If mineral intake of beef cattle is below mineral requirements, mineral deficiencies will occur. Determining the requirements for trace mineral supplementation of beef cattle can be complex. Mineral requirements for beef cattle depend on body weight, animal performance, stress and health. Mineral intake of beef cattle can be calculated as dry matter intake times concentration. This seems simple, but particularly in grass-based systems for grazing beef cattle, it can be difficult to determine dry matter intake and dry matter concentration of trace minerals. The presence of antagonists may however reduce mineral availability, which may result in mineral deficiencies of beef cattle.

Mineral deficiencies in livestock can be classified as primary deficiencies or secondary deficiencies. Primary deficiencies are caused by low mineral intake. Secondary deficiencies occur when a diet for beef cattle contains antagonists. This can be a common problem. Particularly in a high fibre diet, a lot of minerals can’t be absorbed because of antagonists in the diet.

Traditionally we see antagonism of trace minerals happening in the small intestine. But in the rumen, there are two ways complex formation can reduce mineral absorption from a beef diet. Firstly, and well discussed in literature, complex formation of copper occurs, for example with molybdenum.

Next to that, there is the possibility of cluster formation. The surface of fibre in the rumen is negatively charged, Bi-valent cation minerals like zinc, copper and manganese have a positive charge. A strong bond between fibre and trace mineral ions occurs, and these trace minerals are not released, not even in the abomasum at low pH. As a result, trace metals ions are not available for absorption in the small intestine of beef cattle.

A nutritional strategy for beef cattle is required to meet beef cattle requirements for trace minerals. Firstly, provide enough mineral to reach the target for performance. Secondly, avoid losses.

A study was carried out in beef cattle¹. The objective of this study was to evaluate the impact of different sources of trace minerals on solubility in the rumen, digestibility of dry matter and the apparent absorption of copper, manganese and zinc.

Four cannulated crossbred steers were used in a Latin square design. The animals were fed corn silage diet and 3 different beef cattle mineral supplements, containing different sources of trace minerals for beef cattle. A third control group was fed the same diet without beef cattle mineral supplements. The level of supplementation was intended to meet beef cattle maintenance requirements for minerals in accordance with the NASEM guidelines for beef cattle. Copper was fed at a level 10, manganese at 30, and zinc at 30 milligrams per kilogram of dry matter plus the minerals in the silage. One group was fed Selko IntelliBond hydroxy chloride copper, manganese and zinc sources, a second group was fed organic sources of copper, manganese and zinc and a third group was fed sulphate sources of copper, manganese and zinc. Negative controls were not supplemented with copper, manganese or zinc. After an adaptation period of 14 days, samples were collected for 7 days. The diet was offered twice daily at 07:00 AM and 03:00 PM. To avoid losses, leftovers were removed before the first meal in the morning. The trace mineral supplements were introduced in the rumen directly.

Dry matter digestibility (DMd) was different between the trace mineral sources (see Table 1).

DMd was similar between beef cattle fed hydroxy chloride trace minerals and beef cattle fed organic sources of trace minerals, but DMd in both groups was better compared to beef cattle fed sulphate trace minerals and compared to controls. Ruminal excess of Cu and Zn in soluble form is known to negatively affect microbial populations and rumen fermentation in beef cattle^2,3. A second hypothesis could be that metal cations can bind to fiber, strongly reducing dry matter digestion in beef cattle.

Apparent absorption was calculated as total trace mineral intake minus trace mineral in the faeces, divided by total trace mineral intake. Apparent absorption for copper, zinc and manganese is presented in Tables 2-4.

Copper endogenous losses were greater than copper intake. Hydroxy copper and organic copper apparent absorption were not statistically different from each other but were higher than apparent absorption of copper sulfate in beef cattle (see Table 2).

Manganese endogenous losses were also greater than manganese intake, with no differences in apparent absorption of manganese between the 3 different sources of trace mineral supplementation for beef cattle (see Table 3).

Also zinc endogenous losses were greater than zinc intake, with apparent absorption of hydroxy chloride and organic zinc sources not being different from each other but higher than apparent absorption of zinc sulfate in beef cattle (see Table 4).

It was concluded that lower rumen solubility of trace mineral sources results in greater dry matter digestibility in beef cattle. Hydroxy chloride and organic sources are better absorbed by beef cattle than sulfate sources. Non-supplementation of beef cattle resulted in net loss of copper, zinc and manganese, regardless of the type of mineral intake.