Nutritional strategies for the prevention of hypocalcaemia at calving for dairy cows in pasture-based systems

Abstract

This review considers the current literature on the macro-mineral nutrition of the soon-to-calve, or transition, dairy cow. Calcium is the main focus, since milk fever (clinical hypocalcaemia) appears to be the most common mineral-related problem faced by the transition cow Australia-wide. The importance of minimising calcium intake and optimising the balance of the key dietary electrolytes, sodium, potassium, sulfate, and chloride, in the weeks before calving is highlighted. Excess dietary potassium can, in some situations, induce milk fever, perhaps even more effectively than excess calcium. Excess sodium remains under suspicion. In contrast, excess dietary chlorine and, to a lesser extent, sulfur can improve the ability of the cow to maintain calcium homeostasis. Diets that promote either a hypomagnesaemia or hyperphosphataemia have also the potential to precipitate milk fever at calving. Current prevention strategies focus on the use of forages with moderate to low levels of calcium, potassium, and sodium, and also rely on or utilise addition of chloride and sulfate in the form of 'anionic' feeds. Anionic salts are one example of an anionic feed. However, legitimate questions remain as to the effectiveness of anionic salts in pasture-feeding systems. The causes and prevention of milk fever are considered from the perspective of the variety of Australian feedbases. Impediments to the use of anionic feeds in Australia feeding systems are outlined. The potential for improving maternal reserves of calcium around calving to reduce the risk of milk fever is also discussed.

Potassium cycling and losses in grassland systems: a review

“…Strategies to prevent milk fever now focus on the use of forages with moderate to low levels of Ca, K and Na, such as maize silage or silage from other cereals (Taube et al. , 1995; McNeill et al. , 2002).…”

Effect of feeding rumen protected rice bran on calcium homeostasis of non-lactating multiparous cows

“…In situations of high‐positive DCAD and alkaline urine, changes in urine pH are small when DCAD decreases (Roche et al., 2003). In fact, McNeill et al. (2002) observed that urine pH is unlikely to respond before DCAD is reduced below 200 meq/kg DM.…”

Survey on the occurrence of milk fever in dairy cows and the current preventive strategies adopted by farmers in New South Wales, Australia

“…grains, hay and silage). 9 An incidence of subclinical hypocalcaemia of approximately 67% and 80% has been reported for dairy farms in the subtropics 10 and southern districts (Victoria) of Australia, 11 respectively. 2 Although the average herd size has increased from 85 to 220 cows, the yield per cow has also increased from 2850 to 5500 L/cow per lactation, which is a result of improved intensive genetic selection as well as improved nutritional and farm management practices.…”