The influence of bulls -sires on phenotypic characteristics milk yield of daughters Black - White breed during four lactations

Reproductive traits and the variability of milk yield and milk fat were investigated on bulls - sires during the first four lactation. By investigations were surrounded 350 cows - daughters of 14 bulls - sires. Number of daughters per bull was 23-26. Investigations were carried out on one society farm of PK "Beograd" (Yugoslavia). The age of heifer at insemination was in significated variation on bulls - sires from 467 days (daughters of bull 505) to 565 days (daughters of bull 508). Bulls - sires did not influence at the age of daughters at second, third and fourth fertilization, and they did not have influence on duration of the first four service period. Bulls - sires had a high significance influence on milk yield in the first three standard lactation. Production of daughters (bull 447 and 578) in first standard lactation was from 915 to 972 kg more than daughters of bulls 490 and 430. In second standard lactation production of daughter (bull 508) was 1183 kg milk more than daughter of bull 505. Milk yield in third standard lactation variated from 4,630 kg (bull 490) to 6,119 kg (bull 454). Content of milk fat show us a significate variation in the first three standard lactations. Different average of milk fat between group of half - sisters from 0.20%-0.27% was statisticly significated. By analysis of variance was found a significate influence of bulls - sires on fat corrected (4%) milk yield in first four lactation. Cows production was average 5096 kg fat corrected 4% milk yield per lactations. Daughters of seven bulls produced in first four lactation 0.7-8.26% milk less than the average of breeding stock. Daughters of bull 454 with 75% HF, realize 10.85%-19.91% more fat corrected (4%) milk in relation on average of the same age cows and daughters of bull 490. Positive influence of the seven bulls had a reflection on increasing milk yield of daughters which production was 5,102 kg 5,649 kg fat corrected 4% milk.