Andersen Inger Lise, Nævdal Eric, Bøe Knut Egil
Behav Ecol Sociobiol. 2011 Jun;65(6):1159-1167. doi: 10.1007/s00265-010-1128-4. Epub 2011 Jan 12.
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.
本研究的目的是检验窝产仔数和胎次对同胞竞争、仔猪存活及体重增加的影响。据预测，随着窝产仔数增加，乳头竞争会加剧，导致因母猪杀婴（即挤压）和饥饿造成的死亡率升高，从而使存活仔猪数量保持恒定。我们预测随着窝产仔数增加，仔猪体重增加会受到负面影响。基于母体投资理论，我们还预测母猪生命后期所产仔猪的死亡率会更高，因此早期产的仔猪中存活数量会更多。正如预测的那样，由于被挤压仔猪比例增加（其中大多数在乳头竞争中失败）以及同胞竞争加剧导致的饥饿，仔猪死亡率随着窝产仔数增加而上升，存活仔猪数量保持恒定。第1天的仔猪体重以及断奶前的生长情况也随着窝产仔数增加而下降。第4胎母猪所产仔猪因饥饿导致的死亡率更高，但存活仔猪数量不受胎次影响。总之，对于大多数母猪胎次而言，因母猪挤压仔猪（其中许多未成功获得乳头）和同胞竞争导致的饥饿所造成的仔猪死亡率，会随着窝产仔数增加而上升。断奶时存活仔猪数量恒定表明，10至11头仔猪可能接近家猪能够照料的上限。
