You ask a very good question and one that is not easy to answer. Chelated minerals -- usually trace rather than macro-minerals -- are minerals that have been through a chemical reaction and bond to amino acids, the building blocks of proteins, or to protein complexes. Amino acids that reach the small intestine are very readily absorbed and are therefore readily available to be used by the animal. The thought is that minerals consumed by the animal are not absorbed very efficiently. So the theory would be that if minerals were tied to something that is readily absorbed naturally in the body, the efficiency of absorption would be enhanced. We know that amino acids are efficiently absorbed, so feed companies have bound minerals to amino acids to, in theory, increase their absorption, and therefore, their bioavailibility to the animal. The data suggests that these mineral-amino acid complexes are more effectively absorbed by the animal.
As far as the data is concerned, results are mixed with chelated trace minerals. What seems to be the most consistent in the data for chelated trace minerals is that there appears to be a positive response in young calves that have been stressed, and it appears that you get an immune response. Chelated minerals have been shown to improve pregnancy rates and embryo production of donor cows.
Chelated trace minerals will provide the greatest responses when cattle are stressed, have increased work demands, or have increased environmental challenges.
