Available Lysine Content of Blood Meals Determined by Turkey Bioassay and Fluorodinitrobenzene Assay

Lysine availability in blood meal as affected by processing method was studied using 53 samples representing 10 manufacturing processes. Each sample was analyzed for total lysine and chemically available lysine using the fluorodinitrobenzene technique (FDNB-lysine). Bioavailable lysine was determined by turkey poult growth assay. The bioavailability was calculated using the slope ratio method where gain was regressed on dietary lysine content (Method A) or on lysine consumption (Method B). Vat-dried blood meal, representing harsh processing conditions, contained significantly less total lysine, FDNB-lysine, and bioavailable lysine when compared to spray, DeLaval-Anderson, ring, and flash-dried blood meal. Content of FDNB-lysine was more correlated with bioavailable lysine than was total lysine. Available lysine as measured by the FDNB-lysine technique overestimated bioavailable lysine in vat-dried samples. Bioavailable lysine contents as estimated by Method B were greater and more variable than those determined by Method A.