Comparative evaluation of milk productivity of Holstein cows different lines in different age periods

Many have studied the influence of Holstein cows in connection to lactation, as well as their linearity on milk productivity. The study of this problem relating to the Orel region is also very relevant and has practical value. The first-calf heifers of the Reflection Sovereign line had a significantly higher milk yield and were characterized by higher milk production rates than the first-calf heifers of the Vis Back Ideal line by 6.48 and 6.06%, respectively (P≤0.05). At the age of the third lactation, the Reflection Sovereign cows exceed the Vis Back Ideal cows in terms of milk yield and milk yield by 10.58 and 9.55% (P≤0.05). A significant margin of indicators of the amount of milk fat and the coefficient of relative fat content of cows of the Reflection Sovereign line was revealed over the cows of the Vis Back Ideal line of the first and third lactation age. The milk of first-calf heifers of the Reflection Sovereign line contained more milk protein than the first-calf Vis Back Ideal by 6.49% (P≤0.05). At the same time, the indicator of the coefficient of specific white milk production exceeded the indicator of first-calf heifers of the Vis Back Ideal line by 6.87% (P≤0.05). The amount of milk protein obtained from the experimental cows of the Reflection Sovereign line in the third lactation exceeded the indicator of the Vis Back Ideal peers by 10.48% (P≤0.01). A fourfold shape of the material is formed. By the second lactation, the cows of the Vis Back Ideal line exceeded the milk yield of first-calf heifers by 16.55% (P≤0.001). Indicators for the third and second lactation did not have significant differences than the milk yield for the fourth lactation by 7.3% (P≤0.05). The milk yield of cows of the Reflection Sovereign line in the second lactation significantly exceeded the milk yield of first-heifers by 10.95% (P≤0.01), and the milk yield in the third lactation exceeded the milk yield in the second lactation by 11.09% (P≤0.01).