ARTICLE IN PRESS The Veterinary Journal ■■ (2015) ■■–■■
Contents lists available at ScienceDirect
The Veterinary Journal j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / t v j l
Guest Editorial
Acute phase proteins for diagnosis of diseases in dairy cattle
During an inflammatory challenge, the body’s defense mechanisms include the acute-phase response and the synthesis and secretion of acute-phase proteins (APPs) by the liver (Wira and Fahey, 2004). Paraoxonase (PON) and albumin, negatively-reacting APPs, and haptoglobin (Hp), a positively-reacting APP, are good indicators of the health status of dairy cows (Bionaz et al., 2007). Liver APP production is stimulated principally by pro-inflammatory cytokines, but this is probably a response to a persistent rise in cytokines rather than acute elevation. For example, heifers injected with intravenous lipopolysaccharides (LPS) had a peak in tumor necrosis factor-α and interleukin-6 concentrations 3–4 h after LPS injection, which returned to normal levels within 6 h (Carroll et al., 2011). However, despite the peak in pro-inflammatory cytokines, concentrations of serum amyloid A (SAA), a positive APP, only moderately increased, while those of ceruloplasmin (another APP) did not change. Such data suggest that chronic conditions are necessary to trigger detectable and stable liver APP production. Subacute ruminal acidosis (SARA) is a common disease of cattle subjected to diets containing high amounts of carbohydrates, characterized by ruminal fluid pH < 6.0 (Plaizier et al., 2009). SARA induces pathological alterations in the rumen wall (Steele et al., 2011) leading to increased absorption of endotoxins (Erdman, 1993) and liver damage (Ainmalamali et al., 1992). Therefore, it should be expected that increasing the amount of grain in the diet to levels sufficient to decrease ruminal pH should result in increased inflammatory signaling. Indeed, cows with SARA do have a small increase in ruminal LPS concentration, although this is not translated into increased serum LPS (Ghozo et al., 2005). The changes were however shown to be enough to trigger small changes in SAA secretion, although not Hp. The study by Dr Joanne Coombe of The University of Melbourne, and her colleagues, published in a recent issue of The Veterinary Journal investigated whether supplementing grain during milking twice daily or as part of a partial mixed ration fed after milking affected ruminal pH and circulating APPs (Coombe et al., 2015). The authors also tested whether the amount of grain fed per day had any effect on these parameters. Their results indicated that both methods of supplementing grain in the diet had the same overall effect on ruminal pH. There was a significant drop in ruminal pH after feeding, with mean pH remaining
Contents lists available at ScienceDirect
The Veterinary Journal j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / t v j l
Guest Editorial
Acute phase proteins for diagnosis of diseases in dairy cattle
During an inflammatory challenge, the body’s defense mechanisms include the acute-phase response and the synthesis and secretion of acute-phase proteins (APPs) by the liver (Wira and Fahey, 2004). Paraoxonase (PON) and albumin, negatively-reacting APPs, and haptoglobin (Hp), a positively-reacting APP, are good indicators of the health status of dairy cows (Bionaz et al., 2007). Liver APP production is stimulated principally by pro-inflammatory cytokines, but this is probably a response to a persistent rise in cytokines rather than acute elevation. For example, heifers injected with intravenous lipopolysaccharides (LPS) had a peak in tumor necrosis factor-α and interleukin-6 concentrations 3–4 h after LPS injection, which returned to normal levels within 6 h (Carroll et al., 2011). However, despite the peak in pro-inflammatory cytokines, concentrations of serum amyloid A (SAA), a positive APP, only moderately increased, while those of ceruloplasmin (another APP) did not change. Such data suggest that chronic conditions are necessary to trigger detectable and stable liver APP production. Subacute ruminal acidosis (SARA) is a common disease of cattle subjected to diets containing high amounts of carbohydrates, characterized by ruminal fluid pH < 6.0 (Plaizier et al., 2009). SARA induces pathological alterations in the rumen wall (Steele et al., 2011) leading to increased absorption of endotoxins (Erdman, 1993) and liver damage (Ainmalamali et al., 1992). Therefore, it should be expected that increasing the amount of grain in the diet to levels sufficient to decrease ruminal pH should result in increased inflammatory signaling. Indeed, cows with SARA do have a small increase in ruminal LPS concentration, although this is not translated into increased serum LPS (Ghozo et al., 2005). The changes were however shown to be enough to trigger small changes in SAA secretion, although not Hp. The study by Dr Joanne Coombe of The University of Melbourne, and her colleagues, published in a recent issue of The Veterinary Journal investigated whether supplementing grain during milking twice daily or as part of a partial mixed ration fed after milking affected ruminal pH and circulating APPs (Coombe et al., 2015). The authors also tested whether the amount of grain fed per day had any effect on these parameters. Their results indicated that both methods of supplementing grain in the diet had the same overall effect on ruminal pH. There was a significant drop in ruminal pH after feeding, with mean pH remaining
