Growth, carcass and sensory characteristics of m. longissimus lumborum from wethers fed silage diets made from maize or various sorghum varieties

Abstract

Growth, carcass characteristics and eating quality of meat from South African Mutton Merino wethers fed maize or different sorghum silage diets were studied. Forty newly weaned wethers (20 kg) were randomly allocated to 10 dietary treatments, viz. non-bird-resistant grain sorghum silage (NGS), maize silage (MS), bird-resistant grain sorghum silage (BGS), forage sorghum silage (FSS) and a standard non-silage control diet consisting of equal proportions of maize meal and milled lucerne hay (C). Silage was included at 2 levels, namely 50% or 70% of the total diet on dry matter basis. Average daily gains of wethers were recorded from weaning to slaughter at 45 kg live mass. Carcass mass, dressing percentage, subcutaneous fat thickness and carcass length were recorded. Samples from the left m. longissimus lumborum were minced and stewed to determine foreign odours and flavours, while samples from the right m. longissimus lumborum were oven-roasted for subsequent sensory evaluation by an analytical sensory panel. Growth responses did not differ between wethers fed MS, NGS or BGS at inclusion levels of 50% or 70%. FSS at the 70% inclusion level resulted in poorer growth rates (p < 0.05) and longer feeding periods (p < 0.05) compared to the other silage diets. The best feed conversion efficiencies and shortest finishing periods were recorded by feeding MS at either the 50% or the 70% inclusion level, NGS at the 50% inclusion level, or BGS at the 50% inclusion level. Dressing percentages and subcutaneous fat thicknesses of wethers fed BGS and FSS at a 70% inclusion level were lower (p < 0.05) compared to those fed the other silage diets. No significant differences in sensory characteristics or cooking losses and no sensory defects were observed among wethers fed different silage diets.


(South African Journal of Animal Science, 2000, 30(1): 36-42)