Effect of the crossbred system on productive and reproductive performance of dairy cows

The performance of six Holstein-Friesian x Gyr grades was analyzed using data from a demonstration farm of EPAMIG, Prudente de Morals. Minas Gerais State. A rotacional crossing system of two generations of Holstein-Friesian and one of Gyr (HHZ) was practiced between January 1983 and October 1995. The performance of MHZ cows was compared to that of the progeny of crossbred Bos taurus x B. indicus bulls of the program "Development of the Brazilian Milking Crossbred Cattle" (MLB). Data consisted of 555 lactation of 182 cows and 468 calving intervals (CI) of 150 cows. Least-square means for HHZ e MLB, were, respectively: lactation yield, 4194.52+/-203.44 and 2946.53+/-3 60.62 kg; 305-day yeld, 3810.19+/-164.00 and 2850.79+/-90.71 kg; lactation length, 340.15+/-13.42 and 254.71+/-23.80 days; CI, 429.82+/-10.48 and 379.12+/-22.94 days; yield per day of lactation, 12.14+/-0.34 and 11.30+/-0.61 kg and yield per day of CI, 9.92+/-0.35 and 8.47+/-0.76 kg. Differences between both groups were not significant (P>0.47). Within the HHZ group, neither the breed additive difference nor the heterosis were significant for all those traits (P>0.44). It was concluded that the results are consistent with the literature, indicating low performance of the progeny of unselected crossbred bulls and similar performances of high and intermediate Bos taurus grades in rotational crossing systems, in situations in which management allows the former to attain milk yield of approximately 10 kg per day of CI.