I have often been asked to compare results of smorgasbord mineral feeding in different situations. Since there is no clear meaning to either ‘organic’ or ‘conventional’ — my quick answer would be, “That depends.”
First of all, it is important to understand that feeding ‘ground-up rocks’’ to supplement minerals is, at best, just a band-aid. The real problems are low mineralization of feedstuffs (from decreased soil fertility) and reduced nutritional diversity (from confinement).
It helps me to envision a spectrum or range of mineralization levels in feedstuffs with highly nutritious feeds at one end and lower quality feeds at the other end. On this continuum, it is possible to plot and compare different responses to cafeteria-style mineral feeding situations.
Animals being fed nutritious, highly mineralized feeds from the top end of the range will generally have low mineral consumption or perhaps eat none at all. Many, but not all, ‘organic’ dairies fall into this category, as do rotational grazers. Minerals consumed will probably be used to correct minor imbalances rather than gross deficiencies. Many of these dairy farms will have a long record of soil building.
On the other end of the spectrum, animals in large, intensive, high stress dairy operations will normally consume more minerals to compensate for the lower mineral content of the feedstuffs. Most of their rations will be composed of feeds of variable quality purchased from various sources.
Then too, feeding a TMR often provides too much calcium and protein. Excess protein (along with high nitrates in the water) increases the need for Vitamin A. The excess calcium forces the cows to eat more phosphorus to balance the important Ca/P ratio. Stress of any kind, especially stray voltage, increases the need for Vitamin B.
When starting out, all animals will eat minerals to satisfy their daily requirements and enough extra to begin to replenish previous long-term deficiencies. Excess mineral consumption in any herd may be a sign of other problems such as stray voltage, geophysical influences, bad water m weather changes or the environment influences.
If any of these problems are present, it would benefit the dairyman to at least partially correct them before starting to feed cafeteria-style minerals.
So where does it work the best? I think it is a toss-up! The farm with fewer problems and less mineral consumption benefits from the superb animal health achieved. On the other hand, ‘conventional’ herds have more room for improvement and will be greatly rewarded as many of their problems are reduced.