Veterinarija ir Zootechnika

This study focuses on enhancing daily milk yield (DMY) in the Saharan environment by exploring the relationships among milking frequency, heat stress, and lactation stage in 187 Holstein dairy cows in the Saharan Ghardaia region over a 12-year period. Key findings indicate that milking three times daily boosts DMY by about 22.67% compared with twice daily milking, with this increase being most significant (P < 0.0001) in cows during their second and third lactations. The temperature-humidity index (THI) plays a pivotal role in DMY. The study shows that the best milk production occurs (P < 0.0001) at lower THI values (below 74), underscoring the importance of optimal environmental temperature and humidity for maximum milk yields. Cows exposed to these lower THI values and milked three times daily achieve the highest milk production (+25%). Thus, combining the right THI conditions with increased milking frequency can significantly (P < 0.0001) enhance milk production. Effective heat stress management is also crucial for optimal milk yields. The study recommends practical strategies like offering sufficient shade, ensuring good ventilation, and giving cows access to cool water. Adjusting their nutrition during high heat stress periods is also vital. Moreover, the timing of milking sessions, especially during the cooler parts of the day, is a key factor in milk production. In conclusion, the research highlights the intertwined roles of various factors, especially milking frequency and THI, in determining the DMY of dairy cows in Saharan areas. It supports the implementation of improved management practices to counter environmental challenges and maximize milk production in such demanding environments.

The purpose of this study was to compare the effects of high temperatures on the behavior, comfort and thermoregulation energy consumption of cows at free-stall keeping in two barns. The first barn had the system of forced ventilation and air irrigation, and the second one had only fans. Barn parameters were (Length × Width × Height) 94 × 32.1 × 10.5 m. The research was conducted in central Ukraine (Kyiv region) during July 2021. The average daily ambient temperature during the study period was +26.4°C. In each of the barns, the groups of similar of non-pregnant and lactating animals (107 ± 14 days in milking) of Holstein breed were formed. Cows were fed the total mixed ration twice a day in both barns. Hours of air cooling elements operation in the barns were from 10.00 to 18.00. The use of fans in combination with irrigation systems during hot periods had a positive effect on the heat transfer of cows compared with the heat transfer of cows that were in the barn with fans. With this combination, the temperature of the skin and the resting place under the lying cow and energy consumption for heat production were 0.5°C and 0.8°C and 3.1 MJ lower. In addition, this combination of air cooling systems had a positive effect on the duration of lying down and eating food (32 and 16 minutes longer, respectively), and the indicators of standing time, physical activity and drinking were lower by 16, 21 and 6 minutes, respectively. Accordingly, the best values were the cow comfort index (CCI), stall use index (SUI) and cow feeding index (CFI) (4.78, 4.87 and 0.08). In terms of stall standing index (SSI), stall perching index (SPI) and cow drinking index (CDI), slightly higher rates were observed in the barn using fans only (3.72, 1.06 and 0.013).

The purpose of this review is to examine the scientific literature on the effects of heat stress on some physiological, productive and reproductive parameters in dairy cows. The article analyzes the scientific papers in which the influence of heat stress and its impact on some indicators is studied. As a result of the review, it became clear that heat stress has an impact on the studied indicators, but there are no clear criteria at which values of temperature-humidity index (THI) this effect is registered. The relationship between heat stress, productivity, successive lactation and physiological and reproductive parameters in dairy cows is still controversial. This poses a challenge, through research, to solve the problems in regards to high temperature and animal welfare and productivity for specific climatic conditions.