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.

Improvement of technological elements of newborn calves keeping in beef cattle breeding.

The unprofitableness in the industry of beef cattle husbandry is associated with the death of newborn calves during the colostral period (calves have insufficient immune protection, which can be obtained only with timely use of colostrum) due to imperfection in the housing technology or its individual elements. We have been conducted two experiments: the first one -on calves and cows of the second calving, and the second -on calves and cows of the third calving and older. At revealing of a problematic cow-calf pair (cow's refusal of the calf or calf's refusal to consume colostrum) in 2017 and 2018, a new technological housing element was introduced in the experimental groups of animals -transfer of the problematic cow-calf pair to a separate correction section, for common housing to stimulate cow's maternal instincts or the calf's eating behavior. According to the data of the first part of our experiment, it was found that the number of problem calves received from cows of the second calving in first group was 2 calves, in second and third group -1 calf each, respectively. The live weight of problem calves at birth between the three groups was not significant. According to this indicator, calves from the first group had lower live weight by 1.5 kg compared to animals from the second group and by 1 kg compared to animals from the third group. The problem calves, which were transferred together with the cows to separate correction sections, reached the highest live weight when weaned, compared with animals kept under traditional farming technology, the preference was 63.3 kg and 64.8 kg, respectively. In general, in the experimental group, which included the problem calves, the calves' live weight at weaning showed a significant difference between animals of first and third groups which amounted to 6.2 kg (P > 0.95). According to data from the second part of the experiment, which was carried out on cows of third calving and older cows with offsprings, three problem calves were identified in each group. With a slight difference in the live weight of problem calves at birth, the advantage in this indicator during weaning was in animals of the second and third groups, which were transferred to separate correction sections, which amounted to 62.0 kg and 63.5 kg. Overall, a significant difference of 3.1 kg (P > 0.95) was revealed in weight during the weaning between first and third groups of calves. It was found that at transference of problem "cow-calf" pair into a separate correction section the survival rate of problem calves increased from 33-50 % to 67-100 %. Thus, by transference of problem cow-calf pairs into separate correction sections during the colostral period with year-round free-range housing, it is possible to increase the survival rate of problem calves and ensure their full-value growth.

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