Serum Ornithine Carbamoyltransferase Activity and Correlation with Fatty Liver in Dairy Cows with Displaced Abomasum

Ken Onda,Fujiko Sunaga,Hideharu Ochiai,Yosuke Sasaki,Kazuhiro Kawai,Hiroo Madarame,Reiichiro Sato

doi:10.3844/ajavsp.2016.85.90

Abstract

Ornithine Carbamoyltransferase (OCT) is a hepatocyte-specific enzyme; elevated serum activity indicates liver damage. Displaced abomasum frequently occurs around the time of parturition in dairy cattle and is associated with fatty liver. We analyzed serum OCT activities to investigate the relationship between displaced abomasum and fatty liver. Lactating Holstein cows, 75 clinically healthy and 22 with displaced abomasum, were used. Serum OCT activities were compared between healthy cows and those with displaced abomasum. Liver biopsies of cows with displaced abomasum were classified by the severity of fat accumulation. Blood samples were collected preoperatively and at 4 and 8 days after surgery and analyzed for serum OCT, aspartate aminotransferase, alkaline phosphatase, γ-glutamyltransferase, urea nitrogen, total protein and hematocrit. Serum OCT activity was significantly higher in cows with displaced abomasumthan in healthy cows. The degree of fatty liver in cows with displaced abomasum was classified as mild (13 cows), moderate (5 cows), or severe (4 cows). Statistical analysis revealed no significant differences in blood test results among cows with different degrees of fatty liver. However, our results indicated significant differences in serum OCT, aspartate aminotransferase, urea nitrogen, total protein and hematocrit when stratified by the number of days after surgical treatment for displaced abomasum. Serum OCT activity is increased in dairy cows with displaced abomasum and the influence of the degree of fatty liver on serum OCT activity is unclear. Therefore, OCT should be reconsidered as a marker of fatty liver in cows around the time of parturition, when displaced abomasum frequently occurs. Fatty liver should be evaluated by various clinical parameters, not by one hepatic enzyme.

Highlights

Fatty Liver (FL) frequently occurs around the time of parturition in dairy cows because of an increase in blood non-esterified fatty acids caused by negative energy balance (White, 2015)
Our results indicate that serum Ornithine Carbamoyltransferase (OCT) activity is higher in cows with Displaced Abomasum (DA) than in healthy cows, which is in agreement with previous studies (Kalaitzakis et al, 2006)
High OCT activity may be caused by an influx of enzyme into the bloodstream as a result of progressive liver damage or by a reduction in the rate of metabolic elimination of OCT

Summary

Introduction

Fatty Liver (FL) frequently occurs around the time of parturition in dairy cows because of an increase in blood non-esterified fatty acids caused by negative energy balance (White, 2015). A mild grade of fat infiltration into the liver is expected even in healthy cows after calving; liver disorders including. Ultrasound examination has recently been widely employed but does not provide a quantitative evaluation of liver function (Haudum et al, 2011). For this reason, blood testing is often used in the field. Kalaitzakis et al (2006; 2007) reported that serum levels of Ornithine Carbamoyltransferase (OCT), Aspartate Aminotransferase (AST) and total bilirubin concentration may be used to diagnose FL and evaluate the degree of fat infiltration into the liver. Serum OCT and iditol (sorbitol) dehydrogenase can differentiate healthy cows from cows with FL and severe ketosis (Gröhn et al, 1983)

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Conclusion