External and internal factors influencing ovarian follicle development in weaned sows and the use of hormonal technology to improve subsequent fertility

The expectation of 90% of sows exhibiting estrus within 6 to 7 d following weaning is an important target for sow productivity. But concerns about the proportion of sows that are delayed in the breeding group remain, with a particular interest in primiparous sows and the internal and external factors affecting their ability to be fertile after weaning. The first experiment was designed to determine whether induced ovulation (OvuGel, a GnRH agonist) and single fixed-time artificial insemination (SFTAI) could be successful for fertility responses in different parities (P1, P2, P3 to 4, P≥7) and seasons (summer and fall) of the year. Results indicated that ovulation induction increased the proportion of sows ovulating by 10.8%, but with no enhancement in fertility outcomes and no substantial improvement with parity or season. Ovulation induction with SFTAI was associated with smaller follicle size at estrus in P1 sows, and these females displayed a reduced proportion of sows ovulating within 6 days of weaning and lower farrowing rates compared to the older parities. The second experiment was a preliminary study conducted to characterize follicles on the ovaries of a small population of P1 sows during lactation and post-weaning and to determine whether these might associate with estrus and subsequent fertility after weaning. In this group of sows, fertility was lower than expected, and results indicated variation in follicle populations during lactation and after weaning, with heterogeneous follicle sizes observed throughout lactation. The average size of the largest follicles during lactation and Day 1 post-weaning tended to be smaller than the largest follicles on Days 5 to 7 after weaning. Only 64.7% of sows were in estrus within 7 days, and of those inseminated, 76.9% became pregnant and farrowed with a mean litter size of 11.7 ± 1.5. Despite the variation in follicle populations during lactation, this did not explain the estrus and fertility responses after weaning. The third experiment tested the hypothesis that body condition loss occurs more frequently in P1 sows nursing a high number of piglets and would impair ovarian follicle development during lactation and post-weaning, and reduce subsequent fertility. This study assigned P1 sows during lactation to receive a high number (HN, 15 to 16 pigs) or low number (LN, 12 pigs) of nursing piglets. At weaning, to evaluate whether the fertility issue occurred at the pituitary or the ovary, half of each treatment received PG600 or none. Results showed that HN sows lost more piglets due to mortality or removal for poor growth than their littermates, and females lost more body condition than P1 sows nursing a low number of piglets (LN, 12). Still, HN sows weaned more pigs without negative effects on reproductive performance. We conclude that there is variation in fertility in the modern P1 sow and a sub-population of these females develop smaller follicles after weaning but without any significant link to differential follicle development during lactation. The same P1 females are also less likely to ovulate within the optimal time following GnRH, are more predisposed to lose body condition during lactation, and show reduced fertility within certain seasons. The majority of modern P1 sows have the potential for high fertility, but a subpopulation is still susceptible to fertility failures, which seems to be highly related to genetics and management. So, there is still an opportunity for management improvement to achieve high fertility in P1 sows.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Sbaraini Arend, Lidia

Contributors dc:contributor

• Knox, Robert V
• Miller, David J
• Wheeler, Matthew B
• Ellis, Michael

• Primiparous sows
• fertility
• follicle
• ovulation induction
• litter size

Statement dc:rights

• Copyright 2022 Lidia Sbaraini Arend

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115411

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115411