Transferrins and milk production in dairy cattle

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Abstract
SUMMARY: Milk and butterfat production data from eight herds of dairy cows in Australia for the years 1963 and 1964 were analyzed for relationship with serum transferrin type. In the 932 lactations considered D2/D2 cows produced 521 ± 152 lb of milk more than A/A cows and lactated 15·3 ± 7·8 days longer after correction for season. There was no difference in fat percentage of the milk. The production of A/D2 cows was also significantly higher than A/A cows, but less than D2/D2 cows. Allowing for differences in lactation length still left a significant difference between D2/D2 and A/A cows in milk yield.The best estimate of the effect of replacing aTfAby aTfD2gene, allowing for season, was 170 lb more milk (PTfD1did not differ fromTfAin either yield or lactation length.