Ruminal protein digestibility of Australian produced oilseed meals

Abstract

Initially, samples of Australian canola, soybean, cottonseed and flaxseed meal produced by solvent-extraction, expeller and cold-press technologies collected from late 2014 to early 2015 were analysed for general chemical composition, protein and ruminal digestibility characteristics. The oilseed meals had levels of ash, neutral-detergent insoluble crude protein, total intestinal digested protein, B1, B2, B3 and C protein content similar to those in previous reports, but lower Fraction A (non-protein N) levels than in previous reports. Acid-detergent insoluble fibre, metabolisable energy, total digestible nutrients, ash (P < 0.05), neutral-detergent fibre, in vitro dry matter digestibility, crude protein (CP), true protein, acid-detergent insoluble CP, soluble protein, in vitro rumen-undegradable protein (RUP), total tract digested protein, Fraction A, B2 and C (P < 0.01) differed among oilseed types. Dry matter, the ratio of RUP to total tract digested protein (P < 0.05), CP, lipid, soluble protein, RUP, Fraction A, B1 and B2 (P < 0.01) differed among oil-extraction techniques. Utilising an in vitro simulated rumen proteolysis procedure by Krishnamoorthy et al. (1983), mean ranges of in vitro RUP were greater and varied more so in canola (18.8–70.1%) than soybean (40.3–54.0%), cottonseed (31.5–33.9%) and flaxseed (18.5–21.8%) meals. Estimated RUP was lower (P < 0.01) in cold-press than expeller and solvent-extraction oilseed meals.