Influence of split marketing on the physiology, behavior, and performance of finishing swine

This study examined the effect of split marketing on selected behavioral, physiological and production parameters in commercial market hogs. One hundred twenty eight-week old high-lean, high-health barrows (20.3 kg BW) were weighed and randomly assigned by weight in a randomized complete block design to one of three treatments: SM (split marketed), 6 pigs/pen (.56 m²/pig): C (control), 6 pigs/pen (.56 m²/pig); or MC (modified control), 3 pigs/pen (1.11 m²/pig). The heaviest (120.3 kg) one half of SM animals were removed one week prior to penmates (116.3 kg) marketing. C (119.2 kg) and MC (121.8 kg) penmates remained grouped together until marketing. Animals were videotaped for the first 72 hours of the study (INITIAL), 72 hours prior to (PRE) and following the removal (POST) of pigs in SM treatment to identify socially dominant, intermediate and submissive pigs. A blood sample was collected from each animal upon completion of INITIAL, PRE, and POST time periods to determine neutrophil:lymphocyte ratio, plasma haptoglobin, total cortisol and corticosteroid-binding globulin levels. Animals were weighed and feed disappearance was calculated every two weeks. Animals also underwent an ultrasound evaluation for tenth rib backfat and loin muscle area at marketing.

Regardless of treatment, animals were more (P < .0001) active (feeding, walking/standing and fighting) at INITIAL than at PRE or POST. Neutrophil:lymphocyte ratio, plasma haptoglobin and corticosteroid-binding globulin levels were greater (P < .0001) during INITIAL compared to PRE or POST but did not differ between treatments. No treatment or time differences were detected in total plasma cortisol. MC exhibited greater (P < .0001) feed efficiency and average daily feed intake compared to 0 or SM treatments up to split marketing. The remaining penmates in the SM group had higher (P < .05) average daily feed intake when compared to 0 or MC treatments during the last week of the trial. There were no treatment differences in carcass characteristics of backfat or loin eye muscle area although 0 tended to be leaner (P = .08) than MC while SM was not different from C or MC. These results indicate that hogs remaining after SM have greater average daily feed intake when compared to the performance of hogs managed in the same way with respect to group size prior to and after marketing of SM animals. Significant differences in performance between the treatment groups cannot be attributed to any physiological or behavioral measures as reported here.