The effect of multiple droughts on cattle in Obbu, Northern Kenya

Drought is the single most important environmental factor that causes cattle population fluctuations in northern Kenya. The way the grazing lands and animal populations are affected by drought requires long-term monitoring. However, in northern Kenya, patterns of cattle mortality following multiple drought episodes and recovery have not been compared before. This study compared effects of two droughts (1983/1984 and 1991/1992) and three recovery periods (1984, 1992 and 1996) on cattle population in Obbu, northern Kenya. Cattle mortality in terms of age-sex classes; calves, immature animals, breeding females and mature males were compared to understand drought impacts, while relative growth rates of herds and percentage of recovery to pre-drought cattle population levels were determined to understand recovery. The droughts altered herd structure and resulted in greater mortality among calves and breeding females (especially during 1983/1984) than immature animals and mature male cattle. Drought stress in terms of cattle mortality varied from area to another but at the regional level it was less during the 1983/1984 drought (69.8 +/- 2-0%) than 1991/1992 (86-8 +/- 1.9%). The pre-1983/1984 drought herd size for the Obbu region explained 12.4% of the variation of the post-drought cattle population, while the pre-1991/1992 drought population explained < 1% of the variation. Although cattle mortality was weakly linked to the pre-drought population, it was influenced by factors such as disease epidemics and poor nutritional quality in forage. Relative growth rates of herds in Obbu averaged 3.5% year(-1) after the 1983/1984 drought leading to full recovery in 7 years, while, after the 1991/1992 drought, mean relative growth rate was 2.8% year(-1), which after 5 years only achieved ca.32% recovery of the pre-1991/1992 drought cattle population. (C) 2001 Academic Press.