Whole-body and tissue protein synthesis in steers losing weight on a low-protein roughage diet: the effect of trenbolone acetate

Abstract

S U M M A R YSix Brahman (Bos indicus) steers implanted with 300 mg trenbolone acetate and six similar nonimplanted steers were fed a low-quality, low-protein roughage diet at 10 g dry matter/kg live weight. They were housed in individual pens for 27 days in 1987 before being placed in metabolism crates for measurement of digestibility, nitrogen retention, and the rate of protein synthesis in the whole body and fractional rate in three muscles and hide.The rate of weight loss of steers treated with trenbolone acetate was significantly (P < 005) less than that of controls (-0-34 v. -0-56 kg/day). Treated steers excreted significantly (P < 005) less 3-methylhistidine (128 v. 202 umol) and urea N (0-5 v. 1 -6 g/day) in urine. There was a more favourable nitrogen retention in animals implanted with trenbolone acetate (-10 v. -12g/day) but this difference was not significant.Whole-body protein synthesis, calculated from plasma leucine flux, was 511 and 508 g/day in treated and control steers, respectively. Treatment also had no significant effect on the fractional rate of protein synthesis, in skeletal muscle or in hide. The fractional rate of synthesis in muscle was < 1 %/day and in hide < 2%/day. These results are discussed in relation to the protein and energy metabolism of undernourished cattle. I N T R O D U C T I O Na su b m ai n tenance diet and related changes in protein metabolism to known changes in energy metabolism Beef production in seasonally dry areas follows a (Hunter & Vercoe 1987) associated with trenbolone pattern of weight gain during the wet season and zero acetate treatment. gain or weight loss during the dry season, resulting in A possible complication with trenbolone acetate is small annual gains. Improvements in production the differential effect on protein transactions in could result from an increase in gain during the wet or different muscles. It can be calculated from the a decrease in loss during the dry season. There is comparative slaughter experiment of Wood et al. evidence that the anabolic agent trenbolone acetate (1986) that a combined implant of trenbolone acetate reduces energy expenditure in cattle (Hunter & and oestradiol increased protein deposition in the Vercoe 1987), and thus has the potential to reduce neck and shoulder by an average of c. 20% and in the weight loss in the dry season. It has been suggested vertebral column and hindquarter muscles by only that part of the mode of action of trenbolone acetate c. 10%. In this paper, the effect of trenbolone acetate in the weight gain of female rats (Vemon & Buttery on protein synthesis in the whole body, in the hide 1976, \91Sa,b)and female lambs (Sinnett-Smith et al. and in three muscles was measured, and the calculated 1983) is its effect on reducing muscle protein synthesis energy costs of protein synthesis were related to and breakdown. As the reduction in breakdown is energy expenditure in the whole animal. The muscles greater than the reduction in synthesis, the net result were the trapezius in the shoulder, the longiss...

Protein turnover and sensory traits of longissimus muscle from implanted and nonimplanted heifers1

“…Testosterone and estradiol were shown to have no effect on muscle cellular protein synthesis or degradation (Roeder et al, 1986;Desler et al, 1996), whereas Martinez et al (1984) and Hayden et al (1992) showed that testosterone and trenbolone acetate increased protein synthesis only. Conversely, Hunter and Magner (1990) found trenbolone acetate decreased protein degradation. In general, our results agree with the body of literature that trenbolone acetate had its strongest effect on protein synthesis and not protein degradation.…”

Quantitative aspects of protein fractional synthesis rates in ruminants

“…A set of 25 publications including 624 observations were found in the literature (Buttery et al, 1975;Lobley et al, 1980;Davis et al, 1981;Bryant and Smith, 1982a, b;Sinnett-Smith et al, 1983;Schaefer et al, 1986;Bohorov et al, 1987;Attaix et al, 1988a, b;Early et al, 1988; Abdul-Razzaq and Bickerstaffe, 1989;Eisemann et al, 1989;Champredon et al, 1990;Early et al, 1990;Hunter and Magner, 1990;Lobley et al, 1990;Baracos et al, 1991;Attaix et al, 1992;Harris et al, 1992;Lobley et al, 1992;Southorn et al, 1992;Crompton and Lomax, 1993;Lobley et al, 1994;Tauveron et al, 1994 (France et al, 1988 (Tomassone et al, 1992 (France et al, 1988). However, this compartment has a short half-life of between 2 and 5 s (Martin et al, 1977) .…”

Mechanisms of steroidal implants to improve beef cattle growth: a review

“…Locally produced IGF-I in skeletal muscle is able to progress bovine satellite cells through proliferation and differentiation into skeletal muscle fibres. This results in increased protein synthesis and decreased protein degradation (Vernon and Buttery 1978;Lobley et al 1985;Hunter and Magner 1990). Moreover, it allows for maintenance of the DNA to protein ratio throughout skeletal muscle hypertrophy.…”