Medicine Lecture 5th Stage 12-12-2017 Dr.Osamah Muwafk
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Fatty Liver in Cattle
(Fat-Mobilization Syndrome, Fat-Cow Syndrome, Hepatic Lipidosis,
Pregnancy Toxemia In Cattle):
is a multifactorial condition occurring in dairy cows after parturition. The
syndrome is characterized by progressive depression and failure to respond
to treatment of other predisposing diseases. It is associated with excessive
mobilization of fat to the liver in well-conditioned or over conditioned cows.
This mobilization of fat is induced by the negative energy balance and
hormonal changes that occur during the periparturient period . This negative
energy balance in most cases is aggravated by concurrent periparturient
diseases that reduce feed intake and increase energy needs.
Etiology:
1. A sudden demand of energy in the immediate postpartum period in
well-conditioned lactating dairy cows
2. Mobilization of excessive quantities of fat from body deposits to the
liver
Epidemiology
a) twins increase the severity
b) it is common in high-producing dairy cattle from a few weeks before
and after parturition
c) A severe form of fatty infiltration of the liver immediately before or
after parturition of cattle can be highly fatal
d) Clinical evidence of hepatic disease may not occur consistently until
liver lipid concentrations are in the range of 35% to 45% or more
e) Outbreaks of the disease have occurred in dairy herds in which up to
25% of all cows were affected, with a case-fatality rate of 90%.
f) Any disease of early lactation that affects appetite and voluntary
intake can contribute to fatty liver (ketosis, left-side displacement of
the abomasum, mastitis, retained fetal membranes, milk fever, and
downer-cow syndrome.)
Medicine Lecture 5th Stage 12-12-2017 Dr.Osamah Muwafk
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g) Peak yields of milk are reached 4 to 7 weeks after calving, but the
highest levels of voluntary feed intake are not reached until 8 to 10
weeks after calving
h) Changing the diet of pregnant beef cows from silage to straw in an
attempt to reduce their body weight and the incidence of dystocia has
resulted in outbreaks of the disease
i) First-calf heifers were more commonly affected than older cows, and
most were in late pregnancy (7 to 9 months)
j) Cattle are prone to fatty liver because their hepatocytes have limited
capacity to export accumulated fat in the hepatocytes
PATHOGENESIS
1. Fatty liver is associated with a negative energy balance in dairy cows
in the first few weeks of lactation
2. Most cows adapt to the negative energy balance through an intricate
mechanism of metabolic adaptation
3. Fatty liver develops because of failure of these adaptive mechanisms
4. Fat mobilization begins about 2 to 3 weeks before calving and is
probably induced by a changing hormonal environment
5. Increased rate of mobilization of fat from body reserves, usually
subcutaneous fat, to the blood that transports it to body tissues,
particularly the liver
6. Increase hepatic lipogenesis with accumulation of lipid in enlarged
hepatocytes
7. depletion of liver glycogen, and inadequate transport of lipoprotein
from the liver
8. decrease metabolic functions of the liver
9. Most of the lipid infiltration of the liver in dairy cows after calving is
in the form of triacylglycerols
10. The serum lecithin : cholesterol acyltransferase activity decreased,
which may be associated with reproductive performance because
cholesteryl esters are utilized for the synthesis of steroid hormones
11. NEFAs transported to the liver are usually oxidized in the
mitochondria and peroxisomes or secreted as VLDL particles into the
blood
Medicine Lecture 5th Stage 12-12-2017 Dr.Osamah Muwafk
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12. uptake of NEFAs by the liver exceeds the oxidation of NEFAs by the
liver to CO2, partial oxidation of NEFAs to form ketones, and export
of phospholipids, cholesterol, and apoproteins from the liver as
lipoproteins
13. there is a concurrent loss of body condition and adipose tissue
14. The degree of mobilization will be dependent on the fatness of the
cow and extent of the energy deficit