Seasonal variation in plasma concentrations of prolactin in castrated rams of breeds of sheep with different seasonality of reproduction

in Reproduction
Authors:
W. R. Carr
Search for other papers by W. R. Carr in
Current site
Google Scholar
PubMed
Close
and
R. B. Land
Search for other papers by R. B. Land in
Current site
Google Scholar
PubMed
Close
Free access

Sign up for journal news

Summary. Finnish Landrace, Scottish Blackface and Tasmanian Merino rams were castrated and bled twice weekly from March to September. The breeds have widely different timing of seasonal variation in reproductive activity, but the plasma prolactin concentrations rose and fell at the same time in all 3 breeds, i.e. at the end of March and in September respectively. It is suggested that, even if major seasonal variations on plasma prolactin reflect primary changes in hypothalamic activity, these changes are modified by other factors to control the seasonal variation which occurs in the reproduction of the sheep.

 

  • Collapse
  • Expand