Oorsig/Review 8. POORLY AUDIBLE (RAPID) HEART BEAT 2. FLEXED NECK OR TORTICOLLIS 9. SHALLOW BREATHING 10. RUMEN STASIS 7. MYDRIASIS, DRY CORNEA 6. CYANOSIS 15. URINE RETENTION 5. DULL EXPRESSION 4. DRY MUZZLE 3. COLD EXTREMITIES Subclinical hypocalcaemia – the number 1 metabolic disease of dairy cows A lot of the economic value in prevention of hypocalcaemia at parturition lies in the prevention of subclinical hypocalcaemia and not so much in the prevention of clinical milk fever. It has, for instance, been demonstrated that diets that were designed to prevent peri-partum hypocalcaemia, increased milk production by 350 - 480kg/cow in the lactation. One can also expect a significant improvement in the conception rate and other reproductive parameters, a reduced incidence of retained placenta and a reduction in the number of cases with udder oedema. It may thus prove to be a good idea to institute steps to prevent milk fever, even in herds where the incidence of the condition is less than 5%. Non-parturient hypocalcaemia Occasionally hypocalcaemia with typical “milk fever” signs occurs in cattle (dairy or beef) at other times than the typical post-parturient presentation. This may be seen as individual cases or even as outbreaks, and the following factors, or combinations of these, may play a role: 1. Conditions that lead to a reduction in dry matter intake that lasts for 12-16 hours: Oestrus, bad weather, other disease conditions such as mastitis/metritis/LDA/ rumen acidosis etc. 2. Dietary factors such as reduced Calcium or Magnesium in the feed, vitamin D deficiency or plants containing Oxalate that binds available Calcium. The feeding of chicken manure is a risk factor. 3. Conditions leading to a metabolic alkalosis such as LDA, dietary intake of rations high in Potassium or protein. 24 11. RUMEN TYMPANY 12. LOW RECTAL TEMP 14. CONSTIPATION 13. BULGING PERINEUM 1. FLACCID PARALYSIS 4. Kidney failure leads to ongoing loss of Calcium and reduced intestinal uptake despite deficiency (vit D deficiency). This presents as an unresponsive hypocalcaemia. 5. Conditions that lead to endotoxaemia cause Ca to be moved into the intracellular compartment, also leading to an unresponsive hypocalcaemia. Herd surveillance for animals at risk in herds using anionic salts as preventative measure When strategies to prevent milk fever are in place, an ongoing surveillance plan should be implemented to monitor the success of the prevention strategies, and to attempt to identify individual animals at risk, in order to make sure that extra measures are taken in these animals to prevent the disease. Firstly one could use Epidemiological knowledge and identify multiparous, high producing cows and cows that have suffered with milk fever in previous lactations as animals at riks. Secondly, and currently the most common method used, is to test urine pH in dry cows to indirectly supply evidence of osteoclastic activity. Urine pH should ideally be in the range 6 to 6.8. It is however common to find individual cows with higher urine pH, and these cows are at risk of developing milk fever. A minimum of 3 days on the anionic salt ration is recommended before urine pH is monitored. The veterinarian must therefore verify the duration on the ration before including cows in a surveillance sample.