CHANGES IN LIVE WEIGHT AND EFFICIENCY OF COWS IN STANDARDIZED LACTATIONS

There is a high correlation between weight of dams after calving and d uring lactation, marked in first calvers (r = 0.812, P < 0.01). The lo ss of weight by 3.2 to 4.3 % in puerperium is due to the milk producti on. Weight gain of lighter dams is activated as early as in six weeks from calving (440 g against 180 g), with reduced milk production-by 8 to 13 %. Higher initial weight is in correlation with higher efficienc y within 200 lactation days +403 kg of milk (r = 0.205 to 0.259, P < 0 .01) and with the guarantee of good reproduction and health. The perio d of 151 to 300 days of lactation is the period of compensating growth between cows with differentiated initial weight. The intensity of wei ght gain is doubled with age and efficiency. Higher efficiency is cond itioned by optimization of dam live weight close to the growth standar d for Black-spotted breed.