Effects of intake of linseed oil or tallow on nutrient digestion and nitrogen balance of beef steers consuming diets based on dry-rolled corn

Abstract

<h2>ABSTRACT</h2> Lipids can have detrimental effects on the ruminal microbiota and, subsequently, diet digestibility. We evaluated effects of amount and source of dietary lipid on nutrient digestibility, ruminal fermentation, and N balance in cattle consuming diets based on dry-rolled corn. Five steers (BW = 392 ± 15 kg) fitted with ruminal, duodenal, and ileal cannulas were used in a 5 × 5 Latin square with 12-d periods. Diets contained no added lipid or 4 or 8% added lipid from either a tallow or linseed oil. Linseed oil tended (<i>P</i> = 0.08) to decrease DMI compared with tallow. Greater amounts of lipid tended to decrease ruminal digestion of DM (<i>P</i> = 0.07), OM (<i>P</i> = 0.14), and NDF (<i>P</i> = 0.05). Microbial efficiency (g of microbial N/kg of OM fermented) tended to increase (<i>P</i> = 0.10) with added lipid, but microbial N flow to the duodenum was not affected (<i>P</i> ≥ 0.19) by amount or source of lipid. Ruminal pH (<i>P</i> ≥ 0.83), ammonia (<i>P</i> ≥ 0.33), and total organic acid content (<i>P</i> ≥ 0.54) were not affected by diet lipid. Added dietary lipid tended (<i>P</i> = 0.10) to decrease ruminal acetate concentrations. Addition of a more unsaturated lipid (linseed oil) decreased (<i>P</i> = 0.05) total-tract NDF digestibility compared with a more saturated lipid (tallow), and addition of lipid tended to decrease digestion of DM (<i>P</i> = 0.13) and NDF (<i>P</i> = 0.08) compared with control. Linseed oil decreased (<i>P</i> < 0.01) fecal N and tended to reduce (<i>P</i> = 0.08) urinary N.