RESEARCH ON THE INFLLUENCE OF THE CALVING INTERVAL ON MILK YIELD

The paper goal was to study the influence of the calving interval on milk yield for the Romanian Brown breed, using 950 lactations, of which: 573 lactations (60.31 %) belonged to the over 400 days calving interval and 377 lactations (39.69%) belonged to the 351-400 days calving interval. The calving interval varied between 446.41±18.94 days, the highest length for the 51 dairy cows which had parturition in September and 373.49 ±14.28 days, the shortest length for 53 cows which calved in October. The average calving interval for the cows with a calving interval longer than 400 days accounted for 425.58±14.10 days, while the average calving interval for the cows with this reproductionindicator between 351 and 400 days was 358.65±10.07 days. For the cows whose calving interval was longer than 400 days, milk yield accounted for 4,682.5±124.92 while for the cows whose calving interval varied between 351 and 400 days registered 4,240.0±215.10 kg. The calculations revealed a gross product of Lei 6,087 per lactation in case of cows whose calving interval was longer than 400 days and Lei 5,512 in case of the cows whose calving interval varied between 351-400 days. For an average difference of 66.93 days calving interval between the two calving interval size groups taken into consideration, the milk yield difference accounted for 442.50 kg in the benefit of the cows with the calving interval longer than 400 days. Also, a difference of Lei 575 was recorded in the favor of the cows with calving intervals longer than 400 days because they registered higher a milk yield. This means Lei 8.59 additional income per cow and calving interval day longer than 400 days.