Maternal investment, sibling competition, and offspring survival with increasing litter size and parity in pigs (Sus scrofa)

Abstract

The aim of this study was to examine the effects of litter size and parity on sibling competition, piglet survival, and weight gain. It was predicted that competition for teats would increase with increasing litter size, resulting in a higher mortality due to maternal infanticide (i.e., crushing) and starvation, thus keeping the number of surviving piglets constant. We predicted negative effects on weight gain with increasing litter size. Based on maternal investment theory, we also predicted that piglet mortality would be higher for litters born late in a sow's life and thus that the number of surviving piglets would be higher in early litters. As predicted, piglet mortality increased with increasing litter size both due to an increased proportion of crushed piglets, where most of them failed in the teat competition, and due to starvation caused by increased sibling competition, resulting in a constant number of survivors. Piglet weight at day 1 and growth until weaning also declined with increasing litter size. Sows in parity four had higher piglet mortality due to starvation, but the number of surviving piglets was not affected by parity. In conclusion, piglet mortality caused by maternal crushing of piglets, many of which had no teat success, and starvation caused by sibling competition, increased with increasing litter size for most sow parities. The constant number of surviving piglets at the time of weaning suggests that 10 to 11 piglets could be close to the upper limit that the domestic sow is capable of taking care of.

Higher preweaning mortality in free farrowing pens compared with farrowing crates in three commercial pig farms

“…Previous studies have established a similar unfavourable relationship between increased parity and preweaning survival (Jarvis et al, 2005;Weber et al, 2009;Andersen et al, 2011). In the present study, first-parity sows gave birth to fewer live-born piglets than older sows.…”

“…In the present study, first-parity sows gave birth to fewer live-born piglets than older sows. Increased litter size has a negative impact on piglet mortality (Andersen et al, 2011) and a greater number of piglets in the pen make more piglets available for crushing when the sow lies down (Weary et al, 1998). However, there were no difference in the number of live-born deaths between sows of parities 2, 3 to 4 and 5 to 8, indicating that not only the number of piglets caused older sows to have a higher piglet mortality.…”

“…Accordingly, a higher number of total born piglets has been shown to have negative effects on preweaning survival in both pens and crates Weber et al, 2009). Piglets that are born in larger litters are more likely to have a lighter birth weight (Quiniou et al, 2002;Wolf et al, 2008), and light birth weight is associated with risk factors such as lower viability (Baxter et al, 2008;Hales et al, 2013), increased risk of hypothermia (Herpin et al, 2002) and increased sibling competition at the udder (Andersen et al, 2011). An investigation into indicators of survival in non-crated systems established that piglets that were born in large litters had increased risk of dying the 1st day after farrowing and that surviving piglets had a higher birth weight than dying piglets .…”

The influence of the thermal environment and other early life events on growth rate of piglets during lactation

“…However, the number of suckling piglets on day 21 did impact the ADG, the ADG being negatively correlated with the number of suckling piglets. This is in agreement with several previous studies showing a reduced weight at weaning in large litters (Milligan et al, 2002;Andersen et al, 2011) and a Danish study indicating that in larger litters (11 to 15 suckling piglets), the addition of one extra piglet results in a reduction in weaning weight of~150 g/extra piglet (Thorup, 2010).…”

Development of a methodology to describe udder conformation in sows

“…Piglets are totally dependent on their mother when they are born, and adequate intake of good quality colostrum is fundamental for their immediate and longer-term survival (Edwards, 2002). In this respect, a short latency to find a teat and suckle is vital for a newborn piglet (Andersen et al, 2011). Udder conformation plays a role in this; modern sows have larger body size and sub-optimal udder conformation that affects the ability of the newborn piglets to find a teat and suckle (Vasdal and Andersen, 2012).…”