Page number 1

Trial cows moving back to their paddock after eating their daily allocation of synthetic zeolite pre-calving. Technical Series: science in action Feeding synthetic zeolite pre-calving reduces milk fever A series of DairyNZ-led experiments have confirmed that supplementing cows with synthetic zeolite for two to three weeks pre-calving reduces the risk of milk fever in pasture-based systems. Here, we describe what to expect from this prevention strategy. Dr Claire Phyn Principal scientist, DairyNZ Dr Scott McDougall Manager, Cognosco, Anexa Veterinary Services Dr Katrina Roberts Herd health veterinarian, Anexa Veterinary Services Milk fever is a common metabolic disorder affecting cows around calving, when they experience a sudden massive demand for calcium at the onset of lactation. Cows tightly regulate their blood calcium concentrations, but if they're unable to keep up with the demand for calcium, blood concentrations decrease. This is known as 'hypocalcaemia’. Milk fever is defined as subclinical when the cow is hypocalcaemic with blood calcium concentrations less than 2.15mmol/L but is not exhibiting signs of disease. Approximately 35-50% of cows in a herd succumb to subclinical milk fever at calving, whereas about 2-5% exhibit clinical milk fever with evident changes in behaviour and rumination 1,2 . In many cases, these cows become recumbent – commonly known as 'downer' cows. Both subclinical and clinical milk fever are associated with an increased risk of other metabolic disorders (e.g., ketosis), infectious diseases (e.g., mastitis, uterine disease), and removal from the herd. For this reason, milk fever is known as a ‘gateway disease’ and considerable research efforts have been undertaken to prevent this disorder and mitigate its effects. Key points • Supplementing cows with synthetic zeolite pre- calving improves blood calcium concentrations at calving, reducing the risk of subclinical and clinical milk fever. • This strategy will be particularly beneficial in herds with ongoing milk fever issues. • Careful management of magnesium supplementation pre- and post-calving is still required when using zeolite. • Large-scale testing did not detect any improvements to herd reproductive performance. 22 Inside Dairy | April / May 2022