Losses due to metabolic disease in livestock
Dr Belinda Edmonstone, District Veterinarian, August 2016
Over recent weeks there has been an increase in cases of metabolic disease in livestock. In many situations it has been lactating ewes and cows grazing cereal crops or grass dominated pastures.
These metabolic disorders are due to complex interactions of minerals available in feed, the ability of the animal to absorb these and/or mobilise them from body stores, the high demand for these minerals in milk production and growth and increase in the metabolism of the livestock during cold wet weather.
Acute hypocalcaemia (milk fever)
Acute hypocalcaemia (milk fever) is a condition when blood calcium levels drop below a critical level. As a result the affected animals become staggery, sit down and can die. Prelambing ewes, lactating ewes and cows and growing weaners have the highest requirement for calcium and cereal crops at times seem unable to supply adequate levels of calcium to these classes stock.
Hypomagnesaemia (grass tetany)
Hypomagnesaemia (grass tetany) is when an animal’s blood magnesium levels drop below a critical level. The animal will die quite quickly. This is most common in lactating animals – sheep and in particular cattle. Grazing cereal crops result in high milk production and have low magnesium levels. In addition to this they are high in potassium which interferes with magnesium absorption. Grass tetany is a risk when grazing lactating animals on cereal crops and highly productive grass dominated pastures.
Rickets. This is like a chronic hypocalcaemia and as a result we see soft bones and fractures in rapidly growing autumn lambs. This is particularly a problem on grazing oat crops. Vitamin D deficiency as well as mineral imbalances is thought to be involved in this condition.
A useful preventive for these conditions is to supply the lacking minerals. Making a loose lick of equal parts lime, salt and causmag will provide the necessary minerals to prevent these conditions.
You need to ensure continual access. Treating autumn drop lambs with an injection of vitamin D at weaning and/or marking will also be helpful in preventing Rickets if lambs are grazing cereals for a long period of time.