Survival of Holstein-Friesian heifers on commercial dairy farms in Kenya.
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Herd health and adaptability are of concern in dairy herds in the tropics because of persistent exposure to multiple stresses of low quality and quantity feeding, heat stress, high disease and parasitic incidences, poor husbandry and breeding practices. The combined effect of mortality and culling is estimated to cause losses of 40 to 60% of dairy heifers conceived or born in the tropics. This study applies survival analysis techniques to evaluate important factors influencing survival to first calving in Holstein-Friesian cattle raised on large-scale farms in Kenya. On average, 25% of all the heifers born were culled prior to reaching first calving. Though the highest proportion of losses was due to unspecified reasons, the relative risk of being culled was highest when an animal had a specific disease, and survival was most critical within the first 60 days of life. Daughters of sires from South Africa and Israel tended to have better survival rates than those sired by bulls originating from other regions. When selecting sires for breeding, it is important for farmers in the tropics to consider information related to survival and fertility for stressful production systems.