How can you possibly say the mineral is not practical? Mineral pays for itself in many ways and is most certainly practical. Do you mean as a method of fly control? I just posted an informative article from an independent nutritionist about IGR. Everyone, and I say EVERYONE in this area that has used IGR in their mineral has put pounds on their calves. Now this is not to say IGR is the ONLY way to control flies.
Here is a bit more from Dave Wieland:
Fly control is a coordination game
Most cow/calf producers-about 81%, according to a 1997 report from APHIS, use some method of fly control. But only a small number have a well-managed program.
Cost, timing of control method and the inablility to implement an adequate program due to lack of facilities or cattle spread out on range are the most common reasons citied for flies not being adeqately controlled.
When setting up a fly control program for a customer, the first thing I show them is the fly number profile for the entire five to six months of the fly season. Although most producers realize that fly numbers peak in June, they don't realize there is also another peak in August, long after most control methods have been forgotten and efficacy of the insecticide used has been drastically reduced.
In recommending programs, I try to coordinate the timing of the application of fly control to be as close as possible to June to give the best results. However, branding calves and sorting cows for the range may be done earlier, and producers do not like to handle cows and calves again just for fly control. Often, this timing is not possible because cattle are on range and away from adequate facilities.
In proposing fly control programs, my first recommendation is to get an inital kill on the adult flies. If we don't knock down the adults, then the other methods will be overwhelmed and not give the desired results.
This is the major reason why most fly control methods fail. I recommend either spraying the cows or using pour-ons to achieve this initial kill. Buildings and corrals may also by sprayed to lower adult population. The
next step is to determine another method of control. I always recommend at least two different methods.
THE USE OF A LARVACIDE IN A MINERAL IS MY METHOD OF CHOICE FOR THESE FUNDAMENTAL REASONS:
*Larvacides may be fed free-choice and may be used in most range conditions.
*Larvacides fed in this manner do not require handling of the cattle.
*Larvacides act on a different stage of the fly life cycle (acting on the larva stage rather thatn the adult fly.) No known resistance has been shown.
*I like to have mineral available for both the cows and calves
Back rubbers and dust bags are also good methods of fly control that may be used around watering places and don't require much labor or expense. Mister-sprayers or foggers may be used where cows congregrate to help reduce the adult flies. Fly tags may be used but need to be put on at the right time for best results. Be sure to use TWO tags and not just one.
Some producers think there shold be no flies on the cows. Regardless of the methods used, we will never be successful in eliminating all flies.
(There is more information about flies in the article, which I chose to skip here. Here is the concluding paragraph

Knocking down the adult fly population, practicing good sanitation, alternating fly tag and other insecticide types (pyrethroid or organophoshate), timing the control measures to coincide with with both peaks of the fly population (June and August) and using multiple methods of fly control should be integral parts of setting up a fly control program.
(If you wish to read the article in its entireity; see page 74 of April 2000 BEEF magazine.)
We consult with a lot of producers on fly control. There is nothing wrong with using one or more methods. Flies steal a lot of money from producers pocketbooks. I know how well the IGR works. I have old-time ranchers that use it and tell me how happy they are that their cattle are out grazing when other cattle they pass along the road are bunched up in the fence corners. One rancher that takes in yearlings sets the rule that the cattle have to be on our IGR mineral product. That is the only way he takes cattle in. That is a pretty impressive testimonial.
One of the most common problems with feeding IGR is not starting it soon enough or leaving it out long enough in the fall. If it is left out until a killing frost, it will prevent the flies from overwintering and you will not get that big hatch in the spring. Therefore, you are ahead of the game right off the bat.
If you want to gather your cattle and spray them, I suggest you wait until the breeding season is over. Do it then and do it again when you precondition your calves. We have had great experience with a product called CYLENCE. It is very easy to apply and is very reasonable as well.
In our Vigortone mineral containing IGR, it is set up so the cattle can consume 2 ozs. and still get enough IGR to control flies. We all know cattle don't eat mineral as well in the early spring and summer when the grass is green, therefore IGR is mixed in so that 2 oz. will be effective.
Vigortone does not make any product available in block form, based on their research that blocks are not an effective way of getting mineral or additives in cattle. And, as the poster mentioned above, the sweetness and softness of the block encourages over-consumption. Based on Vigortone's research, I would NEVER recommend block form.
Hope this helps!