UDC 636.2.082.13
DOI 10.36461/NP.2026.77.1.018

AGE-IMPACT AT FIRST INSEMINATION ON ECONOMIC AND BIOLOGICAL FEATURES OF HOLSTEIN BREED
I.A. Vasyagin, Postgraduate; I.V. Kaeshova, Candidate of Agricultural Sciences, Associate Professor;
V.V. Lyashenko, Doctor of Agricultural Sciences, Professor;
A.V. Gubina, Candidate of Agricultural Sciences, Associate Professor
Penza State Agrarian University, Penza, Russia, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

This article deals with age optimization for the first successful insemination of Holstein heifers under the conditions of a modern dairy complex. Current research is aimed at identifying a balance between dif-ferent ages at first insemination of heifers to reduce costs and the risk of impaired reproductive function, and to increase milk yield and quality. This research is a comprehensive study and devoted to the age-impact at first insemination on reproductive traits, body type, milk productivity, and the physicochemical and technological composition of milk of heifers. The research was carried out in 2023-2026 on Holstein cattle. Four groups of heifers were formed depending on the timing of successful insemination: Group I – 12 months, Group II – 13 months, Group III – 14 months, Group IV – 15 months. Methods of zootechnical recording, laboratory analysis, and variational statistics were applied.
It was observed that the earliest insemination (12 months) increases milk yield over 305 days of lacta-tion (10,718.8 kg). It exceeded the milk yield of primiparous cows in the compared groups by 2.9%, 5.4%, and 3.4%, respectively, with a significant difference noted only with the third group (p ≤ 0.05). along by an elongation of the service period (115.6 days) and the calving interval (393.7 days). The best balance of re-productive indicators, milk productivity, and milk quality was recorded when heifers were inseminated at the age of 13 months: the shortest service period (106.7 days), high yields of milk fat (386.4 kg) and milk protein (338.7 kg), and higher milk density (1,029.5 kg/m³).
The optimal age for successful insemination of Holstein breed under the conditions of an intensive dairy complex should be considered 13 months.
Keywords: Holstein breed, heifer, insemination, milk yield, milk quality.

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