Evaluation of highly productive cows by selection and genetic parameters

Abstract

Under the conditions of intensive technologies used in production of livestock products, the main selection feature that characterizes the economic feasibility of dairy farming and breeding value of animals is milk productivity. One of the factors that affects, not only the economy of production, but also the improvement of herds and breeds of cattle, is the use of highly productive cows. Therefore, the aim of our research was to assess the level of development of productive traits in Holstein cows under the conditions of intensive milk production technology, according to selection and genetic parameters. To conduct the study, a group of 1089 first-born cows was formed with the help of the Dairy Comp program and Microsoft Excel. The material for the research was the milk productivity of Holstein cows during the first three lactations. The level of development of selection traits in animals was determined by selection and genetic parameters. It was found that from the sample n = 1089 to the group of highly productive animals (“>10560”) were included 266 cows, and low-productive animals (“<8706”) – 249 first-borns. They had an average milk yield for the first lactation, 11439 kg of milk with a fat content of 3.96 % and 7737 kg of milk and 3.95 %, respectively. There is a difference in milk yield, milk fat and protein between the groups of cows “>10614” and “<8706”, but there is a general tendency towards changes in productivity with age. Based on the data of milk recurrence and the amount of milk fat of high-yielding cows (group “>10614”), it was found that higher values of the coefficient are characteristic of lactations I–III (rw= 0.105; rw= 0.135). As a result of comparative analysis it was found that low-yielding animals (group “<8706”) were characterized by higher recurrence rates for I–II and I–III lactation (rw = 0.345;rw = 0.316;rw = 0.320 and rw = 0.664;rw = 0.646;rw = 0.651, respectively). Higher rates of recurrence of traits of milk productivity are the characteristic of low-yielding cows (group “<8706”), i.e. they had more consistency of traits during different lactations and animals with a high level of productivity did not differ in age constancy. At a high level of milk yield in cows of group “>10614” appeared a negative correlation of low and medium level (r = -0.423). It was also found a negative correlation of low and medium level between milk yield and protein content in milk (r = -0.007… -0.332). At lower milk yields, there is no negative correlation between milk yield and fat content in milk. Thus, the existence of a negative correlation between milk yield and fat content in milk at a high level of animal productivity, and between milk yield and protein content in milk at both high and low levels of cow productivity was proved.