Effects of oats grain supplements on performance, rumen parameters and composition of beef from cattle grazing oats pasture

Abstract

The impacts of supplementing with whole oats grain (OG) upon performance and beef quality traits of growing steers grazing oats pasture (OP) were measured. The trial used Angus steer calves (203 kg mean bodyweight) assigned to three treatments: Control, unsupplemented OP (CON); OP plus OG fed at 0.25% BW daily (OG1); and OP plus OG fed at 0.50% bodyweight daily (OG2). All steers grazed the same paddock but were removed momentarily once daily so OG could be fed to each steer individually. Daily intake of OG averaged 597 and 1294 g DM for OG1 and OG2, respectively. Steers were slaughtered after grazing for 130 days to determine carcass characteristics and lipid profiles. In parallel with the grazing trial, four ruminally cannulated steers (613 kg mean bodyweight) were allocated to treatments CON and OG2 (n = 2) to monitor ruminal pH, volatile fatty acids, and NH3-N. Steers fed OG2 had greater (P < 0.01) average daily gain than CON; final liveweight for OG2 steers was significantly higher than both CON and OG1 steers. Although variations in plasma haematocrit and alkaline phosphatase were they did not affect animal performance. Dressing percentage was not affected by the experimental diets but OG2 steers had greater (P < 0.05) marbling scores. Although rib-eye area was numerically greater for OG1 and OG2 than CON steers (8% and 14%), these differences were not significant statistically (P = 0.3493). Intramuscular lipid content of Longissimus dorsi muscle was not significantly increased by OG supplementation but of the intramuscular fatty acids, contributions of vaccenic and α-linolenic acids decreased (P < 0.05). Linoleic acid content was lowest (P < 0.05) for OG1 steers. A no significant decrease in conjugated linoleic acid was detected when more OG was supplemented. No treatment differences in the contributions of eicosapentaenoic acid, docosahexaenoic acid, monounsaturated fatty acids, polyunsaturated fatty acids, saturated fatty acids, n-6 or n-3 to intramuscular fatty acids were detected although the n-6 : n-3 resulted numerically higher (11% and 23%) for OG1 and OG2 steers than CON steers. Rumen pH, NH3-N and volatile fatty acids were not significantly altered by OG supplementation. Supplementing diets of cattle grazing OP improved performance without rumen digestion impairs or inducing substantial changes in the lipid profile of intramuscular fat. Thus, OG supplementation would be expected to improve the efficiency of cattle grazing of OP without substantial changes to ruminal measurements or the lipid profile of beef.