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Nitrogen Balance Responses and Abomasal Lysine Levels in Wethers Fed Supplemental Polymerized L-Lysine-HCl

Field Crops Utilization and Marketing Research Laboratory Richard B. Russell Agricultural Research Center Science and Education Administration, USDA, Athens, GA 30604

Abstract

Three trials were conducted to determine the in vivo stability and availability of lysine (lys) present in polymers prepared from L-lys-HC1, urea and formaldehyde. In trial 1, the molar ratios of L-lys-HCl, urea and formaldehyde were varied: .25.-.75.1 (polymer 2), .4.-.6.1 (polymer 2A) and .5:.5:1 (polymer 2B), respectively. These polymers were fed to mature rumen- and abomasum-cannulated wethers in a 4 x 4 Latin square experiment to provide a daily intake of 4.8, 4.7 and 4.6 g L-lys for polymers 2, 2A and 2B, respectively, above the control (no supplemental lys) treatment. The lys recovered from abomasal digesta was 4.1 (control), 7.8 (2), 7.7 (2A) and 7.6 (2B) g/day and was increased (P<.005) due to feeding the polymers. Varying the ratios of lys to urea in the polyers had no effect (P>.10) on the quantity of lys reaching the abomasum. Lys as a percentage of the total trichloroacetic acid precipitable protein was increased (P<.10) due to feeding the polymerized lys. Trials 2 and 3 were nitrogen balance trials with growing wethers to evaluate in vivo availability of lys in polymer 2. In trial 2, nitrogen retained (g/day) was increased (P<.10) in wethers receiving 4.0 g L-lys by abomasal infusion compared to control (no supplemental lys) and increased by the addition of the polymer to the control diet (P<.025); a portion of this increase was due to increased nitrogen intake from the polymer. Fecal nitrogen excretion was highest in wethers fed the polymers (P<.05) but excretion of lys in the feces was not affected by treatment (P>.10). In trial 3, the infusion of urea into the abomasum increased nitrogen retention (P<.01) as did lys + urea (P<.05). There was no difference in nitrogen retained by wethers receiving lys + urea by abomasal infusion and lys + urea in polymer 2 when nitrogen intake was equal. Concentrations (µmoles/100 ml) of plasma lys were increased by supplemental lys and equal responses were obtained by infusing 2.1 g lys and feeding 4.2 g lys in the polymer. These results indicate that approximately 50% of the lys fed in the polymer reached the lower gastrointestinal tract and was absorbed.