Influence of Fasting, Water Deprivation and Stress on Carcass Shrink of Pigs and Rats

Pigs slaughtered after feed and water were removed for 20 hr. dressed (head on) 78.6% based on unshrunk liveweight. Withholding feed or water singly or in combination for an additional 24 hr. resulted in a 5.0 to 5.7% liveweight shrink and 1.0 to 2.1% carcass weight shrink. Mixing the pigs with strange pigs during this period had no additional effect on dressing percent. Withholding feed for an additional 48 hr. resulted in a 7.9% liveweight shrink and 3.1% carcass weight shrink.Rats had liveweight and carcass weight shrinkages similar to those for pigs. Rats exposed to a wind velocity of 60 m./min. did not shrink more than the corresponding group when food and water were withdrawn for 24 hr., but they shrank more than the corresponding group when food and water were not withdrawn. Rats killed at 8 p.m. had a lower dressing percent than those killed at 8 a.m., although weight of digestive tract and contents did not differ significantly between these groups.Average backfat thickness was reduced 0.32 cm. when feed and water were withheld from pigs for 48 hr., but other carcass measurements were not significantly affected. Liver weight of rats decreased when food or water were withheld, but heart weights did not change.