The objective of this trial was to evaluate the bioavailability of L-Met considering dl-Met as the standard source (100% availability) based on average daily gain (ADG) and feed conversion (FC) of piglets. A total of 135 barrows (14.77 ± 1.46 kg) 24 d old were distributed in a completely randomized block design into 5 treatments with 9 replicates and 3 animals per pen. The treatments were a basal diet (BD) formulated to meet or exceed the nutritional recommendations of all nutrients (except for methionine), BD + 0.041% dl-Met; BD + 0.082% dl-Met; BD + 0.041% l-Met and BD + 0.082% l-Met. The calculated content of Met and Met+Cys in basal diet were 0.206% and 0.441% respectively. The experimental period lasted 28 d and individual pig body weight and feed intake were recorded to calculate performance: ADG, average daily feed intake (ADFI) and FC. Multiple regression model was obtained from linear regression analysis using SAS PROC MIXED procedure at probability level of P < 0.05 was regarded as statistically significant. The regression coefficient ratios were utilized to determine bioavailability of l-Met considering that both equations had the same intercept. A linear increase was observed in ADG (P < 0.05) with the supplementation of both dl-Met and l-Met. dl-Met supplementation levels increased ADFI linearly (P < 0.05). However there was a linear decrease (P < 0.05) in ADFI with supplemental sources of l-Met. The l-Met bioavailabilities estimated by ADG and FC were 105.48 and 130.94%, respectively. Table 1. Performance and bioavailability (BV) of l-Met for piglets from 15 to 30 kg¹

Item	BD	dl-Met		P-value	l-Met		P-value	s
0.0%	0.041%	0.082%	0.041%	0.082%
ADG, g	581	648	714	0.001	664	715	0.001	0.246
ADFI, g	1121	1275	1368	0.003	1320	1312	0.052	0.487
FC, g/g	2.085	1.975	1.916	0.001	1.990	1.839	0.001	0.427
l-Met BV	Intercept	bD	bL	Bioavailability
ADG	0.584	1.581	1.668	105.48
FC	2.086	−2.196	−2.876	130.94

¹Linear regression analysis; b^D = dl-methionine regression coefficients; b^L = l-Met regression coefficients