Relationship between growth and non-nutritive massage in suckling pigs

Nursing in the domestic pig is a complex act comprised of five distinct phases. The fifth phase involves a lengthy massaging of the udder following milk ejection and is energetically costly to the piglet. Because of this cost, it is speculated that this massage functions as a form of begging that may alter milk production at individual teats or for the entire litter during the early stages of lactation. The objective of this experiment was to determine if there is a relationship between non-nutritive massage and growth in the young pig over the course of lactation. The suckling behaviour of 195 piglets from 20 litters was observed during at least three nursing bouts on each of three separate days. Piglets were weighed at birth and at 15 days post-partum, and 15-day growth rates were calculated. There was a significant difference between and within litters in suckling behaviour performed after milk ejection. Growth rates were negatively correlated with suckling during the final massage for individual piglets (r = −0.26; P < 0.003) and entire litters (r = −0.79; P < 0.001). Slower growing piglets also performed more suckling behaviour between nursing bouts (r = −0.23; P < 0.05) and during incomplete nursing bouts (r = −0.30; P < 0.01) Piglets that performed the final massage consistently grew slower than those not involved with this costly behaviour. These data support the hypothesis that massage after milk ejection is representative of piglets’ nutritional need. However, it appears that a lengthy massage does not result in an overall net return on piglet growth rate.