Abstract Dairy farming is one of the most important branches of animal husbandry, as it provides essential food products to the population and raw materials to milk processing enterprises. The study was aimed at investigating how the conditions of keeping and feeding with complete monomixes affect the level of milk productivity of Holstein first-calf heifers during first lactation period. The animals in the experimental group were kept in a microclimate controlled cros-barn, while those in the control group were kept in a pavilion-type barn with natural ventilation. The intensity of lactation in the first half was analysed and it was found that in cows of the experimental group, the yield per 100 days and on the peak day of lactation was, respectively, 103.3 kg (p 9643 kg) had a longer period of reaching peak lactation. This indicator exceeded the duration of the same period in cows from the groups with productivity “<8423” and “8424-9642” by 20.3 (p < 0.001) and 5.9 (p < 0.001) days, respectively. In addition, within the experimental group, cows with shortened, average, and prolonged reproductive cycles had higher milk yields during the first 100 days of lactation – by 94.0 kg (p < 0.001), 115.6 kg (p < 0.001), and 93.4 kg (p < 0.001), respectively, compared to their peers in the control group with a similar distribution of cycle duration. A summary of the results for the combined indicators showed that the animals in the experimental group demonstrated better production and physiological characteristics compared to the control group. Thus, keeping Holstein cows in a cros-barn provides a comfortable technological environment that meets biological needs in the first half of lactation, minimises heat stress, and promotes the realisation of genetic potential for high productivity. The material is relevant for livestock breeders and technologists in milk production in industrial complexes
Pidpala et al. (2025) studied this question.