Effects of porcine somatotropin on growth and carcass composition of Meishan and Yorkshire barrows.

Effects of porcine somatotropin (pST) on growth and carcass characteristics of Meishan (Ms) 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 108 kg. Second, another 18 Ms barrows were treated to 108 kg BW. Age- and weight-matched treatments were analyzed. Results for both groups indicated pST effects (P < .05) for feed conversion (+) and intake (-), dressing percentage (-), percentage of carcass fat (-) and protein and water (+), leaf fat (-), backfat (BF) thickness (-), longissimus muscle area (LMA; +), skin thickness (+), muscle firmness and marbling scores (-), organ weights (+), belly (-), clear plate (-), ham (+), and total boneless cuts (BC; +). Somatotropin effects were also present for loin (-) and boneless Boston butt (BBB; +) in the age-matched group and 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 wholesale cuts (WC; +) except clear plate (age-matched), all trimmed cuts (TC; +) except picnic shoulder (weight-matched), and all BC (+). Breed effects, in favor of Y barrows, were also determined for carcass length (+), percentage of carcass ash (-), leaf fat (+), average BF thickness (+), and heart (-) and liver (-) weights in age-matched animals and percentage of carcass fat (-), protein (+), water (+), leaf fat (-), 10th rib, average, and P2 BF thicknesses (-), marbling score (-), femur length (-), and liver weights (+) in weight-matched animals. A higher response to pST (P < .05) was determined in Ms barrows than in Y barrows 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).