ISSN 2756-3707
International Journal of Histology and Cytology ISSN 2756-3707 Vol. 13 (1), pp. 001-009, January, 2025. Available online at www.internationalscholarsjournals.org © International Scholars Journals
Full Length Research Paper
Analysis of Genetic and Environmental Trends in Dairy Cattle Improvement Programs: A Study in the Central Tropical Highlands of Ethiopia
Kefena Effa1, Zewdie Wondatir1, Tadelle Dessie2 and Aynalem Haile3
1Ethiopian Institute of Agricultural Research, Holetta Agricultural Research Center, P. O. Box 2003,
Addis Ababa, Ethiopia.
2International Livestock Research Institute (ILRI), P. O. Box, 5689, Addis Ababa, Ethiopia.
3International Center for Agricultural Research in Dry Areas, P. O. Box 5466, Aleppo, Syria.
Accepted 30 November, 2024
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.
Key words: Genetic trends, environmental trends, genetic parameters, breeding objectives, variance components.