Effect of flax grain inclusion on rumen fermentation, digestion, and microbial protein synthesis in growing and finishing diets for beef cattle

Abstract

Four Holstein steers (339 ± 10 kg initial BW) fitted with ruminal and duodenal cannulae were used in a 4 × 4 Latin square design to evaluate the effects of flax inclusion in diets for growing and finishing cattle on intake, ruminal fermentation, and site of digestion. Flax at 80 g/kg of dietary DM in growing (0.4 concentrate) and finishing (0.8 concentrate) diets replaced linseed meal and a portion of the corn. Data were analyzed as a 2 × 2 factorial; the main effects were ration type (growing or finishing) and flax inclusion (with or without flax). Diets were formulated to contain 140 g/kg CP for growing and finishing. No differences (P≥0.24) were observed for DM intake (10.2 ± 0.54 kg/d; 2.4 ± 0.09% of BW). Flax inclusion decreased microbial OM flow at the duodenum (P=0.02). Total tract OM digestion was greater for steers fed finishing diets (P=0.02) and apparent ruminal OM digestibility tended to be greater for steers fed finishing diets (P=0.09). Steers consuming finishing diets had greater (P=0.001) total tract CP digestion. Microbial efficiency was not affected (P=0.36; g N/kg OM) by diet type or flax inclusion. Steers fed growing diets had greater (P≤0.004) ruminal aNDF and ADF digestion. Steers consuming flax had lower (P=0.02) ruminal ammonia. There was no effect (P≥0.19) of flax on CP, aNDF, ADF, and OM ruminal and total tract digestion. Results indicate that substituting 8% flax for part of corn and linseed meal in growing and finishing diets by beef cattle did not alter OM and CP digestion.