Factors affecting pre and post-weaning growth of crossbred cattle genotypes at Songa Research Station in Rwanda
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To assess the growth performance of the different cattle genotypes from birth to 18 month of age at Songa Research Station in Rwanda, this study was designed. Records of animals born between 1998 and 2008 were evaluated using nested statistical model. Four cattle genetic groups: crossbreds of Ankole dams with Brown Swiss, Friesian, Jersey and Sahiwal were used in the study. Birth weight was not significantly affected by genotype, sex of the calf year and season of birth. However the calves sired by Brown Swiss and Friesians were heavier than those sired by Jerseys, while calves sired by Sahiwal were intermediate. Effects of genotype, year of birth and season of birth on weaning weight were all highly significant (P<0.001) Weaned Friesian x Ankole calves (FA) were significantly heavier than those of all other genotypes except Brown Swiss X Ankole (BA) and Sahiwal X Ankole (SA) crossbreds. The heaviest calves were born during season 4 of the year, though weaning weights across seasons did not differ significantly (P>O.05). Male weaned calves (179.3 ± 6.0 kg) were heavier than female weaners (164.6 ± 9.9 kg). A wide range of weaning weight for BA and FA genotypes were observed, compared with the range of mean weights for JA, SJA, SA, and SJA suggesting that genotypes containing Jersey and Sahiwal genomes are more resilient to environment pressure. Mature weights of animals was significantly affected by genotype (P<0.01), sex (P<0.0001), and year of birth (P<0.0001) while season and its interaction with genotype (P>0.05) did not influence it. Overall, genotype BA grew faster??? than all other genotypes though its growth rate was not significantly higher than . genotype FA, while the lowest growth rate was registered in genotype SA. However, the speed of growth was similar to those in genotypes JA, SJA, SA and SJA. From results, it was concluded that AS, AJS and ASJ were suitable genotype for Rwanda. The major factors to consider during the breeding of the various genotypes include season of birth and year of birth.