Minerals requirement of small ruminants with special reference to their role in rumen fermentation – A review

Minerals are non-nutrient constituents of feed and food and play an important role in nutrient utilization, growth and production. They are integral constituents of several enzyme systems of living organisms. Mineral sufficient feeds are utilized very efficiently in animal system. The imbalance of minerals not only impairs minerals utilization but may also alter rumen environment, reproduction and health status of animals leading to their lower productivity. Mineral status of feeds and fodder is influenced by soil and environmental conditions. Se can exist either as selenite, biselenite or selenate depending on the pH of soil. In neutral and acid soils, selenite in aqueous state is predominant and for most part unavailable due to adsorption on clay and hydrous oxides. The oxidation-reduction potential and soil texture influence the distribution of Se. Pastures from acidic soils have more Mn, while higher pH reduces it. The Mo content of plant is also affected by soil pH, which is quite large in legumes than in grass. The Co, B, Cu and Zn are less affected due to soil reaction or pH. Minerals of herbage differ markedly in S, Ca and Mg concentration but not in P. The tropical grasses contain twice as much as Ca as the stem. Dry season pasture contains less P than green season pasture and tender leaves contain more P than older leaves. The Ca and P are higher but Na, K, Fe and Cu are generally lower in dry season as compared to wet season while Mg and Zn content are not affected by season. Leguminous species are generally richer in macro-elements than grasses growing under comparable conditions. The trace elements, such as iron, copper, zinc, cobalt and nickel are also generally higher in leguminous than in graminaceous species in temperate climates. Grasses and cereals commonly contain higher contents of manganese and silicon than legumes. Small ruminants require adequate minerals in their diet depending on level of feeding, physiological state of animal and type of production system for harvesting their maximum potential.