An important selection peculiarity of dairy cows is their productive longevity. Besides, the indicators of cow productivity along with genetic potential are the most important criteria of the economic efficiency of their use. Low or not sufficient level of lifetime productivity indicators and of the period of the economic use of cows determine the necessity of monitoring of the selection information according to these indicators in the breed herds as well as the of using corresponding selection methods for their improvement. The goal of our research was the estimation of an economic use of lifetime cow productivity of Ukrainian Black-and-White dairy breed depending on the reasons of their disposal from the herd and genotype. The research was conducted at a private agrarian firm (PAF) «Yerchyky» Zhytomyr oblast according to the data of breeding and productive use of 497 cows which were disposed from the herd on different reasons. The reasons for the cow disposal were determined according to the veterinary disposal acts. The indicators of cow economic use and lifetime productivity were determined on the ground of the term of rearing, life duration, term of economic use, amount of lactations, the total duration of lactation period, milk yields, milk yield per one lactation day, per life, and per economic use. Statistical processing was performed by means of Microsoft Excel software kit using the methods of variation statistics. As follows from the results of the research, in the process of holsteinization the dynamics of the parameters of the economic use of cows is characterized by curvilineal type: as follows from the heterotic effect they increased in animals with an conditional share of genetic heredity of Holstein breed from 50 and 62.5 to 75%, and then when the genetic heredity share of the improved breed increased by more than 75% they got worse due to the contradiction “genotype-environment”. At the same time within the determined genotypes (1st group-up to 50%, 5th group-87.6–100%) the indicators of lifetime productivity increase in case of 66% of reliable results. Besides, the interconnection level of the indices of lifetime use of the dairy cows of different genotypes has been studied. The criteria of the significance of the correlation coefficients according to Student has been used. The closer the linkage, the higher the correlation coefficients and the higher the criteria of their reliability. Generalized criteria of reliability on the grounds of all indicators of lifetime use was the lowest in cows of the 1st and 2nd groups, and the highest in cows of the 3rd group with further decrease in high half-bred cows and pure-breed cows of the 4th and 5th groups. It testifies to the fact that there is a close interconnection between given parameters and real milk yields in 3rd group cows (62.6–75.0% of the improved Holstein breed). At present, the reason of the shortening of the period of economic use is an early disposal of cows from the herd. A greater part of milking cows is disposed in the most productive period or even before it. At the given enterprise, a vast majority of holsteinized cows (77.5%) was disposed from the herd on four main reasons: unsatisfactory reproductive capability (32.2%), limbs diseases (22.3%), postpartal complications (13.9%) and low productivity (9.1%). The other reasons for cow disposal were within 1.6–7.0% (totaled up 22.5%) as to the total number of cow population that were disposed of the herd. It should be mentioned that the disposal caused by low productivity was only in the first calvers of the 1st and 2nd groups, in which the conditional share of genetic heredity of a Holstein breed did not exceed 62.5%. The parameters of the economic use and of lifetime productivity of Ukrainian Black-and-White dairy cows of different genotypes which were disposed of the herd because of their unsatisfactory reproductive capability, limbs diseases, postpartal complications and low milking productivity have been also analyzed. It has been determined that the indicated reasons for the disposal had different effects on the parameters of an economic use and on cow productivity. Because of any of four indicated reasons for cow disposal of the herd under condition of in-barn keeping and optimal feeding the preference on lifetime productivity belongs to the cows of the 4th and 5th groups (with a conditional share of Holstein heredity of more than 75%) with simultaneous worsening of the indicators of economic use. As a third part of cows at this enterprise was disposed of the herd ahead of time on the reason of unsatisfactory reproductive capability, that results in breeding value and in the results of the economic use of cows, the updating of the technology of artificial animal insemination and renewal will promote to solving the problem.
Production and body composition traits of broilers in relation to breast weight evaluated by path analysis
