Yakubets T. Improvement of the system of selection of rabbits in cross schemes

The dissertation presents the results of research aimed at improving the system of selection and selection of rabbits when working with various structural elements of the cross. As a result of the research, we obtained new data on the productivity, reproduction rates of rabbits of ancestral and parental forms of the cross. The theoretical data on the patterns of growth of rabbits in the postembryonic period of ontogeny were expanded and supplemented. The influence of males of the paternal form on the growth and productivity of rabbits of the maternal form of the cross was proved. For the first time, the use of males of the paternal line of the maternal form of the cross with different weight indexes to obtain highly productive rabbits of the maternal form of the cross was substantiated. The theoretical base of knowledge on the selection and genetic parameters of the rabbit population has been supplemented. New scientifically substantiated data on the effectiveness of using males of different genotypes as the paternal form of the cross to obtain rabbits of the final hybrid were obtained. The material of the research was rabbits of different structural elements of the Hyla cross - males of the paternal form, maternal line maternal form, males of the paternal line maternal form, maternal form, as well as young animals of the final hybrid. Also used in the experiments were males of the HyPlus cross parental form and purebred males of the Thermon White and Poltava Silver breeds. The research was conducted in two stages. At the first stage, we studied the efficiency of using males of the ancestral form of the cross with different weight indices, their influence on the productivity of rabbits and their daughters. The second stage of the research involved determining the effectiveness of using males of different genotypes as a parental form. The use of males with different weight indices affects the level of reproductive traits of maternal female rabbits of the maternal line of the maternal form. Rabbits that were mated with males with a weight index of ≥ 120 units had 2.2% higher fertility and 12.8% higher milk yield than their counterparts covered with males with a weight index of ≤ 100 units. The advantage in the level of reproductive traits in rabbits mated with males with a high weight index is confirmed by the calculated complex indices. It was found that the relationship between the multiplicity and large-fecundity of the rabbits of the ancestral form was medium inverse (r = -0.561 (p ≤ 0.05)), while between the indicated traits in the rabbits of the maternal form of the cross the relationship was strongly inverse (r = -0.841 (p ≤ 0.05)). The probable coefficients of heritability of milk yield (h2 = 0.07) and largefecundity (h2 = 0.21) of rabbits were obtained. The influence of males of the ancestral form on multiplicity was found to be 4% (p≥0.05), milk yield - 21% (p ≤ 0.001) and large-fruited - 18% (p ≤ 0.001). Studies of the effectiveness of the use of males of different genotypes as a parental form showed that the highest rates of multiplicity were in rabbits inseminated with sperm of Hyla Max males. There was no significant difference between the fertility of rabbits inseminated with Hyla Max males and Thermon White males. The analysis of the indicators of meat productivity of rabbits obtained from males of different genotypes indicates that rabbits obtained from PS59 males had the highest pre-slaughter, slaughter weight and weight of the longest back muscle. As a result of calculations of the economic efficiency of using males of the maternal line of the maternal form, it was found that the most economically feasible is the use of males with a weight index of ≥ 120 units. The maternal form of the cross, obtained from these males due to increased fertility and safety of rabbits, provide profitability of rabbit production at the level of 33.11%. It was found that the use of PS59 males as the parental form of the cross allows to obtain a profitability of 38.67%, which is the highest among the studied male genotypes. However, the profitability of using Thermon White males as the parental form was only 3.45% less. Given the cost of delivery of rabbits of foreign crosses, as well as the possibility of importing resistant diseases with them, we consider it advisable to use males of the Thermon white rabbit breed as the parental form of the cross.