luteinizing hormone concentration in serum of pregnant gilts on different levels of feed consumption. Can. J. Anim. .Blood serum progesterone (P) and luteinizing hormone (LH) were determined in 31 Lacombe gilts at a 3-to 4-day interval from I 0 to 56 days of pregnancy.

Summary. The

concentrations of luteinizing hormone and estrogens in sows: Effect of featment with pregnant mare's serum gonadotropin or esradiol-l7B plus progesterone Can. J. Anim. .The plasma concentrations of luteinizing hormone (LH) and estrogens (E) were determined for I 2 sows, from a herd with a history of postweaning anestrus, from the day of weaning to 32 days after weaning (trial I). A linear increase in plasma LH and E was observed in six sows which remained in anestrus (LH, 0.32-0.47 ng/ml; E, 16.l-24.'7 pg/ml). These concentrations were similar to those observed in cycling sows during diestrus. In the remaining sows concurrent peaks of LFtr and E were observed during proestrus and estrus. In a second trial, two groups each of five sows were treated with a single injection of pregnant mare's serum gonadotropin (PMSG, l50O IU) or steroids (estradiol-17B, I mg plus progesrerone, 2 mg) on the day after weaning. The plasma concentrations of LH and E for I 0-I 2 days after weaning were compared with those of five untreated control sows. In the PMSG-treated group, concurrent peaks of LH (4.7 + 0.5 ng/ml) and E (l2l + 4l pg/ml) were observed at estrus. The control group produced a lower LH peak at estrus ( I .5'+ 0.4 ng/ml) which durant I'oestrus. Le groupe t6moin a produit un pic LH moins d6velopp6, 1 .5 +0.4 ng/rnl, lequel par ailleurs n'6tait pas accompagn6 par une mont6e de la teneur en oestrogbnes. Le groupe pal st6roides n'a pas donn6 de r6actions hormonales coh6rentes.

Yurneslsrurosor, P., Howr.rNo, B. E., Srlren-lrs, S. AND PeI-uEn, W. M. 1974. Estrogen-induced LH release in progesterone-treated ovariectomized ewes.Can. J. Anim. Sci For personal use only.

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