Transferrin Type and Milk Yield in Dairy Cattle
Production data for 932 lactations from approximately 460 cows from eight herds in Northern N.S.W., Australia for the years 1963 and 1964 were examined in relation to serum transferrin type. The mean milk yield of A/D2 cows was 151 ±72 lb (P < 0.05) more than that of the A/A cows, and they lactated 7.4±3.7 days (P < 0.05) longer. The mean yield of D2/D2 cows was 521 ±152 lb (P < 0,001) more than the A/A cows.
The best estimate of the effect of replacing a TfA gene with a TfD2 gene was to increase yield by 170±56 lb (P < 0.005) and lactation length by 6.5±2.8 days (P < 0.025). Replacement by a TfD1 gene had no effect.
It is suggested that there may be a breed difference in the relationship between transferrin type and milk yield.
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