Influence of stress resistance on technological and productive qualities of cows

Abstract

The paper presents the research results on the level of stress resistance influence on technological indicators of udder, component structure of milk and reproductive ability of the Ukrainian Black-and-White dairy cows. The relevance and practical significance of the research is in fact that only constitutionally strong and stress-resistant animals can be healthy and high-producing. The scientific novelty is resulted in the study of energy characteristics of cows and fluctuations in the component composition of milk of different stress-resistant cows at different times of the day. The method of dividing cows into groups was used taking into account the minutely milk flow during milking cows by "unfamiliar milkmaid". The level of inhibition of the lactation reflex caused by sudden changes of milking conditions was determined, in particular, pre-milking udder preparation and milking cows by an "unfamiliar milkmaid", i.e. an experimenter, which can cause retardation of the lactation reflex. Due to the formation of experimental groups from half-sibling cows, the variability of indicators based on the influence of genetic factors is minimized. It is established that stress-resistant cattle are more technological and productive. Factorial analysis revealed the effect of stress resistance on the functional parameters of the udder of cows. It was found that the impact factor is 27.60% on the duration of milking (P> 0.99), 55.66% on milking during the first minute (P> 0.999), 25.53% on milking during the first three minutes (P> 0.99), 40.40% on the average milking rate (P> 0.999), 32.52% on the maximum milking rate (P> 0.999), and 69.57% on the intensity factor of milk flow inhibition (P> 0.999). The qualitative composition of milk under the influence of technological stress has changed in both experimental groups. However, acute fluctuations were observed in stress-sensitive cows in terms of fat milk yield by 0.11%, protein milk yield by 0.08% and dry matter content by 0.11%, compared to stress-resistant peers. Stress-resistant animals released more energy with milk by 4.03 MJ per day (12.6%; P> 0.999); they had a higher energy index by 3.26% (P> 0.99), spent less energy on synthesis of milk with energy value of 1 MJ by 0.19 MJ (8.3%; P> 0.95) and released more energy with milk per 1 kg of metabolic mass by 0.038 MJ (12.1%; P> 0.99).