Product Application

Pasture-Mag 21 IGR is a supplement that is designed to provide sufficient (S)-Methoprene insect growth regulator to prevent the emergence of adult horn flies from manure of treated cattle. This unique supplement is second to none when compared to other low moisture blocks. Pasture-Mag 21 IGR is an exceptionally nutrient dense all-weather block that will give you the most for your money.

Here’s how:

  • Pasture-Mag 21 IGR supplement is fortified with Altosid® which offers the most effective and convenient way to control horn flies in beef and dairy cattle.
  • Economical: A low feeding rate means lower feeding costs (on a per head per day basis).
  • High Mineral Fortification: This supplement is mineral fortified, eliminating the need for additional free-choice minerals, resulting in significant cost savings.
  • Weather Resistant: Our patented, “continuous flow” manufacturing system creates a high quality, low-moisture, exceptionally nutrient dense block that maintains its integrity even in hot, humid weather or precipitation.
  • Minimal Labor: Pasture-Mag 21 IGR is easy to feed. Simply place the blocks in areas of easy access to the cattle.
  • Returnable Steel Barrels are economical and environmentally friendly and eliminate the expense of additional feeding equipment. Ask us about other available packaging options and package sizes.
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Feeding directions for cattle supplements

Feeding Directions

When used as directed, Pasture-Mag 21 IGR will provide sufficient (S)-Methoprene insect growth regulator to prevent the emergence of adult horn flies from manure of treated cattle. Existing adult horn flies will not be affected. Start feeding before horn flies appear and continue use until cold weather marks the end of the horn fly season. Allow free choice to cattle. Cattle should consume an average of 0.8 ounces of Pasture-Mag 21 IGR per 100 lbs. of animal body weight per day, which is equivalent to 8 ounces per day for a 1,000 pound animal.

Provide access to fresh water and free-choice salt at all times.

Guaranteed Analysis

Contains Altosid®

Active Ingredient
(S)-Methoprene (CAS #65733-16-6) 0.005%
Other Ingredients 99.995%
Total 100.000%
Crude Protein, minimum 21.0%* Copper, minimum 300 ppm
Crude Fat, minimum 3.0% Iodine, minimum 15 ppm
Crude Fiber, maximum 2.0% Manganese, minimum 1,200 ppm
Calcium, minimum 1.5% Selenium, minimum 6.6 ppm
Calcium, maximum 2.4% Zinc, minimum 1,200 ppm
Phosphorus, minimum 1.0% Vitamin A, minimum 80,000 IU/lb
Magnesium, minimum 2.0% Vitamin D, minimum 8,000 IU/lb
Potassium, minimum 2.5% Vitamin E, minimum 80 IU/lb
Cobalt, minimum 3 ppm

*This includes not more than 10% equivalent crude protein as non-protein nitrogen.

ALTOSID® Insect Growth Regulator is a registered trademark of Wellmark International. Made in U.S.A.

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