Genetic analysis of reproductive and productive performance of Friesian cattle in Kenya. II. Genetic and phenotypic trends

Abstract

The Kenya Livestock Recording Centre progeny testing data base covering the period 1968 through 1987 was used to estimate genetic and phenotypic trends in Friesian cattle for milk yield of all lactations, first lactation milk yield, age at first calving, and calving interval. Annual genetic and phenotypic trends were estimated at 2.5 and 1.2 kg, -5.2 and -5.5 kg, -14.4 and 3.1d, and -.1 and .7d, respectively for these traits. None of these trends was significantly different from zero, except the genetic trend for age at first calving. There were differences in ranking of bulls. This was a possible cause of extensive use of genetically poor bulls at the expense of superior ones. However, high semen demand was the main cause of low genetic progress.