A Feeding Test of Polychlorinated Biphenyl (PCB): Its Accumulation and Disappearance in Hen's Eggs and Fat, and Its Effect on Egg Produetion

Abstract

Experiment 1 was designed to elucidated PCB accumulation and disappeance in egg. Seventy-five laying hens were divided into 5 groups of 15 hens each. Each of 4 groups was fed one of 4 diets containing 0, 10, 20, or 40ppm of PCB for 6 weeks and thereafter fed PCB-free diet for 20 weeks. To the rest, one group was fed diet containing 20ppm of PCB for 20 weeks to find the PCB effect on the egg production.Experiment 2 was designed to exmine the PCB accumulation in hen's fat by feeding PCB. Ninety-six hens were divided into 2 groups of eighteen and seventy-eight hens each. Each of 2 groups was fed one of 2 diets containing either 0 or 20ppm of PCB for 6 weeks, and then fed PCB-free diet for 20 weeks.1. Change in PCB composion: PCB used in this experiment was KC-500 of Kanegafuchi Chemical Company which is known as a mixture of PCB isomers. The gas chromatographic analysis differentiated 14 to 18 peaks in KC-500 by chlorine number and their position in PCB molecule. The method of gas chromatography was used to estimate PCB contents and to analyze PCB peaks in eggs and fat. PCB peaks with fewer chlorines have been detected in early period, then they decreased rapidly, while PCB peaks with more chlorines remained longer. The trend of change in PCB composition in eggs and fat was similar.2. PCB accumulation in eggs and fat during PCB feeding: The change in content of PCB in eggs of hens fed 10, 20, or 40ppm of PCB for 6 weeks and those fed 20ppm of PCB for 20 weeks could be explained by Equation 10. The change in PCB content in adipose tissue could be explained by Equation 5.y=x(0.231+0.291lnt)……(10)where, t(6_??_t_??_1) is length of PCB feeding (weeks) and y is PCB content (ppm) in eggs.y=8.822+45.607lnt……(5)where, t(6_??_t_??_1) is length of PCB feeding (weeks) and y is PCB content (ppm) in adipose tissue.3. Disappearance of PCB from eggs and fat after the withdrawal of PCB feeding. Two separable periods are noticed on PCB disappearance. The first period is the first week after the withdrawal of PCB feeding. In this period, PCB disappeared rapidly, and one thirds of the PCB accumulated in eggs was excreted. In the second period, remaining two thirds of PCB were excreted slowly. PCB disappearance from eggs in the first and second period could be explained as exponential, respectively. Pattern of PCB disappearance from eggs of hens fed 10, 20, and 40ppm of PCB for 6 weeks could be explained by Equation 6, 7, and 8, respectively as the following.y=3.266e-2.418•t+5.398e-0.0855•t……(6)y=5.043e-1.671•t+10.319e-0.0628•t……(7)y=14.112e-2.525•t+23.127e-0.0785•t……(8)where, t(20_??_t_??_1/7) is length after PCB withdrawal (weeks) and y is as in Equation 10. Pattern of PCB disappearance from adipose tissue of hens fed 20ppm of PCB for 6 weeks could be described by Equation 9, y=88.677e-0.0424•t……(9)where, t and y are as in Equation 6.4. No significant effect was observed by feeding PCB at 10, 20, and 40ppm on performance of laying hens. No significant effect was observed on average egg weight, egg production per hen per day, feed intake, body weight, and viability among the hens fed various levels of PCB.