Glycerin is a low-cost byproduct from biodiesel production, and is also a potential source of carbohydrates. This study was conducted to determine the optimal amount of glycerin in the diets of lambs. Forty-four crossbreed male lambs (23.9 ± 3.4 kg) were distributed in a completely randomized design, and fed with a TMR that contained 50% of Cynodon sp. chopped hay and 50% of concentrate composed of corn bran, soybean meal, mineral premix, and the amounts of glycerin: 0; 7; 14 and 21% of total DM. Those amounts were the treatments. The feed trial lasted 78 d. The last day the animals were submitted to feed fasting, and slaughtered. The carcasses were stored in a cold chamber for 24h, and then the Longissimus lumborum was collected, stored in a freezer, and all measurements were made on this muscle, after thawing. The pH was measured by a digital potentiometer (skewer type extremity) directly in the muscle. The color measurement was made using a colorimeter to determine the parameters: L* - luminosity, a* red content and b* yellow content. Cooking losses were calculated by the weight difference from the samples before and after cooked, and results expressed in percentages. Tenderness was measured through the shear strength, using a texturometer equipped with a Warner Bratzler blade. The data were subjected to ANOVA and regression testing. Significance was declared as P < 0.05.There are no effects of glycerin inclusion on instrumental characteristics (Table 1). The similar values of pH, which is correlated with the glycogen source in muscle, can be related to the similarity among the other parameters. Glycerin, derived from biodiesel production, can be added up to 21.0% (DM) in the diets of lambs without compromising meat quality. Table1. Cooking losses (CL), shear force (SF), pH, and color of L. lumborum of lambs fed diets containing glycerin from biodiesel production

Item	Glycerin (%DM)				SEM	P-value
0.0	7.0	14.0	21.0	Linear
CL (%)	28.25	25.01	25.74	30.71	1.64	0.27
SF (Kgf)	3.41	2.41	2.43	3.45	0.30	0.92
pH	5.60	5.82	5.65	5.67	0.06	0.87
Color
L	36.21	35.87	35.82	36.36	0.62	0.89
a	19.48	19.08	19.36	19.65	0.36	0.63
b	6.05	5.33	5.74	5.90	0.38	0.98