Evaluation of recombinant porcine somatotropin on growth performance, carcass characteristics, meat quality, and muscle biochemical properties of Belgian Landrace pigs

The dose related effects of recombinant porcine somatotropin (rpST) on growth, carcass characteristics, muscle properties, and meat quality were investigated in lean Belgian Landrace finishing pigs. Ninety-six pigs (48 barrows and 48 gilts) were injected daily with either vehicle, 1.5, 3, or 6 mg of rpST from 60 to 97.5 kg live weight. Each treatment group consisted of six pens of four pigs each (two of each sex). Pigs were given ad libitum access to a high-protein (20.4% CP) cereal-based diet. Administration of rpST increased (P < 0.05) growth rate (16.3 to 25.4%) and improved (P < 0.05) feed efficiency (16.9 to 29.4%). Feed consumption was reduced (12%; P < 0.05) only in the 6 mg of rpST group. Liver, kidney, and heart weights were increased (P < 0.05) in the 3 and 6 mg of rpST groups. Although the Belgian Landrace pigs are bred for superior carcass quality, rpST further improved (P < 0.05) carcass composition at aH dose levels as evidenced by a reduction (10 to 50%) in a number of subcutaneous fat depth measurements, an increase (10 to 20%) in longissimus muscle area, and an improvement in the lean cut:fat cut ratio. Rate of pH decline in the gluteus and longissimus muscles was similar, but rapid, in all groups (pH after 30 min = 5.74 to 5.94); the ultimate (24 or 72 h) pH was 0.1 5 to 0.2 pH units higher (P < 0.05) in the pigs that received the 3 and 6 mg of rpST doses. Longissimus tenderness (measured by shear force and penetration), water holding capacity, myofibrillar protein concentration, and sarcomere length were not affected by rpST administration. Protein content of the longissimus was increased (P < 0.05) by rpST treatment, whereas percentage of lipid, moisture, DM, and collagen were unchanged. In summary, administration of rpST to genetically lean finishing pigs stimulated growth performance and improved carcass composition and had no adverse effects on meat quality, processing properties, or tenderness.