The effect of dietary energy and the inclusion of a β-adrenergic agonist in the diet on the meat quality of feedlot lambs

Ts Brand,Lc Hoffman,R Swart,Gf Jordaan,Wfj Van De Vyver,Mp Genis

doi:10.4314/sajas.v43i5.27

Abstract

β-adrenergic agonists are commonly used in livestock production to enhance meat production and decrease the fat content of the body. β-adrenergic agonists normally improve growth performance. Recent increases in meat prices and the change in consumer preference towards leaner meat have resulted in more lamb producers opting to finish leaner mutton/lamb on farms in a feedlot system. The aim of this trial was to determine the effect of dietary energy, as well as the inclusion of a β-antagonist, on the meat quality of feedlot lambs. South African Mutton Merino lambs (108) of different sexes (rams and ewes) were weaned at 120 days of age and were randomly divided into six groups (18 lambs per group). The treatment consisted of three different dietary energy levels (high 12.7 MJ ME/kg feed, medium 12.0 MJ ME/kg feed and low 11.3 MJ ME/kg feed) with either the inclusion of a β-adrenergic agonist (zilpaterol hydrochloride) at 8.4 g/ton or not. Data were analysed according to a 3 (dietary energy) x 2 (inclusion of a stimulant) x 2 (sex) factorial analysis. No interaction occurred between treatments and the data were presented as the effect of dietary energy level, the inclusion of a stimulant and sex on proximate components, fat thickness and the tenderness of the meat. The factors β-adrenergic agonists and dietary energy level had no effect on the proximate components, fat thickness or the tenderness of the meat. The ewe lambs’ 9-11th rib-cut had a significantly higher fat content than the ram lambs (27.9% vs. 23.1%, respectively). Meat from ram lambs was less tender (63.60N) compared to that from ewe lambs (57.82N). Neither the inclusion of the β-adrenergic agonist (59.8N vs. 61.9N) nor the dietary energy level (59.3N vs. 63.5N vs. 59.3N) had an effect on the tenderness of meat from lambs in this study.Keywords: Meat quality, β-agonist, energy, South African Mutton Merino

Highlights

The recent increase in mutton and lamb prices have resulted in many lamb producers opting to finish more lambs on farms in a feedlot system rather than marketing directly from the field
No interaction occurred between the treatments and the data is presented as the effect of dietary energy, β-agonist and sex on the fat thickness, percentage of moisture, protein, fat and ash in the meat as well as the tenderness of the meat
It was hypothesised that the meat from lambs receiving a high energy level diet would contain a higher fat percentage than lambs receiving a low energy level diet; no difference was found between the fat percentages of the lambs fed different dietary energy levels

Summary

Introduction

The recent increase in mutton and lamb prices have resulted in many lamb producers opting to finish more lambs on farms in a feedlot system rather than marketing directly from the field. Another aspect that has occurred in South Africa is where the sheep abattoirs have become more vertically integrated and are buying young weaned lambs and finishing them off in their own feedlot – which is often adjacent to the abattoir. Shelver & Smith (2006) mixed ZH into the diets of lambs; these lambs received 15 mg/kg BW/day (this level is used by the industry). Shelver & Smith (2006) found that after a 2 day withdrawal

Methods

Results

Conclusion