POSTWEANING PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE AND ESTROGENS IN SOWS: EFFECT OF TREATMENT WITH PREGNANT MARE’S SERUM GONADOTROPIN OR ESTRADIOL-17β PLUS PROGESTERONE

Abstract

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.

Plasma concentrations of LH, prolactin, oestradiol-17 and progesterone in sows weaned after lactation for 10 or 35 days

“…Such an increase could serve to trigger the preovulatory release of oestrogen, as has been shown to occur with maleinduced puberty in mice (Bronson & Desjardins, 1974). However, in the present results there was no post-weaning elevation in basal LH before that seen at ovulation, which is in agreement with results from other workers (Dyck, Palmer & Simaraks, 1979;Stevenson & Britt, 1980). The low lactational and post-weaning plasma LH levels observed in Group E sows is further reflected in a greatly attenuated ovulatory surge, as has been reported for sows after a 3-week lactation (Edwards & Foxcroft, 1983).…”

Response of sows to oestradiol benzoate treatment after weaning at two stages of lactation

“…The majority of sows treated two days after weaning with 30 µg oestradiol benzoate/kg body weight returned to oestrus on or before Day 5, a time which compares favourably with the mean of 7-85 days recorded by Burger (1952) for Large White sows and with the results obtained in many commercial herds employing 3-week weaning (M.L.C., 1980). Although the interval of 3 days from oestradiol benzoate injection to overt oestrus in sows injected with 30 µg/kg on Day 2 is in agreement with published data (Rasbech, 1953;Dyck et al, 1979), the marked reduction in fertility and prolonged oestrous periods associated with the previous use of synthetic oestrogens (de la Cerna, 1956;Rigor et al, 1968;Schmidt et al, 1968) were not observed.…”

“…The treatment of sows with gonadotrophins and steroids at, or shortly after, weaning has been more successful. Weaning to oestrus intervals have been shortened by use of diethylstilboestrol (Rigor, Villareal & Illagan, 1968) or a combination of steroids (Schmidt, Jochle & Thume, 1968 ;Dyck, Palmer & Simarks, 1979) but conception rates and litter size were reduced. Gonadotrophin therapy (PMSG : hCG combina¬ tions) can shorten the weaning to oestrus interval with no detrimental effects on fertility (Rasbech, 1953;Whyte, 1977).…”

Hormone Profiles Around Weaning in Cyclic and Anoestrous Sows

“…In the sows that remained anoestrus after weaning, there was a significant increase in mean LH concentration, but there was no accompanying linear increase in Ez secretion. Other studies have indicated that there is a linear increase in LH secretion (DYCK et al, 1979;ALMOND and DIAL, 1990) and that E2 secretion remains relatively low (ARMSTRONG and BRIIT, 1985) in sows remaining anoestrus after weaning as follicles fail to develop. In the present study, the overall mean and basal LH concentrations were higher in the sows that resumed cyclicity compared with those that remained anoestrous after weaning.…”