Improving the efficiency of breeding for fox's reproductive qualities advasing is associated with the selection of individuals with certain economically useful traits and evaluated for their ability to transfer and fix ones in subsequent generations. A combining ability of parental lines determination, as well as individual characteristics of animals, is paramount. The factors characterizing the contribution of each parents, as well as their combination with each other in the formation of the descendant's productive potential, are the combinational capacity components, which are disclosed on the basic fur animal farming of Kharkiv region. The analysis of six lines of the breeding core of silver-black foxes was carried out and the general and specific combining ability of maternal and paternal forms were determined by fertility. The probable influence of the specific combining ability of the combinations to the studied parameter was established, which allowed a clear differentiation of the lines according to the level of fertility: improvers, neutral and degraders. In addition to the obvious fundamental value, the information obtained is also important practical point of view. In particular, it was concluded that it is advisable to use individual representatives of the lines, as well as the most promising options for combinations of parental pairs. Using components of combining ability, outsiders are defined, which should be excluded from the further selection process. The actual research materials illustrate the results of dispersive analysis of differences in fertility of females, average fertility rates of combinations of maternal and paternal lines, combination capacity of lines, effects of general combining ability, constants and variants of specific combination ability of linear foxes.

The article presents the results of the study of the growth and development and reproductive abilities of heifers of different linear origin of the Znamyansky type Poliska meat breed Experimental research was carried out in the Agrofirma "Kolos" Znamyansky district, Kirovograd region. The object of research was the heifers of the Znamyansky type of different lines: I-control-animals, which are not included in the experimental lines, II-Mazun 6; III-Radyst 113; IV-Darovanyy 400. As a result of the carried out research, we found out that heifers of control and experimental groups at identical conditions of feeding and maintenance, have shown various intensity of growth. Heifers of experimental groups by live weight indicators in all age periods exceeded peers of the control group with a true difference. Among the experimental groups there was an obvious advantage for the animals of the third experimental group. The same tendency is observed in the indicators of the daily average and relative increments. High daily average increment of the animals of the third experimental group was 828,8 g per day during the period of 12-15 months. Comparing the body measurements of heifers of different experimental groups, we can note the advantage of animals of the III experimental group in all altitude and latitude parameters. The other three groups had lower and rather similar indicators. In general, the animals are quite large, harmoniously built, with a strong, but not massive skeleton, which is confirmed by the indicators of animal physique. By physique indexes the highest marks were given to heifers of III and IV experimental groups. They had higher indexes of physique such as breast, index of blockiness, which characterizes their better meat forms. The growth energy of animals in meat cattle breeding is an indicator that has a direct impact on reproduction ability, because a fully developed animal is able to reach puberty quite