Mineral Toxicity?

Many myths and misconceptions about cafeteria-style mineral feeding programs abound in the agricultural community. I thought I had heard them all, until I was recently confronted with the following situation.

A livestock owner who was planning to begin a self-regulated mineral program was cautioned that mineral deficient animals would tend to over-consume deficient minerals to the point of toxicity. He was advised to start out by feeding a blend of the same minerals that would be offered individually later on.

In my opinion, there are several problems with this approach.

1. While it is true when starting a self-select mineral program some individual animals will eat an alarming amount of some products, I have never seen a confirmed case of actual toxicity when the full array of recommended minerals is provided.
2. If an animal consumes an inordinate amount of a blend to compensate for a previous deficiency of one mineral, it is, in effect, being force-fed all the other minerals in the blend which it may not need. It is expensive to force feed minerals the animals do not need.

Here are some other key points to consider.

• The essence of the Cafeteria style system is Choice— giving the animals the choice to exercise their innate nutritional wisdom. If you are concerned, you can start them off slower by only putting out small amounts at first and then gradually increasing the amount. That way they maintain their choice and are not forced to eat minerals they do not need.
• When starting on a program like this, animals may eat what appears to be excess minerals because they are not only eating to satisfy their daily needs but also to remedy the deficiencies they may have experienced in the past.
• Minerals are team players. You need the entire team on the playing field to win the game; minerals are the same way. You need to provide the full team to have a successful mineral program.
• Feeding other mineral blends, either top-dress or in the ration, should be minimized or avoided.
• Always provide a separate, free choice source of plain white salt.

The following incident illustrates another aspect of this ability:

 

Weather had made it a bad year for crop quality. In late winter, a good client called me about two problems. His cattle were eating excessive amounts of mineral, and his heifers would abort a live calf about 10 days before they were due to calve. The calf would live, but the heifer would usually die. Focusing first on his mineral problem, he decided to try a “cafeteria” mineral program in which each mineral was fed separately. He had to carry each bag of mineral through his cow-lot to get to the mineral feeder. His first few trips were uneventful. Then suddenly several of the normally docile cows surrounded him, tore a bag of mineral from his arms, chewed open the bag and greedily consumed the contents … a zinc supplement. 

Within a week after the mineral change, consumption returned to normal, and his remaining heifers calved normally. Apparently, the previous year’s stressful growing season had resulted in crops that were deficient in zinc or perhaps high in zinc antagonists. His mineral mix was high in Calcium with only small amounts of zinc. Their quest for zinc impelled them to over-eat the mixed mineral. Excess calcium interferes with zinc absorption. Every mouthful they took increased the imbalance and escalated their need for zinc. Inevitably, metabolic problems began in the most vulnerable group - young, growing heifers in the last stages of pregnancy. Finally they just gave up and checked out ... all for want of a few grams of zinc.

Check out: https://docrjhollidaydvmblog.blogspot.com/2020/08/hey-doc-my-cows-are-eating-dirt-waddya.html