48 INTRODUCTION Chronic arsenic toxicity has been discovered for more than a half century in some areas of the world. Arsenic in high doses generally decreases animal performance and causes abnormalities in the skin and hair (McDowell, 1992). However, organic arsenicals i.e., Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) and arsanilic acid, has been used as feed additives in poultry industries to improve production and control coccidiosis for decades (McDougald et al., 1992; Waldroup et al., 1995). Roxarsone is readily hydrated and coagulated by absorbing moisture, and therefore, it is difficult to prepare feedstuffs containing an even mix of ROX. As a result, chickens tend to overdose on ROX by taking in coagulated ROX (Chen and Wu, 2000). When a higher amount of ROX is used in the feedstuff, a number of physiological and other effects appear in the chicken. When the amount of ROX in laying hen’s diet reaches 156 mg/kg, significant decreases in feed intake and egg production are observed; whereas with 312 mg/kg, egg production ceases in two weeks. Furthermore, formation of fatty liver is observed one week after ROX withdrawal (Chiou et al., 1997). When intake of nutrients is excessive, lipogenesis is promoted dwarfing the lipid catabolism in the liver, resulting in the fatty liver (Chen et al., 2000; Chen and Chiou, 2001; Chen et al., 2005). It is therefore desirable to examine the recovery rate of the after-effects of ROX. In previous research, the effect of ROX withdrawal has been examined for one or two weeks after the withdrawal and on production performance (Chiou et al., 1997). Therefore, in the present trial, the time after the withdrawal was extended up to seven weeks to see the duration of ROX after-effect on a number of phenomena including the performance and functions of some internal organs. MATERIALS AND METHODS Chicken and feeding One hundred healthy (force-moulted) 84-week-old Single Comb White Leghorn laying hens with comparable weight and egg producing rate was placed in individual wire floored cages (38×18.5×39 cm), and received a photoperiod of 14L:10D (Park et al., 2005). The feed and water was available ad libitum. The basal diet was formulated according to the National Reasearch Council (NRC, 1994) Nutrient Requirements of Poultry as listed in Table 1. The ROX premix was prepared with dextran as carrier, and was added to the mixer in the last stage of mixing. Hens were randomly allocated to the five groups with 20 hens in each group. Twenty hens in each group were further divided into five smaller groups of four hens, and the hens in each group were fed with the same batch of feed Recovery over Time of Production Performance and Biological Functions of Laying Hens after Withdrawal Toxic Levels of Dietary Roxarsone Chean-Ping Wu, Shiow-Min Tsay, Peter Wen-Shyg Chiou 1 and Kuo-Lung Chen* Department of Animal Science, National Chiayi University, 300 University Road, Chiayi 600, Taiwan, ROC ABSTRACT : Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) has been used as feed additives in poultry industries to improve production and control coccidiosis. The effect of high dietary levels of Roxarsone (ROX) on the performance and function of internal organs and the kinetics of recovery as well as its after-effects were examined in laying hens. The inclusion rates of ROX were 0, 100, 200, 300, and 400 mg per kg feed. Inclusion up to 200 mg did not show any adverse effects (p>0.05), whereas in the 300 and 400 mg groups, significant effects, particularly in the latter, were observed for three weeks after ROX addition (p<0.05). Recovery of the physical appearance occurred soon after ROX addition was withdrawn. Recovery of performance and internal organs, however, appeared to be dependent on the amount of residual ROX in the body; as the amount of ROX decreased, the toxic effect of ROX also decreased. In the third week after the withdrawal of ROX, complete recovery was observed in the lower dosage groups (100 or 200 mg groups) (p>0.05), whereas in the higher dosage groups (300 or 400 mg groups), recovery took at least five weeks; when complete recovery was observed in egg production and in liver weight (p>0.05). On the other hand, ROX might have damaged the liver and other tissues. The recovery of liver weight was probably due to accumulation of fatty particles rather than repair. It appeared, therefore, there were little after-effects of ROX on the hen’s physical appearance, but some internal organs were probably damaged. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 1 : 48-54) Key Words : Roxarsone, Laying Hen, Egg Production, Liver Function, Lipid Metabolism * Corresponding Author: Kuo-Lung Chen. Tel: +886-5-2713252, Fax: +886-5-2717527, E-mail: ckl@mail.ncyu.edu.tw 1 Department of Animal Science, National Chung-Hsing University, 250 Kuo- Kuang Road, Taichung 402, Taiwan , ROC. Received February 15, 2005; Accepted September 19, 2005
