Diet and milk secretion in the sow.

Information on the effect of diet on milk secretion in the sow is limited. Sow’s milk lacks the commercial interest of cow’s milk, and experimental studies of milk secretion are inherently more difficult to conduct in the sow than in the cow. The sow does not voluntarily eject milk in response to stimuli other than those provided by the suckling pig, and manual or mechanical removal of milk from the udder is obstructed. Braude, Coates, Henry, Kon, Rowland, Thompson & Walker (1947) introduced a technique of intravenous injection of oxytocin into an ear vein to induce milk ejection and to permit manual removal of the milk, and this approach has since been used extensively in conjunction with mechanical removal of the milk by machine (Lodge, 1957; Salmon-Legagneur, 1959; Smith, 1959a; Hartman & Pond, 1960). Using this technique, a sample of milk suitable for analysis may readily be obtained but, for meaningful measurements of milk yield, a routine of weighing piglets before and after suckling, over a period of 12-24 h and with suckling intervals of not more than about I h, has to be adopted.