EFFECTS OF PORCINE SOMATOTROPIN ON GROWTH AND CARCASS COMPOSITION OF MEISHAN AND YORKSHIRE BARROWS

Effects of porcine somatotropin (pST) on growth and carcass characteri stics of Meishan (M s) and Yorkshire (Y) barrows given 3 mg of pST or saline daily were determined for two end points. First, 26 Ms and 26 Y barrows were treated from 119 d of age until the Y barrows reached 10 8 kg. Second, another 18 Ms barrows were treated to 108 kg BW. Age- an d weight-matched treatments were analyzed. Results for both groups ind icated pST effects (P < .05) for feed conversion (+) and intake (-), d ressing percentage (-), percentage of carcass fat (-) and protein and water (+), leaf fat (-), backfat (BF) thickness (-), longissimus muscl e area (LMA; +), skin thickness (+), muscle firmness and marbling scor es (-), organ weights (+), belly (-), clear plate (-), ham (+), and to tal boneless cuts (BC; +). Somatotropin effects were also present for loin (-) and boneless Boston butt (BBB; +) in the age-matched group an d for ADG (+), carcass weight (-), loin (-), jowl (-), and tenderloin (+) in the weight-matched group. Breed effects (P < .05), in favor of Y barrows, in both treatments existed for ADG (+) and feed intake (+), carcass weight (+), dressing percentage (+), LMA (+), skin thickness (-), muscle color and firmness scores (-), muscling score (+), all who lesale cuts (WC; +) except clear plate (age-matched), all trimmed cuts (TC; +) except picnic shoulder (weight-matched), and all BC (+). Bree d effects, in favor of Y barrows, were also determined for carcass len gth (+), percentage of carcass ash (-), leaf fat (+), average BF thick ness (+), and heart (-) and liver (-) weights in age-matched animals a nd percentage of carcass fat (-), protein (+), water (+), leaf fat (-) , 10th rib, average, and P2 BF thicknesses (-), marbling score (-), fe mur length (-), and liver weights (+) in weight-matched animals. A hig her response to pST (P < .05) was determined in Ms barrows than in Y b arrows for percentage of carcass protein (+), liver (+), and heart (+) in the age-matched treatment and 10th rib BF thickness (-) and heart weight (+) in the weight-matched treatment. Yorkshire barrows treated with pST had more improved values for color score (+; age-matched) and BBB (+; weight-matched).