COMPARACIóN DE LOS NIVELES DE HORMONAS TIROIDEAS ENTRE DOS LíNEAS DE AVES PONEDORAS

objective. to establish reference values for tsh and free t4, in two lines of laying hens (hy-line w-36 and lohmann brown-classic),as well as to compare the thyroid hormone levels in serum between those two lines. materials and methods. one hundred, 25 weeks of age laying fasting hens serum (50 hy-line w-36 and 50 lohmann brown-classic) was obtained and tsh and free t4 levels were measured using enzymatic inmunoessay. results. the values obtained for tsh for high-line w-36 (uui/ml) were: mean, minimal, maximal, and standard deviation, 0.09, 0.00, 0.82, 0.15 respectively. for the lohmann brown-classic (uui/ml) the values were, 0.29, 0.00, 4.98, 0.78, respectively. the p value of test f was greater or equal to 0.05 reason why there is not statistical significant difference, with a 95% confidence for tsh between the lines studied. the free t4 values obtained for hy-line w-36 in ng/dl were mean, minimal, maximal, and standard deviation of 0.95, 0.11, 2.00, 0.53 respectively while the values found for the lohmann brown-classic line in ng/dl were 1.54, 0.21, 2.58, 0.49 respectively. the p value for the f test was inferior to 0.05, showing statistically significant difference with a 95% confidence for free t4 between the lines studied. conclusion. statistical difference was observed for free t4 between the two studied lines. this could be explained because the semi-heavy line (lohman brown-classic) deposits a higher quantity of fattening in the organism influencing the increase of t4 levels for this line and not for the light hy-line w-36. reference values for the two laying hens studied lines are presented.