Abstract
Simple SummaryNutrient restriction is known to decrease the milk production and milk quality of dairy cows. However, providing cows with abundant nutrients also has a disadvantage because it will increase feed costs. Under such a situation, the use of feed additives can be a good strategy to reduce the feed cost. The objective of this study was to investigate the effects of histidine and sodium acetate on β-casein expression in nutrient-restricted bovine mammary epithelial cells. The results indicate that histidine has the potential to increase the β-casein levels in bovine mammary cells when the nutrient is restricted, suggesting that histidine is a potential feed additive for cows in a nutrient-insufficient environment.Nutrient restriction is a challenging condition for the mammary glands of dairy cows. In this condition, supplementing amino acids and energy sources might be a good strategy to improve the concentration of one of the most important caseins in bovine milk. Therefore, the objective of this study was to investigate the effects of L-histidine (His) and sodium acetate (Ace) in a nutrient-restricted (NR) immortalized bovine mammary epithelial cell line (MAC-T cells). The treatments for the MAC-T cells are as follows: experiment (1) 0–5% diluted basal medium; experiment (2) supplementation of 0–9.6 mM of His or Ace in NR or normal conditions; experiment (3) supplementation of 0–9.6 mM of Ace plus 0.15 mM of His in NR or normal conditions. The 1% diluted medium showed no significant effect on the cell viability with the basal medium; thus, it was selected as the NR condition. The relative expression of β-casein was significantly increased in the NR condition with the inclusion of 0.15 mM His alone or with Ace compared to that in control. The supplementation of Ace increased the β-casein level under normal conditions. However, it did not change the expression of β-casein under the NR condition. The results suggest that His has the potential to increase the β-casein expression under the NR condition.
Highlights
Lactating cows require significant amounts of nutrients and energy to produce milk for their offspring; nutrient restriction (NR) is a challenging condition for dairy cows
The cell viability decreased with an increase of the dilution rate in the differentiation medium (p < 0.001)
Thu5so,f9139%differentiation medium (DIF) was selected as the NR condition for the MAC-T cells
Summary
Lactating cows require significant amounts of nutrients and energy to produce milk for their offspring; nutrient restriction (NR) is a challenging condition for dairy cows. Bovine mammary glands can produce milk proteins. Amino acids (AAs), energy sources, and hormones are essential components for milk protein synthesis [1]. AAs, as components of proteins, have biological roles in animal bodies. Many studies have reported that treatment with AAs can stimulate protein synthesis in mammary epithelial cells in vitro [2,3,4]. Protein synthesis mediated by nutrients is related to the mammalian target of rapamycin (mTOR) pathway [1,5,6]. The mTOR is a central protein complex of the protein synthesis cascade, and is activated by several factors. MTOR can phosphorylate ribosomal protein S6 kinase 1 (S6K1) and ribosomal protein S6 (RPS6). Casein gene expression and protein synthesis are achieved through the translation initiation and elongation process [7]
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