Using the indicator “age of positive profitability” to assess the effectiveness of the productive life of cows
The work aimed to develop and test a phenotypic-economic indicated - the age of positive profitability (APP), reflecting the age at which the animal fully recoups raising and maintenance costs and begins to bnng profits. APP was calculated over a limited life span of a cow, equal to 2100 days, as the difference between the number of days lived and the ratio of the lifetime profit brought to the average daily profit for a productive life. Accorcling to the results of the calculations based on the APP values, all animals were divided into 3 groups: “from 0 and below”, “from 1 to 2100”, “from 2101 and above”. The most effective in terns of payback rates were the cows from the “1 to 2100” group. Evaluation of the relationship between the characteristics of productivity and fertility, as well as productive longevity and the economic efficiency of animals, showed that APP was maximally dependent on life-long milk yield (г = -0.91) and duration of productive life (г = -0.57). The duration of sereice penod and age of firet calving also affected productive life. The animals that reached 4-5 lactations within the 2100 days of the study showed the maximum efficiency when the age of firet calving and the duration of the serace penod decreased. Thek payback was higher due to a higher lifetime milk yield (г = -0.58), an increase in the total number of milking days (r = -0.85) and the number of lactations over a lifetime (r = -0.49). The developed APP indicated can be used to select the most effective cows by the complex of signs of milk productivity and fertility.