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.
No takes yet. Share an insight, caveat, or question.
Carr et al. (1982) studied this question.