3) Global Epidemiology: variation by regions, systems, and breeds
3.1. Prevalence at slaughter
Slaughterhouse studies report variable prevalences, often < 5%, but occasionally higher depending on age, production system, and inspection sensitivity. Cull cows (older animals) show more stones than younger beef cattle. In some regions of South and East Asia, where diet and dairy cattle longevity differ, reported figures may be higher, whereas in intensive Western systems, detection remains modest but not negligible.
3.2. Risk factors
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Age: accumulation of inflammatory episodes and biliary stasis increases the likelihood of nucleation.
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Diet: very high-concentrate rations alter lipid metabolism and bile composition. Conversely, deficient diets can affect bile acid synthesis and gallbladder motility.
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Hydration and water access: relative chronic dehydration promotes bile concentration.
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Pathogens: enteric or hepato-biliary infections (bacterial, parasitic) may damage the epithelium or bile flow.
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Genetics and breed: data are limited, but polymorphisms in bile acid or cholesterol transporters (ABCG5/8, ABCB11, etc.) may play a role, as shown in other species.
3.3. Seasonality and environment
Heat stress and periods of reduced watering can increase bile viscosity. Extensive systems in arid areas (Africa, Central Asia) sometimes report more detected cases, but comparability of data remains difficult in the absence of standardized inspections.
4) Clinical and zootechnical consequences
Most bovine gallstones are asymptomatic. When clinical:
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Biliary colic or nonspecific abdominal pain (rare).
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Cholecystitis: fever, anorexia, reduced milk yield.
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Biliary obstruction (exceptional): jaundice, elevated liver enzymes, pale feces.
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Septic complications: if bacteria pass through, risk of cholangitis.
Economically, the direct impact on growth performance is minor in most cases, but concomitant hepato-biliary conditions (parasitism, hepatitis, abscesses) may impair feed efficiency and milk production.
To be continued next week: Diagnosis and inspection