乳牛における血清α-グルコシダーゼ活性：負のエネルギーバランスの新たな指標

Enzymes of the α-glucosidase group cleave α-D-glucose from the non-reducing end of short oligosaccharides. They contribute to carbohydrate digestion as maltase-glucoamylase in the intestinal brush border and as neutral α-glucosidase in other tissues. Neutral α-glucosidase is also active in blood, but little is known about its relevance as an indicator of the body's metabolic state. Therefore, we proved whether the α-glucosidase activity level in blood does reflect the state of negative energy balance (NEB). As NEB commonly occurs in dairy cows around calving, our study included blood (serum, plasma) samples of 73 Holstein Friesian cows collected ±14 d to parturition. After the establishment and characterization of a fast and low-cost activity assay, these blood samples were analyzed for α-glucosidase compared to known NEB biomarkers. This analysis revealed the lowest α-glucosidase activity 5 d post partum (-25% compared to 14 d ante partum) by using two different α-glucosidase substrates. The reduced activity recovered 14 d post partum; however, the degree of recovery depended inversely on the number of parities. In this regard, α-glucosidase activity changed peripartum in line with known biomarkers (e.g., NEFA, IGF-1, glucose). In conclusion, the α-glucosidase activity is a new and easily detectable blood parameter of NEB in dairy cows.