Low quality rice straw forage increases the permeability of mammary epithelial tight junctions in lactating dairy cows.

BACKGROUND: It is known that milking frequency and plasma hormones play important roles in regulating mammary permeability. However, whether nutritional factors can influence udder permeability is still unknown.

DESIGN: This study was conducted to investigate mammary epithelial tight junction permeability in lactating dairy cows fed different forage-based diets. Twenty mid-lactating dairy cows were allocated into 10 blocks based on their parity and milk yield and then randomly assigned into rice straw-based diet and alfalfa-based diet groups. Both diets contained 15% of corn silage and 55% of concentrate (dry matter basis). In terms of forage source, rice straw-based diets (RS) contained 30% rice straw, whereas alfalfa-based diets (AH) contained 23% alfalfa hay plus 7% Chinese wild rye hay.

RESULTS: The concentrations of Na+ , Na+ /K+ ratio, bovine serum albumin, and plasmin in the milk, plasma lactose concentration, and the mRNA abundance of BCL2 Associated Agonist of Cell Death, Phosphatase And Tensin Homolog, and Insulin Like Growth Factor Binding Protein 5 in the mammary gland were greater in RS-fed cows than in AH-fed animals. Mammary expression of Proliferating Cell Nuclear Antigen and Occludin was lower in RS-fed cows compared with the AH-fed group. The expressions of Growth Hormone Receptor, Claudin-1, -3, -4, and ZO-1 were similar between the two diet groups.

CONCLUSION: The cows fed RS showed higher mammary alveolar permeability, likely through affecting proliferation/apoptosis rates of mammary epithelial cells. This article is protected by copyright. All rights reserved.