Genetic Parameters of Libyan Dairy Cattle

heritability, repeatability, and genetic and phenotypic variances for milk yield 3.5% FCM, fat yield and fat percentage in Libyan Holsteins were estimated by lactation using a derivative free; iterative algorithm of REML (MTDFREML). The animal model contained herd-year, calving month, age at calving, permanent environment and animal effects. In all cases, the inverse of the additive genetic relationship matrix was included. Separate estimates were obtained from records projected to 305-d basis and unadjusted data for lactations one through four. Heritability were higher for the average of first and second lactations than separate first and second lactations. Heritability, repeatability and variances for milk yield, fat corrected milk yield (FCM) and fat yield were within the range of values from temperate areas, but those for fat percentage were lower. Age at calving follow patterns similar to those of more temperate areas. There is adequate genetic variance in Libyan dairy herds to make large genetic gains in milk production through conventional selection methods. Genetic parameters are a characteristic of the population in which they were estimated and may change overtime due to selection and management decisions .Therefore, these production traits may be preferred by breeders as selection criteria for development of effective genetic improvement programme.