Dairy animals require minerals to serve various metabolic functions that are essential for growth, development, reproduction, production, and antioxidant status. Thus, ruminant diets are supplemented with adequate minerals asper animals’ status, though some interactions may inhibit the mineral absorption in rumen. At least 17 minerals (i.e.,Macro and Micro) are required in the diet of dairy cattle and buffaloes for ideal herd health, milk production, and reproductive performance, which ensures dairy profitability. Deficiencies or slight imbalances of these minor nutrients can develop health, reproductive, and milk production problems in dairy, which are the key factors for better productivity. Deficiency of minerals in the daily ration leads to reduced dairy animal production by 20 to 30 %. Hence, to ensure animals’ rapid growth in boosting the performance and to improve immune response, supplementation of trace elements is essential in animals’ diet.
Basic Requirements
Minerals are classified into two major categories as per the dairy animals requirements. Macro-minerals, which include calcium, phosphorus, potassium, magnesium, sulphur, sodium, and chloride, that are required in more than 100 ppm in the diet. Trace or micro minerals includes cobalt, copper, iodine, iron, manganese, selenium, and zinc, that are required less than 100 ppm in the diet. Whether the requirement of the mineral is large (measured as a percent of dry matter and calculated as in g/kg) or small (measured in ppm or mg/kg), proper level to achieve optimum performance and herd health was fed as recommended in Table I.
Overfeeding and under feeding of minerals are expensive and associated with major health problems in animals. Thus, maximum amount of a mineral fed over a period without negatively affecting dairy performance is calculated as “maximum tolerable level”. Commercial dairies are prone to mineral toxicity due to unaccounted mineral supply, especially when multiple minerals are supplemented while developing or assessing the rations.
As ruminant diets are high in fiber portion, digestion occurs through microbial fermentation in the rumen and reticulum, which precedes the enzymatic digestion in abomasum and intestine. Due to the association of minerals with fiber fractions in feedstuffs, and/ or binding of minerals to undigested fiber constituents in gastrointestinal tract (GIT), bioavailability of some trace minerals (TM) in ruminants are highly questionable. Hence, mineral content of a feed or supplement is invaluable in ration formulation unless the bioavailability of minerals, mineral interactions, solubility, dissociation, absorption, and retention of the mineral is known.
Trace Mineral Interactions/Antagonism
Various challenges notice the absorption and mineral status of rumen in cattle and buffaloes because of trace mineral interactions. These interactions occur in rumen before intestinal absorption, as the competition for absorption between minerals decreases the concentrations of absorbed minerals. Specifically, a variety of known trace mineral interactions occur between iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn). For example, the mineral interaction of iron antagonizes the absorption of Cu and Mn. As shown in Figure-1, mineral interactions alter the bioavailability of trace minerals. Therefore, a supplementation strategy that may conquer these antagonisms decreases the concentrations required to supplement and increase the efficiency in absorption of trace minerals.
Solubility and Dissociation of Minerals
Solubility of a mineral can readily dissociate or segregate, as solubility substantially affects the total concentration of minerals fed to animals. Out of which, soluble and dissociated minerals are available for rumen microbes to use or interact. Trace minerals with metal oxides, sulfates, carbonates, chlorides, phosphates, etc., have high rumen and low intestinal solubilities, thus have a relatively low chance for cellular uptake. Adversely, organic Zn, Mn, Cu,Fe,etc. sources are often soluble in intestine than inorganic sources, thus have more chances of cellular uptake and serum concentrations, which improves the health status and milk production of animals.
Bioavailability of Trace Minerals
Modifications in interactions of trace minerals fed can alter the absorption and metabolism in ruminants. Studies noticed that decreased bioavailability for the absorption of inorganic trace minerals at GIT is due to their higher availability in the rumen (because of higher solubility and dissociation), where inorganic minerals get reduced easily. In contrast, research studies indicated that organic trace minerals are less available in rumen, and its unsolubility, dissociation at intestinal pH is key for greater bioavailability in intestine of ruminants, as they can avoid ruminal dissociation and antagonisms. Hence, organic trace minerals in feed results in improvement of bioavailability, reduced dietary inclusion levels, improved efficiency, and lesser economic inputs in dairy animals performance.
Source dependency on Bioavailability, Retention, Absorption and Dissociation of TM
Absorption of distinct trace mineral sources depends on its form and varies based on the ligands, binding agent, stability/ retention of chelate, and molecular weight of minerals. Inorganic salts of minerals is present as a cation for absorption in intestinal mucosa. These cations bind the carrier, transported to the cytoplasm via passive diffusion or active transport in the small intestine when interactions to antagonize the absorption of such salts don’t occur.
Conversely, increased stability/ retention of organic chelated minerals are not ionized before absorption. Instead, they get absorbed following the pathway of low molecular weight peptide into the mucosal cells without luminal hydrolysis by choice. If the molecule weakens, it loses its significant portion of bioavailable action and may get absorbed as that of inorganic salts. This process primarily depends on the stability of chelated minerals and the dissociation to break bonds before the complex gets absorbed into small intestine. Thus, the complex or chelate can deliver mineral in a protected form to the absorptive epithelium of small intestine, where acidic, low pH conditions prevail for uptake by animals body. Organic component in trace minerals functions as the link. Metabolic benefits of organic trace minerals reflect as a result of increased mineral dispatch to the small intestine, rather than as a direct function of the trace mineral complexes.
A variety of supplementation strategies are available in the market today and nothing is greater than the rest. Producers determine the strategy based on the composition of animal diets. For achieving high levels of milk production, maintain animal health and reproductive performance, and consider the said parameters as in Table II. Also, selection of minerals depends on maintaining the profitability of dairying.
Conclusion
Ensuring accurate mineral supplementation of organic sources or the form of trace minerals improve mineral status in dairy animals (ruminants) through the ‘complexation’ or chelation that impact its bioavailability. Thus, providing a bioavailable or anorganic form of trace mineral would effectively reduce the dietary requirement and minimize the environmental impact resulting from fecal excretion of unabsorbed trace minerals.
Note: References available on request.
by Dr. Chetan B Shembekar, Kemin Industries South Asia
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