If sows are heat-stressed their daily feed intake decreases to decrease heat production. The reduced feed intake can result in increased tissue loss from the sow, lower piglet weaning weights, and possibly higher mortality rates (Spencer et al., 2003). Early weaning and use of milk replacer may alleviate these effects (Ratliff et al., 2004), and milk replacer may also decrease piglet weight variation at weaning (Wolter et al., 2002).
Spencer et al. (2003) researched the effects of lactation period, milk replacer, and ambient temperature using 39 Parity 1 sows and 100 Parity 2+ sows. Treatments included lactation room temperature (21° C and 32° C), and lactation lengths (14 or 19 d). Pigs weaned at 14 d were given milk replacer to 19 d. Heat stress decreased sow feed intake and increased weight loss. Early weaning during heat stress reduced sow weight loss. Parity 1 sows lost more backfat overall, and all sows in the hot room lost more when lactating for 19 d. Parity 1 sows weaned early in the hot room had a shorter average wean-to estrus interval than their counterparts lactating 19 d in the same room. Pigs in the hot room given milk replacer were heavier at 19 d than those nursing for 19 d without supplementation. Milk replacer also decreased the variation in 19 d weights between first-litter and multi-parity sows.
In another study, Ratliff et al. (2004) used 703 sows and 7,301 piglets on a commercial farm over a 12-month period to evaluate the interaction between milk supplementation, parity, and season on pig growth and pre-weaning mortality. Litters within sow parity groups were randomly allotted to receive milk replacer or no supplementation at 48 h post-parturition. Supplementation increased the number of pigs weaned, weaning weight, and total litter gain and lowered pre-weaning mortality across all parity groups. Parity 1 and 2 sows weaned more pigs per sow, and had lower pre-weaning mortality than parity 3 sows. Warm weather also decreased piglet ADG.
Wolter et al. (2002) used 32 sows and litters to look at the effects of piglet birth weight (heavy vs. light) and liquid milk supplementation during lactation on growth performance to slaughter weight. Pigs heavier at birth were heavier at weaning, tended to be in larger litters at weaning, and consumed more milk replacer. After weaning the heavier pigs had greater ADG, average daily feed intake, similar gain:feed ratios, and reached market weight seven days faster than lighter pigs. Feeding milk replacer had no effect on growth performance from weaning to slaughter.
Ratliff, B.W., A. M. Gaines, G. L. Allee, M. O’Brien, and J. A. Coalson. 2004. Interactive effects of milk supplementation, parity and season on preweaning mortality and growth performance of piglets on a commercial farm. J. Anim. Sci. 82 (Suppl. 1):797 (Abstr.).
Spencer, J. D., R. D. Boyd, R. Cabrera, and G. L. Allee. 2003. Early weaning to reduce tissue mobilization in lactating sows and milk supplementation to enhance pig weaning weight during extreme heat stress. J. Anim. Sci. 81:2041-2052.
Wolter, B. F., M. Ellis, B. P. Corrigan, and J. M. DeDecker. 2002. The effect of birth weight and feeding of supplemental milk replacer to piglets during lactation on preweaning and postweaning growth performance and carcass characteristics. J. Anim. Sci. 80:301-308.
By Brandi Cole and C. M. Wood, VA Tech - Livestock Update Newsletter