OSORIO, José Henry; SALAMANCA, Diana Marcela    PEREZ, Jorge Enrique. COMPARISON OF THYROID HORMONE LEVELS BETWEEN TWO LINES OF LAYING HENS. []. , 10, 1, pp.61-68. ISSN 1657-9550.

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.

: hens; TSH; free T₄; metabolism.

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