The influence of piglet body weight on milk production of sows

Thirty sows were allocated at their first farrowing to three experimental treatments: Control foster (CF), sows which suckled piglets which were between birth and 29 days of age; newborn foster (NBF), sows which suckled piglets between birth and 17 days of age followed by piglets between 2 and 28 days old; or two-week foster (TWF), sows which suckled piglets between 17 and 29 days of age. Within each experimental block, CF and NBF sows farrowed on the same day and the TWF sows farrowed 15.0 +/- 0.3 days later. Litter size was standardized to 9 pigs by fostering within one day of farrowing. Litters were exchanged between each of the three cross foster treatments 1.7 +/- 0.3 days after TWF sows farrowed; litters suckling NBF sows were transferred to CF sows, litters suckling CF sows were transferred to TWF sows and the relatively newborn litters suckling TWF sows were transferred to NBF sows. This experimental design enabled the separation of the effect of body weight of the piglet from the effect of stage of lactation of the sow, on sow milk production. Pigs were weaned at about four weeks of age which resulted in lactation lengths for CF, NBF and TWF sows being 28.9 +/- 0.4, 42.5 +/- 0.8 and 15.0 +/- 0.4 days, respectively. TWF sows produced more milk between d 4-8 of lactation than NBF or CF sows (9.13 versus 7.61 and 6.85 kg/d, respectively) but between d 11-15 of lactation, milk yield was not significantly different. After cross-fostering, the milk yield of NBF sows was less than that of CF sows between d 18-22 of lactation (6.65 versus 8.49 kg/d). But, again, between d 25-29 of lactation there was no significant difference in milk yield between NBF and CF sows. The cross-foster treatments had no significant effect on the composition of milk collected from sows throughout lactation. The positive relationship between piglet body weight and milk consumption indicates that older, heavier piglets are able to remove more milk from the mammary glands of lactating sows. (C) 1997 Elsevier Science B.V.