Combined effects of clenbuterol and various concentrations of protein on performance of broiler chickens

Abstract

1. The effects of the beta-adrenergic agonist, clenbuterol (1 mg/kg diet) on the growth and muscle composition in female broiler chickens (14 to 32 d of age) fed on diets containing various concentrations of protein (220, 240 or 260 g protein/kg) were examined. 2. Body weight gain over the 18 d period increased linearly with increasing protein intake. The rate of gain was significantly higher in clenbuterol-treated chickens than in control birds. 3. Dietary clenbuterol increased thigh muscle weight and protein concentration of breast and thigh muscle, regardless of dietary protein content. Protein/DNA ratio in thigh muscle was enhanced by clenbuterol feeding, and the magnitude of difference of the ratio was higher in chickens fed on the 240 and 260 g CP/kg diets than in those fed the 220 g CP/kg diet. 4. It was concluded that clenbuterol-treated chickens require increased dietary protein to maintain maximal growth, and that increased protein consumption is an important factor in improving growth in clenbuterol-fed broilers.

Involvement of lipoic acid in plasma metabolites, hepatic oxygen consumption, and metabolic response to a β-agonist in broiler chickens

“…Further, chickens have been shown to be insensitive to b-agonist administration (Weppelman, 1984;Wellenreiter, 1991). More recently, nutritional factors such as level of dietary protein and energy, and thiamin administration were shown indirectly to inhibit or improve the repartitioning impact of a b-agonist, clenbuterol, in chickens (Hamano et al 1994(Hamano et al , 1998(Hamano et al , 1999. Vitamins including LA that act as cofactors in enzyme systems catalysing metabolic processes might be prerequisites for enhancing the subsequent response to b-agonists in the tissues.…”

“…Furthermore, although this vitamin has been shown to be associated with insulin and thyroid hormones (Segermann et al 1991;Streeper et al 1997), whether there is an interrelationship with b-adrenergic response is unclear. With regard to repartitioning nutrients in chickens, the metabolic response to b-agonist supplementation, which stimulates protein deposition and decreases adipose tissue accretion (Dalrymple et al 1984;Weppelman, 1984;Buyse et al 1991), is dependent on nutritional and hormonal states (Hamano et al 1994(Hamano et al , 1995(Hamano et al , 1998. In addition, the b-adrenergic response of leanness in chickens is thought to be generally weaker than that of mammals (Yang & McElligott, 1989;Wellenreiter, 1991).…”

Influence of lipoic acid on lipid metabolism and ?-adrenergic response to intravenous or oral administration of clenbuterol in broiler chickens

“…In domestic animals, clenbuterol (CLE), a selective b 2 -adrenergic agonist, is well known to be a potent growth promoter that increases muscle mass and protein deposition or decreases adipose tissue accretion [3,5,15,16,20]. Moreover, recent studies have reported that this repartitioning action is dependent upon nutritional states such as dietary protein level [2,6,7]. With regard to vitamins, thiamine supplementation enhances the lipolytic response of broiler chicks to CLE administration [8].…”