Ovarian follicle development and genital tract characteristics in different birthweight gilts at 150 days of age

Abstract

In the last decades, selection for improved prolificacy has resulted in higher litter sizes and has thereby increased the proportion of low birthweight (LW) piglets. It is well documented that LW piglets have lower growth performance, muscle accretion and poor carcass quality. However, little is known about the relations of birthweight with subsequent reproductive performance in gilts. This study investigated the effects of birthweight on reproductive tract and ovarian follicle development in 150-day-old gilts. Twenty eight female pigs of different birthweight ranges (high-HW: 1.8-2.2 kg; low-LW: 0.8-1.2 kg) from higher parity commercial sows were reared until 150 days of age, and their body weights were recorded at weaning, end of nursery and end of the grower-finisher phase. The animals were killed and their reproductive tracts collected for biometrical and histomorphometrical analysis. LW gilts showed significantly lower body weights and growth rates during all phases of production compared to their HW counterparts (p < .01). Most biometrical measurements of the reproductive tract were similar between the experimental groups, except vaginal length and the gonadossomatic index (relative ovarian weight), which were affected by birthweight class (p < .05). LW females also showed fewer medium size (3-5 mm; p < .01) ovarian follicles, pre-antral follicles (p < .07) and more atretic follicles per ovarian cortex area (p < .05). Therefore, besides the effects on post-natal growth performance, birthweight affects vaginal length and the follicular dynamics process, which may impair the reproductive performance of replacement gilts.

Farm data analysis for lifetime performance components of sows and their predictors in breeding herds

“…Gilts with a low birth weight are associated with intrauterine growth retardation [46], and have fewer medium size follicles and more atretic follicles on the ovary than gilts with a high birth weight, when approaching expected puberty age [47]. Therefore, gilts with a low birth weight should not be selected, nor should those born to sows that have farrowed a large litter with large variation in birth weights.…”

Gilt Management for Fertility and Longevity

“…Within-litter variation has been attributed to factors such as the duration of ovulation, oocyte maturation, the implantation capability of conceptuses and position within the uterus, placental efficiency, uterine space, breed differences and intrauterine growth retardation [12]. There is consensus that low birth weight gilts have increased preweaning mortality [13,14] and those low birth weight gilts that do survive past the nursery phase have poor growth until finishing and are significantly lighter than their higher birth weight litter mates [13,15]. Additionally, as future replacement females, low birth weight negatively impacts their reproductive potential.…”

“…Additionally, as future replacement females, low birth weight negatively impacts their reproductive potential. Variation in birth weight is negatively correlated to ovarian and uterine development [16] and low birth weight gilts have different populations of follicles on the ovary and shorter vaginal length at 150 days of age, suggesting ovulation rate and consequently litter size may be adversely affected [15]. Collectively, the reports of Valet et al [17] and Calderon-Diaz et al [18] suggested that, in high health environments, the birth weight and overall growth rate of contemporary commercial gilts are not limiting for age at puberty, but preweaning growth rate was inversely related to age at puberty and birth weight was positively associated with uterine weight.…”

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

“…In recent years, focus on gilt development and sow longevity has identified litter of origin, birthweight, growth rate, and body composition as key factors. Almeida et al (2017b) reported that low birthweight gilts had different populations of follicles on the ovary when approaching expected age at puberty (Almeida et al, 2017a). In addition, low birthweight gilts have slower growth and often cannot achieve the target growth rate of 600 g/d at the time of selection (Kummer et al, 2009).…”