Influence of pig substitution on milk yield, litter weights, and milk composition of machine milked sows.

This study was conducted to 1) determine milk yield of sows that were machine milked up to four times daily; 2) determine the effect of pig substitution on milk yield; 3) assess litter weight changes for sows that are milked; and 4) determine milk composition. Eight sows were milked four times daily to d 51 postpartum. Sows either maintained their own litter or had a week-old replacement litter to replace 25-d-old pigs. Individual gland milk yields were obtained on random days throughout lactation, and different diameter and weighted teat cups were rotated so that all glands received all combinations. Composite milk samples were analyzed for fat, protein, and somatic cells. Milk yields peaked at about 19 d postpartum and declined to 45 d postpartum in sows with their own litter, whereas milk yields peaked earlier and had a more dramatic decline after fostering of a younger litter. Litter weights were 17.1 ± 1.0 kg at farrowing with 13.6 ±.6 pigs born alive. Final litter weights were 34.4 ± 11.7 kg for sows with replacement litters and 74.4 ± 13.5 kg for sows with their own litters, and numbers of pigs weaned were 6.5 ± 1.3 and 9.7 ± 1.5, respectively. Milk fat was influenced by route of oxytocin administration (6.53 ±.12 for i.v. vs 7.21 ±.19% for i.m. administration; P <.05). Milk fat percentage was highest on d 2 and declined to 13 d postpartum. Milk protein was influenced by time of day of milking (lowest at the fourth milking, 5.57 ±.11%) and followed a pattern similar to that for milk fat. Milk protein was affected in a linear manner by milk yield, with highest protein associated with lowest milk yields. Somatic cells in milk were influenced by litter replacement ( P <.05) and oxytocin administration ( P <.01). There was a linear increase in somatic cells from about 8 × 10 6 cells/mL milk at d 2 to more than 12 × 10 6 cells/mL milk at d 51 postpartum. These results show that pig replacement affects the amount of milk obtained. Moreover, milk composition changes throughout lactation. However, milk removal from sows has a severe impact on litter weight gains, and in systems where sow's milk is needed for commercial purposes, pig supplementation is necessary.