Effects of season and distance moved during loading on transport losses of market-weight pigs in two commercially available types of trailer

This study evaluated effects of trailer design and season on physical indicators of stress dur- ing loading and unloading and transport losses (dead and nonambulatory pigs) in market-weight pigs (BW = 129.6 ± 0.40 kg). A total of 109 trailer loads of pigs (n = 17,256 pigs) from 1 farm were used in a random- ized complete block design with a 2 × 4 factorial ar- rangement of treatments: 1) trailer design (pot-belly vs. straight-deck) and 2) season (spring vs. summer vs. fall vs. winter). A subset of loads (n = 42) was used to examine effect of distance pigs were moved during loading (short (<24 m) vs. long (47 to 67 m)) on physi- cal indicators of stress and transport losses. This study was conducted on 7 d per season at 1 farm with 4 loads (2 on pot-belly and 2 on straight-deck trailers) being transported each day to 1 commercial packing plant. Pigs from different farm groups were mixed on the trailer and provided with 0.45 m 2 /pig floor space dur- ing an approximately 4-h journey to the plant. The per- centage of pigs exhibiting open-mouth breathing, skin discoloration, and muscle tremors was recorded during loading and unloading. Additionally, dead pigs on ar- rival at the plant and nonambulatory pigs at the farm and at the plant were recorded. Effects of trailer design on open-mouth breathing and skin discoloration dur- ing unloading were dependent on season (trailer de- sign × season interaction; P < 0.05). Pigs unloaded from pot-belly trailers had a greater (P < 0.05) incidence of open-mouth breathing in the spring and summer and a greater (P < 0.05) incidence of skin discoloration in the spring, summer, and winter than pigs unloaded from straight-deck trailers. The incidence of total nonambu- latory pigs at the plant was greater (P < 0.05) in the winter than in the spring and summer. The long com- pared with short distance moved treatment resulted in a greater (P ≤ 0.001) incidence of open-mouth breath- ing and skin discoloration during loading and tended (P = 0.06) to increase the incidence of nonambulatory pigs at the farm. However, there was no effect of trailer design, season, or loading distance on total losses at the plant. In summary, physical indicators of stress (open-mouth breathing and skin discoloration) were increased with the long distance moved during load- ing treatment and were greater during unloading for pot-belly than straight-deck trailers; however, trailer design, season, and loading distance had minimal ef- fects on total transport losses.