Effects of beta-1,3-glucan supplementation on concentrations of serum metabolites in transition Holstein cows

Highlights

• beta-1,3-glucan supplementation regulates lipid metabolism in transition cows.

• beta-1,3-glucan treatment improves negative energy balance in transition cows.

• beta-1,3-glucan exerts hepatoprotective effect for the transition dairy cows.

Abstract

Objectives of this study were to evaluate the alleviating effects of a commercial beta-1,3-glucan product (Aleta, containing 50% beta-1,3-glucan, Kemin Industries) on metabolic stress in transition Holstein cows as reflected by circulating metabolites and enzymes. Fifty-four multiparous Holstein cows were randomly allocated to three groups with 18 cows each. Cows in each group received a commercial basal diet or the basal diet supplemented with Aleta calculated to supply 5 or 10 g of Aleta per cow per day. Blood samples were collected at day −21, 1, and 21 relative to calving for determination of serum triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDLC), very low density lipoprotein (VLDL), glucose, insulin, β-hydroxybutyric acid (BHBA), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamyl transpeptidase (GGT), and non-esterified fatty acid (NEFA). Supplementation with Aleta markedly elevated serum concentrations of TG, TC, HDLC, LDL-C and VLDL, implying its positive effect on lipid metabolism in transition dairy cows. Aleta treatment significantly decreased the serum concentrations of NEFA and BHBA, but markedly elevated the serum concentrations of glucose and insulin. Also, Aleta treatment significantly elevated the dry matter intake and milk production in postpartum cows, indicating the alleviating effect of Aleta on negative energy balance in transition cows. Moreover, Aleta treatment significantly reduced the serum activities of AST, ALT and GGT, indicating its hepatoprotective effect on transition cows. These results suggest that Aleta supplementation may help to improve fat metabolism disorder initiated by negative energy balance in transition dairy cows.

Introduction

The transition period (i.e., the time between 21 days before calving and 21 days after calving) is a critical time in the lactation cycle for dairy cows as they are faced with important physiological changes and are vulnerable to metabolic disorders (Brandstetter et al., 2019; Zebeli et al., 2015). During this period, cows have weakened immunity and excessive oxidative stress (Safari et al., 2018). Moreover, dairy cows need plenty of nutrients not only to satisfy their maintenance requirements but also to satisfy the synthesis of colostrum and milk, but a decreased dry matter intake (DMI) fails to let them accommodate this metabolic challenge (McArt et al., 2013; Safari et al., 2018; Szenci et al., 2018; Trimboli et al., 2019), leading to negative energy balance (NEB) (Hu et al., 2015; Lacasse et al., 2018). This NEB triggers decreased blood glucose levels and increased mobilization of body fat, resulting in elevated serum levels of two NEB markers, namely non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) (Bicalho et al., 2017; Đuričić et al., 2020). Overproduction of NEFA and BHBA due to altered lipid metabolism are also predictors of metabolic disorders diseases, such as fatty liver and ketosis (Bicalho et al., 2017; Cao et al., 2017b; Dong et al., 2019). Thus, regulation of fat metabolism in periparturient dairy cows is of great significance to mitigate the adverse effect caused by NEB.

β-glucans extracted from cell wall of fungi, algae, and cereals are natural bioactive polysaccharides, which contain three sources of specific glycosidic linkage such as β-(1,3)/β-(1,4)/β-(1,6) (Maheshwari et al., 2017). β-1,3-glucan mainly extracted from cereals is the most common water-soluble form and the most investigated β-glucans among three glycosidic linkages (Bashir and Choi, 2017; Maheshwari et al., 2017). Recent evidence has demonstrated that β-1,3-glucan possesses anti-inflammatory, anti-obesity, anti-oxidation and immune-enhancing activities (Bashir and Choi, 2017). β-1,3-glucan strengthens immunity primarily by activating the complement system and enhancing the ability of macrophages and natural killer cells (Ning et al., 2016). It can alleviate inflammation and accumulation of reactive oxygen species (ROS) in LPS-treated human hepatocytes (Chen et al., 2017). Moreover, supplementation with β-1,3-glucan can decrease hepatic lipid accumulation, and improve insulin sensitivity in mice fed with a high-fat diet (Choi et al., 2010). Orally administered β-1,3-glucan also contributes to regulate glucose and lipid homeostasis in diabetic mice (Cao et al., 2017a). Nevertheless, few investigations about beneficial effects of β-1,3-glucan have been reported in dairy cows. It remains unknown whether there is positive effect of β-1,3-glucan on metabolic stress in periparturient dairy cows.

Based on the physiological changes in dairy cows during the transition period and the beneficial effects of β-1,3-glucan, we designed this study to investigate whether supplementation with Aleta (a highly-concentrated β-1,3-glucan product) can improve the lipid metabolic disorder initiated by NEB in periparturient dairy cows.