FIXED EFFECTS OF PRODUCTIVE PERFORMANCE IN BROWN SWISS WITH ZEBU CROSSBREEDING

Abstract

Data of Brown swiss (S) x Zebu (C) cows were evaluated to determine the effect of some fixed factors on the milk production adjusted to the 305 days (PAJ, n=147) in double purpose system. The study was carried out in the productive milk unit of the experimental facility El Ejido, from 1996 to 2003. The studied fixed factors were racial group (GR), intensification level (NI), calving number (NP), calving season (EP), and days in lactation (DL) as covariate. The racial group studied was ½ SxC (n=80) and ¾ SxC, (n=67). The overall mean and standard deviation of PAJ was 1918,55 ± 555,71 kg. All factors had significant effects on the productive performance (P>0,05) except the EP. The racial groups between ½ and ¾ SxC, showed a good performance in the productive system. The genotype ¾ SxC was the best with 10% of response over ½ SxC. The NI 2 showed best result over NI 1 with 17% of increment. The best milk production were given in the fifth and sixth lactation with 2471,67 ± 154,24 and 2492,72 ± 168,80 kg, each one. We conclude that the GR, NI and NP had had an influence over the milk production and it is very important to make a plan of genetic improvement over the basis of intensification level of the productive system. On the other hand it is recommended to increase the number of samples in subsequent studies.