Genetic variation in alpha-lactalbumin in relation to milk volume
1997
Lunden, A. | Lindersson, M. (Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Animal Breeding and Genetics)
The existence of the alpha-lactalbumin (+15) polymorphism, previously reported to be present in Holsteins, was investigated in the two major dairy breeds in Sweden. Altogether 239 cows of the Swedish Red and White breed (SRB) on two experimental farms belonging to the Swedish University of Agricultural Sciences were genotyped, along with a group of 59 cows of the Swedish Friesian (SLB) from one of the farms. The SRB cows belonged to two selection lines established and maintained through the use of sires with either high or low breeding values for milkfat content, all of them having high breeding values as regards total energy production from the milk. The same two alpha-lactalbumin alleles (denoted A and B), earlier described in Holsteins, were found both in the SRB and SLB breeds, which was verified by sequencing the PCR-products from one AA and one BB individual of each breed. Among the SRB cows the A variant was less frequent in the low fat line than in the high fat line in both herds. Also, this variant was not as common in the present material as in the previous study on Holsteins. To address the relationship between genetic variation in alpha-lactalbumin and milk production a sample including 99 of the genotyped SRB cows along with the group of SLB cows within the same herd were genotyped. The results pointed towards a relationship between alpha-lactalbumin (+15) polymorphism and yields of the major milk components, including lactose. However, compared to the previous results obtained on Holstein cattle, in the SRB breed the opposite relationship was observed. Thus, cows of the BB genotype had significantly higher yields of milk and all major components. These results indicate a linked effect of the alpha-lactalbumin (+15) polymorphism on yields of milk components, rather than a direct effect. The influence of variation in the 5'-untranslated region of the alpha-lactalbumin gene on milk production traits awaits confirmation in a larger material.
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