The biological basis for prenatal programming of postnatal performance in pigs1,2

Abstract

The main purpose of this review is to discuss associations between within-litter variation in birth weight, and preweaning survival and postnatal growth in the pig, as the basis for suggesting that the developmental competence of pigs born, as well as the size of the litter, need critical consideration. Extremes of intrauterine growth retardation (IUGR) occur within a discrete subset of fetuses, substantially smaller than their littermates and commonly described as runt piglets. The lower preweaning growth of runt pigs cannot be entirely explained based on their lower birth weight, nor do they show full postnatal compensatory growth. Interestingly, this more complex reprogramming of development in runt pigs can already be identified by d 27 to 35 of gestation. Recently, we reported more universal IUGR effects in commercial dam-line sows, as an indirect response to selection for increased litter size. High ovulation rates (>30 ovulations) in a proportion of greater parity sows are associated with increased numbers of conceptuses surviving to d 30 of gestation, resulting in detrimental effects on placental development of uterine crowding in the early postimplantation period. In turn, this limits nutrient availability to the embryo during a critical period of myogenesis. Consequently, although a reduction in the number of conceptuses occurs by d 50, placental development in the surviving fetuses remains compromised, resulting in IUGR and reduced numbers of muscle fibers at d 90 and at birth, in all surviving littermates. These effects of uterine crowding on fetal and postnatal development are analogous to the detrimental effects of nutritional restriction in gestating sows on fetal myogenesis, birth weight, and postnatal growth. The incompatibility between increased numbers of conceptuses surviving to the postimplantation period, in the absence of increased uterine capacity, offers a biological explanation for increased variability in birth weight and postnatal growth performance reported in greater parity sows. We conclude that a strategy of introducing hyperprolific females into the breeding nucleus, as a means of increasing the numbers of pigs born, needs to be critically evaluated in the context of the overall efficiency of pork production.

Within-litter variation in birth weight: impact of nutritional status in the sow

“…As gestation progresses, the negative effects of limited uterine space on fetal development also increase (Vonnahme et al, 2002). The great within-litter variation in birth weight and increased proportion of small piglets born to the highly prolific sows as used today are likely related, in part, to intra-uterine crowding from at least the end of the first month of gestation (Foxcroft et al, 2006), especially when there are more than 14 fetuses present within the uterus (Webel and Dziuk, 1974). Moreover, intrauterine crowding can alter the pattern of development of fetal muscle fibers in the immediate postimplantation period (Foxcroft et al, 2007), when mesenchymal stem cells of the embryo undergo differentiation for myogenesis, adipogenesis or mesenchymal cells (Cossu and Borello, 1999;Du et al, 2010).…”

“…Heterogeneity is a problem mainly for piglets with low birth weight that have suffered from IUGR (Foxcroft et al, 2006), which is associated with high pre-weaning mortality, variable weights at weaning, and poor growth performance post-weaning, resulting in lower production efficiency and economic losses. Furthermore, withinlitter homogeneity in birth weight may also be related to a decrease in stillbirths (Damgaard et al, 2003;Canario et al, 2006).…”

Compensatory growth feeding strategy does not overcome negative effects on growth and carcass composition of low birth weight pigs

“…Responsible for this outcome are gestational factors such as intrauterine crowding and impaired placental development resulting in insufficient nutrient supply and therefore impaired foetuses development (Foxcroft et al, 2006;Wu et al, 2006). Because piglet's survival rate during lactation is closely related to their birth weight (Quiniou et al, 2002) and the percentage of piglets weighing < 1 kg increases with increasing litter size (Bérard et al, 2008;Campos et al, 2012), overall reproduction efficiency in terms of number of weaned piglets and total weaning weight might be compromised in high prolific sows.…”

Growth and development of adipose tissue and gut and related endocrine status during early growth in the pig: impact of low birth weight

“…In the pig, intrauterine growth retardation, leading to LBW, occurs naturally. The aetiology and underlying mechanisms of intrauterine growth retardation in livestock as well as in humans and rodents have been recently reviewed (McMillen and Robinson, 2005;Foxcroft et al, 2006;Murphy et al, 2006;Wu et al, 2006). It results from alteration in foetal substrate supply.…”