Fræðaþing landbúnaðarins - 04.02.2005, Síða 98

very similar pattem as shown by the incidence of clinical ketosis. The point at which
physiological ketosis becomes pathological is not clearly defined. Possibly
hypoglycaemia is necessary to produce clinical symptoms (Kronfeld 1972).
For all the above-mentioned metabolites, there is a very considerable individual variation
between cows (Ingvartsen et al., 2003a; Ingvartsen et al., 2003b) illustrating that some
cows have a higher risk of developing production diseases such as the fatty liver
syndrome and ketosis.
Fatty liver is the term used to describe livers that contain more visible lipid in liver cells
than one expects to see in that organ. This includes the physiological accumulation seen
in lactating cows, but clinically normal animals may have fatty livers. The synthesis and
transport of lipoprotein within the liver cell are processes requiring a small energy input.
Any disturbance of this metabolism has the potential to inhibit lipoprotein synthesis or
secretion. Triglyceride synthesis from incoming fatty acid, being less dependent on
energy expenditure may continue, resulting in the accumulation of excess triglyceride in
the liver cells. The fat accumulates in small globules which may fuse to form a large
globule, if the condition prevails for some time. Severe fatty liver may not necessarily
produce severe hepatic dysíunction and the liver can retum to normal stmcture and
function once the metabolic defect has been corrected, especially if the duration of the
lipid accumulation has not been long (Jubb et.al. 1993). Bovine ketosis is associated with
fatty liver with fatty infiltration most severe in the periacinar area of the liver i.e. the
areas furthest away fforn the arterial blood supply.
Methods and Materials:
Sixty cows at the research station Stóra Armót, 28 primiparous and 32 multiparous in 12
blocks, were assigned to one of four treatments in a 2 x 2 factorial design. In the early
dry period cows were given high dry matter forage with a medium digestibilty ad libitum.
In the transition period i.e. 3 weeks before expected calving, the cow received different
amounts of concentrates and good quality forage ad libitum. After calving the cows
received good quality forage ad libitum and the amount of concentrates was increases at
different rates until the maximum of 11 kgs was reached (table 2.).
Table 2. Feeding programme
Treatment Early dry period Transition period* Early lactation*
LL Ad libitum medium quality forage 1.5 kg concentrates 0.3 kg conc./d/d
LH 1.5 kg concentrates 0.5 kg conc./d/d
HL 3.5 kg concentrates 0.3 kg conc./d/d
HH 3.5 kg concentrates 0.5 kg conc./d/d
* Primiparous heifers received 83% of this amount.
Blood samples were collected weekly (weeks -3 to 8 and 10 and 12) at 9 am after feeding
of forage but before concentrates were given. After collection the samples were
immediately chilled in icy water, centrifuged and the serum frozen at -20°C. Serum
96