Mineral biofortification of plants
One sustainable agricultural approach to reducing the mineral deficiencies in livestock animals is to enrich major staple food crops (rice, wheat, maize) with minerals through plant breeding strategies. Biofortification of plants with minerals may be a promising and cost-effective intervention. The idea is to breed food crops for higher micronutrient content through crossbreeding or genetic engineering.
Direct methods of mineral supplementation
In India the livestock farmers provide some quantity of cakes, bran, rice polish and husk as concentrate supplement to productive animals. Unproductive animals are generally allowed to graze on left over fields. Except in some parts of Punjab, Haryana and Uttar Pradesh, green fodder is not fed to the animals. Some quantity of greens is offered during rainy season which are grown on the bunds in the field. The animals do not receive any mineral supplement and even salt is not being fed. The possible reasons would be the high cost involved and lack of awareness. The direct approach of supplementing micronutrients in the diet of cattle depending on the severity of deficiency may be a more practical method. The most efficient method of providing trace minerals is through mineral mixture mixed with concentrate feed ingredients. This assures an adequate intake of mineral elements by each animal. This procedure represents an ideal system for providing supplemental minerals but it cannot be used with grazing cattle, which receive little concentrates and depend on forages or where concentrates are not fed. Use of mineral supplements in the form of mineral mixture or mineral licks and premixes are most commonly used methods. Supplementation can also be achieved through feeding compound feeds, oral drenching or dosing or by administering slow releasing mineral boluses which are retained in the gut and in the form of injectable preparations. Heavy pellets of the mineral or soluble glass which has the specific mineral impregnated into it are lodged in reticulorumen are useful in steady supply of specific minerals continuously for long periods. This approach is
useful during peak period of milk production to overcome certain metabolic disorders like milk fever and grass tetany.
Supplementation of area-specific mineral mixture
Feeding of ‘free - choice’ mineral supplements could be the easiest way of supplementing minerals. Alternatively providing area - specific mineral mixture based on the deficiency of minerals in different agro-climatic zones is most appropriate and cost effective method of mineral supplementation. The former approach could sometimes lead to deleterious effect, as some of the minerals may be available in excess than requirements affecting utilization of other minerals. For example, excess of calcium disturbing the Ca - P ratio, excess of selenium affecting sulphur utilization, excess of molybdenium and sulphur reducing copper absorption and excess of iron disturbing copper metabolism. More practical method is of supplementing only the most deficient minerals through area specific mineral mixture by assessing the mineral content in soil, feeds and fodders and in animals in different agro-climatic zones. This approach has been found to improve the reproductive efficiency in crossbred cattle under field conditions and this technology has been a success.
Supplementation through local resources
One of the other cost effective method of mineral supplementation is to provide feed and plant sources rich in the specific micronutrient, which are commonly being fed / grown in that particular region. For example cakes, brans and rice polish are rich sources of phosphorus. Similarly top feeds / tree leaves and legumes are good sources of calcium, copper and zinc. Some of the unconventional feed resources are also rich in certain minerals. In general legume fodders, cultivated green fodders and tree leaves are good sources of Ca, Fe, Zn, Cu, Co and Mn and oil cakes and bran are good sources of P, Zn, Cu and Mn