Effect Of Propionic Acid On Blood Parameters, Histomorphology And Expression Of Relative Genes In Goat Abomasum Tissue

Displacement of Abomasum (DA) is a common internal disease in the industry of diary production, but there is currently little knowledge on its pathogenesis. Propionic acid is one of important ingredients of volatile fatty acids (VFA) in ruminants. Some research have shown that increased VFA can inhibit the motility of the abomasum. The goats’rumen were perfused with propionic acid in different concentrations via rumen fistula which were set up by surgical operation. The blood routine indexes, blood biochemical indexes and the mRNA expression of M2、M3 receptors and eNOS in abomasum tissue were detected, which provide experiment materials for the pathogenesis of DA.Twelve healthy goats were selected, with a body weight of (30.0±2.6) kg. The goats were divided into control group, low-dose group, mid-dose group and high-dose group randomly. The goat rumens in three experimental groups were perfused with propionic acid daily at a dose of 0.5g/kg, 1.0g/kg,1.2g/kg respectively and the control group perfused the same volume of saline, the perfusion of propionic acid last for a week. The blood and rumen fluid samples were collected daily after 4h of perfusion, blood samples were used to record the complete blood count and biochemistry indexes, pH value and VFA concentration of rumen fluid were tested. Abomasum tissue samples were collected by surgical operation in the day after a week of propionic acid perfusion, it was used to observe the histomorphology changes, The genes expression of M2、M3 receptors and eNOS in abomasum tissue were detected by qPCR. The results are as follows.1. After the perfusion of propionic acid, the biochemistry indexes of all three experimental groups indicated that the physiological indexes of the liver, kidney and blood calcium were normal compared with the control group; the content of blood glucose in the high-dose group was significant increased (P<0.01) and the result of blood count showed that the number of WBC was not raised obviously (P>0.05), there was no significant differences in the low-dose group and mid-dose group compared with the control group.2. After the perfusion of propionic acid, compared with the control group, the rumen pH value in the low-dose group, mid-dose group and high-dose group were all normal (P>0.05), the concentration of acetic acid, propionic acid, butyric acid in the rumen was normal in the low-dose group and mid-dose group, it was the same as the acetic acid concentration in the high-dose group (P>0.05), the concentration of propionic acid in the rumen was increased significantly in the high-dose group(P<0.01).3. After the perfusion of propionic acid, the histomorphology observation of abomasum tissue showed that the abomasum mucosa of the low-dose group and mid-dose group had no variation apparently. The abomasum mucosa epithelium of high-dose group showed that the gastric pit disappeared, morphology of the simple columnar epithelial cells which form the mucosal epithelial cells disappeared, glands of the lamina propria mucosae were loosely arranged and distributed, muscle fiber of smooth muscle were impaired.4. After the perfusion of propionic acid, the mRNA expression of M2、M3 receptors and eNOS were detected in abomasum tissue. Compared with the control group, the mRNA expression of M2 and M3 receptors were decreased both in abomasum mucoma and entire tissue layer (P<0.01). The expression of eNOS mRNA increased in both abomasum muscoma and the entire tissue layer (P<0.01).In conclusion, propionic acid had no significant impacts on the blood count and biochemistry indexes in goats, but high doses of propionic acid caused damage to the abomasum mucosa and increased the content of blood glucose, the mRNA expression of M3 and M2 receptors were down-regulated and eNOS was up-regulated, the propionic acid may as the main reason that lead to the weakening of abomasum motility, afterwards result in DA.