Ovulation and fertility responses for sows receiving once daily boar exposure after weaning and OvuGel® followed by a single fixed time post cervical artificial insemination

Abstract

Boar exposure is used to stimulate follicle development and estrus in sows after weaning and also to improve semen uptake and sperm transport with insemination. However, the need and value of boar exposure is uncertain when ovulation induction is used. These studies were designed to determine the effect of daily boar exposure after weaning when used with ovulation induction and fixed time post-cervical artificial insemination (PCAI). In experiment 1, sows were weaned into stalls and assigned to receive 3 min of daily fenceline boar exposure (BE, n = 7) or no boar exposure (NBE, n = 8). All sows received OvuGel at 96 h after weaning and BE or NBE 30 min prior to a single PCAI 24 h after OvuGel. Ovaries were assessed daily for follicle size from weaning until ovulation. Cervical contractions were measured 30 min following BE or NBE and before PCAI, while uterine contractions were measured for 1 h following PCAI. In experiment 2, weaned sows (n = 244) were assigned by parity to receive once daily BE for 1.5 min each day or NBE. OvuGel, PCAI and ultrasound methods were performed similarly as in experiment 1. Results from experiment 1 indicated BE did not significantly influence follicle size or measures of fertility. However, BE did increase the frequency of cervical contractions (P < 0.05), but with no effect on the uterus. Results from experiment 2 indicated BE had no effect on catheter passage for PCAI but did increase the proportion of sows ovulating within 48 h after OvuGel (77.7 vs 67.5%, P = 0.05), and tended (P = 0.10) to increase the proportion of sows inseminated 24 h before ovulation (70.3 vs. 61.0%). However, BE had no effect on adjusted farrowing rate (84.4 vs. 77.4%) or total pigs born (13.2 vs. 12.5) for BE and NBE, respectively. There were treatment and parity interactions for follicle size at time of OvuGel and at time of PCAI (P < 0.05) with BE minimizing parity effects on follicle size. Parity effects were also evident on farrowing rate and litter size when inseminations occurred >24 h from ovulation but not when inseminations occurred ≤24 h before ovulation. The results indicate that boar exposure for only minutes each day after weaning had beneficial effects for improving follicle development, ovulation induction, and AI timing, most notably in parity 1 sows, but had no beneficial or detrimental effects on the ability to perform PCAI.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Factors influencing follicle development in gilts and sows and management strategies used to regulate growth for control of estrus and ovulation1

“…At estrus, the follicles present can be heterogeneous in size, granulosa cell numbers, and estrogen (Hunter and Wiesak, 1990). Most ultrasound data identify large follicles averaging 7 to 8 mm at estrus (Nissen et al, 1997;Lucy et al, 2001;Knox et al, 2002), but these measures can also vary by parity (Ulguim et al, 2018) and among sows before ovulation (Soede et al, 1998). Soede et al (1992) counted all follicles >4 mm at estrus and observed counts were closely related to number of corpora lutea (CL).…”

Weaned Sows with Small Ovarian Follicles Respond Poorly to the GnRH Agonist Buserelin

“…In this regard, Driancourt et al [17] showed that weaned primiparous sows are less responsive than weaned multiparous sows to the GnRH agonist buserelin. It is also interesting to note that a substantial number of weaned sows with few parities had small ovarian follicles at weaning [23,31]. Sows had shown clear individual differences in average follicular size at weaning [23] and even also by the third day after weaning [32].…”

PMSG Pretreatment Before Fixed-Time Artificial Insemination Improves the Reproductive Performance in Replacement Gilts

“…Successful insemination of gilts depends primarily on the ovulation and inseminationtime [30] . In theory, sperm show optimal fertility at 24 hours after insemination [31,32] . However, if insemination is done too late, the oocytes would be degraded [33] , which negatively impacts the sow fertility, including reductions in pregnancies, fertilization rates [34] , and embryo survival [35] .…”