| As the breeding of ruminants becomes intensive and large-scale, feeding high concentrated fodder can improve the production performance, which may lead to ruminants’ gastrointestinal function disorders. Bovine abomasum displacement (DA) is one of the digestive disorders of internal medicine. It is generally agreed that adding a large amount of high concentrated fodder into diet is one of the important reasons to induce the disease. Excess concentrated fodder ferments in the rumen produce large amounts of volatile fatty acids (VFA), of which acetic acid accounts for 70% to 75%. The VFA which cannot be absorbed by the rumen enters the abomasum, leading to weakened stomach contractions and bradykinesia. This is the pathological basis on DA occurring.In order to explore the mechanism of DA induced by acetic acid in ruminants, this study were performed using adult hybrid goats as experimental animals. Observationing the changes in complete blood count and blood biochemistry, the changes in the rumen environment (pH, VFA concentration), the changes in the organizational structure of abomasal tissue wall and the changes The changes in mRNA expression of M2, M3 and eNOS in abomasal tissue induced by rumenal perfusion with varying doses of acetic acid solution through a fistula. Test Method: twelve body weight approximately 30-40kg adult hybrid goats were randomly divided into four groups:control group, low dose group, middle dose group and high dose group, permanent rumen fistula was installed in each goat of each group. Every day the goats of the three experimental groups were respectively perfusioned of acetic acid at a concentration of 0.5g/kg, 1.0g/kg and 2.0g/kg, while the goats of the control group were perfusioned the same volume of saline, perfusions continued for a week. On each day, four hours after perfusions, blood and rumen fluid were collected for complete blood count, blood biochemistry, rumen pH and rumen fluid VFA concentration. After one week, abomasal tissues were collected using sterile surgical methods for paraffin section HE colour and the mRNA expression of M2, M3 and eNOS by RT-PCR. Conclusions were as follows:1. After rumenal perfusion with acetic acid solution, there were no significant changes inRBC and WBC counting compared to the control group (P>0.05). The AST values in the middle and high dose group were up-regulation, which had very significant difference compared to the control group (P<0.01), and beyond the normal physiological range; The AST values in the medium and high dose group were up-regulation, which had significant difference compared to the control group (P<0.05), while the high-dose group had a very significant difference (P <0.01); Comparing with the control group, the ALP, BUN, CREA and Ca values did not change significantly (P>0.05).2. After rumenal perfusion with acetic acid solution, the tissue structure of the abomasal fundus wall in the low and middle dose group were completely, glands arranged closely, each tissue structure were clear, there had no obvious pathological changes been found in the microscopic examination which compared to the control group. In the tissue structure of the abomasal fundus wall which in high dose group, mucosal epithelial cells were enhanced by eosinophilic enhancement, nuclear dissolution, the gland in the intrinsic layer was sparse, and the submucosal layer became thinner.3. After rumenal perfusion with acetic acid solution, there were no significant difference in the low and middle dose groups compared to the control group (P>0.05). The ruminal pH value in the high dose group was decreased which had a very significant difference compared to the control group (P<0.01). The concentration of acetic acid in rumen was increased, which had a very significant difference compared to the control group (P<0.05). The concentration of propionate and butyrate in the low and middle dose group had no significant difference compared to the control group (P>0.05). The concentration of propionate and butyrate in the high dose group was decreased, which had very significant difference compared to the control group (P<0.01).4. After rumenal perfusion with acetic acid solution, the M2 、M3 mRNA levels in the full-thickness of the abomasum tissues in the low dose group were up-regulation which had no significant difference compared to the control group (P>0.05); The M2、M3 mRNA levels in the middle and high dose group were down-regulation, there were no significant difference in the middle dose group compared to the control group (P>0.05), and a significant difference in the high dose group compared to the control group (P<0.05). The eNOS mRNA levels in each dose group were up-regulation, comparing to the control group, the low dose group had a significant difference(P<0.05), the middle and high dose group had a very significant difference (P<0.01). In the mucosa of the abomasum tissues, the M2 and M3 mRNA levels in the low dose group were up-regulation, comparing to the control group, the M2 mRNA levels had a significant difference (P<0.05), the M3 mRNA levels had no significant difference (P>0.05). The M2、M3 mRNA levels in the middle and high dose group were down-regulation, comparing to the control group, the M3 mRNA levels in the high dose group had a significant difference(P<0.05). The eNOS mRNA levels in each dose group were up-regulation, comparing to the control group, the low dose group had a significant difference (P<0.05), the middle dose group had a very significant difference (P<0.01), the high dose group had no significant difference (P>0.05).Conclusion:Rumenal perfusing with acetic acid solution did not result in changes of the kidney damage or systemic inflammatory response, but might lead to liver damage; High doses of acetic acid caused the gastric mucosa damage, blocked the experssion of M2 and M3 genes, promoted the experssion of eNOS gene, which led to bradykinesia, decreased contractions of the abomasum, and then might lead to abomasum displacement. |
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