Effects of age and liveweight of heifers at puberty and first conception on cow productivity and safety

The effects of the optimal liveweight of heifers, reaching the age of completed puberty and first conception, on the lifespan, the milk yield, and the welfare status of cows after three lactations have been studied. The survey was performed with the mature domestic Black-and-White cows (п=7171) born in the farm enterprises, Belgorod Region in 2010 to 2014. The milk yield 7746-8570 kg per cow per indicated period was recorded; the milk fat and protein contents comprised 3.82-3.81% and 3.37-3.30%, respectively. Isemination of 15-16-month-old heifers of no less than 412 kg liveweight and 17-18-month-old heifers of 426 kg liveweight, taking into account their 12-month weights of 327-347 kg and 316-344 kg, rspectively, has been proved reasonable in order to improve the Black-andWhite cows' welfare, lifespan, and milk production as 20.4-31.8 thousand kg over three entire lactations