Application Of Different Attapulgite Products In Laying Hen Diets

This study was conducted to evaluate the effects of original (OA), thermal modified (TMA) and citric acid wasterwater treated (CTA) attapulgite on performance, egg quality, metal element contents in tissues, digestive enzyme activity, intestinal mucosal morphology, and mRNA expression of pancreatic digestive enzymes and intestinal mucosal glucose transporters in peak-phase laying laying hens. The objective of this study was to provide some references for further exploration of the action mechanism and application of attapulgite in laying hen diets.A total of 540 Hy-line Brown laying laying hens aged of 32 weeks with similar body weight and laying rate were divided into 5 groups with 6 replicates per group and 18 laying hens in each replicate. Laying laying hens in the control group were fed the basal diet, and other groups were fed the basal diet supplemented with 2%OA,2%TMA,1%CTA or 2% CTA. The adaption period was 1 week, the test period was 8 weeks. The study included three parts:Trial 1:The experiment was conducted to study the effects of different attapulgite products on performance, serum biochemical indexes, egg quality and metal element contents in tissues in laying hens. The results showed as follows:Laying rate and egg weight were increased, while feed intake and feed:egg ratio were decreased by OA, TMA and 1%CTA supplementation in diet (P>0.05). Compared to the 2%CTA group, OA, TMA and 1%CTA supplementation significantly increased egg weight, decreased feed:egg ratio (P<0.05). The activity of serum alkaline phosphatase was decreased by OA, TMA and 2% CTA significantly at 4 wk (P<0.05 or P<0.01). Serum albumincontent was increased by 2% CTA at 8 wk (P<0.05).1%CTA increased serum insulin content significantly (P<0.01). Yolk colour was decreased by OA and TMA at 4 wk (P<0.05). Compared to the 2%CTA group, OA and 1%CTA supplementation significantly improved eggshell thickness at 8 wk (P<0.05). Different attapulgite products could increase the contents of Fe, Zn and Mg in egg.1% CTA improved Fe and Zn content in egg (P<0.01), OA and TMA increased Zn content in egg (P<0.05).1%CTA decreased Cr content in egg (P<0.05). Compared to the OA group, other groups reduced Cu content in egg (P<0.05).2% CTA increased Fe content in liver (P<0.05). Compared to the OA and 1% CTA group,2% CTA decreased Zn content in liver (P<0.05). TMA and 1% CTA decreased Cu content in pancreas (P<0.05). The Zn contents of pancreas in TMA and 1% CTA groups were lower than those in OA group (P<0.05orP<0.01).Trial 2:The aim of this experiment was to study the effects of different attapulgite products on digestive enzyme activity, intestinal mucosal morphology and intestinal pH value of laying laying hens. The results showed that OA and 1% CTA increased amylase activity in pancreas of laying hens (P<0.05). OA increased protease activity in jejunum of laying hens (P<0.01). Different attapulgite products tended to increase the maltase and sucrase activities in mucosa of duodenum and jejunum, but the difference was not significant. Villus height of duodenum was improved by dietary OA (P<0.05). Duodenal villus height/crypt depth (V/C) ratio in the 1% CTA group was increased by dietary 1% CTA (P<0.05). The jejunal mucosal morphology could be affected by different attapulgite products (P>0.05). All test groups reduced the pH in gizzard, duodenum and jejunum of laying hens, at the same time,2% CTA reduced the duodenal pH significantly (P<0.01).Trial 3:The experiment was conducted to determine the effect of different attapulgite products on the mRNA expression of pancreatic enzymes and intestinal mucosal glucose transporters. The results showed that adding different attapuigite products in laying hens could improve the mRNA levels of pancreatic amylase and trypsinogen. Pancreatic amylase mRNA expression in the OA and TMA groups were significantly higher than that of the control group (P<0.05), and 1% CTA improved the pancreatic amylase mRNA expression very significantly (P<0.01). Different attapulgite products tended to improve the intestinal mucosal SGLT 1 and GLUT 2 mRNA expression, but the difference was not significant.These results implied that OA, TMA and 1% CTA could improve performance and increase the contents of Fe, Zn and Mg in egg. Meanwhile they could improve digestive enzyme activity, increase mRNA expression of pancreatic enzyme and intestinal mucosal glucose transporters (SGLT 1, GLUT 2). Under the condition of this test, dietary supplementation of 1% CTA exerted the better effects.