| dc.description.abstract | The Red Maasai and Dorper lambs born from 1991-1996 in Coastal region
of Kenya (Diani Estate) were compared using survival analysis. The Red
Maasai lambs had a lower risk of death (i.e., relative risks of 0.28 and 0.26 in
pre-weaning and post-weaning periods respectively) compared to the Dorper
(i.e., the standard) when a standard Cox model was fitted to the data. When
a frailty term was fitted, there was little change in the value of the parameter
estimates. The deaths of the Dorper lambs were higher compared to those
of the Red Maasai with the contribution of mis-mothering being about 32%
for Dorper lambs and about 30% for Red Maasai and endoparasites being
about 16% for Dorper and about 9% for Red Maasai lambs in pre-weaning
period. In post-weaning period, the proportions of deaths for endoparasites
were about 41% for Dorper and about 33% for Red Maasai while pneumonia
contributed about 17% of the deaths of the Dorper and about 7% of the
deaths of the Red Maasai lambs.
There were significant effects due to birth weight and weaning weight. The
age of the dam was not significant in pre-weaning period but from the standard
and frailty Cox models, the lambs born to older ewes had a lower risk
of death compared to those born to younger ewes.
The most frail lambs tend to die m~re as compared to the stronger lambs
in both the pre-weaning and post-weaning periods with these differences in
deaths becoming more pronounced in post-weaning period. | en |
