Follicular development of sows at weaning in relation to estimated breeding value for within-litter variation in piglet birth weight

Abstract

In this study we aimed to identify possible causes of within-litter variation in piglet birth weight (birth weight variation) by studying follicular development of sows at weaning in relation to their estimated breeding value (EBV) for birth weight variation. In total, 29 multiparous sows (parity 3 to 5) were selected on their EBV for birth weight variation (SD in grams; High-EBV: 15.8±1.6, N=14 and Low-EBV: -24.7±1.5, N=15). The two groups of sows had similar litter sizes (15.7 v. 16.9). Within 24 h after parturition, piglets were cross-fostered to ensure 13 suckling piglets per sow. Sows weaned 12.8±1.0 and 12.7±1.0 piglets, respectively, at days 26.1±0.2 of lactation. Blood and ovaries were collected within 2 h after weaning. The right ovary was immediately frozen to assess average follicle size and percentage healthy follicles of the 15 largest follicles. The left ovary was used to assess the percentage morphologically healthy cumulus-oocyte complexes (COCs) of the 15 largest follicles. To assess the metabolic state of the sows, body condition and the circulating metabolic markers insulin, IGF1, non-esterified fatty acid, creatinine, leptin, urea and fibroblast growth factor 21 were analysed at weaning. No significant differences were found in any of the measured follicular or metabolic parameters between High-EBV and Low-EBV. A higher weight loss during lactation was related to a lower percentage healthy COCs (β= -0.65, P=0.02). Serum creatinine, a marker for protein breakdown, was negatively related to average follicle size (β= -0.60, P=0.05). Backfat loss during lactation was related to a higher backfat thickness at parturition and to a higher average follicle size (β=0.36, P<0.001) at weaning. In conclusion, we hypothesise that modern hybrid sows with more backfat at the start of lactation are able to mobilise more energy from backfat during lactation and could thereby spare protein reserves to support follicular development.

Ovarian Follicle Growth during Lactation Determines the Reproductive Performance of Weaned Sows

“…The metabolic rate during lactation differs between sows with equitable feeding [39] and sows with higher weight loss during lactation have longer weaning-to-estrus intervals [40]. The ovarian response to gonadotropins post-partum and during lactation are regulated by insulin and the insulin-like factor (IGF-I), and sows metabolically compromised after farrowing have reduced both insulin and IGF-1 levels [41], which has a negative impact on the ovarian follicular development [19,42,43]. Lucy [41] indicated that this mismatch could persist during lactation and weaning.…”

Coping with large litters: the management of neonatal piglets and sow reproduction

“…The sow is supposed to eat enough to meet the nutrient requirements of growing litters prior to farrowing, which may cause some of the problems seen around the time of farrowing [9,10]. During the early stage of lactation, sows with large litters loose more energy while producing more milk that cannot match up with the energy from their feed, ending up in a negative energy balance (NEB) [11,12]. Negative energy balance impacts follicle development after weaning [13][14][15], oocyte quality [13,14], embryo development [11,16], and piglet birth weight [17].…”

Factors affecting estrus and ovulation time in weaned sows with induced ovulation by GnRH administration in different seasons

“…Therefore, follicular growth after weaning in these sows might be compromised. Recently, Costermans et al [8] demonstrated that a higher weight loss during lactation was also related to a lower percentage of healthy cumulus-oocyte complex. These findings indicate that season or climatic factors may influence feed intake and body weight loss of sows during lactation, and thus, has a significant impact on the response of sows to GnRH treatment.…”