Polymorphisms of Kappa-casein and Beta-lactoglobulin genes and their association with milk fat and protein contents in Tanzanian goats

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Sokoine University of Agriculture


This study was conducted to assess the polymorphisms of beta-lactoglobulin (-Lg) and kappa-casein (-Cn) genes and determine the effects of -Lg polymorphism on percentage of milk fat and protein contents in indigenous goat breeds found in Tanzania. Blood samples were collected from 22 - 24 unrelated animals for each breed. Genomic DNA was isolated from whole blood samples using Sepa gene extraction kit with some modifications. The -Lg and -Cn genes were amplified using Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) technique was used to determine variations at the -Lg and -Cn loci. The amplified products for -Lg and -Cn genes had the sizes of 426 and 459 bp, respectively. Digestion of β-Lg gene using SacII endonuclease restriction enzyme revealed the presence of two common alleles (A and B) in all goat populations. The frequency of B-allele (0.583) was higher than that of the A-allele (0.417) for β-Lg gene in indigenous goats, while exotic goats had higher frequency of A allele (0.688) than the B-allele (0.312). The frequencies of AA, AB and BB genotypes were, respectively, 0.250, 0.333 and 0.417 in Gogo goats, 0.318, 0.273 and 0.409 in Pare white, 0.417, 0.333 and 0.250 in Malya, 0.500, 0.375 and 0.125 in Saanen. The analysis of  -Cn gene variation in the four goat populations indicated that there were three alleles (A, B and C) at this locus. The observed allelic frequencies of A/B and C were 0.917 and 0.083 in Gogo white, 0.955 and 0.045 in Pare white, 1 and 0.00 in Malya, 0.875 and 0.125 in Saanen goats, respectively. The effects of β-Lg genotypes on milk fat and protein percentages were analyzed using a general linear model (GLM). The results show that there was no significant effects (P>0.05) of β-Lg alleles on milk fat and protein percentages.



Polymorphisms, Kappa-casein, Beta-lactoglobulin, Tanzanian goats, Genes and their association, Milk fat