The effect of litter hierarchy and teat allocation on suckling piglets' growth

The objective of the current study was to adjust a growing curve to suckling piglets as a function of the hierarchical position achieved and of mammary gland allocation (anterior, medium, or posterior) for the investigation of, eventually, different growing patterns. For this purpose, 280 piglets from 20 sows (14 per sow) were weighed and observed from birth to weaning. The birth weight of piglets in the three groups was found to be significantly different ( $P<0.05$ ), with heavier piglets gaining access to the more productive anterior teats. The quadratic curve was found to be the best fit to model piglets' growth up to weaning. Higher hierarchical positions chose the most productive mammary glands in decreasing order: the anterior, medium, and posterior areas of the venter of the sow. Piglets in the different teat-suckling groups (anterior, medium, and posterior) studied have significantly different growing patterns. The anterior-teat-suckling piglets' growth curve can be differentiated almost immediately from the beginning and up to weaning from the medium- and the posterior-teat-suckling groups. These last two teat-suckling groups (medium and posterior) can be differentiated from day 20 and up to weaning. At weaning (28 d), the three distinct groups have significantly different weights ( $P<0.001$ ). Piglets' birth weights correlate positively with a higher hierarchy. A higher hierarchy results in heavier weaning once the piglets gain access to the more productive teats. The number of functional teats in relation to larger litter sizes needs attention from pig breeders to mitigate welfare issues while maintaining reproductive performance.