Relation between Liver Lipid Content and Plasma Biochemical Indicators in Dairy Cows

Abstract

Background: The incidence of metabolic disorders in dairy cows has increased as a result of intensive production practices and genetic selection for milk yield. Among such disorders, liver lipidosis is very frequently observed and has significant negative effects on cow health and milk yield. Severe energy supply deficit causes high fat mobilization, resulting in rapid body condition loss and liver lipid infiltration, which cannot always be detected by known blood biochemical indicators. The main objective of the study was to determine possible associations of blood biochemical parameters with liver lipid infiltration severity in high-yield multiparous Holstein cows along prepartum and postpartum periods.Materials, Methods & Results: Fifty-four high-yield Holstein cows from a herd managed in a free-stall system in the northwest region of the state of Rio Grande do Sul, Brazil were evaluated. Cows were divided in two groups according to their physiological status. Group 1 included 19 prepartum cows, with an average milk yield of 44.7 L/d in the previous lactation, and 2.8 average parity, and Group 2 included 35 postpartum cows, with an average milk yield of 46.8 L/d in the previous lactation, and 2.5 average parity. The farm produced 10,000 kg milk per year, containing 3.5% of fat, 3.2% of protein and 4.7% of lactose. Total cholesterol (CH), plasma triglycerides (TGp), beta-hydroxybutyrate (BHB), albumin (ALB), non-esterified free fatty acids (NEFA) levels, and aspartate aminotransferase (AST) and creatine kinase (CK) activities were analyzed in the plasma and liver triglycerides (TGl) levels were determined in liver tissue samples.The SPSS statistical software was used for the statistical analyses. The obtained data were analyzed for normality by the Shapiro-Wilk test and for homoscedasticity by Bartlett test. Data were submitted to analysis of variance, and means were compared by the t-test (PROC TTEST). Pearson correlation test (PROC CORR) was used to compare the results between prepartum and postpartum cows, and between those with and without lipidosis.An overall incidence of 20% severe hepatic lipidosis was determined both in prepartum and postpartum cows. Positive significant correlations were obtained between days in milk (DIM) and AST (r= 0.43; P < 0.01), CH and TGp (r= 0.44; P < 0.01), TGl and AST (r=0.32; P < 0.05), NEFA and AST (r= 0.45; P < 0.01) and CK and AST (r= 0.447; P < 0.01). Negative significant correlations were detected between TGp and DIM (r= -0.45; P < 0.01), and between TGl and TGp (r= -0.30; P < 0.05).Discussion: Prepartum cows showed moderate fat infiltration in the liver, while 25.7% of postpartum cows presented severe lipidosis. AST values increased as lactation progressed, suggesting a greater tendency of liver damage, in early postpartum. The obtained CK values were within the reference range, except for the cows with hepatic lipidosis, indicating that the measured AST activity was originated from the liver and not from the muscle tissues. TGp, NEFA and AST values indicate the degree of fat mobilization and, possibly, liver infiltration, while TGl indicates fat infiltration in the liver. Although negative energy balance (NEB) may trigger lipolysis and some degree of hepatic lipidosis, plasma BHB values did not significantly increase. The obtained results show that the evaluated plasma parameters may be useful to establish guidelines for the identification of changes in the metabolic profile of dairy cows during different production stages, as well as measures for the prevention and control of metabolic disorders.

Changes of Plasma Fatty Acids in Four Lipid Classes to Understand Energy Metabolism at Different Levels of Non-Esterified Fatty Acid (NEFA) in Dairy Cows

“…Decreasing concentrations of triglycerides could have been detected during the first few days of lactation as in the study of Oikawa et al [51]. Contrary to Batista et al, in our study the negative correlation existing between the plasma concentrations of NEFA and TG is not respected [47]. Dairy cows with high mean values of NEFA and BHB (NEFA1 group) should had a plasma triglyceride concentration lower than animals in a normal state of health (NEFA0 group).…”

“…The drop in TAG concentrations in the blood postpartum may indicate low hepatic synthesis and secretion of VLDL due to the accumulation of TG in the liver [53,54]. Batista et al showed a negative correlation between plasma triglycerides and serum NEFA (r = −0.39) confirmed by countless studies in which the plasma concentrations of triglycerides decrease in the immediate postpartum, the moment in which the maximum release of NEFA occurs [46,47,52]. Yamdagni and Schultz showed that in HK dairy cows, the values of TG decreased by 53% when compared to concentrations in healthy animals [34].…”

“…In serum of dairy cows, LCAT activity decrease after calving due to excessive hepatic deposition of triglycerides that damage liver function [46]. In the study of Battista et al, dairy cows with liver lipidosis (53.77 ± 43.69 mg/dL) had lower CE concentrations than animals without fatty infiltration (63.06 ± 27.38 mg/dL) [47]. Therefore, ketotic cows reduced blood CE and LCAT concentration compared to healthy cows [36,45].…”

“…Therefore, the condition of hepatic infarction affects TAG concentrations in plasma [46]. It is known in the available literature that there is a negative correlation between plasma TG and liver TG (r = −0.30) [47]. The drop in TAG concentrations in the blood postpartum may indicate low hepatic synthesis and secretion of VLDL due to the accumulation of TG in the liver [53,54].…”

The effect of N-arachidonoylethanolamide administration on energy and fat metabolism of early lactating dairy cows

“…The synthesis and secretion of TG in cows occurs primarily in the liver through the re-esteri cation of NEFA and subsequent export as VLDL. A previous study described negative correlations between plasma TG and NEFA concentrations and between plasma and hepatic TG levels 52 . This nding is supported by Van den Top et al, who reported an association between fatty liver and decreased plasma TG concentrations 53 .…”