Maternal investment,sibling competition,and offspring survival with increasing litter size and parity in pigs (<Emphasis Type="Italic">Sus scrofa</Emphasis>) |
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Authors: | Inger Lise Andersen Eric Nævdal Knut Egil Bøe |
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Institution: | 1.Department of Animal and Aquacultural Sciences,Norwegian University of Life Sciences,?s,Norway;2.Frisch Centre,Oslo,Norway |
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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. |
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