Abstracts Category : Other

Lysine Bioavailability of Two Lipid Coated Lysine Products After Exposure to Silages with Different Acidity

by Jessica N Reiners

Three experiments were conducted to determine bioavailability of 2 lipid coated Lys products (EB and EC). In an initial experiment, Lys disassociation from 2 lipid coated Lys products was best described by a first-order kinetic model after incubation in alfalfa- or corn-silage at 2 different amounts of acidity. Greater amounts of Lys immediately disassociated from EC (15.7%) than EB (4.9%; P < 0.05). Lysine that initially disassociated in corn silage at low pH (0.5%) was less than corn silage at a more neutral pH (18.7%), whereas Lys that initially disassociated in alfalfa silage was not affected (P = 0.26) by pH. Lysine that slowly disassociated from lipid coated Lys differed by product (P = 0.01), and acidity (P < 0.01) affected amounts of Lys that slowly disassociated differently within alfalfa- or corn-silage (pH silage = 0.02). Greater amounts of Lys disassociated from acidic corn silage (79%) than neutral corn silage (32%; P = 0.01). However, amounts of Lys that slowly disassociated from alfalfa silage was not impacted by acidity (P = 0.40). Additionally, amounts of Lys that did not disassociate (P < 0.04) within 24 h were greater (P < 0.04) when lipid coated Lys was mixed with neutral silages (44%) compared to acidic silages (21%). However, rate of Lys disassociation from lipid coated Lys products was not affected by acidity or exposure to alfalfa- or corn-silage (P = 0.21). In a second experiment, we measured in vitro ammonia release from EB and EC after mixing with alfalfa- or corn-silage at different amounts of acidity with or without monensin. Ammonia release from Lys increased (Quadratic < 0.01) with greater amounts of time; however, differences between in vitro cultures with added Lys and negative control were not detected until 36 h of incubation. By 36 h, all cultures containing added Lys were greater than the negative control. After 42 h of incubation, ammonia release from Lys was greatest from EC and when lipid and Lys-HCl in amounts identical to EB were provided to cultures; EB, Lys-HCl, and lipid and Lys in amounts identical to EC were intermediate. After 48 h of incubation, ammonia release from Lys in EB was greatest and Lys-HCl was least, but EC and amounts of lipid and Lys-HCl identical to either EB or EC were intermediate. Ammonia release from Lys were less from cultures containing monensin after 48 h of incubation. In experiment 3, 9 white-faced ewes (70.1 5.2 kg BW; 5.3 0.6 yr) were used to measure Lys bioavailability by a slope-ratio analysis from 2 lipid coated Lys products and Lys-HCl after mixing in corn silage. Plasma Lys concentrations increased (Linear < 0.01) in response to abomasal infusion of Lys, and bioavailability of EB, EC, and Lys- HCl were calculated to be 10.74%, 18.82%, and 11.87%, respectively. However, increases in plasma Lys from EB (Linear = 0.41) and Lys-HCl (Linear = 0.36) were not different from plasma Lys supported by diet alone, but the rate of increase in plasma Lys in response to EC tended (Linear = 0.15) to be greater than plasma Lys levels from diet.Advisors/Committee Members: Derek Brake, Jeffrey Held.