Role of the Ovary in Controlling Luteinizing Hormone, Follicle Stimulating Hormone, and Prolactin Secretion During and After Lactation in Pigs1

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Abstract
Concentrations of LH, FSH, prolactin, estrogen, and progesterone were measured in blood samples collected at various intervals during and immediately following lactation to determine the role of the ovary in controlling gonadotropin and prolactin secretion and initiation of estrous cycles in the pig. Ten primiparous sows were ovariectomized (ovex, n = 5) or left intact (n = 5) 2 to 4 days after farrowing. Serum progesterone and estrogens in samples collected daily during lactation were not different between intact and ovex sows. Serum FSH increased immediately after ovariectomy and remained elevated during lactation, but LH concentrations were similar between ovex and intact sows. Both LH and FSH were higher during the last 2 weeks of lactation than during the first 3 weeks.