OXIDATION OF NUTRIENTS IN BULL CALVES TREATED WITH BETA-ADRENERGIC AGONISTS

Oxidation of protein (OXP), carbohydrate (OXCHO) and fat (OXF) was inv estigated with 12 growing bulls treated with beta-agonist (L-644, 969) during two 6 weeks trials (Section A and B) at a mean live weight of 195 and 335 kg. Heat production and nutrient oxidation was calculated from gas exchange, with CO2 reduced for CO2 from fermention processes, and nitrogen excretion in urine. The beta-agonist had no effect on th e level of rumen fermentation as indicated by the same methane product ion for control and treated animals. Heat Production (HE, RQx) increas ed by the treatment of beta-agonist corresponding to the increment in the protein retention. OXP/HE,RQx was reduced to about 10% in treated animals, indicating that in order to supply amino acids for an increas ed protein deposition oxidation of protein is decreased. OXF/HE,RQx we re markedly higher in treated animals, but as indicated by the same CH 4 production the level of the short chain fatty acids (SCFA) productio n was the same. Therefore, it was concluded that the increase in OXF w as not caused by an increase in SCFA but by a direct influence of beta -agoinst on mobilization and oxidation of body fat.