Dynamics of hypotrophic changes in the morphological formations of the ovaries of heifers of mating age on the 7-9th day of luteogenesis

Real-time in vivo studies of the physiological or pathological state of the ovaries of cows and heifers are currently relevant because it is the morphological and functional state of the gonads of female cattle that directly affects the effectiveness of biotechnical procedures used in practice: fertilisation, stimulation, and synchronisation of sexual function. The purpose of this study was to find the quantitative and qualitative indicators of the morphological and functional state of the ovaries of Ukrainian red dairy heifers during the economic year under loose housing conditions of industrial dairy complex. The study used a modified differential diagnosis of the morphometric and functional state of the ovaries at a fixed time of the sexual cycle – from 7 to 9 days after ovulation of the dominant follicle (Day 0 of the cycle). To compare the results of transrectal examination of heifers in different seasons of the year, the technique of visualisation of palpation data in vivo was used. 175 heads of heifers of mating age were examined, among which on the 7-9th day of the sexual cycle, 55.42% were found to have a palpable corpus luteum in the ovary according to the stage of development, 26.96% had premature lysis of the corpus luteum, 8.57% had morphological and functional formations on the surface of the ovary, and 9.14% had symptoms of degenerative gonadal pathologies. Subsequently, animals with degenerative changes in the ovaries (follicular kytosis) did not take part in the study. The remaining heifers had ovaries with symptoms of indepth hypotrophic changes in the tissues (30.00%) or signs of premature lysis of the corpus luteum (33.33%). During the economic year, a pronounced dynamics in the growth or decrease of hypotrophic phenomena in ovarian tissues was noted; the best indicators of morphometry and functional activity of heifers were observed in the warm season, which indicated a considerable effect of fresh air and solar insolation on the sexual function of heifers of mating age. It was found that the level of fertility of heifers during the year (an average of 40.02%) indicated the presence of errors in the technology of growing replacement stock in an industrial enterprise. The findings can be useful for optimising the schemes of hormonal synchronisation of the sexual cycle of replacement heifers and for the correct selection of hormonal therapy in case of symptoms of decreased sexual activity