The assessment of breeding value of first calving holstein - frisian heifers by applying selection index methodology
2021
Lazarević, Marina | Maksimović, Nevena | Mićić, Nenad | Marinković, Miloš | Pantelić, Vlada | Nikšić, Dragan | Stanojević, Dragan | Škrbić, Zdenka
The research was performed on Holstein-Friesian and Black and White cattle, reared on farms of Agricultural Corporation of Belgrade - PKB. The study included 5238 first calving heifers reared on 6 farms in the period from 2006 - 2014 and represent progeny of 61 bulls. The following dairy traits were analysed in a standard lactation (305 days): milk yield (kg) - MY, milk fat content (%) - % MF, milk fat yield (kg) - MFY, protein content (%) - % PC and protein yield (kg) - PY. The relative economic weight of milk traits included in selection index is expressed through single standard deviation. The first calving Holstein - Friesian heifers, in standard lactation produced on average 7765.35 ± 1401.80 kg of milk, with a milk fat content of 3.49 ± 0.22 and protein content of 3.23 ± 0.13. The impact of bull, farm, year and season of calving on the variability of milk traits was present at the level of very high statistical significance, while the genetic group did not influence the variability of yield and protein content, however it influenced other milk traits at different levels of statistical significance. Heritability of observed milk traits was medium to low. The content of milk fat and protein had the lowest values of heritability, 0.052, and 0.042, respectively. The heritability of milk yield was 0.305. Negative genetic correlation were determined between milk yield and milk fat content (-0.380), also between milk yield and protein content (-0.500). Coefficient of correlation of selection index and aggregate genotype was 0.3829.
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