Oxidation of nutrients in bull calves treated with ß‐adrenergic agonists

Abstract

Oxidation of protein (OXP), carbohydrate (OXCHO) and fat (OXF) was investigated with 12 growing bulls treated with ß‐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 CO₂reduced for CO₂ from fermention processes, and nitrogen excretion in urine.

The ß‐agonist had no effect on the level of rumen fermentation as indicated by the same methane production for control and treated animals.

Heat Production (HE, RQx) increased by the treatment of ß‐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 increased protein deposition oxidation of protein is decreased.

OXF/HE,RQx were markedly higher in treated animals, but as indicated by the same CH₄ production the level of the short chain fatty acids (SCFA) production was the same. Therefore, it was concluded that the increase in OXF was not caused by an increase in SCFA but by a direct influence of ß‐agoinst on mobilization and oxidation of body fat.

Key words:

• Bulls
• ß‐agoinst
• Protein oxidation
• Carbohydrate oxidation
• Fat oxidation
• Heat production