Abstract
Thyroid hormones are known for their stimulation of feed efficiency and growth performance in different farm animals. More interestingly, the level of thyroid hormones is influenced by selection for growth in some animal species. Therefore, it was the aim of the current study to investigate whether a correlation exists between the blood triiodothyronine (T-3) level and some production traits (daily feed intake, average daily gain, and feed conversion ratio). To test this hypothesis, six male goat kids (21.9 +/- 2.4 kg; 5 months old) belonging to Aardi, Damascus, and their cross breed (two kids from each genotype) were used in the current study. The obtained results revealed a positive linear correlation of plasma T-3 level with both average daily feed intake and average daily gain with correlation coefficients of 99% and 97%, respectively (P <= 0.001). On the other hand, feed conversion ratio was negatively correlated to the plasma T-3 level with a correlation coefficient of 81% (P = 0.05). The obtained results indicate the possible use of blood T-3 level for the prediction of feed intake, daily body weight gain, and feed conversion ratio in addition to the possible use of blood T-3 level as a criterion of breeding selection for growth performance in the future.