By Naomi Paley
Regional Livestock Specialist, Yorkton Ministry of Agriculture
For many cow-calf producers, free-choice feeding of vitamins and minerals is the only way to supplement their animals on summer pastures. Field studies have demonstrated that free-choice intake can be highly variable; however, there are things you can do to manage and reduce this variability.
“Free choice” doesn’t mean “set it and forget it.” Supplement intake needs to be monitored. During the grazing season, minerals and salt are very important for gestating cows and growing calves. Most pastures do not contain adequate levels or balances of macro and trace minerals.
Consider some of the following ideas for improving intake:
• Intake is usually better with loose rather than block supplements.
• Mixing loose minerals with salt, dried molasses or protein supplements can increase intake.
• Put out small amounts frequently to keep the supplements fresh.
• Locate the mineral feeders in areas where cattle tend to congregate, and make sure there are enough for all cattle to have sufficient access (one feeder per 50 animals).
• Read the label. Calculate how long it should take your cattle to go through a bag when they are eating the recommended amount each day. Normal daily intake for mature cows is two to four ounces per head.
There is a lot of confusion when it comes to determining the type of minerals that are best suited to your situation. Mineral supplements are usually categorized by a number describing the ratio of calcium to phosphorous in them (i.e. 1:1, 2:1, 3:1). Generally, legume forages (alfalfa type) are higher in calcium; grass forages are lower in calcium. We need to keep the ratio of calcium to phosphorous in the total diet at a minimum of 2:1 (twice as much calcium as phosphorous). If you are grazing a grass pasture with little or no legumes, you may consider using a 2:1 or adding some limestone to your 1:1 mineral to bring up the level of calcium.
Once you have established the appropriate type of mineral to use according to the forage type being grazed, you need to select a product with adequate levels of trace minerals. The following table is a quick reference guide to selecting minerals or trace mineral salt of suitable trace element content.
Guides to selecting minerals of suitable trace element content (the recommended range is for milligrams per kilogram (mg/kg):
Copper – 2,000 - 3,000
Zinc – a10,000 - 12,000
Manganese – 8,000 - 10,000
Iodine – 70 – 200
Cobalt – 40 – 60; and
Selenium – 30 – 80.