Subacute ruminal acidosis (SARA) challenge, ruminal condition and cellular immunity in cattle.

Subacute ruminal acidosis (SARA) is characterized by repeated bouts of low ruminal pH. Cows with SARA often develop complications or other diseases, and associate physiologically with immunosuppression and inflammation. Ruminal free lipopolysaccharide (LPS) increases during SARA and translocates into the blood circulation activating an inflammatory response. Ruminal fermentation and cellular immunity are encouraged by supplementing hay with calf starter during weaning. SARA calves given a 5-day repeated administration of a bacteria-based probiotic had stable ruminal pH levels (6.6-6.8). The repeated administration of probiotics enhance cellular immune function and encourage recovery from diarrhea in pre-weaning calves. Furthermore, the ruminal fermentation could guard against acute and short-term feeding changes, and changes in the rumen microbial composition of SARA cattle might occur following changes in ruminal pH. The repeated bouts of low ruminal pH in SARA cattle might be associated with depression of cellular immunity.