THE USE OF INTRA-LINE SELECTION AND LINE CROSSING IN DAIRY CATTLE BREEDING

The retrospective analysis allowed us to assess the effectiveness of various selection options (intra-line and line crossing) used in the Holstein breeding herd of Komyshuvatsky Dairy Complex LLC, Kharkiv region. The selection of sires, successors of the Chief line from both the paternal and maternal sides, did not improve the milk yield of the first-cows (7850 kg) compared to the cross of five maternal lines. The best variant in terms of milk yield of the first-calf cows was obtained from the inter-line cross of the Chief and Elevation lines (8143 kg). However, the insignificant difference in milk yield of the group of first-calf cows obtained from the intra-line selection of the Chief paternal line in comparison with the inter-line cross of the maternal lines (J. Besna, Bell, Marshall and Elevation), indicates the good combining ability of the sires of this line in inter-line selection. The largest number of offspring was obtained from breeding bulls of the Elevation line by intra-line selection with a first-calf cows producing an average milk yield of 8272 kg. A comparison of this group of first-calf cows with peers obtained through inter-line selection revealed unsuccessful combinations with peers of the maternal lines of Bell and Starbuck, showing differences in milk yield of 420 (P < 0.05) and 594 kg (P < 0.001), respectively. Crosses of the paternal line of Elevation with J. Besn, Marshall and Chief maternal lines by the first-calf cows milk yield parameter were on a par with peers obtained by intra-line selection with a milk yield higher than eight thousand (8054–8267 kg). Among the inter-line selection involving the paternal line Bell and various maternal lines, the most successful combination was the cross Bella × J. Besna, the first-calf daughters of which produced the highest milk yield of 8724 kg among all estimated animals, regardless of the selection methods. In second place there was the cross of Bell × Chief lines with a milk yield of 8407 kg. These two groups of successful inter-line selection demonstrate hereditary superiority over the offspring from crosses of the paternal line Bell with maternal lines Elevation, Starbuck and Valiant, respectively, that evidenced by significant difference in first lactation milk yield of 817–1067 (P < 0.05–0.001) and 500–750 kg (P < 0.05–0.01). The established reliable differentiation of milk productivity traits of first-calf cows depending on the selection options indicates the feasibility of monitoring linear breeding in the selection process for the productive improvement of dairy cattle, as a result of which the best options with the prospect of their use can be identified.