Effects Of Wheat Straw-Fed On Feed Intake And Appetite Of Hu Sheep And Its Mechanism

Roughage is an indispensable energy source for ruminants.In this study,the alfalfa group was a control,and wheat straw-fed on the feed intake of Hu sheep and the related molecular mechanisms were discussed,including the following three parts:1.Effects of wheat straw-fed on weight gain,feed intake and blood biochemical indexes of Hu SheepUnder the condition of iso-energy and iso-nitrogen,the effects of two different roughages on the appetite and feed intake of Hu sheep were studied.12 healthy male Hu sheep 5～6 months old,weight(41.21 ± 2.92)kg were selected in the experiment.After the pre-experiment for 30 days,Hu sheep were randomly divided into alfalfa group(ALF)and wheat straw group(WS)according to the principle of similar body weight,with six in each group.The concentrate/roughage ratio was 3:2 in both groups.The roughage of alfalfa group was alfalfa,and the roughage of wheat straw group was wheat straw.They were fed at 8:00 a.m.and 17:00 p.m.every day,drinking freely.The temperature,humidity of sheep shed and feed intake were recorded daily.At the day 0,7,14,21 and 28 of the experiment,blood was collected from the jugular vein.The routine biochemical indexes,enzyme content and hormone level in blood were measured.Results:1)under the condition of similar initial weight(40.63 ± 1.48&41.32 ± 1.52),the weight of Hu sheep in the two groups increased(46.44 ± 1.17&45.52 ± 1.49)kg,the average daily increment(207 ± 33&150 ± 35)g and relative growth rate(14.14 ± 2.14&10.40±2.57)%in alfalfa group were better than those in wheat straw group,and the average feed intake of Hu sheep in the alfalfa group(1738.50 g·d-1)was significantly higher than that in wheat straw group(1430.53 g·d-1).2)On the 28th day,blood GLB and Urea content in Hu sheep from wheat straw group were significantly lower than those in alfalfa group(P<0.01),and A/G(albumin and globulin ratio)was significantly lower than those in alfalfa group(P<0.05);there were no significant differences in blood glucose,T-BIL,TG,D-BIL and I-BIL in alfalfa group and wheat straw group(P>0.05).The blood AST and LDH content in Hu sheep from wheat straw group was significantly lower than that in alfalfa group(P>0.01,P<0.05),and the content of ALP in wheat straw group was higher than that in alfalfa group(P>0.05).3)INS in Hu-sheep blood sample from wheat straw group is significantly lower than the alfalfa group(P<0.01),CCK and Leptin value is significantly higher than the clover hay group(P<0.01,P<0.05),GLP-1 is slightly higher than the alfalfa group(P>0.05);Ghrelin is lower than the alfalfa group,but COR and T4 is slightly lower than the alfalfa group with no significantly differences.Conclusion:different roughages-fed such as alfalfa and wheat straw have different effects on the production performance of Hu sheep.Alfalfa group is better than wheat straw group mainly in the feed intake and body weight gain;there is no significant difference in the blood related indicators between the two groups,but the appetite inhibiting hormone CCK in wheat straw group is significantly higher than that in alfalfa group,the appetite promoting hormone ghrelin content in wheat straw group is lower than the alfalfa group.The results showed that there is no significant impact on the health of all the Hu-sheep when feed with wheat straw alone,however,the feed intake is lower than alfalfa group.This feed intake reduction in wheat straw group maybe related with the hormone secretion.2.Effects of wheat straw-fed on gastrointestinal health and long fatty acid(LCFAs)production of Hu SheepIn the experiment,12 healthy male Hu sheep 5～6 months old,weight(41.21 ±2.92)kg were selected in the experiment.After the pre-experiment for 30 days,Hu sheep were randomly divided into alfalfa group(ALF)and wheat straw group(WS)according to the principle of similar body weight,with six in each group.The concentrate/roughage ratio was 3:2 in both groups.The roughage of alfalfa group was alfalfa,and the roughage of wheat straw group was wheat straw.They were fed at 8:00 a.m.and 17:00 p.m.every day,drinking freely.After feeding for 4 weeks,all the sheep were slaughtered,and different tissue samples were taken to carry out the following experiments:1)pH value of each gastrointestinal content was measured and the weight of the content was recorded;2)LPS content in rumen,cecum content and blood was measured by ELISA;3)activity of pectinase,xylanase,cellulase and liquid phase carboxymethyl cellulase in rumen content was measured by biochemical method;4)The contents of volatile fatty acids in rumen and long-chain fatty acids in blood were determined by GC-HPLC;5)the liver,pancreas,spleen and thymus were taken and weighed,and each organ index was calculated,respectively;6)the tissues of duodenum,jejunum and cecum were taken and sliced.Results:1)the rumen pH of Hu sheep in wheat straw group was lower than that in alfalfa group(5.72±0.18&6.34±0.18),and the pH of other gastrointestinal tract was within the normal range;the rumen,reticulum,omasum and abomasum contents of Hu sheep in wheat straw group were higher than those in alfalfa group,and the rumen and omasum contents were significantly higher(P<0.05),and the contents of other intestinal contents were not significantly different.2)There was no significant difference in the concentrations of LPS in rumen,cecum and blood between the two groups.3)There was no significant difference in the activity of rumen liquid-phase,solid-phase carboxymethyl cellulase and pectinase between alfalfa group and wheat straw group,but xylanase activity in wheat straw group was significantly higher than alfalfa group(P<0.01).4)There was no significant effect of wheat straw-fed on rumen volatile fatty acids(including acetic acid,propionic acid,butyric acid,isobutyric acid,valeric acid,isovaleric acid)and acetic acid/propionic acid(P>0.05).However,the contents of margaric acid(C17:0)and oleic acid(C18:1)in the blood of Hu sheep in the wheat straw group increased significantly(P<0.05).5)There was no significant change in spleen index and thymus index between the two groups.Liver index and pancreas index in alfalfa group were slightly higher than those in wheat straw group.6)The histological results of duodenum,jejunum and ileum in the two groups showed no abnormal changes.The results showed that wheat straw-fed alone had no effect on gastrointestinal health of Hu sheep,but had different effects on rumen pH value,content emptying,xylanase activity and blood long chain fatty acid content.The change of these indexes,especially the difference change of long-chain fatty acids oleic acid,may be related to the decrease of appetite of Hu sheep caused by using wheat straw as roughage.3.A preliminary study on endocrine signal mechanism of appetite reduction induced by wheat straw feedingMouse intestinal endocrine STC-1 cells were used for the following experiments.1)STC-1 cells were treated with low,medium and high concentrations of oleic acid(0.025,0.05,0.1 mmol/L);the content of CCK and GLP-1 in cell supernatant was determined by ELISA;intracellular Ca2+concentration was determined by flow cytometry;2)when it was treated with oleic acid,GPR40 antagonist GW1100 and GPR120 antagonist AH7614 were added to treat the cells respectively,and the CCK and Ca2+ contents in the cell supernatant were measured;3)the protein expression levels of GPR120,GPR40,PLCβ,IP3R,PKC and GLUT4 were detected by Western Blot.Results:1)compared with the control group,the CCK content in cells treated with oleic acid at different concentrations was significantly increased(P<0.01)and GLP-1 content was significantly increased(P<0.05).The intracellular Ca2+concentration increased significantly(P<0.01);2)the CCK and Ca2+concentration decreased significantly(P<0.01)and the GLP-1 content did not change significantly after AH7614 inhibitor was added.There are no significantly changes in all above index when added with GW1100(P>0.05);3)compared with the control group,the expression of GPR120 protein was significantly up-regulated in cells treated with medium concentrations(P<0.05),and the expression of IP3R protein was significantly up-regulated in cells treated.with medium and high concentrations(P<0.05).The up-regulated expression of GPR120 and IP3R protein was reversed after the addition of AH7614 inhibitor.There was no significant difference in the expression of GPR40 receptor protein in each concentration group(P>0.05);after GW1100 inhibitor was added,GPR120 and IP3R protein expression was not reversed(P＞0.05).4)The expression of PLCβ,PKC and GLUT4 proteins were all increased in cells treated with oleic acid at different concentrations.Compared with the control group,the difference of PLCβ in the cells treated with the medium and high concentration groups was significant(P<0.05),the expression of PKC protein in the low,medium and high concentration groups was significantly up-regulated(P<0.05),and GLUT4 protein in the high concentration group was significantly up-regulated(P<0.05);after the addition of AH7614 inhibitor,the expression of the above proteins was reversed.However,there was no significant inhibitory effect after adding GW1100.Conclusion:Long chain fatty acid(LCFAs)oleic acid can enhance the CCK and GLP-1 release to reduce feed intake by activating GPR120 receptor whose probable mechanism is GPR120-IP3/Ca2+-PKC signaling pathway.