AbstractsMedical & Health Science

2016-04-30 The effect of dietary energy content and the provision of a β-adrenergic agonist in the diet, on the production and meat quality of South African Mutton Merino feedlot lambs

by Maria Petronella Genis




Institution: Stellenbosch University
Department: Animal Sciences
Degree: MScAgric
Year: 2014
Keywords: Mutton Merrino; feedlot; lambs; dietary energy; Animal Sciences
Record ID: 1453530
Full text PDF: http://hdl.handle.net/10019.1/86749


Abstract

ENGLISH ABSTRACT: Two studies were conducted on Elsenburg Experimental Farm, Western Cape, South Africa. The aim of these trials was to determine the following: 1) the effect of dietary energy as well as the inclusion of a β-adrenergic agonist (β- AA) on the production of South African Mutton Merino (SAMM) feedlot lambs 2) the effect of the trial diets on the rumen pH 3) the effect of varying dietary energy levels and the inclusion of a β-AA in the diet on the relationship between slaughter weight, commercial cut yield and bone:fat:muscle ratio of SAMM feedlot lambs 4) the effect of dietary energy as well as the inclusion/absence of a β-AA on the meat quality of SAMM feedlot lambs 5) the effect of dietary energy as well as the inclusion/absence of a β-AA on the sensory, physical and chemical characteristics of SAMM feedlot lambs. To quantify the effects of these parameters the study was conducted in two separate experiments. In the first experiment one hundred and eight (108) SAMM lambs, weaned at ca 120 days of age of different gender (rams and ewes) were housed in individual pens for approximately 6 weeks. The treatments consisted of three different dietary energy level diets (high – 12.7 ME MJ/kg, medium – 12.0 ME MJ/kg and low 11.3 ME ME/kg) with either the inclusion or absence of a β-AA (Zilpaterol hydrochloride, at 8.6 g/ton) in the diet. The experiment was arranged as a 2 x 2 x 3 factorial design with gender (rams or ewes), β-AA (provided or not) and dietary energy level (low, medium or high) as main factors. In the second experiment one hundred and twenty (120) SAMM lambs, weaned at ca 120 days of age of different gender (wethers or ewes) were housed in individual pens for approximately 6 weeks. The treatments consisted of three different dietary energy level diets (low – 11.3 ME MJ/kg, medium – 12.0 ME MJ/kg and high – 12.7 ME MJ/kg). The experiment was arranged as a 2 x 3 factorial design with gender (wethers or ewes) and dietary energy level (high, medium or low) as main factors. Where no interaction occurred the data is presented as the effect of dietary energy level, β-AA and gender on parameters. Three ruminally cannulated sheep were used for measuring the rumen pH. No differences were found between the three experimental diets on the rumen pH. Overall a gradual decline in pH from the time the animals were fed was observed. Dietary energy level only affected the dressing percentage in the first experiment, while it affected several parameters in the second experiment. The β-AA had no significant (P>0.05) effect on any parameters. While gender significantly (P<0.05) effect several of the production and carcass yield parameters. Main effects dietary energy and gender affected the leg yield and fat percentage in the bone:muscle:fat relationship respectively. While positive correlations between slaughter weight and the following parameters were observed: carcass weight, leg yield, shoulder yield, neck yield, flank yield and cranial fat thickness. Beta-adrenergic agonists…