<p>It was estimated the conversion of feed into milk, content of urea, fat, protein, somatic cells in the milk of cows of different breeds in different seasons and months of the year. It was established that the peculiarities of the organization of feeding process significantly influence the productive indicators. Thus, in the conditions of a modern milk complex for 1500 cows with an unattached system of keeping in boxes and feeding with the use of mixed rations, the average value of feed conversion (the measures of digestibility of the feed when it "converted" into dairy products) is 1.38 kg of milk per kilogram of dry matter of<br />feed, and the ratio of fat to protein is 1.10, which is lower than the existing standards. It was established that changes in the conditions by months of the year significantly influenced practically all analyzed qualitative characteristics of milk. And this fact entails the corresponding monthly fluctuations of indicators of safety of products, emissions of by-products of metabolism, and, consequently, fluctuations of dairy cattle breeding impact on the environment and ecology. It was found that milk yield positively and significantly (P≥0.999) correlated with the consumption of feed dry matter (r = 0.454) and feed conversion rate (r<br />= 0.547). At the same time, the milk yield is negatively related to the fat content (r = –0.211) and the protein content (r = –0.192) in milk. The level of urea in milk positively correlates with the content of protein in milk (r = 0.130; P≥0.99). The influence of the factor "breed" on the following important economic-useful traits such as daily milk yield (η2 = 0.131) and feed conversion rate (η2 = 0.130) are proved.</p>

Introduction. At the present stage of livestock development in Ukraine, rabbit breeding as a sub-sector of livestock that meets the needs of society in dietary meat, fur and furs develops rather unstable, which is associated with numerous problems, the unsatisfactory level of breeding. Rabbit breeding features such as live weight, growth rate, meat yield, etc. are required to be improved. This will increase the production of valuable meat products rabbit meat. The main indicator of meat productivity of rabbits is their live weight. It is this sign of breeding that is the main factor in obtaining more meat.  The increase in live weight is associated with the biological ability of rabbits to intensive growth, which is characterized by daily increments. It is proved that in rabbits of specialized breeds of meat – New Zealand and California – the highest average daily gain is observed in the age from 20 to 135 days and makes up 35 g, while in rabbits of meat-and-fur breeds in the period from 45 to 150 days is 30 g. The studies confirm the existence of a connection between body measurements and live weight of rabbits, in particular between the chest and livestock weight between 0.45 and 0.56 and between the width of the lumbar and the live weight of 0.44–0.55, as well as a reliable positive the correlation between the width of the lower back and the slaughtered level at the level of 0,35–0,83, which makes it possible to increase the meat productivity due to the selection of rabbits with a wider width. According to the recommendations for working with the "HYLA" cross, the rabbit of the final hybrid in certain age periods should have the following values of live weight: when weaning at 35 days – 950–1050 g; at the age of 42 days – 1150–1400 g; at the age of 56 days – 1800–2300 g; at the age of 70 days (when slaughtered) – 2350–2650 g. The average daily gains of rabbit from weaning to slaughter, according to recommendations, should be from 43.5 to 47.5 g. The relevance of the work is in the studying of weight and linear growth of rabbits will reveal the most valuable genotypes of rabbits that are capable for intensive growth and production of enough valuable rabbit meat and allow to efficiently control the process of rabbit production. Purpose. The purpose of the research is to study the intensity of the weight and linear growth of the rabbits of the final hybrid of the "HYLA" cross, depending on the live weight of their father. Materials and methods of research. Studies of the weight and linear growth dynamics of the rabbits of the final hybrid of the "HYLA" cross were conducted in the conditions of LLC "Krolikoff" of Cherkasy oblast. For the experiment, there were formed 5 groups of rabbits, which were obtained from various male-female parents of the parental form of HYLA MAX and females of the HYLA NG cross type "HYLA". Dynamics of weight and linear growth of rabbits was studied after they were weaned from the mother. The following indices were determined: live weight, straight length of the body, chest circumference, shoulder width, lumbar width. To determine the type of body structure of animals, the mortality index was calculated, which is equal to the percentage of the chest circumference of the shoulders to the straight length of the trunk. Volume of ejaculate of males was determined according to zootechnical records. The live weight, the body size of the rabbits and the index of infirmity were determined in the corresponding age periods – 35, 56 and 70 days. The dynamics of animal growth was determined by absolute and average daily increments of live weight and body measurements.  Biometric processing of the obtained results was carried out using the PC in the MS Excel spreadsheet using the accepted techniques. Main results of research. At the age of 70 days, the highest value of live weight was found in the V-grope rabbits, which outweighed the young rabbits of the II group in 163.95 g (p < 0.001). Rabbits of I, III and IV groups have 0.45, 6.55, and 30.94 less live weight, compared to the young group V. In the chest circumference of the rabbit's shoulders of group I, the youngest of the group V was 0.81 cm dominant (p < 0.01). The width of the waist in the rabbits of this age was in the range from 5.14 (group IV) to 5.24 (V group). Obvious difference between these groups on this basis was not detected. In the period from weaning rabbits to slaughter, the young rabbits of V group were characterized by the highest absolute increments of live weight and width of the waist – 1590.01 g and 1.70 cm respectively.  However, with an absolute increase in the direct length of the trunk, the rabbit of the group I were ahead from those in group II by 0.94 cm (p < 0.001), while the young II group was 1.71 cm higher than the IV group (p < 0.001). It should be noted that for these characteristics, low and average coefficients of variation are observed during this period. By studying the average daily increments in live weight and rabbit weights from weaning to slaughter, it was found that the rabbits of the V group were characterized by the largest increase in live weight gain and dominated by analogues from the second group to 2.86 g (p < 0.001).  During this period, the direct length of the trout body of the I group was increased most intensively – the average daily gain of the sample was 0.34 cm, which is 0.03 cm more than the young of the second group (p < 0.01). For the period from 35 to 70 days of age, the coefficients of variation of average daily increments in live weight and body weight of the rabbits were low and average, indicating the consolidation of the studied characteristics in the crossbars of the final hybrid of the "HYLA" cross. Conclusion. The results of the conducted studies provide the opportunity to state that the rabbits, which are characterized by high growth intensity from weaning to slaughter, were obtained from the most-live-weight mass (26301 – 7.12 kg) (AP = 1590.01 g, SDP = 45,43 g), whereas the offspring of a male with a close to average live weight (No. 26351 – 6.90 kg) has the lowest rates of growth (AP = 1489.88 g, SDP = 42.57 g).  In general, the weight and linear growth of the rabbits of the final hybrid is at a high level and complies with the recommendations for working with the "HYLA" cross.

The maternal form of modern rabbit crosses is obtained by crossing ancestral lines. Therefore it is relevant to investigate the effect of using males of the parental line of the Hyla cross with different weight indices on the performance of the main breeding traits of the female rabbits of the parental form of the cross. The purpose of the study was to investigate the level of productivity of rabbits of the maternal form of cross by reproduction signs and to consider the dynamics of the main breeding traits for a number of births. The experiments used 223 rabbits of the maternal form of the Hyla cross, which came from males with different weight indices. To achieve this goal, groups of rabbits were formed, depending on the value of their father's weight Index – Group 1 – ≤ 100 units, Group 2 – from 100 to 120 units, Group 3 – ≥ 120 units. The live weight of rabbits after kindling, multiparity, the weight of newborn rabbits, milk yield, and the live weight of rabbits at the time of weaning were determined. Female rabbits that came from males with a high weight index at first kindling significantly outnumbered their peers in multiparity by 1.16-1.23 animal units (p ≤ 0.05), and in milk yield – by 6-6.5%. Rabbits whose parents were males with a high weight index according to the results of the 3rd kindling prevailed over their peers from other males in multiparity (p ≤ 0.05), milk yield (p ≤ 0.05), and also had significantly higher values of complex indices (p≤0.05). From the 1st to the 3rd kindling, the multiparity of rabbits increases, on average, by 6.5%. Live weight at birth of rabbits in Groups 2 and 3 had a positive trend and increased by 3.2% and 4.2%, respectively. On average, the milk yield of rabbits increased by 38.6% from the first to the third kindling. The practical significance of the results lies in the fact that to obtain highly productive rabbits of the maternal cross form, it is advisable to use males of the ancestral form with a weight index ≥ 120 units

Introduction. Rabbit meat production can be an important element in solving the problem of lack of dietary protein for the growing human population all over the world, especially in developing countries. Compared to other types of animals, the advantage of rabbits is that rabbit meat has a high protein content and low fat and cholesterol content, has excellent taste qualities, and is a product of healthy and dietary nutrition. Using crossbreeding increase the productivity of rabbits due to the effect of heterosis. However, taking into account the fact that the modern technology of industrial rabbit breeding involves the use of rabbits of various crosses, which are imported into our country, there is a need to investigate the possibility of using males of different genotypes as the parent form of the cross and their influence on the reproductive characteristics of female rabbits. Thus, the purpose of the study was to study the selection characteristics of males of different genotypes and the effectiveness of their use as parental forms of the cross. Materials and methods of research. The research was carried out in the conditions of "Krolikoff Farm" LLC, which is located in the Uman district of the Cherkasy region, during 2022. The research was conducted using males of four genotypes: males of the parent form of the Hyla – Hyla Max cross (HM, n = 15), males of the parent form of the Hyplus PS59 cross (PS59, n = 15), males of the Termon white breed (TB, n = 12), males of the Poltava silver breed (PS, n = 9). Males were used on female rabbits of the maternal form of the Hyla – Hyla NG cross, from which 4 groups were formed, depending on the genotype of the breeder, with the sperm of which the female rabbits were inseminated. Females of group I were inseminated with sperm of Hyla Max males, group II – Hyplus PS59, group III – Termon white breed, group IV – Poltava silver breed. The females of the experimental groups were similar in age, live weight, and number of hatchlings. Research results. Analyzing the results of research on the productivity characteristics of males of different genotypes, it was established that males of the Hyplus PS59 parental form had the highest live weight, it was 0.41 kg more (p ≤ 0.001) than males of the Hyla – Hyla Max parental form. The live weight of the males of the Termon white breed was 14% lower (p ≤ 0.001), and that of the males of the Poltava silver breed was 18% lower (p ≤ 0.001) than that of the Hyla Max males. This fact can be explained by the implementation of directed selection work with males of the original lines of crosses based on live weight indicators. Hyla Max males had the highest ejaculate volume values. However, it should be noted that the males of the Thermon white breed were slightly inferior to the males of the parent form of the Hyla cross in terms of this indicator. Males of the Poltava silver breed had the lowest value of ejaculate volume. As a result of the research, it was established that female rabbits inseminated with the sperm of Hyla Max males had the highest litter size. Rabbit does inseminated with PS59 males had 5.6% lower fertility than female rabbits inseminated with Hyla Max males, and rabbits inseminated with Termon White males had a 6.9% lower fertility rate. The highest value of high fertility was recorded in female rabbits inseminated with the sperm of PS59 males. There was no significant difference between the high fertility of female rabbits on which Hyla Max males and Termon white males were used. Female rabbits inseminated with males of the Poltava silver breed had the lowest fertility. Conclusions. According to the results of the conducted research, it can be stated that the most effective as a parent form of the cross is the use of Hyla Max males, however, the use of males of the Termon white breed of rabbits as a parent form of the cross is expedient due to the high cost of imported cross males. At the same time, the productivity of female rabbits remains at a high level, and according to some signs, female rabbits on which cross males were used prevail.