Effect of season, genetic line, and sire on growth concentrations of somatotropin in serum of Holstein cows in early lactation.

Abstract excerpt

To determine the effect of selection for milk yield on somatotropin concentrations, blood samples were collected from 128 Holstein cows whose sires had either high or average predicted differences for milk. The phenotypic difference in milk yield between the high and average yielding groups was 1726 kg on a 305-d mature equivalent basis. At 37 +/- 7 d postpartum, four blood samples were taken from each cow at 1-h...

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