Abstract
Simple SummaryThe use of soybeans as a dietary protein source in ruminant diets is environmentally, economically and socially unsustainable. It is for this reason that canola meal (CM) has emerged as a more sustainable alternative protein source to soybean meal (SBM). However, expeller CM is quickly broken down in the rumen resulting in inefficient utilization by rumen microbes, while a small rumen bypass protein fraction means that few of the essential amino acids in CM reach the small intestine. Consequently, the utility of CM protein as an alternative to soybean protein for high-producing ruminants is lower, requiring pre-feeding treatments such as heating to enhance its feed value. This study investigated whether heat treatment could improve the feed value of CM protein sufficiently to partially (50%) or completely substitute SBM in finishing diets of Meatmaster lambs. The results showed that while CM can completely replace SBM in diets of lambs without compromising growth performance and meat quality, heat treatment of CM did not offer any additional benefits.The study investigated whether heat treatment (190 °C for 90 min) could improve the quality of expeller canola meal (CM) protein in finishing diets of Meatmaster lambs. Five isonitrogenous and isoenergetic diets were formulated by partially (50%) or completely replacing SBM as the major protein source with untreated or heat-treated CM in a commercial lamb finishing diet. Diets were randomly allocated to 40 lambs (24.73 ± 1.311 kg; 4.5 months old) for 77 days. No dietary differences were observed for growth performance, carcass characteristics and meat quality. Diets had no effect (p > 0.05) on blood parameters, except for hemoglobin and aspartate aminotransferase (AST). Lambs that were fed the control diet had higher hemoglobin concentration compared with lambs on CM-containing diets. The highest AST value was observed when SBM was completely replaced with untreated CM (159.88 IU/L), while complete replacement with heat-treated CM resulted in the lowest AST value (103.25 IU/L). All lambs had a body condition score of 3 at slaughter. It was concluded that heat treatment did not improve the protein value of CM. However, CM inclusion promoted similar growth performance and meat quality parameters in lambs as SBM. Untreated CM can be used to completely substitute SBM in finishing diets of Meatmaster lambs.
Highlights
Soybeans (Glycine max) have several uses that include direct consumption by humans, production of cooking oil, protein source in animal feed and biodiesel production
Experimental diets: CON, commercial lamb finishing diet in which soybean meal (SBM) was the major protein source; CM50, commercial finishing diet in which 50% of SBM was replaced with untreated canola meal; CM100, commercial finishing diet in which all SBM was replaced with untreated canola meal; HCM50, commercial finishing diet in which 50% of SBM was replaced with heat-treated canola meal; and HCM100, commercial finishing diet in which all SBM was replaced with heat-treated canola meal
Experimental diets: CON, commercial lamb finishing diet in which SBM was the major protein source; CM50, commercial finishing diet in which 50% of SBM was replaced with untreated canola meal; CM100, commercial finishing diet in which all SBM was replaced with untreated canola meal; HCM50, commercial finishing diet in which 50% of SBM was replaced with heat-treated canola meal; and HCM100, commercial finishing diet in which all SBM was replaced with heat-treated canola meal
Summary
Soybeans (Glycine max) have several uses that include direct consumption by humans, production of cooking oil, protein source in animal feed and biodiesel production. These multiple uses create a huge demand for limited supplies of this commodity resulting in high market prices. The competition between humans and animals as well as the high input requirements for growing soybeans in SA contribute to the unsustainability of using soybean meal (SBM) as an animal feed ingredient. The demand for soybeans in SA is largely driven by expanding animal production enterprises [2], where SBM is preferred as a concentrated source of dietary protein (44–48%) in livestock feeds. The high protein and energy content [3] as well as low fiber content of SBM are desirable attributes in the formulation of high-energy animal finishing diets
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