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.
• Feed supplements.
• Trace elements to soil.
• Avoid general purpose or free access minerals.
• General poor performance: Energy and/or protein deficiency.
• Low intakes: Phosphorus, copper, iodine, potassium and sodium, chlorine (rarely), cobalt-vitamin B12.
• Milk fever: Calcium, phosphorus and vitamin D.
• Grass staggers: Magnesium.
• Anaemia: Copper, Iron.
• Scours: Copper.
• Reduced disease resistance: Zinc.
• Abortions and stillbirths: Iodine.
• Reabsorbed embryos: Copper, iodine, selenium.
• Cows not bulling: Copper, iodine, manganese.
• Retained cleansings: Copper, selenium.
• Coppery coat: Excess molybdenum.
• High performance levels.
• Low concentrate regimes.
• Lime and high fertiliser use.
• Incorrect energy and protein in diet.