier kids (p =0 .00 00). Similarly, birth type was found to be associated with kid mortalities RR=l.60 (CI: 1.35, 1.88, p=0.0000). Individuals from multiple births had 1.60 times at risk than single born kids (p=0.0000). Amongst the three age cohorts; pre-weaned kids (0-3 months) and weaned (>3-6 months) were at 5.8 and 3.92 times, respectively, the risk of the >6-9 months age group; these results were unlikely to have arisen by chance (p=0.0000), and the risk ratios were quite high. Sex had no significant effect on kid mortality (RR=l.14, p=0.1971). The prospective study revealed that respiratory conditions were responsible for 22.7% of the deaths and the pneumonia­ helminthoses complex accounted for 19.7% of kid mortalities. It is concluded from this study that kid mortality is associated with strain, birth type, birth weight and age, but sex had no effect on kid mortality