UDC 636.082.22: 636.2.034
When improving breeding herds and developing dairy cattle breeding programs, an important factor that must take into account the causes of animal disposal. Factors contributing to the occurrence of diseases in highly productive cows and their premature culling are the effects of the «transport», «traumatic», «alimentary» and «technological» stresses. What in the body of cows and heifers leads to a decrease in their resistance against the occurrence of various diseases. As well as factors contributing to the suppression of the immune system, impaired liver, kidney, digestive and respiratory systems are a number of environmental factors – the imbalance of diets with protein, carbohydrates, macro and microelements, vitamins. All this causes premature depletion, intoxication, violation of body functions, the occurrence of infectious diseases, culling or death of animals.
Intensification of dairy cattle breeding and breeding improvement of the herds in order to increase the productive qualities of animals leads to a significant reduction in the life of the cows. As a result, the average period of use of cows on dairy farms is limited to only 3-4 lactations.Considering that cattle has a biological cycle of development and reproduction that is long in time and complex in terms of physiological and economic structure, the problem of the duration of productive use of cows is particularly important in the intensification of milk production.To date, the issue of the early retirement of cows and the duration of their productive longevity remains unresolved. Recently, the duration of economic use has been reduced due to the culling of cows before they reach the age of the highest milk productivity.Given the problem of productive longevity of cows, the goal was to investigate the duration of economic use, lifelong productivity and their factorial conditionality in a herd of red steppe cattle of different lines.
We have found that it is not by accident that cows of different ages leave. That is, among uneven-aged animals, the cases of their rejection were associated with various reasons and had a certain dependence on age, confirmed by the calculation of the criterion χ2. The frequency of age-related retirement is described by a polynomial curve of degree 2 and adequately describes the culling of cows, namely, to 4 lactations, the culling intensity is low, and then with age the intensity of cows leaving sharply increases. Moreover, a certain relationship was established between the age of animals and the reasons for their culling. On the graph, this interdependence is in the form of a wave that oscillates around experimental points. And with an increase in the order of the polynomial, the number of maximum and minimum values of the approximating curve increases.
It has been established that the animals of the Cirrus line have the highest milk yield for the first lactation and an intermediate one for the third, and retain the constancy of milk productivity in the following years. The fat content in the milk of these cows is expectedly worse among peers, but the intergroup difference in this indicator is insignificant.However, the active culling of the representatives of the line is noted at the age of eight lactations and in a smaller number than in other groups, therefore the average number of calvings during their life is much more and amounts to 8.56.Analyzing the Arik line, in the first lactation, the lowest milk yield is noted, and by the fat content, on the contrary, the highest, but already for the third lactation, the milk yield significantly increases, the fat content in milk is at the average level in the sample. However, the representatives of this line are characterized by unstable milk productivity, their advantage over other groups of cows included in the study is not observed in subsequent years. According to the results of grading, they are subject to active retirement throughout their productive lives, especially since the seventh lactation.Comparing the efficiency of lifelong use of cows of different lines, we can conclude that with an increase in the period of economic use, the productive life of animals and, consequently, lifelong milk production is extended. Thus, during the study, the daughters of the Cirrus line did not differ in the high productivity of the compared groups of their peers, however, they kept it at an average level during the entire period of productive use, due to which they moderately exhausted their bodies and dropped out later than their counterparts. This allowed them to have the highest lifetime productivity.
Thus, the culling according to the rating data is the main reason for the departure of the bulk of the representatives of the Arica line, whereas in the Cirrus line, therefore, the smallest number of cows among the studied groups is eliminated. But the threat to these animals is a high level of injury. The number of animals retired due to the disease is almost equal in all experimental groups and is explained by the deficiencies of maintenance and care. It is no coincidence that retirement of cows of different ages takes place, that is, a certain dependence of the causes of retirement on age is established: at different age periods, cows drop out of certain causes. The duration of the economic use of cows has a certain dependence on their productive characteristics, namely, more productive animals deplete the resources of their body more quickly and, as a result, are subject to rejection faster. On the other hand, animals with a uniform, although slightly lower, manifestation of dairy productivity during life longer retain the ability for productive use and this is more advantageous from an economic point of view.
Keywords: retirement of cows, reasons for culling, productive longevity, duration of economic use, lifetime performance, coefficient of utilization of cows.
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