12 January 1996

No simple way to fight mineral deficit in cows

By Jessica Buss

DAIRY cow mineral deficiencies may be becoming more common but solving the performance and fertility problems that result demands more than extra general purpose minerals.

The message comes from Diana Allen, Genus senior nutritionist. She warns of clever sales talk convincing some producers their stock are mineral deficient when in fact adding more minerals to the diet may aggravate the situation.

The remedy for poor performance and fertility may be to correct energy and protein levels in the ration, adds Mrs Allen. "But cows in high yielding herds, and those fed low concentrate diets, or straights and maize silage-based diets, may be more prone to mineral and vitamin deficiencies," she says.

"Problems can also occur on improved grassland when perennial ryegrass varieties and fewer weeds cut available trace minerals. High fertiliser use and lime can also alter the mineral balance of forage."

These deficiencies can affect performance and health and, in the most extreme cases, a deficiency or excess causes death.

Part of the mystery of minerals is that their availability is affected by interactions between soil and plants. Key factors include soil type and pH, weather, fertiliser use, plant maturity and pasture type.

According to Mrs Allen, there may also be plant and animal interactions affecting the amount of mineral the animal can use. And loss of minerals in the diet can occur during digestion and absorption.

Another problem is that one mineral commonly affects uptake or use of another. "So a deficiency or excess of one can result in a deficiency of another," she says.

Mrs Allen advises producers to check cow rations carefully for energy and protein when fertility or health is a concern. When the ration is adequate, check the mineral levels in the diet. "Initially take forage samples and have them analysed for minerals. Discuss these results with the vet, who may suggest blood testing cows to check specific mineral levels."

Once a deficiency is identified, find the best way to overcome that taking care to avoid overfeeding other minerals. She cites possible solutions as feed supplements, injections or applying trace elements to the soil, although that may work out to be expensive.

Feeding extra general purpose mineral should be avoided as a solution, she warns, for it increases the amount of other minerals given. Some minerals can quickly reach toxic levels when fed to excess.

Mrs Allen also cautions against offering free-access minerals, because individual cow intakes can vary.

&#8226 Feed supplements.

&#8226 Injections.

&#8226 Trace elements to soil.

&#8226 Avoid general purpose or free access minerals.

&#8226 General poor performance: Energy and/or protein deficiency.

&#8226 Low intakes: Phosphorus, copper, iodine, potassium and sodium, chlorine (rarely), cobalt-vitamin B12.

&#8226 Milk fever: Calcium, phosphorus and vitamin D.

&#8226 Grass staggers: Magnesium.

&#8226 Anaemia: Copper, Iron.

&#8226 Scours: Copper.

&#8226 Reduced disease resistance: Zinc.

&#8226 Abortions and stillbirths: Iodine.

&#8226 Reabsorbed embryos: Copper, iodine, selenium.

&#8226 Cows not bulling: Copper, iodine, manganese.

&#8226 Retained cleansings: Copper, selenium.

&#8226 Coppery coat: Excess molybdenum.

&#8226 High performance levels.

&#8226 Low concentrate regimes.

&#8226 Lime and high fertiliser use.

&#8226 Incorrect energy and protein in diet.