The influence of threonine:lysine ratios on growth performance and on plasma urea nitrogen in growing-finishing pigs fed from 85 to 240 lb

摘要

Eighty crossbred pigs (initially 85.2 lbBW) were used in a 2 × 4 factorial arrangement to determine the influence of dietary threonine:lysine ratios on growth performance and plasma urea N in growing-finishing pigs. The experiment was conducted in three phases from 85.2 to 124.2, 139.1 to203.1, and 204.9 to 241.1 lb, with pigs fedone of eight dietary treatments. Two levelsof dietary lysine were fed (low vs high) andfour levels of dietary threonine were fedwithin each lysine treatment (60, 65, 70,and 75% of dietary lysine). Dietary lysinedecreased from 1.0% and .8% at 85.2 to 124.2 lb to .9 and .7% at 139.1 to 203.1, then to .7 and .5% at 204.9 to 241 1 lb. Average daily gain (ADG) and feed efficiency (F/G) were not influenced by lysine or threonine treatment from 85.2 to 124.2 lb. However, average daily feed intake was decreased for pigs fed 1.0% dietary lysine compared to .8% dietary lysine. From 139.1 to 203.1 lb, an interaction between dietary lysine and threonine existed for ADG. Average daily gain was maximized at 65 and 70% of dietary lysine for pigs fed .7 and .9% dietary lysine, respectively. Conversely, ADFI and F/G were not influenced by threonine:lysine ratios. From 204.9 to 241.1 lb, ADG and ADFI were not influenced by dietary treatment. However, F/G was improved for pigs fed .7% dietary lysine compared to pigs fed .5% dietary lysine. Plasma urea N was increased at 124.2 and at 203.1 for pigs fed greaterdietary lysine. At 241.1 lb, plasma urea Nwas decreased linearly at the percentage ofthreonine increased from 60 to 75% of lysine. The data from this experiment indicate that excess lysine and threonine intakes do not decrease growth performance.Because high ADFI resulted in high aminoacid intake, growth performance was notinfluenced by the amino acid ratios used inthis experiment.