Background: Bovine Milk fever (MF/hypocalcaemia) and ketosis (CK/hypoglycemia and hyperketonemia) both in clinical and sub-clinical forms are the most important metabolic diseases caused by metabolic disorders of calcium and carbohydrate respectively that affect mainly high milk yielding dairy cows worldwide. Sub-clinical form may be more costly due to comparatively high prevalence and consequence of high risk of decreased productive and reproductive performances with increased reproductive and other disorders.
Objectives: The objectives of this study were to determine the prevalence of sub-clinical hypocalcaemia (SCHC) and sub-clinical ketosis (SCK) and to investigate important potential risk factors for SCHC and SCK with their therapeutic management in lactating cross-bred dairy cows.
Materials and Methods: A cross sectional study was conducted on 220 dairy crossbred (HF L = 190, SH L = 20 and JS L = 10) cows maintained in nine dairy farms and one smallholder farm during the period from July to November 2016. The parity (1 to 8), lactation stages (1 to 13 weeks), body condition score (BCS), breed (3 crossbreds), age (3.5 to 14 years) and milk yield (liter/day) were evaluated as possible risk factors. The serum calcium, inorganic phosphorus, magnesium and glucose concentrations of the 220 dairy cows were determined by using imported commercial kits. Dairy cows with serum calcium concentrations 8.0 mg/dl and serum glucose 44.0 mg / dl with positive ketone tests but not showing any clinical signs were considered SCHC and SCK respectively.
Results: The overall prevalence of SCHC was 30.0%, of which 32.11% were recorded in HF L, 15.0% in SH L and 20.0% in JS L cross-bred cows. The overall prevalence of SCK was 25.0%, of which 27.37% in HF L, 10.0% in SH L and 10.0% in JS L cross-bred cows. The SCHC was recorded 10 times greater than MF and SCK 6 times greater than CK in Bangladesh. The hypocalcemia and hypophosphatemia with hypermagnesemia status were recorded in SCHC affected lactating cows which were more significantly (p < 0.05) higher (46.67%) at 4th parity and lower (16.67%) at 1st parity. The significantly (p < 0.01) higher prevalence of SCK was recorded at the 4th (53.33%) in comparison to other parity especially lowest at 1st (2.78%) and 2nd (4.0%) parity. The significantly (p < 0.1) highest prevalence of SCHC and SCK were recorded at high milk yield during the 1st (94.44%; 77.78%) and 2nd (66.67%; 56.67%) weeks of lactation period than the higher lactation stages respectively. The effects of BCS on the milk yield and the prevalence of SCHC and SCK are presented and discussed. Encouraging results with increased blood calcium and glucose levels were obtained on the therapeutic response of SCHC with oral calcium and SCK with oral propylene glycol.
Conclusions: The SCHC and SCK have detrimental effects on cow health, productivity and reproduction and also predisposes to other diseases and disorders. The efficient balanced ration, periodic screening blood, milk and urine for determination of concerned biochemical constituents and ketone bodies considering risk factors could help to early detection of SCHC and SCK to limit their effects in dairy cattle. The high prevalence of SCHC and SCK recorded in this study should be viewed as a potential health risk to the transition cows that requires further research.
Keywords: Sub-clinical milk fever, Sub-clinical ketosis, crossbred cows, prevalence, risk factors, calcium, magnesium, phosphorus, glucose, ketone bodies, therapeutic management, Bangladesh
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