NURSING IN PIGS - COMMUNICATING NEEDS AND DISTRIBUTING RESOURCES

When nursing, the sow has a problem to solve different from that of most other mammals because she gives birth to a large number of precocial young. The sow has to incorporate elements into its nursing process that enable it to distribute milk evenly among its young in spite of their being able to fight with and suckle independently of their litter-mates. This paper described the different features of the nursing process, discussing the functions of a long initial massage before ejection, the grunting of the sow during the first phases of nursing, the postejection massage, and nonnutritional nursings in the context of a process of communication. Through tactile stimulation of the udder by the pigs, the sow releases a number of pituitary, gut, and pancreatic hormones. The physiological response of the sow is suggested to be quantitatively related to the tactile input given by the pigs. Evidence is presented to support the idea that a fault in the communication process disturbs the nursing-suckling interaction and, thus, the transfer of milk from the sow to its pigs. Also, the importance of some environmental factors that affect this process is discussed.