High concentrate-induced subacute ruminal acidosis (SARA) increases plasma acute phase proteins (APPs) and cortisol in goats

The aim of this study was to investigate changes of stress status in dairy goats induced to subacute ruminal acidosis (SARA). The level of acute phase proteins (APPs) including haptoglobin (HP) and serum amyloid A (SAA) in plasma and their mRNA expression in liver, as well as plasma cortisol and genes expression of key factors controlling cortisol synthesis in adrenal cortex were compared between SARA and control goats. SARA was induced by feeding high concentrate diet (60% concentrate of dry matter) for 3 weeks (SARA, n=6), while control goats (Con, n=6) received a low concentrate diet (40% concentrate of dry matter) during the experimental time. SARA goats showed ruminal pH below 5.8 for more than 3 h per day, which was significantly lower than control goats (pH>6.0). SARA goats demonstrated a significant increase of hepatic HP and SAA mRNA expression (P<0.05), and the level of HP but not SAA in plasma was markedly increased compared with control (P<0.05). The level of cortisol in plasma showed a trend to increase in SARA goats (0.05<P<0.1). In adrenal cortex, mRNA expression of 17α-hydroxylase cytochrome (P450_17α) (P<0.01) and 3β-hydroxysteroid dehydrogenase (3β-HSD) (P<0.05) was significantly increased in SARA goats. The contents of 3β-HSD and P450 side-chain cleavage protein were increased by 58.6% and 39.4%, respectively, but did not reach the statistical significance (P>0.05). These results suggested that SARA goats experienced a certain stress status, exhibiting an increase in HP production and cortisol secretion.