Effects of oestradiol benzoate treatment on the reproductive performance and endocrine status of sows after lactations of 10 or 35 days

Abstract

Forty-two Landrace X Large White sows were used in 3 studies of oestradiol benzoate treatment 24 h (E1) or 48 h (E2) after piglet removal, following lactations of 10 (S) or 35 (L) days, or were untreated controls (C). For Exp. 1, oestradiol benzoate doses were 4, 16 and 64 micrograms/kg body weight; since highest mean LH peaks followed use of the 16 micrograms/kg dose, this treatment was used in later studies. Treatments for Exp. 2 were S-E1 and L-E1 (N = 3). Pregnancy rates were 1/3 and 2/3, respectively, while 10-day weaned sows tended to have longer weaning-remating intervals, shorter oestrous periods and lower post-injection oestradiol peaks. Post-treatment LH peaks were recorded from all L-E1 sows, but only one S-E1 animal. Treatments S-E2, L-E2, S-C and L-C (N = 6) were used in Exp. 3; pregnancy rates were 1/6, 6/6, 5/6 and 6/6, respectively, while peak oestradiol levels were 49.5 +/- 8.3, 74.8 +/- 15.1, 21.7 +/- 2.0 and 51.8 +/- 26.5 pg/ml, respectively. Weaning-remating intervals were extended in S-C sows (P less than 0.05), while oestradiol treatment prolonged behavioural oestrus. LH peak values were reduced after short lactations, but not affected by oestradiol treatment. Plasma prolactin concentrations at weaning were higher in sows in treatment S than in treatment L, while at the subsequent oestrus in oestradiol-treated sows they were elevated more and for longer periods than in controls. These results demonstrate that reduced gonadotrophin secretion and fertility after short lactations are not overcome by treatment with oestradiol benzoate.

Endocrine bases of lactational anoestrus in the sow

“…Finally, in lactating sows, the hormones and neurotransmitters associated with suckling could block the discharge of GnRH and that of LH in response to high levels of oestrogens. In weaned sows, the duration of lactation influences the responsiveness to OB; the amplitude of the oestrogen-induced LH surge is higher after 35 than after 21 or 10 d of lactation (Edwards and Foxcroft, 1983b;Kirkwood et al, 1984b).…”

Effect of Lactation Feed Intake and Gonadotrophin-Releasing Hormone on the Reproductive Performance of Sows

“…It has recently been suggested that the mechanism(s) involved in reducing embryo survival following previous short lactation lengths or lowlevel lactation feed intake have a common cause involving either a reduction in plasma gonadotrophin levels (Aherne and Kirkwood 1985) or a reduced ovarian response to gonadotrophic stimulation (Kirkwood et al 1984b(Kirkwood et al , 1987. This hypothesis is indirectly supported by evidence from recent studies with cattle demonstrating an improvement in pregnancy rates of 8-13% following the administration of gonadotrophin -releasing hormone (GnRH) at insemination or during the 6 h preceding it (Schels and (Table 3).…”

Effect of intrauterine infusion of Escherichia coli on hormonal patterns in gilts during the oestrous cycle

“…Additionally, a decrease in LH plasma level in the treated gilts could be eventually the consequence of the inhibitory effect of the proinflammatory cytokines released from an inflamed uterus on the hypothalamicpituitary unit, as was suggested earlier [33]. The reduction of PRL secretion observed in E. coli-treated animals can be caused by the decreased oestrogen secretion [34,35] and/ or cytokine effect [9,36].…”