Mineral nutrition in sheep

Mineral Nutrition in Sheep
September, 1997
Brian Bell, Agriculture and Rural Representative, Gore Bay, OMAFRA
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Table of Contents

1. Introduction
2. A. Types of Minerals
3. B. Factors Affecting Feed Mineral Content
4. C. Factors Affecting Requirements
5. D. Health Problems Associated with Mineral Levels and/or Interactions
6. E. Methods of MineralSupplementation
7. Conclusion
8. Table 1. Mineral Requirements of Sheep
9. Table 2. Minerals for Sheep
10. For more information...

Introduction

Minerals play a substantial role in sheep nutrition. Mineral nutrition is a complex part of feeding management. Jargon like "chelation; bioavailability; magic bullet; interaction, macro, micro, mg/kg and so on often makes understanding difficult.Regardless, your feeding of minerals has extreme importance in the maintenance and production of healthy sheep and lambs.
Deficiencies and toxicities can occur through inattention to feeding management or simple availability. These effects can be subclinical in nature affecting gain and reproduction. Typical mineral-related problems stem from providing inadequate amounts or minerals in incorrectproportions.
Other difficulties arise in supplying proper dietary mineral requirements. These are as follows:
• availability of minerals from feed sources can vary
• interaction between minerals affects availability
• availability from actual mineral source can vary
• particular geographic regions are mineral deficient
• forage type affects mineral accumulation
Not allthese factors are directly in your control. Learning from sessions such as this one today will help you in preparing properly balanced diets for maximizing returns.

A. Types of Minerals 

1. Macro Minerals - These are mineral that are required in relatively large amounts in the diet. Requirements are expressed in grams or in terms of ration per cent. Some examples of macro minerals are:calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), and sodium (Na) and chloride (Cl).
2. Micro Minerals - These are minerals that are required in relatively small amounts and are expressed in parts per million (ppm) or milligrams per kilogram (mg/kg) of the ration. Examples of micro minerals are: selenium (Se), copper (Cu), zinc (Zn), iodine (I), manganese (Mn) and iron (Fe).

B.Factors Affecting Feed Mineral Content

1. Plant, Soil and Management Factors

Mineral content will vary depending on plant species and soil types and is affected by the stage of maturity, level of fertilization and harvest conditions. Legumes, for example, are usually greater in Ca content than grass forages which in turn are generally higher in Ca content than cereals. Mature foragesand crop residues (eg. corn stover) generally contain low levels of P, while cereal grains and oilseed meals are moderate to high in P. Potassium content is lower in cereals than forages.

The amount of grain fed on pasture can be controlled by adding salt to the grain mix. However, salt intake is affected by forage intake, palatability of the grain mix, salt content of water and forage, andthe ability of pastured animals to adapt to grain mixes with salt added. As salt is a mineral, too much in a ration can cause scouring and, in pregnant animals udder edema. A prolonged salt deficiency can cause reduced appetite, unthriftiness, and a drop in production.

Mineral levels in feed can vary from farm to farm depending on the soil and fertilizing method. Differences from 20 to10 times the mineral concentration between farms can occur. Grasses growing in water-logged soils and potentially low in Mg and are often causative factors in grass tetany. Drainage of these soils will encourage the uptake of Mg in the plant and therefore increase its availability to livestock.

Harvesting and storage losses are other sources of mineral variability. Over conditioning or...