Decreased follicular size during late lactation caused by treatment with charcoal-treated follicular fluid delays onset of estrus and ovulation after weaning in sows1

Abstract

The weaning to estrus and weaning to ovulation intervals in sows are controlled by ovarian follicular growth after weaning. Longer intervals could be caused by smaller diameter follicles at weaning that take more time to reach a preovulatory size. We addressed this hypothesis by decreasing the diameter of follicular populations before weaning and then measuring follicular development and interval to estrus and ovulation after weaning. The posterior vena cava, cranial to the entry of the ovarian vein, was cathetered for blood sampling and infusion in 20 sows at 12 +/- 1 d after farrowing. Sows were assigned randomly to receive either 30 mL of charcoal-treated follicular fluid (FF, n = 9; a treatment known to decrease serum FSH and follicular diameter) or 30 mL of saline (n = 11) by venous infusion thrice daily (0700, 1500, and 2300 h) for 96 h beginning at 14 +/- 1 d after farrowing. Sows were weaned 48 h after the last infusion. Blood samples were collected for FSH analysis thrice daily beginning on the day of catheterization and continuing until ovulation. Follicular diameter was determined once daily by transrectal ultrasonography. A treatment x time interaction was detected for serum FSH (P < 0.001) and follicular diameter (P < 0.001) because serum FSH and the diameter of follicular populations decreased in FF sows during the infusion period. After the infusion period, serum FSH rebounded in FF sows, and follicles resumed growth but grew at the same rate as those of saline-treated sows, thus failing to achieve equivalent diameters relative to saline-treated sows on a given day after weaning. As a result, sows treated with FF had longer (P < 0.05) weaning to estrus (6.1 +/- 0.4 d) and weaning to ovulation (8.6 +/- 0.5 d) intervals compared with saline-treated sows (4.7 +/- 0.4 d and 7.2 +/- 0.4 d, respectively). We conclude that the diameter of the follicular population at weaning is one factor that controls interval to estrus and ovulation in sows. Small follicles at weaning cannot undergo compensatory growth and require additional time to reach a preovulatory size.

Peripheral concentrations of inhibin A, ovarian steroids, and gonadotropins associated with follicular development throughout the estrous cycle of the sow

“…The results are consistent with the detection of relatively constant levels of mRNAs encoding inhibin a and b A subunits in follicles 1 mm or more in diameter (Guthrie et al 1992, Garrett et al 2000; expression of aromatase mRNA dramatically increases once the follicles reach 6 mm in diameter (Liu et al 2000). Consideration of these findings in combination with the finding that treatment of pigs with inhibin preparations decreases FSH secretion (Guthrie et al 1987, 1988, Knox et al 1991, Knox & Zimmerman 1993, Bracken et al 2006 strongly suggests that inhibin A acts as a feedback regulator of FSH throughout the porcine estrous cycle; in contrast, E 2 has inhibitory effects only during the follicular phase.…”

“…To overcome this major limitation in inhibin assays, we have developed a sandwich-type time-resolved immunofluorometric assay (Tr-IFMA) for dimeric inhibins, which uses a combination of a and b A or b B antibodies (Hasegawa et al 1997, Kaneko et al 2002a, 2003. Tr-IFMA has proven to be applicable to the measurement of inhibin A or/and B in humans (Hasegawa et al 1997), rats (Hasegawa et al 1997), cattle (Kaneko et al 2002a, 2003, 2006, Todoroki et al 2004, and boars (Ohnuma et al 2007). Other groups have quantified dimeric inhibins in the circulation of humans (Groome et al 1994, rats (Fahy et al 1995, Woodruff et al 1996, cattle (Bleach et al 2001), and sheep (Knight et al 1998) with sandwich-type ELISAs.…”

Effects of Feeding Level During Lactation on FSH and LH Secretion Patterns, and Follicular Development in Primiparous Sows

“…(2001) have demonstrated wave‐like follicular growth during lactation that was associated with a temporary increase in FSH, suggesting that FSH support is necessary for stimulation of antral follicular growth during lactation. In a most recent study, treatment of sows with multiple injections of charcoal‐extracted porcine follicular fluid starting day 6 pre‐weaning over 4 days significantly decreased FSH and reduced follicular growth, with a mean follicular size of approximately 1 mm observed the day of weaning compared with approximately 3 mm in sows treated with saline (Bracken et al. 2006).…”

“…However, a temporary increase in FSH has been associated with lactational follicular growth (Lucy et al. 2001) and artificial reduction of FSH during lactation, induced by administration of charcoal‐treated follicular fluid, reduced follicular growth and delayed weaning‐to‐oestrus interval by several days (Bracken et al. 2006).…”

Effects of Breeding at the Second Oestrus or After Post‐Weaning Hormonal Treatment with Altrenogest on Subsequent Reproductive Performance of Primiparous Sows

“…2010) may account for the faster oestrous manifestation in Altrenogest‐treated sows (Lucy et al. 2001; Bracken et al. 2003, 2006).…”