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KROWY MLECZNE ZDROWIE I WYDAJNOŚĆ

Ketosis  a common disease of adult cattle

 


Ketosis is a common disease of adult cattle. It typically occurs in dairy cows in early lactation and is most consistently characterized by partial anorexia and depression. Rarely, it occurs in cattle in late gestation, at which time it resembles pregnancy toxemia of ewes. In addition to inappetence, signs of nervous dysfunction, including pica, abnormal licking, incoordination and abnormal gait, bellowing, and aggression are occasionally seen. The condition is worldwide in distribution, but is most common where dairy cows are bred and managed for high production.
Etiology and Pathogenesis:
The pathogenesis of bovine ketosis is incompletely understood, but it requires the combination of intense adipose mobilization and a high glucose demand. Both of these conditions are present in early lactation, at which time negative energy balance leads to adipose mobilization and milk synthesis creates a high glucose demand. Adipose mobilization is accompanied by high blood serum concentrations of nonesterified fatty acids (NEFA). During periods of intense gluconeogenesis, a large portion of serum NEFA is directed to ketone body synthesis in the liver. Thus, the clinicopathologic characterization of ketosis includes high serum concentrations of NEFA and ketone bodies and low concentrations of glucose. In contrast to many other species, cattle with hyperketonemia do not have concurrent acidemia. The serum ketone bodies are acetone, acetoacetate, and β-hydroxybutyrate (BHB).
There is speculation that the pathogenesis of ketosis cases occurring in the immediate postpartum period is slightly different than that of cases occurring closer to the time of peak milk production. Cases of ketosis in very early lactation are usually associated with fatty liver. Both fatty liver and ketosis are probably part of a spectrum of conditions associated with intense fat mobilization in cattle. Ketosis cases occurring closer to peak milk production, which usually occurs at 4-6 wk postpartum, may be more closely associated with underfed cattle experiencing a metabolic shortage of gluconeogenic precursors than with excessive fat mobilization. 
The exact pathogenesis of the clinical signs is not known. They do not appear to be associated directly with serum concentrations of either glucose or ketone bodies. There is speculation that they may be due to metabolites of the ketone bodies. 
 
Epidemiology:
All dairy cows in early lactation (first 6 wk) are at risk of ketosis. The incidence in lactation is estimated at 5-16%, but incidence in individual herds varies substantially. Ketosis occurs in all parities (although it appears to be less commin in primiparous animals) and does not appear to have a genetic predisposition, other than being associated with dairy breeds. Cows with excessive adipose stores (body condition score ≥3.75 out of 5.0) at calving are at increased risk of ketosis, compared with those with lower body condition scores. Lactating cows with hyperketonemia (subclinical ketosis—serum BHB concentrations >12 mg/dL) are at increased risk of developing clinical ketosis, compared with cows with lower serum BHB concentrations. 
 
Clinical Findings:
In cows maintained in confinement stalls, reduced feed intake is usually the first sign of ketosis. If rations are offered in components, cows with ketosis often refuse grain before forage. In group-fed herds, reduced milk production, lethargy, and an “empty” appearing abdomen are usually the signs of ketosis noticed first. On physical examination, cows are afebrile and may be slightly dehydrated. Rumen motility is variable, being hyperactive in some cases and hypoactive in others. In many cases there are no other physical abnormalities. CNS disturbances are noted in a minority of cases. These include abnormal licking and chewing, with cows sometimes chewing incessantly on pipes and other objects in their surroundings. Incoordination and gait abnormalities occasionally are seen, as are aggression and bellowing. These signs occur in a clear minority of cases, but because the disease is so common, finding animals with these signs is not unusual. 

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