Polymorphism of the <i>Kappa Casein</i> gene and milk production in cows resulting from crossbreeding with holstein or montbeliarde in the peri-urban area of Bamako

Abstract

The objective of this contribution is to study the polymorphism of the kappa casein gene in crossbred cows in the peri-urban area of  Bamako. Fifty (50) cows, including 22 Montbeliarde crosses and 28 Holstein crosses, were subjected to descriptive analysis comparing  average milk production and milk fat and protein percentages and genetic analysis of the kappa-casein gene and its interaction with the  crossbred types or breed. The results showed 2 types of crosses for each breed, ½ and ¾ exotic blood. The average daily milk production was 8.2±0.46 kg/d for the Holstein crosses and 7.2±0.73 kg/d for the Montbeliarde crosses with a significant difference. No significant  differences were observed for the fat and protein content between Holstein crosses (3.56 ± 0.14% and 3.68±0.02%) and Montbeliarde  crosses (3.79 ± 0.10% and 3.74±0.02%). Genetic analysis revealed three genotypes of kappa casein (AA, AB and BB). The AA genotype (0.5)  was the most frequent followed by AB (0.41) and BB (0.09). A close link was observed between milk production and the polymorphisms of  the kappa casein gene. Individuals with the AB genotype had the highest daily milk production followed by individuals with the AA  genotype and those with the BB genotype with respective mean values of 8.6±0.64 kg/d; 7.3±0.56 kg/d and 6.6±1.58 kg/d. Individuals of  the BB genotype presented a higher fat content (4.0±0.08%) than that of the other genotypes. The mean milk protein content varied little  among the genotypes. These results will contribute to the strengthening of knowledge on the genetic effects of kappa casein     polymorphisms on milk production performance and milk composition of crossbred cows in Mali.