There are 21 minerals thought to be nutritionally necessary for cattle. They can be classed as major minerals and trace elements depending on the amounts the animals need. In Soil Grass & Cancer, André Voisin delves into the link between human and animal health and the mineral balance of the soil. Although this work was penned more than half a century ago, it retains a profound insight into the all-important role played by soil minerals.
In my previous article, I described how a shortage of copper in the soil adversely affects animal production. I now wish to expand on copper and talk about manganese, another soil mineral that can markedly affect animal fertility. Copper and manganese are both trace elements. At the International Congress of Physiology and Pathology of Animal Reproduction held in Copenhagen in 1952, SL Hignett presented a paper on copper and herd fertility. Voisin writes: “Hignett observed that districts with copper deficiency are increasing in Great Britain and that he has never seen a herd of cows suffering from copper deficiency in which the fertility was satisfactory.”
A lack of sexual activity is common in cows with copper deficiency. Dosing cows with copper led to a “spectacular improvement in reproductive efficiency”. As I noted last time, feeding animals minerals may be a quick fix, but it’s not the best solution, because a shortage of a mineral in soil will most often have a detrimental effect on the productive capacity of the forage plants. Soil mineral corrections of intensive pastures are, in the long-run, by far the best solution for herd profitability.
The importance of Manganese
In Chapter 15 of Soil Grass & Cancer, ‘The fertility of the animal is a function of the fertility of the soil’, Voisin reports on
studies conducted by the University of Wisconsin on cow fertility. These were undertaken because, in some districts, there were numerous herds in which the fertility of both bulls and cows was unsatisfactory. This was linked to forage that was particularly low in manganese – less than 20ppm on a DM basis. Tests done on forage in a district where fertility levels were satisfactory revealed that manganese exceeded 50ppm.
A trial was undertaken by the university with two groups of heifer and bull calves. One was fed forage grown in districts with sufficient soil manganese levels, the other on forage from soil lacking manganese. There was no difference in the growth rate and appearance of the calves. It was only when they reached reproductive age that the lack of manganese in the forage expressed itself. Heifers fed forage with sufficient manganese calved normally, whereas those fed forage deficient in manganese either aborted or produced weak calves. A manganese deficiency also resulted in bulls producing sperm of lower quality.
Mineral deficiencies and imbalances can cause deficiency diseases. Fertility, calving percentage and milk production are all affected by shortages of minerals. Animals required to maintain levels of high production need higher amounts than low producers. Farmers may not be aware of mineral deficiencies until they are picking up the tab for lost pregnancies or low milk production.
John Fair is a pasture consultant. He heads up Fair’s Biofarm Assist, and can be contacted on 058 622 3585 or [email protected].