Full Length Research Paper

Effect of transient postpubertal hypo- and hyperthyroidism on reproductive parameters of Iranian broiler breeder hens

A. Akhlaghi¹*, A. Zare Shahneh¹, M. J. Zamiri², A. Nejati Javaremi¹ and G. Rahimi Mianji³

¹Department of Animal Science, College of Agriculture, Tehran University, Karaj, Iran.

²Department of Animal Science, College of Agriculture, Shiraz University, Shiraz, Iran.

³Department of Animal Science, Faculty of Animal Science and Fishery, Sari University of Agricultural Science and Natural Resources, Sari, Iran.

*Corresponding author. E-mail: amirakhlaghi837@yahoo.com. 

Tel.: +981212251566. Fax: +982612246752.

Accepted 27 May, 2009

   Abstract

One hundred and thirty two 26-week-old broiler breeder hens were randomly assigned into one of three treatments as control, hypothyroid (HYPO; propylthiouracil (PTU)-treated) or hyperthyroid (HYPER; thyroxine (T₄)-treated) group. PTU and T₄ were administered between weeks 30 and 33 of age. Blood sampling was started at week 29, and repeated every week until week 35, coinciding with weekly body weighing. Using ELISA, plasma levels of T₃, T₄ and estradiol were assayed. Egg number, fertility, hatchability, grading of day-old chicks and embryonic developmental stage of unhatched eggs were determined for individual artificially inseminated hen. Effects of PTU and T₄ treatment on plasma T₄ levels were significant (P < 0.05), but T₃ levels were only affected by PTU. No significant effect was observed in plasma estradiol levels. Increased body weight following PTU treatment was not observed in other groups. Weekly egg number of HYPER was significantly lower (P = 0.0435) than other two groups, while the effect of PTU was not significant. Hatchability of fertile eggs (%) in HYPO was significantly decreased (0.00%, P < 0.0001); while other groups did not significantly differ. The number of grade 1 chicks in control was greater than in HYPER group. Fertility (%) was not affected by PTU or T₄. In unhatched eggs, percent of non-pipping or internal pipping stage of embryonic life in HYPO was more than other groups; but external piping was not affected by treatments (P > 0.05). In conclusion, among the different reproductive parameters in this study, hatchability and weekly egg production were the most responsive parameters to decreased or increased plasma thyroid hormone levels, respectively.

Key words: Hypothyroidism, hyperthyroidism, broiler breeder hens, reproduction, egg production, fertility, hatchability.