The negative effect of heat stress on dairy cows, with a temperature humidity index (THI) over 72, has been extensively studied. However, there are few studies on THI values under 72 that compare the effect of heat stress in different lactation stages. The objective of this study was to determine the heat stress effect on two lactation stages with a THI below the threshold 72. Thirty-nine multiparous, non-pregnant Holstein cows with more than 30 kg/cow.day of solid-corrected milk were used in a randomised complete block design to evaluate six treatments. The experimental design had a 3 by 2 factorial arrangement with three heat stress mitigation strategies: No shade (CON), access to shade only, and access to shade combined with sprinkling and ventilation, and two stages of lactation: early (S1) and late (S2), 12 ± 10.3 and 201 ± 45.8 days in milk respectively, for a duration of 81 consecutive days. All treatments, except CON had access to artificial shade from 0900 hours to 0500 hours next day. From 0500 hours to 0900 hours all cows were managed together in a grazing session. Additionally, sprinkling and ventilation cows had two 30-min sessions of ventilation and spray (0900 hours, 1530 hours). The average THI was 70.1 ± 4.46 (minimum THI: 60.4; maximum THI: 81.7) and the average hours above 72 were 7.8 ± 5.98. Animals in S1 presented higher solids-corrected milk reduction (P < 0.0001; 5.4 and 1.9 kg/cow.day), and protein yield (<0.0001; 0.13 and 0.54 kg/cow.day) than animals in S2 when shade was not allowed (CON). It was concluded that under these conditions, animal productivity is more negatively affected in early lactation animals. The use of shade with or without spray and ventilation mitigates heat stress effects on both stages of lactation.

The results of the influence of the conditions of keeping Ukrainian red dairy cows on the manifestation of clinical symptoms of damage to the lateral surface of the tibia and the level of reproduction are presented. The study was conducted on the basis of an industrial dairy complex (600 dairy cows with an average productivity of 6050 kg of milk per lactation) as part of agricultural associations in Odessa region. The objects of the study were cows during lactation, which were kept loose in sections with rest boxes (where the floor was a special rubber mat with a thickness of 30 mm). Evaluation (in points) was performed on the clinical manifestation of symptoms of damage to the skin epithelium of the lateral surface of the leg, which was injured by the rubber coating of the stall compared to the level of reproduction (service period, days/%) and the severity of skin pigmentation of the body surface (selection melanism). Clinical, zootechnical, biometric methods were comprehensively applied to realize the purpose of research. Comparison of data (n = 462) visual-clinical assessment of the condition of the skin of the lateral surface of the leg, as an indicator of the adaptability of lactating cows to keep in sections with rubber flooring and the area of pigmented hair of animals of different phenotypes by coat color, showed that cows typical pigmentation, characteristic of red dairy breed (red hair occupied more than 80 % of the body surface), wound lesions of the lower leg are much less common, namely: in comparison with red-spotted animals by 28.41–15.98 %, with mostly white – by 39.03–20.23 %, respectively. Due to the negative impact of open wounds of the skin of the leg on the immunity of lactating cows, it was found that increasing the number of animals with damaged epithelium as a gateway to infection, provokes an increase in the service period in cows with predominantly white or mottled color to 140.97 and 141.07 days, which is higher by 6.74 and 6.84 days, respectively, compared with red animals (P < 0.05).

-This study investigated the effect of a supplement containing whole rice bran and crude glycerin for 21 days before mating on metabolic, productive, and reproductive responses of 28 primiparous suckling beef cows. Cows were randomly assigned to a control group (CON, n = 14), grazing on grasslands, and a supplemented group (SUP, n = 14), grazing on grasslands and supplemented daily individually with 1 kg dry matter (DM) of whole rice bran + 550 mL crude glycerin (224 g kg −1 DM of methanol) per cow. After 33 days of natural mating, cows that had not expressed estrus were subjected to a fixed-time artificial insemination protocol. Ten days after the insemination program, bulls were reintroduced for 21 days. . The percentage of cows on superficial anestrous after supplementation was greater in SUP than in CON group (57 vs. 21%, respectively); however, no difference in final pregnancy rate was found (SUP: 79 vs. CON: 64%). There was no evidence that the ingestion of crude glycerin with high content of methanol induced clinical or hepatic disorders. Supplementation of whole rice bran and crude glycerin is not toxic, and can improve the energy balance, reflecting in increase in milk yield and calf growth, with a slight effect on the reproductive activity.

The article presents the results of a study of the efficiency of transcervical embryo transplantation obtained from donor- cows in vivo. The aim of the experiment was to compare the effectiveness of ipsilateral transfers randomized laterally from the uterine horn of embryos of different stages of development (blastocysts and morulas). The embryos were located in the left or right horn of the uterus of recipient heifers (n = 283 cows). It was experimentally established that the functional asymmetry of the ovaries of the recipients affects the level of survival of preimplantation embryos. Thus, in case of transfer to the left horn of the uterus of the recipients blastocysts 60.91% of pregnant heifers were found; morulas - 45.45%. In case of similar procedures in the right horn of the uterus - were found respectively 58.78% and 14.29% pregnant. The obtained results indicate the need for further scientific research to study the structural and physiological features that affect the survival rate of pre-implantation embryos.

The results of the influence of complex probiotic defence of the mucous membranes of the reproductive system and intestines on the development of the corpus luteum of the cycle in heifers have been presented. By the method of differential palpation diagnostics in vivo, it was reliably examined that in the experimental group after carrying out procedures for the normalization of mucous membranes with the multicomponent probiotic drug “Multibacterin Veterinary Ba + La”, the number of heifers with high-quality of corpus luteum the ovaries was 48.21% more, and the number of cases of premature luteolysis was 12.50 % less (P < 0.01). The level of pregnancy in heifers in the experiment was on average 60.38 %, in the control – 46.94 %, which confirmed the positive effect of the probiotic protection of the mucous membranes on increasing the embryo survival by optimizing the conditions for embryonic nutrition on the surface of the endometrium.