Hereditary and ecological patterns in the long haul dairy cows hereditary change programs in the focal tropical high countries of Ethiopia

Abstract

A total of 1979 lactation records from 550 selected crossbred dairy cows that born between 1974 and 2005
were used to estimate annual genetic and environmental trends in milk production and reproduction traits
at Holetta Agricultural Research Center, Ethiopia. Annual genetic and environmental trends were estimated
by regressing BLUP estimated breeding value on year of birth. Variance components and genetic
parameters were estimated using univariate analysis of individual animal model based on restricted
maximum likelihood procedures. Annual genetic trends were -3.384 days, - 8.00 kg and -5.96 kg, -0.26
months, -0.29 months and -0.88 days, for lactation length (LL), lactation milk yield (LMY), adjusted 305 milk
yield (305-days MY), age at puberty (APU), age at first calving (AFC) and calving interval (CI), respectively.
Environmental trends for LMY was positive (6.717 kg) and was in the desired direction. Heritability
estimates were 0.14, 0.44, 0.39, 0.38, 0.40 and 0.17 for LL, LMY, 305-d MY, APU, AFC and CI, respectively.
Negative genetic trends in all milk production traits reflect ineffective selection program and/or lack of
using sires that have positive breeding values. The result from the environmental trends shows substantial
improvement in the management practices over time. Contrasting directions in genetic and environmental
trends reflect ineffective breeding objectives. This warrants reconsideration of the existing breeding
program in the country.