EFFECTS OF A BETA-ADRENOCEPTOR AGONIST ON GROWTH-PERFORMANCE, NITROGEN-BALANCE, BODY-COMPOSITION AND RETENTION OF NITROGEN, FAT AND ENERGY OF FINISHING PIGS DURING RESTRICTED AND AD-LIBITUM FEEDING

The β-adrenoceptor agonist Ro 16-8714 was administered perorally to castrated male Large White pigs from 60 to 100 kg to study effects on growth rate, nitrogen balance, body composition and nitrogen, fat and energy retention. The diets contained 0 or 20 mg in restrictively fed pigs and 0, 20, 60 or 180 mg Ro 16-8714 kg-1 in ad libitum fed pigs. Ro 16-8714 increased growth rate by 6.9% (P < 0.01) in restrictively but not significantly in ad libitum fed pigs. Feed/gain ratio was decreased up to 12.6% (P < 0.01). The ratio of retained/ingested nitrogen was enhanced with increasing amounts of Ro 16-8714 in ad libitum fed pigs (by 26%; P < 0.05), associated with reduced urinary nitrogen and increased urinary creatinine excretion (P < 0.1). Protein content in the carcass was increased by 9-10.5% and fat content decreased by 5.9% (P < 0.1). In ad libitum fed pigs Ro 16-8714 increased the part of nitrogen in the carcass fraction from 83.1 to 84.8% (P < 0.05) whereas nitrogen in the non-carcass fraction decreased from 15.2 to 13.6% (P < 0.05). Daily nitrogen deposition in the carcass was enhanced dose-dependently up to 21% (P < 0.15), whereas in the non-carcass fraction nitrogen deposition was lower for pigs receiving Ro 16-8714. Daily fat accretion was reduced by 14.4% with 60 mg Ro 16-8714. Gross efficiency of nitrogen deposition was improved dose-dependently by 22% (P < 0.05), while gross efficiency of energy conversion remained unaffected. In conclusion, Ro 16-8714 favored nitrogen accretion in the carcass but reduced non-carcass nitrogen deposition and fat retention, and thus (re)partitioned nutrients. © 1990.