The aspects of reasonableness in developing the line breeding strategy at the current status stage of dairy breeds and its significance as a factor for genetic variability have been reported. The value for milk production of the first-calf heifers within the line-bred pedigree Red-and-White cattle is estimated. Particular characteristics of the progeny produced from mating in the inbred and crossbred lines are recorded. The lower trait variability of traits was found with selecting within the crossbred lines than that in the inbred lines. Thus, the variables for the milk yield, the mass fraction of fat (MFF) in milk, and the mass fraction of protein (MFP) were less by 4–13% of the mean square deviation, 11,3–20,6%, and 14,3%, respectively. Livestock breed differentiation between the breeding lines was previously executed with the artificial elements of isolation systems. At present, the breeds widely distributed in the Russian Federation are usually “improved” with the use of Holsteins. Therefore, their genealogy and breeding structures depend on the foreign gene pool. Selection strategies for the improvement of milkability traits were implemented along with selection of bull sires capable of improving the conformation. In addition, certain herd bulls were used repeatadly. The variables for genetic values for milkability traits, which changed over time, were monitored. The herd milk production within the lines over a generation increased by 624–786 kg milk (P<0,001), while the MFF deacresed by 0,18–0,25% (P<0,001). Depending on the types of breeding, the differences in the milk yields and the MFF of the first-calf heifers between the lines comprised 178–444 kg (P<0,001) and +0.01%, respectively. However, a statistically significant difference between the lines was recorded only for the MFP, which comprised 0,03% (P<0,001).
Evidence for use of both capital and income breeding strategies in the mangrove tree crab, Aratus pisonii
