Milk production by dairy cows and yield of the compo-nents, fat, protein and lactose are closely related to nutritional intake. The individual proteins in milk respond differently to a change in nutritional status, giving rise to significant differ-ences in milk protein composition (DePeeters and Cant, 1992). For instance, Gray and Mackenzie (1987) noted a decrease in α-lactalbumin and increase in serum-derived proteins, serum albumin and immunoglobulin, in animals on restricted pasture for 10 days. Although β-lactoglobulin concentration decreased, the response was not significant. Treatment of concentrate-fed dairy cows with a single injection of atropine caused a similar, though temporary, decrease in milk yield, total protein and α-lactalbumin content of milk (Roets and Peeters, 1981). Changes in other milk proteins were not evaluated. The observed responses arise from the ability of atropine to rapidly and specifically depress plasma amino acids used for milk protein synthesis and provide a means of experimentally manipulat-ing supply of substrates for milk protein synthesis. The present study was designed to evaluate the use of atropine in pasture-fed cows.
Proceedings of the New Zealand Society of Animal Production, Volume 56, , 51-52, 1996
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