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

Abstract

Piglets were weaned from multiparous sows at 10 days (Group E; N = 7) or 35 days (Group C; N = 8) of lactation. Blood samples were collected at 8 h intervals from the day before weaning (Day--1) until and including the day of first mating, then once daily until 10 days post coitum. Additionally, 5 sows in each group were sampled at 30 min intervals for 12 h on Days--1, 0 and 1, then at 30 min intervals for 6 h daily until mating, finally at 30 min intervals for 2 h daily until 5 days post coitum. Group E sows had relatively longer weaning to remating intervals (8.3 +/- 0.8 compared with 5.0 +/- 0.7 days; P less than 0.01) and tended, but not significantly, to produce smaller subsequent litters (10.2 +/- 1.9 compared with 12.0 +/- 0.6). Sows in group E had lower lactational and post-weaning plasma LH levels (P less than 0.001). They also had greatly attenuated preovulatory LH rises and the area under the peak was reduced (P less than 0.01 and P less than 0.001, respectively). Preweaning plasma prolactin levels were higher at 9 days of lactation than at 34 days and levels in both groups dropped precipitously subsequent to piglet removal. Although peak levels of prolactin at oestrus did not differ between treatments, they tended to occur before the LH peak in sows of Group C and after the LH peak in Group E.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of feed intake during lactation and after weaning on sow reproductive performance

“…The results of the present experiment confirm previous data from our laboratory showing that restricted feeding during lactation increases the duration of the rematins interval and reduces the rates of pregnaicy and embryo survival (Kirkwood et al 1981a(Kirkwood et al ,b, 1990 Edwards and Foxcroft (1983a,b) and Kirkwood et al (1984) (Smith 1986 For personal use only.…”

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

“…Key words: Sows, feed intake, estrus, GnRH Notably, both short lactation lengths (Kirkwood et al 1984a) and low feed intakes during lactation (Kirkwood et al 1987 (Reese et al 1982) and in a reduction in pregnancy rates (Kirkwood et al 1987). …”

“…Studies with sows having short lactation lengths have also demonstrated a decrease in embryo numbers (Cole et al 1975). This may be a result of an attenuated luteinizing hormone (LH) surge at estrus, adversely affecting subsequent follicular luteinization (Kirkwood et al 1984a). Kirkwood et al (1984a) suggested that adverse effects on luteinization could influence gestation steroid profiles which, via an influence on the uterine environment, may influence embryo viability.…”

“…This may be a result of an attenuated luteinizing hormone (LH) surge at estrus, adversely affecting subsequent follicular luteinization (Kirkwood et al 1984a). Kirkwood et al (1984a) suggested that adverse effects on luteinization could influence gestation steroid profiles which, via an influence on the uterine environment, may influence embryo viability. Indeed, the improvement in conception rate noted in cattle following a GnRH injection at insemination was associated with an elevation in plasma progesterone levels (Lee et al 1985).…”

Influence of follicular ablation during lactation on postweaning interval to estrus, ovulation rate, and endocrine function in sows

“…Most studies have indicated that, after weaning, increases in gonadotropins cause follicular growth which results in elevated concentrations of circulating estrogens (6,7,8,9). Increasing concentrations of estrogen in peripheral cir culation appear to be the major trigger for the preovulatory surge of gonad otropins and subsequent ovulation (5,10,11).…”