University of Missouri and PIC-USA researchers have found that weaning early, at day 14, lessens the negative impact of heat stress on females, especially gilts, and improves subsequent reproductive performance.

In the experiment, 139 PIC Camborough 22 females (39 gilts and 100 P2 or greater sows) were housed in farrowing rooms at either 70ºF or 90º F. Litters were weaned at either 14 or 19 days of age.

Sow diets were the same, and included 1.07% total lysine and 3365 ME/kg. Litters were standardized at 10-11 pigs.

Body weight, real-time ultrasound backfat and loin eye area (LEA) were taken at farrowing and weaning. Milk was analyzed from 10 P3 or greater sows and litter weights were taken, from both environments, on days 0, 5, 10, 15 and 19.

Researchers found a 40% decrease in feed intake when comparing the 90º F.-housed sows to the 70º F. group. For heat-stressed sows, 19-day lactation increased body weight loss 64%, as compared to the 14-day lactation.

First litter and P2 or greater sows lost 13% and 74% more backfat and twice as much LEA from a 19-day lactation in 90ºF. compared to a 14-day lactation in 90º F. Milk yield was reduced by 30% by the hot environment, but milk protein, fat and lactose were identical.

Heat-stressed gilts returned to estrus in 9.2 days when they were weaned at 14 days. Gilts lactating for 19 days took an average of 22.8 days to return to estrus when heat stressed.

Heat stress reduced subsequent litter size for both first litter and P2 or greater sows.

Fourteen-day weaning in the 70º F environment had a negative effect on subsequent litter size or P2 or greater females at 10.68 vs. 11.53 pigs. However, the opposite was true for gilts and sows weaned at day 14 under heat stress, with 9.23 and 10.45 pigs, respectively, for gilts and sows, as compared with 8.18 and 9.75 pigs, respectively.

Researchers found that the reduced lactation length, in the hot environment, saves tissue loss on the sows and improves subsequent reproduction.

Researchers: Joel Spencer, Gary Allee, University of Missouri, and Dean Boyd, R. Cabera, J. Vigness, R. Graves, PIC-USA. For more information, e-mail Boyd at

Milk replacer lessens impact of hot farrowing on nursery weights

The Missouri and PIC researchers continued their study on heat stress by testing the effectiveness of milk replacer (MR) in increasing pig weaning and nursery weights. The pigs were from litters housed at 70º or 90º in farrowing and were weaned from the sow at 14 or 19 days. The litters weaned at 14 days were fed MR to 19 days. All pigs were weaned to a nursery on day 19.

Milk replacer (Advanced Birthright Nutrition) was offered on day 10 to specified litters to acclimate the pigs prior to weaning. Pig weights were taken at 19 (weaning) and 47 (end of nursery) days of age.

Pigs from gilts and P2 or greater sows provided MR under heat stress had heavier weaning weights than pigs nursing to 19 days. Weights were 16.24 lb. and 17.99 lb. for gilts and sows litters fed milk MR vs. 12.28 lb. and 13.31 lb. for litters not fed MR.

On day 14, pigs in the 90º F. farrowing were lighter (17.5 lb.) than those in 70º F. (18.35 lb.). By day 19, pigs on MR in 90º F. had weaning weights similar to the pigs fed MR in 70º F.

More than 70% of the pigs provided MR in both the control and hot farrowing had pig weaning weights above 14.96 lb. In contrast, 50% and 27% of the pigs nursing for the entire 19 days had weaning weights above 15 lb., for the 70º F. and 90º F. farrowing temperatures.

During the 47-day nursery period, pigs fed MR prior to weaning had higher ADG in the nursery. Pigs born of gilts and fed MR in the 90ºF farrowing had the biggest advantage. ADG was 0.90 LB vs. 0.81 lb, respectively.

On day 66 of age, 67% and 54% of the pigs fed MR in the control and heat stressed environments weighed more than 60 lb., compared to 52% and 34% of the pigs nursing for 19 days in the cool and hot environment, respectively.


The researchers found that early weaning the sow and supplementing milk replacer preserves the sows physical condition and prevents lower weaning and nursery pig weights.

Researchers: Joel Spencer, Gary Allee, University of Missouri, and Dean Boyd, R. Cabera, J. Vigness and R. Graves, PIC-USA. For more information, e-mail Boyd at