Effect of methionine:lysine ratio on growth performance and blood metabolites of growing-finishing pigs

摘要

Eighty growing-finishing pigs (40 barrowsand 40 gilts) were used in three consecutive growth assays to determine the optimum methionine:lysine ratio for pigs weighing from 48 to 107 lb, 120 to 179 lb, and 191 to 245 lb, respectively. Each growth assay was to be conducted for a 28-d period with a 14-d transition period between assays. Pigs were allotted by weight and placed in pens each containing one barrow and one gilt. Pigs were assigned to one of eight experimental treatments with five replicate pens per treatment. Pigs were fed diets containing either high lysine (1.0, .9, or .8%, respectively) or low lysine (.8,.7, or .6%, respectively) with dietary methionine at 24.5, 28, 31.5, or 35% of lysine. This would correspond to total sulfur-containing amino acids (methionine + cystine) of 49, 56, 63, and 70% relative to lysine. During the first study (48 to 107 lb), average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (F/G)improved with increasing dietary lysine.Although no differences occurred in growthperformance with increasing methionine ratio,there was a numeric improvement in growth performance for those pigs receivingdiets containing 28% methionine relative tolysine. A lysine × methionine interactionwas observed for blood urea N with pigshaving the lowest BUN values observedwith methionine at 24.5 and 31.5% oflysine for pigs fed .8 and 1.0% lysine, respectively. During phase II (120 lb to 179lb), ADG improved with increasing dietarylysine and showed a linear response to increasing methionine ratio. Feed efficiencywas also improved with increasing dietarylysine. For the third phase (191 to 245 lb),ADG also improved with increasing dietarylysine. There were no significant differencesin feed intake; however, feed efficiencyimproved with increasing dietary lysine. In summary, because of high ADFI observed in these studies, the dietary methioninelevels used closely met or exceeded the pig's requirement on a grams/day basis.Therefore, these data suggest that increasingdietary methionine does not improve pigperformance.