The interconnection between the first calving age and milk yeild of the dairy red cattle

Purpose: A regression analysis was used to study the relationship between age at first calving and lactation duration with first-lactation milk production indicators for subsequent consideration in breeding index modeling. Materials and Methods. The study was conducted using the SELEX-Dairy Cattle information database from 18 breeding farms breeding dairy red cattle. Over 12 000 records of cows that comleted their first five lactutions from 2018 to 2023 were analised. The relationship between the characteristics was determined by calculating the regression coefficient in programm "Statistica". After determining whether the sample conformed to the normal distribution, milk production data from 10,284 cows were used in the calculation. The average milk yield of first-calving cows in the sample was 5,683 kg, with a fat content of 4,13 % and a protein content of 3,26 %. The first calving age in the sample group was an average of 32,2 month. The average lactation duration for cows that completed their first lactation was 359 days. Results. The study showed that the age increase of the first cows calving age impacted negatively on milk yield over 305 days lactation period, reducing it by 25,4 kg per month based on average observations during 5 years. A decrease in milk fat yield by an average of 2,0 kg and milk protein yield by 0,3 kg was observed. The age of the first cows calving showed the most significant impact on cows dairy productivity, that completed their first lactation in year 2022: with a one-month increase in age at first calving, milk yield decreased by 110 kg over 305 days lactation period, milk fat yield by 6,6 kg, and milk protein yield by 3,4 kg. The age of the first calving of cows, that were under our examination, was more than 26 months, which significantly increases raising costs.