3 June 2008

4 minute read

North America

“Cattle need a balance of macro minerals and trace minerals in their feed,” says Barry Yaremcio, beef and forage specialist with Alberta Agriculture and Rural Development’s Ag-Info Centre, Stettler. “Feeds grown in Alberta are deficient in most of the trace minerals, necessitating supplemental feeding of the missing elements. Feed testing, especially if feeding local feeds, is the first step in ensuring that cattle have the nutrients they require and that money isn’t being wasted on unnecessary supplementation.”

According to the Alberta Agriculture and Rural Development, copper supplied by forage will supply approximately 50 per cent of the minimum amount required. Manganese is marginally adequate and zinc is deficient in most feeds. Regulations in the Canadian Feeds Act limit selenium supplementation to 3.0 mg per head per day for mature cows. In some cases, this is not adequate, performance is compromised. A veterinarian prescription is needed to increase the amount supplemented and meet animal requirements. Cobalt and iodine levels in Alberta and Saskatchewan are virtually zero for forages, cereal crops and grains.

“Molybdenum is a concern in Manitoba, but not so in Alberta,” says Yaremcio. “There is very little molybdenum in Alberta soils. Having a high amount of copper tie-up due to interactions with Molybdenum is not very common.

“Blue salt provides the micro minerals cobalt and iodine to animals. Work done by Rob Hand at the Pembina Grazing Reserve found a 20 pound increase in calf weaning weight when animals were provided a fortified trace mineral salt versus blue salt. It is a good practice to use a fortified trace mineral salt with selenium year-round for cows, bulls, feeders and replacement animals. In many situations, as pasture matures, producers may want to feed a mineral to supply calcium and phosphorus to meet requirements.”

Salt blocks can be a grazing management tool. Placing blocks or salt stations in areas where the animals are grazing or in areas where excess grass needs to be grazed will improve utilization. Placing salt and mineral in watering areas is not recommended as this will kill out the forages and weeds will establish in these areas. If salt and mineral consumption is marginal, place the salt and mineral in the area where the cows sleep. Cows can consume up to 75 per cent of their salt or salt and mineral product at night.

Salt is made up of 39 per cent sodium and 61 per cent chloride by weight. Animals do not have a craving for salt, but rather crave sodium. Voluntary salt intake is dependant on total sodium intake from feed and water.

“In some areas of Alberta, including parts west of Highway 2, sodium levels in the water can be 300 ppm or greater,” notes Yaremcio. “When cows drink 10 to 20 gallons of water per day, this may provide enough sodium to meet their needs and they will not come to the trough or block for salt. This results in poor free choice salt and mineral intake. On pasture, if sodium levels are high in the water, the best you can do if you are not feeding grain or silage is to add dried molasses or another flavoring agent to the salt and mineral to improve intake. Having a chelated form of mineral mix will not help if the animals are not consuming the product.”

A general rule is that 100 cows should consume 55 pounds of salt per week free choice if sodium levels are low in the feed and water. If a mineral is to be fed at 100 grams per head per day, 100 cows should go through two bags of mineral every seven days.

Live forages are high in vitamin A and E precursors. When fresh forage is consumed, microbes in the rumen take the precursors and convert them into a biologically available form for the animal. Approximately 90 days after the forage is cut, these precursors have oxidized and have lost their usefulness to the animal. Fermentation in pit or bale silage destroys the vitamin precursors. If hay is cut in early July, by the middle of October, vitamin supplementation is required. If animals have been on green pasture material that froze at the start of September, vitamin supplementation can be delayed until the start of November. The fermentation process in pit or bale silage destroys the vitamin precursors.

“It is critical to have adequate amounts of vitamins for the last trimester of pregnancy because vitamin E and selenium work in tandem to improve immune function, and the quantity and quality of colostrum for newborn calves,” says Yaremcio.

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