Effect of lipid-coated lysine on digestion and nitrogen metabolism by wethers.

Four mature wethers (70 kg) fitted with permanent abomasal cannulas were assigned to a 4 X 4 Latin square design to study the effect of coating supplemental lysine with coconut oil on nutrient digestion, nitrogen retention and recovery of amino acids in the abomasum and plasma. Dietary treatments were: Control (C) = basal diet; Lysine (LYS) = Control + 1% supplemental lysine; Coconut oil-coated lysine (CN-LYS) = Control + 1% supplemental lysine coated with coconut oil; and Coconut oil + diet (CN-DIET) = Control + 1% supplemental lysine + an equal amount of coconut oil added to the entire diet. Lysine supplementation significantly increased total apparent dry matter, ether extract and energy digestibilities. Total nitrogen and protein nitrogen flows to the abomasum were decreased (p less than .1) in lambs consuming CN-LYS and CN-DIET compared with LYS. Urinary nitrogen excretion (p less than .05), ruminal ammonia nitrogen and plasma urea nitrogen (p less than .05) concentrations were higher for LYS, CN-LYS and CN-DIET compared with C and highest for CN-LYS. There were no differences in nitrogen retention among treatments. Recovery of lysine in the diets after coating (CN-LYS) or lipid addition (CN-DIET) was reduced indicating degradation of supplemental lysine to other nitrogenous compounds during the coating process or storage since total dietary nitrogen content was equivalent to LYS. Flow of abomasal lysine (% of lysine intake) was higher (p = .15) for CN-LYS and CN-DIET than LYS. Flow of total essential amino acids (% of total amino acid flow) was greater (p less than .02) when lysine was added to diets. Essential amino with LYS. Plasma amino acid concentrations did not differ among treatments. Coating lysine with coconut oil did not protect the amino acid from ruminal degradation and was ineffective in improving total nitrogen status of mature wethers.