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Influence of the first calving age on the cow productivity indicators
Bibliogr.: p. 92
Age at first calving is considered an important predictor of subsequent milk yield and is an extremely important economic trait determining the profit of cow milk production [1, 2]. Cow longevity and lifetime performance traits are good indicators of breeding effectiveness and animal welfare. They are also interrelated with the economics of dairy herd [3]. Our study aimed to analyze and to determine the influence of the first calving age on cow productivity. In the investigated farm, the cows were raised under loose-housing conditions in a modern cold-type barn throughout the year. Cows were fed a complete mixed diet that met their physiological needs. For the study, 362 cows with their completed first lactation were selected. According to the age of the first calving, the cows were divided into 4 groups according to the calving age: up to 22 months, 22.1–24.0 months, 24.1–26.0 months, and over 26.1 months. For the analysis of the data, statistical indicators (arithmetic mean, standard error of mean and statistical reliability of the data (P) were calculated for each evaluated trait. The obtained results were considered statistically significant when P < 0.05. The first calving age of cows ranged from 20 to 29 months, with an average of 23.7 months. We found that 1483.16 kg (P < 0.05) more milk was produced in cows of 22.1–24 months of age compared to the cows up to 22 months of age, and 300.35 kg milk more compared to the cows over 26.1 months of the first calving age. The milk fat content of the first-calved cows that calved before the age of 22 months was 0.16% (P < 0.05) higher than in the 22.1–24-month-old group of cows with the lowest milk fat content of all groups of cows. Milk protein content was the highest in milk of cows of calving under 22 months and in cows from 26.1 months of age; it was 0.1% (P < 0.05) higher than in the group of cows aged 22.1–24 months and 0.06% higher than in cows aged 24.1–26 months. The number of somatic cells in milk increased with the increasing first calving age. The number of somatic cells in the milk of cows that calved at age from 26.1 months and over was 137.71 thousand/mL (P < 0.05) higher than in the group of cows up to 22 months of age.