Quantitative protein and fat metabolism in bull calves treated with ß‐adrenergic agonist

Abstract

Protein and energy utilization and quantitative retention of protein, fat and energy was investigated with 12 Red Danish bulls during two subsequent 6 weeks trials (Sections A and B) at a mean live weight of 195 and 335 kg respectively. Treatments were control (Group 1) and beta-agonist (L-644,969) treated animals (Group 2 and 3). Beta-agonist supplementation was 5 and 10 mg/d in Group 2 and 3 respectively in Section A and 10 and 20 mg/d in Section B. Measurements were performed by means of nitrogen and carbon balances and with use of indirect calorimetry. In each section the mean intake of dry matter, metabolizable energy and digestible protein was of the same magnitude for all groups. The beta-agonist had no significant effect on protein digestibility and metabolizability of energy, but daily live weight gain was significantly higher in the treated bulls. The utilization of digested protein was strongly influenced by treatment, with the highest values for Group 2 in both sections. The protein retention increased with 25% in Group 2, with the highest increment of 113 g/d in Section B. The fat retention decreased in treated animals, most pronounced in Group 3, where the reduction was about 50% with a mean decrease of 145 g/d in Section B. The total energy retention was not different between control animals and Group 2 in both sections, but there was a shift in energy retention from fat to protein. The higher levels of beta-agonist used in Group 3 generated the same increase in protein retention, but fat retention was markedly lower and consequently the total energy retention was reduced.

Overview of the effects of beta-adrenergic receptor agonists on animal growth including mechanisms of action.

“…It is not possible to decipher the differences between these more recent studies on lipid deposition rates in pigs fed b-AR agonists. In bovine males fed L644,969, protein deposition rates are increased and fat deposition rates are decreased (Chwalibog et al, 1996).…”

Effects of ractopamine hydrochloride supplementation on feeding behavior, growth performance, and carcass characteristics of finishing steers1,2

“…The distribution of β 2 -adrenergic receptor in cattle is largely concentrated in skeletal muscle (>99%) and adipose tissue (>90%; Mills and Mersmann, 1995 ; Mersmann, 1998 ) and feeding ractopamine at 200 mg/d for the last 28 d does not increase β 1 -, β 2 -, or β 3 -adrenergic receptor mRNA expression in biceps femoris or longissimus dorsi muscles ( Walker et al, 2010 ). Ricks et al (1984) proposed that β-adrenergic receptor agonists reduce adipose tissue accretion by decreasing lipogenesis ( Blum et al, 1982 ; Eisemann et al, 1988 ) and stimulating lipolysis ( Thornton et al, 1985 ; Mitchell et al, 1991 ; Chwalibog et al, 1996 ). Furthermore, the net effect of increased muscle tissue ( Smith et al, 1989 ; Grant et al, 1993 ; Schroeder et al, 2003 ) is thought to be because of reduced muscle degradation ( Eadara et al, 1989 ; Wheeler and Koohmaraie, 1992 ; Scramlin et al, 2010 ) and increased protein synthesis ( Scramlin et al, 2010 ).…”

Transcriptomic Biomarkers in Safety and Risk Assessment of Chemicals

“…Screening for anabolic agents such as steroid hormones (testosterone or estrogen) and beta-agonists in meatproducing animals demonstrates an application of transcriptomics for use in safety and regulatory monitoring. In agricultural meat-producing animals, the myotropic, growth-promoting properties of steroid hormones and beta-agonists are beneficial because of increased productivity and reduced costs with weight gain and feed efficiency (Chwalibog et al, 1996). As a consequence, hormone and drug residues in meat are increased and adverse side effects to the consumer occur (Daxenburger et al, 2001;Lange et al, 2001;Maume et al, 2001;Swan et al, 2007).…”