# Serum α-Glucosidase Activity as a New Parameter of Negative Energy Balance in Dairy Cows

## TL;DR

This study introduces serum α-glucosidase activity as a new, easy-to-measure indicator of negative energy balance in dairy cows around calving.

## Contribution

The study identifies and validates serum α-glucosidase as a novel biomarker for detecting negative energy balance in dairy cows.

## Key findings

- α-glucosidase activity in blood was lowest 5 days post partum, reflecting the energy deficit in dairy cows.
- The activity recovered 14 days post partum, with recovery depending on the number of previous calvings.
- α-glucosidase activity changes align with known NEB biomarkers like NEFA, IGF-1, and glucose.

## Abstract

Dairy cows suffer from a calorie deficit, i.e., negative energy balance (NEB), around calving because their bodies expend more calories than they consume. Various biomarkers are routinely recorded on farms or in scientific studies to assess the extent of NEB. Our present study identified and described a new parameter that also effectively reflects the body’s metabolic state in dairy cows. This parameter is called neutral α-glucosidase. Neutral α-glucosidase belongs to the enzyme group of α-glucosidases that cleave glucose, the most abundant sugar, from short oligosaccharides. Its activity is detectable by a fast and low-cost enzymatic assay. Our study established and characterized this assay for bovine blood (serum, plasma) samples.

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.