Effects of Sorting Frequency During Harvest on Pig Growth Performance, Morbidity and Mortality, and Carcass Characteristics

Frequent sorting during the harvest period may be advantageous to swine producers to ensure accurate and timely removal; however, this may cause excess stress for the animals. This study aimed to determine the effect of frequency of sorting during the harvest period on growth performance, morbidity and mortality, and carcass characteristics. A total of 1,496 pigs (49.8 kg ± 1.38 BW) were allotted to pens of 34 pigs, blocked by gender and location within the barn, and assigned one of two sorting strategies: either sorting pigs bi-weekly (Bi-Weekly) or twice a week (2x-Week) during the 42-d sorting period (n = 22 pens/treatment). The initiation of sorting program (d 0) began at a fixed weight of 102.5 ± 1.58 kg. For both treatments, the heaviest 26.5%, 44.1% and 29.4% of the pigs were marked, sorted, and removed from pens on d 14, 28, and 42, respectively, to be sent for harvest. For the 2x-Week treatment, the pigs that would have been sent for harvest at that scheduled time were also marked and sorted out of their pens on d 3, 7, 10, 17, 21, 24, 31, 35, and 38 to simulate a harvest sorting event and then were immediately placed back into their pens. All pigs were fed a commercial diet program that met or exceeded nutrient requirements. Pigs were harvested at a commercial packing plant where hot carcass weight, backfat depth, and loin depth were measured, and carcass yield and predicted lean content were calculated. Growth performance and carcass data were analyzed using the lmer function of R with pen as the experimental unit, the fixed effect of treatment, and random effect of block. Morbidity and mortality data were analyzed with pig as the experimental unit using Chi-squared procedures. Pigs in the 2x-Week group weighed less at the time of allotment compared to the Bi-Weekly group (49.7 vs 49.9 kg, respectively; P = 0.05); however, the weight at the start of sorting period was similar (P > 0.10) between treatments. From the start of the sorting period to the end of study, ADG, ADFI, and G:F were all similar (P > 0.10) between treatments. Carcass characteristics were not impacted (P > 0.10) by sorting treatment. Overall morbidity and mortality were similar (P > 0.05) between treatments. In conclusion, the frequency of sorting during the harvest period did not result in poorer growth performance or carcass characteristics in this study.