Bovine Fat Cow Syndrome and Subclinical Fatty Liver Study Guide

Overview and Clinical Importance

Fat cow syndrome (FCS) and hepatic lipidosis (fatty liver) are major metabolic disorders affecting periparturient dairy cattle. These conditions represent a spectrum of the same pathophysiological process, characterized by excessive accumulation of triacylglycerol (TAG) in hepatocytes due to negative energy balance (NEB) around calving. Fat cow syndrome specifically refers to the clinical manifestation in overconditioned cows, while subclinical fatty liver affects up to 50% of high-producing dairy cows in early lactation without overt clinical signs. These conditions are economically devastating, costing the U.S. dairy industry an estimated $60 million annually due to decreased milk production, impaired fertility, increased disease susceptibility, and death.

Etiology and Pathophysiology

The Transition Period and Negative Energy Balance

The transition period (3 weeks prepartum to 3 weeks postpartum) represents the most metabolically challenging time for dairy cows. During this period, dry matter intake (DMI) decreases by 30% or more while energy demands for lactation increase dramatically. This creates a state of negative energy balance (NEB), triggering mobilization of body fat reserves to meet energy demands.

Mechanism of Hepatic Lipid Accumulation

When adipose tissue is mobilized, non-esterified fatty acids (NEFAs) are released into the bloodstream. The liver takes up approximately 15-20% of circulating NEFAs. Under normal conditions, hepatocytes process NEFAs through three pathways: