Phenotypic and genotypic characteristics of the milk yield of Bulgarian Rhodopa cattle for first lactation
2008
Gadzhev, D. | Nikolov, V.
Phenotypic and genotypic characterization of the milk production traits at the first lactation of the Bulgarian Rhodopa cattle - BRC was made based on the breeding records from the bull producing herds. It was found that the average milk yield of the first lactation calves for 305-days lactation period was 2701 kg, with a fat percentage of 5.122%, and protein content – 3.710 %. The relative milk yield per 100 kg live weight for a normal lactation period was 900 kg, and the corrected yield to the basic fat content - 3.6 % – 1281 kg. A basic problem for the milk productivity of the BRC was the shorter period of lactation – 257.6 days on average, and the tendency for change of the trait was unfavourable. The basic traits which characterize the milk productivity of the BRC cows showed first lactation heritabilities h2 = 0.300-0.398. The genetic variability of the lactation length – h2 = 0.076, was lower. In general the phenotypic, non-genetic and genetic correlations between the traits which characterized the first lactation milk productivity were in favour of a decrease in the number of the selected traits when selection indices were constructed.
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