Dairy productivity of the milking herd is one of the main indicators that characterize the effectiveness of dairy cattle breeding. Optimal internal and external factors of cow productivity are directly dependent on the dynamics of yields throughout the lactation displayed by the lactation curve. In production conditions, preference is given to cows whose yields curve is gradually increasing and decreasing evenly, what means such animals have high lactation activity. The high and steady lactation curve indicates the ability of cow withstand a long physiological load for a long time. The purpose of our work was to study the nature of lactation curves and lactation resistance in different cows’production types of Simmental breed.
Researches were carried out in agricultural limited liability company “Litinske” of Drohobych district of Lviv oblast on Simmental cows. A sample includes 161 mature cowbanes cows with the third full lactation. The distribution of cows into production types was performed by the method, described by Z. Aysanov.
It was found that cows' yields for 305 days of first lactation at average over the herd was 4358 kg, and in 305 days of the third lactation – 4850 kg. When dividing animals into production types we found that the highest milk yields for the studied lactation were characterized dairy cows. Lactation curves of cows of the studied production types were quite stable. They had the highest average monthly yields from the second to the fifth month of lactation, and the maximum yields were mostly in the third month.
The heifers and mature cowbanes of dairy production type compared to the same year cows of dairy-meat and meat-dairy types have higher monthly average milk yields. The minimum difference between the average milk yield per third lactation between dairy and dairy-meat and meat-dairy production types were observed at the first months of lactation, and the maximum – in the last. This indicates that animals of dairy production type lactation curves were more stable than the same year of different types. The best lactation activity of dairy production cows is show also indices calculated by different methods.
In particular, these animals are mostly have significantly higher values of indices of dairy constancy by H. Terner, lactation constancy by I. Yoganson and A. Hanson, the full value of lactation according to V. B. Veselovsky, A. Zhyrnov, lactation resistance according to J. I. Weller et al., lactation decline according to D. V. Elpatyevskyi and index of actation curve forms by P. Mahadevan.
A certain dependence of lactation resistance in cows of different production types was established on their age. In particular, dairy production animals had more stable third lactation, than the first. Higher lactation resistance of dairy cows shows only half of the calculated indices, and the meat-dairy type animals had more valuable first lactation.
The yields of the cows depends to some extent on the shape of the lactation curve. Among the animals of the production types under study, cows with a highly stable form had the highest yield lactation curve. The second position in this indicator had animals with a medium-stable lactation curve and lowest milk yields had low-stability lactation curve. However, it should be noted that significantly higher milk yields highly stable lactation curve was observed only in mature cowbanes dairy production type.
In order to choose the best method that will most objectively allow to establish individual and group characteristics of cows by nature of lactation activity, we calculated the coefficients of correlation of yield with the indices that characterize lactation activity of cows of different production types. Correlation analysis showed that between lactation yields and indices calculated by H. Terner, V. Veselovskyi, and A. Zhirnov and J. I. Weller et al., exists mostly a positive high-quality correlation. These indexes are the most predictive about the nature of lactation activity of cows of the studied production types. The lowest values correlation coefficients, and in some places negative indices, are noted between animal yields and indices, calculated by I. Yohansson and A. Hanson, D. V. Elpatyevskyi, and P. Mahadevan.
It is established that the character of lactation activity of cows is influenced by their belonging toproduction type. This factor both heifers and mature cowbanes had greatest affected at the constancy of the yield by H. Terner (63.7 and 32.0% of the total phenotypic variability, P < 0.001), the value of lactation according to V. B. Veselovskyi and A. Zhirnov (73.4 and 34.5%, P < 0.001) and lactation resistance according to J. I. Weller et al. (41.9 and 31.3%, P < 0.001).
Antagonism in the carbon footprint between beef and dairy production systems
