Somatotropin treatment of U.S-breed finishing hogs improves feed efficiency, growth rate and carcass lean-to-fat ratio. Because Chinese-bred hogs have poorer feed efficiency, growth rate and lean-to-fat ratio than U.S. bred hogs, the characteristics affected by porcine somatotropin (PST) may respond differently to treatment. In the present experiment, Beijing Black finishing hogs (a composite of a local Chinese, Berkshire and Yorkshire breeds) were treated with PST for 28 d from average initial to final weights of 67.8 to 96.6 kg. In hogs individually fed as much as they would eat four times a day (n = 12/treatment group, six gilts and six barrows), feed efficiency was improved by 22.4 and 29.9% by 2 and 4 mg/d PST, respectively (P less than .01), primarily due to increased growth rate (22.1 and 32.6% greater than control, respectively, P less than .01); feed intake was not affected. Performance of group-housed and group-fed hogs (six/pen, four pens/treatment) administered 2 mg/d PST for 28 d (average initial and final weights of 66.5 +/- 1.7 and 94.0 +/- 2.4 kg, respectively) was similar (22.7% improved feed efficiency, P less than .01; 25% increased growth rate, P less than .01). At slaughter, last rib backfat thickness was decreased an average of 19.2% for hogs treated with 2 and 4 mg/d PST (P less than .01). Percentage of total muscle, obtained by physical separation of the half-carcass, was increased an average of 13.5% (P less than .01), whereas percentage of total fat was decreased 21.8% (P less than .01) in PST-treated hogs. The pH, water-holding capacity and meat color scores of longissimus muscle from PST-treated hogs did not differ from those of control hogs. Growth rate, feed efficiency and muscle weight responses to PST treatment were at least as large as those for U.S. breeds.

An 8-week feeding trial was conducted to investigate the effects of dietary phosphorus levels on growth performance, plasma biochemical parameters, and lipogenesis gene expression of bighead carp. The results showed that weight gain (WG) and specific growth rate (SGR) increased with increasing dietary phosphorus levels up to 1.12%, and after that decreased. Feed conversion ratio (FCR) showed a converse trend compared with WG. Whole body protein and lipid contents significantly increased and decreased with increasing dietary phosphorus levels, respectively (P<0.05), whereas moisture and ash contents were not significantly affected by the dietary phosphorus levels (P>0.05). The highest values of the hepatosomatic index (HSI), total protein, and albumin contents were observed with 1.12% dietary phosphorus supplementation (P<0.05). Glucose levels increased with dietary phosphorus up to the level 1.32% phosphorus supplementation, and then decreased. Serum total cholesterol, total triglyceride, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphates activity were not significantly affected by dietary phosphorus levels (P>0.05). Excess phosphorus levels (1.32% and 1.59%) significantly down-regulated the relative gene expression levels of sterol regulatory element binding protein (SREBP)-1 and fatty acid synthase (FAS) (P<0.05). Based on WG and FCR, the optimal dietary phosphorus level should be 1.16%, using quadratic regression analysis. The IJA appears exclusively as a peer-reviewed on-line open-access journal at http://www.siamb.org.il. To read papers free of charge, please register online at registration form. Sale of IJA papers is strictly forbidden.