Influence of Rearing Environment and Season on Growth Performance of Growing-Finishing Pigs

An eight-year study was conducted to determine the effects of three different rearing environments on growth performance of growing and finishing pigs (from 28 to 107 kg avg. body wt.) reared during the summer or winter in the southeastern U.S. (31 °N latitude). The three rearing environments were two outside dirt lot types with minimal shelter that (1) had ("old") or (2) had not ("new") been occupied previously by pigs, and (3) concrete-floored pens in a semi-confinement building. Two trials were conducted each year (summer and winter), and each involved 36 crossbred pigs. All pigs were routinely dewormed. Overall, pigs reared during the summer on average grew 3% slower (0.83 vs. 0.86 kg/d; P < 0.001) but required 3% less feed (3.32 vs. 3.41 kg/kg; P < 0.001) per unit of gain than pigs raised during the winter. Rearing environment influenced average daily gain (0.82, 0.85, and 0.86 kg/d for old, new, and concrete pens, respectively; P < 0.001) and feed/gain (3.48, 3.35, and 3.26 kg/kg; P < 0.001). A pen x season interaction (P < 0.01) was noted for feed/gain. Average backfat thickness was influenced by rearing environment (P = 0.01) and somewhat by season (P = 0.08). Growing-finishing pigs can be effectively reared on outside dirt lots under the environmental conditions of the southeastern U.S., in particular if the lots are periodically rotated to new ground.