Effects of different induced moulting methods on plasma thyroid hormones of laying hens

Abstract
The objective of the study is to assess the effect of two different induced moulting methods on plasma thyroxine (T4) and triiodothyronine (T3) concentrations of laying hens. In this study, 96 Isabrown hens, 72 ­weeks of age were used. The hens were randomly divided into two rooms. Two control groups (FAST CON and Lo Na CON) were caged in the first room, each containing 24 hens, and two treatment groups (FAST and Lo Na) were caged in the second room, each containing 24 hens.  Feed was withdrawn from the hens in the first treatment group (FAST) for 10 days and water were providedad libitum. The photoperiod was reduced to 7 h/day. On day 11, hens consumed the standard pullet grower rationad libitum until day 41 and hens were returned the standard full feed layer ration and received. Lo Na group was fed layer ration containing 0.08 % sodium until 41 days. The hens in the control groups were fed the standard layer ration during experimental periods. In both experimental groups, plasma T3 concentrations in the premoult period were lower than moulting periods (p<0.05). The plasma T4 concentrations in premoult period were also measured lower than moult and postmoult periods (p<0.05). When two moulting procedures compared with each other, T4 concentrations of Lo Na group were higher than FAST group. But, T3 concentrations of both experimental groups were nearly similar with each other, except postmoult period. As conclusion, results of this study indicated that low sodium diet as effective as fasting method, when T3 and T4 concentrations were taken into consideration. 
Keywords : Fasting method,Laying hence,Low sodium diet,Moulting,Thyroid hormones