Effect of season on ovarian and pituitary activity in cows
K.P. McNatty, D. Heath, S. Lun, K.M. Henderson, N. Hudson, M.
Gibb, J. McDiarmid, G.W. Montgomery, D.C. Thurley
Wallaceville Animal Research Centre, Ministry of Agriculture and
Fisheries, Upper Hutt
Proceedings of the New Zealand Society of Animal Production.
1984, 44: 19-20
The preovulatory follicle in oestrous cycling Angus cow was
larger (P<0.01) and contained more granulosa cells (P<0.01) in May and
June than in October. Also in May and June, the corpora lutea were
heavier (P<0.05) and secreted more progesterone (P<0.01) than in
October. In contrast, the luteinizing hormone peak frequency and plasma
prolactin concentrations were higher (P<0.01) in October than in May and
June.
Seasonal differences in ovarian activity are probably a direct
consequence of seasonal differences in pituitary gonadotrophin
secretion.
Keywords: NZSAPAB;
Cows; seasonal influences; ovaries; pituitary hormones;
granulosa cells; corpus luteum; LH; progesterone; prolactin
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Last Updated 03-05-1997
