BEEF-PRODUCTION THROUGH THE DAIRY-HERD .4. GROWTH UNTIL AI INCORPORATION

Growth data until AI incorporation of 183 female hybrids corresponding to the beef breed crosses (Zebu, Charolais, Santa Gertrudis and 3/4 Limousin 1/4 Criollo) with female dairy breed crosses (5/8 H 3/8 Z and 3/4 Holstein 1/4 Zebu) were used with the objective of comparatively evaluating the growth potential of these crosses under commercial exploitation conditions. Traits studied were: age at incorporation (AAI) to AI and average daily gain (ADG) adjusted to a liveweight of 300 kg. The analysis of the data was carried out by least squares according to two linear models of fixed effects. The first included the effects of paternal genotype (4), maternal genotype (2), contemporary group (6), year of incorporation to AI (2) and the paternal x maternal genotype and paternal x year of AI incorporation interactions. The second model only differed from the first in that it considered the sources of genetic variation, which included genetic group (calf genotype 8) and the genetic x year of AI incorporation interaction. The genetic effects studied in both models were not significant, with the exception of the paternal x maternal genotype interaction. This showed a superiority of Charolais x 5/8 H 3/8 Z heifers with respect to the Zebu x 5/8 H 3/8 Z and 3/4 Li 1/4 Cr x 5/8 H 3/8 Z, being the differences of 2.4 months and 45 g/day for AAI and ADG, respectively. The remaining crosses had an intermediate performance. The contemporary group and the year of AI incorporation were the two main sources of variation in the study. Means obtained were of 22.6 months and 397 g/day for AAI and ADG, respectively.