Relationship between Yield and Composition of Sows' Milk and Weight Gains of Nursing Pigs

Data from 100 lactations, in which conditions were carefully standardized, were analyzed to investigate the relationships between sow milk yield and composition and pig weight gain. The mean efficiency of conversion of milk to gain was found to be 4.5 g of milk per 1 g of pig gain, but this was subject to wide individual variation. Correlations between milk yield and solids percentage and milk yield and nitrogen percentage were very low. Analysis of the data by multiple regression procedures indicated that 34% of the variation in pig gain could be attributed to variation in milk yield. The relationship was improved when the solids content of the milk was also included in the equation (R2 = 44%), but there was little advantage to the further inclusion of nitrogen content (R2 = 45%). The study indicates that weekly pig weight gains provide a limited estimate of a sow's lactation performance and that they are substantially influenced by other factors in addition to the sow's milk yield.