Metabolic disease around calving usually involves one of three different syndromes or a combination of these syndromes.
1. Ketosis – a lack of available glucose / energy, so the cow utilizes body fat by converting it to ketones as an alternative (but inferior) energy source. This can be the fat cows that have had a sudden change in the levels of feed; or can be the skinny cows with severe malnutrition. It is a common cause of cows going down pre-calving. Ketosis can sometimes be referred to as acidosis, because the ketones make the blood acidic. However, “acidosis” is more correctly used when there is excessive carbohydrate ingested (e.g. grain overload, swede overload) which causes the pH of the rumen to be acidic.
Ketosis is normally treated with IV dextrose and ketol drenching (for energy) and with steroids, to stimulate the cow’s metabolism and induce calving.
2. Hypomagnesaemia (Grass Staggers or Grass Tetany) - Low magnesium levels in the blood. Clinically these cows become trembly, agitated, staggery, aggressive and violent before they go down and die very quickly. It can occur in any animal at any time of year.
Grass staggers can be difficult to treat. It is usually done with a mixed calcium/magnesium metabolic bag IV for immediate relief, a straight mag sulphate bag under the skin, and some magnesium by drenching.
3. Hypocalcaemia (Milk Fever) - Low calcium levels in the blood. These cows are more like drunken animals, with wobbly staggering before they sit down. The cow will eventually lie on its side, bloat up and die of suffocation and heart failure. It is most common in older, fatter cows within a day or two either side of calving.
Early milk fever cases can be treated with oral supplements (eg Calol), but cows down usually require at least two injectable products (there is a range available – speak to your vet).
These can be frustrating, time consuming, and difficult-to-treat problems. Caring for these cows can take up a lot of valuable time which could be better applied to the care of the rest of the herd. Prevention is far better than cure in this case! These cows may also be the tip of the ice-berg and can indicate there is sub-clinical disease occurring which will be affecting the production of the whole herd.
Prevention of metabolic disease (ketosis, milk fever, grass staggers) around calving time involves management of the animal in the late dry period. Feeding to maintain appetite, good rumen function and energy levels, and supplementation of appropriate minerals are both required for prevention of disease and maintenance of optimum production levels over the transition period.
5. If you have to make changes try to keep at least ½ the diet constant – e.g. if you are going from feeding crop to grass, increase the hay &/or silage and continue to feed hay / silage when the animals are on grass. If you are going to an all grass diet, reduce hay/silage slowly.
6. Make sure the trace element status is monitored and adequate. Copper and selenium are the most important.
7. Macro minerals status, particularly magnesium and calcium are vital. Cows have a daily requirement for magnesium as this is not stored like calcium. Magnesium chloride (Mag-C) is best to be used before calving. It is best delivered mixed with the feed by diluting the required amount (120 grams/cow/day) with water, adding a little molasses for improved palatability and spraying the silage / hay. It is ideally given on food, as absorption of magnesium occurs in the rumen and not the abomasum (where most of the water goes when drunk).
8. Immediately post calving consider a starter drench, especially where transition is not ideal. Starter drenches individually given to each cow provide readily available calcium and energy and are useful in preventing milk fever and ketosis. “Head Start” is best, but there are a number of cheaper copies available. Alternatively a “home brew” can be made (300ml monopropylene glycol; 300g vegetable fat prills; 300-400g calcium enriched molasses).
10. After calving when cows are in the colostrums mob it is important to supplement magnesium, and in some instances calcium. The best form of magnesium to use after calving is magnesium oxide (Caus-mag). Dose rate depends on the delivery method.
i. It delivers only 10% elemental magnesium as opposed to 50% from magnesium oxide (so much more is required).
In general Magnesium is best supplemented by mixing with feed as this ensures the magnesium reaches the rumen which is the main site for magnesium absorption.
11. Calcium may also be supplemented after calving. A suitable product is Calcimate. Calcium levels are in the order of 0.4 – 0.6% in Autumn and spring grass; but the cow’s requirements are in the order of 0.8% to 1.0%. Cows are a walking bank of calcium stored in their bones so can survive this deficit for a short time. However in some cases it makes good sense to supplement calcium, it being a macro element. Calcimate can be drenched or dusted on to pasture with a suitable motorbike drawn fertilizer spreader.
In general it is necessary to continue drenching or dusting until at least the start of mating or when milk peaks, and at least well into November when grass becomes harder and firmer and clover content increases. At that time calcium levels will rise above 1% in the pasture.
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