Effects Of Subacute Ruminal Acidosis On Proliferation And Apoptosis Of Rumen And Omasum Epithelial Cell

Eight healthy Guanzhong dairy goats were selected as experimental animals and were randomly allocated to three groups based on body weight, milk yield similar principles: control group、SARA group and recovery group. Control group dairy goats were fed basal diet, SARA group dairy goats were fed diets with different NFC/NDF ratios, which were1.02、1.2、1.63、2.58respectively. Meanwhile, subacute ruminal acidosis (SARA) was induced by gradually increasing dietary NFC/NDF ratios; recovery group were fed hay for4weeks after successful induction of subacute ruminal acidosis. Dairy goats were killed at the end of each experiment, ruminal and omasal epithelia were collected.(1) SARA was induced by gradually increasing dietary NFC/NDF ratios, ruminal pH, volatile fatty acids and lactic acid were measured to evaluate the SARA model. The results showed that when NFC/NDF ratio was2.58, duration time of ruminal pH between5.2and5.5last for7.58h/d, SARA occurred in dairy goats. The concentrations of rumen total volatile fatty acids (TVFA)(p<0.05), propionate (p>0.05) and butyrate (p<0.05) increased, while acetate concentration increased (p<0.05). Lactate concentration was not significantly changed (p>0.05).(2) Histological slices analyzed by Image-ProPlus6showed that the length,width and stratum corneum thickness of rumen papilla were lowest in SARA group. In addition, the thickness of omasum stratum corneum, central muscularis and muscularis mucosae were lowest in the SARA group. TEM observation showed that rumen epithelial microvilli irregularly arranged, mitochondria swelling, nuclear condensation, chromatin aggregated to the margin with irregular and more apoptotic bodies formed were found in SARA group compared with control group and recovery group.(3) The protein, DNA, RNA contents of the rumen and omasum epithelium were measured to study effects of SARA on proliferation and apoptosis of rumen and omasum epithelial cell. The results showed that SARA had a significant effect on the rumen epithelial proteins, DNA and RNA content. The rumen epithelial protein, DNA and RNA contents decreased significantly in SARA group, While SARA had no significant effect on the proteins, DNA and RNA contents of omasum epithelium. Rumen and omasum epithelial PCNA expression decreased significantly and apoptotic index increased significantly for SARA group relative to control and recovery group.(4) ATP enzyme activity were determined to study effects of SARA on rumen and omasum epithelial ATP enzyme. The results showed that rumen epithelial Na+-K+-ATP and Ca2+-Mg2+-ATP enzyme activity were lowest in SARA group, and their activity in recovery group significantly higher than that in SARA group but significantly lower than that in control group. Omasum epithelial Na+-K+-ATP and Ca2+-Mg2+-ATP enzyme activity were lowest in SARA group and highest in recovery groupThe above results indicated that SARA not only altered the morphological structure of rumen and omasum epithelium, but also inhibited epithelial cell proliferation and promoted apoptosis, which may play an important role in rumen mucosal barrier dysfunction caused by SARA.