This review aims is to explore different authors’ views about mineral contents of crop residues, aiming to demonstrate the benefit of supplementing minerals from soil with crop residue minerals, as well as point out effects on livestock productivity. Crop residue is the second main livestock feed resource, followed by natural pasture in Ethiopia, which has poor nutritive values. Nutrient composition of plant materials/crop residue depends on the nutrient availability of the soil, while nutrient availability of the soils depends on the nature of soils, season, climate, the topography of the land, interaction between animals and humans, time/period of sampling and application of inorganic fertilizers. Trace minerals deficiency of grazing land causes different effects on livestock and the plants themselves. Many incidences of mineral inadequacies in forages and soils have turned out the main causes of reproduction failure and low production rates by Ethiopian livestock.

Keywords: mineral, crop residues, soil mineral, interaction, protein

In Ethiopia, crop residue is the second main livestock feed resources followed by natural pasture.¹ Different authors were investigate different experiments on crop residue atdifferent time to evaluate its impact on livestock productivity.^1–7 This crop residue has contains different nutrients but lowin protein content. Most of the researchers were concerned about its macronutrient content rather than micronutrient content. Only a few researchers were tried to investigate the micronutrient content of crop residue but limited only on calcium and phosphorus.

Plants are the feed sources of animals but the nutrientscontent of the plant is depending on the nutrient availability in the soil that determines the productivity of animals.Also besides, soil formation is depending on the geologic and climate condition of the areas.⁸ According to FAO (1998),⁹ there are 19 general clusters of similar soil types and identified soil map descriptionsina different part of the country.Types of soil and environmental conditions are affecting the presence of sufficient amounts of minerals in the soils and plant uptake. For example, uptake of Ca, Mg and Mo can be limited in acidic soils. These causes for the inadequate presence of minerals in forage and plant materials. This indicated thatit is the principal cause of livestock reproduction failure and low production rate.^10–12 Therefore, this review aimsare to explore different views of authors about crop residue minerals content and to show the interaction of soil mineral contents and its effects on livestock productivity.

According to Helias A, et al. (2012)¹³ reporta research investigation on soil minerals deficiencies has been starting from the 1920s while more intensified after the Second World War.The analysis of soil chemistry grew and modernized from time to time with cost-effective. In early periods, only determine the total levels of micronutrients in the soil yet now determine the actual level of micronutrients in the soil and plant materials by using least-cost methods like infrared radiation measurements by taking a sample. About 42% of Ethiopian highland agricultural areas, Vertisols, Nitosols, Acrisols, and Cambisols are the most common from more than 17 soil types.¹⁴ According to his description,Nitosols and Acrisols are not suitable for agriculture due to its acidity, low nutrient content, and readability. Different minerals are existingin the soil in different concentration amounts and states. Organic matter is closely associated with the nutrient status of soil because it contributes to the soil cation exchange capacity (CEC).¹⁵ It is also an important source of inorganic nutrients for production in natural ecosystems.¹⁶ Most of the Ethiopian highland areas are rich in potassium and CEC with international standard but the availability of nitrogen, phosphorus, and organic content is very low that causes low crop yield.⁹ Ethiopian wheat cultivar grew sample soils are deficient in copper, zinc, molybdenum, boron, and iron.^9,17,18 In recent years, researchers indicated that the main causes of Ethiopian crop yield losses are depletion of macro and micronutrients in the soil.⁹ There are sufficient amounts of K, Ca, Mg, Fe, Cu, B, and Mo in the soils butdue to the acidity of the soil, the plant couldn’t uptake enough amount of Ca, Mg, and Mo from the soil.

Soil and forage mineral concentration is affected by sampling periods and seasons.¹⁹ For example, soil Cu, Fe, Mn, Zn, and Se and all forage minerals except Se were affected by sampling periods and season, respectively. All soilminerals level except Co and Se were found above the critical levels in all seasons and adequate for normal growth of plantsbut Cu and Mn were lower during winter.¹⁹ In addition to carbon, hydrogen, and oxygen, most important macro minerals (N, P, and K), secondary macro minerals (Ca, Mg, and S) and micro minerals (B, Cl, Cu, Fe, Mn, Mo, and Zn) are indispensable for the health and growth of plants. Due to the deficient of these one or more minerals, the optimum yield of the crop will fail and the quality of foods will be inadequate.  To afford adequate and quality food for the population, micronutrient deficiencies in agricultural and horticultural crops should be acknowledged and treated.⁹

In our world, around 3.8 billion tones of crop residuesare produced annually.²⁰ It contains different amounts and types of nutrients, basically, Nitrogen (3 to 8.2 kg /tones DM), Phosphorus (0.2 to 0.6 kg/tones DM) and Potassium (7.2 to 23.3 kg/tones DM).²¹ Crop residues are the most available and low-cost animal feed resources in the majority of developing countries.³ According to Adugna(2012),¹ it is the second major livestock feed resource in Ethiopia followed by natural pastures.Crop residues have low nutritional contents (protein and energy), poor digestibility and intake and high fiber content, which is un-degradable by the host enzymes.^1–7 However, the mineral contents of crop residues are not well described. Researchers have examined several crop residues and agro-industrial by-products, available in Ethiopia as a potential for ruminant feeds concerning to their prospective supply of crucial dietary minerals.²² Due to the inadequate supply of Na, P, Cu, Mo, I, Se, and Zn and crop residues based animal rationhas significantly affected livestock reproductivityand production performances.By different research investigations,21 essential minerals are identified for crops, livestock, and humans as present in Table 1.

According to Khalili (1993),²³ the analysis of feed samples showed that all feed types are deficient in Na. Hay, pasture grass, barley straw, grains, and teff straw were also low in P, Mg, Cu, and Zn but in all feeds, Fe content was found extremely high and Mn levels were also higher than the dietary requirements as present on (Table 2 & 3).

According to Khaliliet al. (1993),²³ low mean level of Cu (0.62 mg/l) and Zn (0.66 mg/l) as compared to the critical levels published by McDowell (1985)¹⁰: 0.65 mg/l for Cu and 0.60 to 0.80 mg/l for Zn in the blood plasma samples. Based on his study, the level of Ca, P, Mg and K, and all trace elements was significantly affected by season’s variation.Besides, most of the animals have low plasma Cu and Zn during the rainy season. 

The mineral composition of crop residues is depending on soil types, climate condition and season. For example; Ca concentration dropped by 55% (from 337 mg/l in the wet season to 153 mg/l in the dry season.The concentration of K, Mg, and Cu are below the critical level during the dry season, but above during the wet season. Chemical fertilizer application also other factors affecting the mineral concentration of crop.¹⁶

Trace minerals deficiency on grazing land causes different effects on livestock and the plant itself. Low digestibility, low crude protein content and low content of available minerals and vitamins in the cereal residues cause weight gain loss in different livestock species.²⁴ Many incidences of minerals inadequacies in forages andsoils have been reported principal causes for livestock reproduction failure and lowproduction rate.^10–12

According to KaatNeckermann (2017),²⁵ the poor quantity and quality of feed resources and its mineral deficiencies are the main causes of zebu cattle milk production reduction in Ethiopia. He has analyzed the concentration of the minerals in feed and serum for dairy cattle. The content of B, Ca, Cu, Fe, K, Mg, Mn, Na, P,Zn,and Mo are deficient in the feed. Both excessive and underprovided amounts of minerals in the ration are cause for toxicity and deficiency, respectively.²⁶ Most minerals have more than one task, which makes it difficult to establish a criterion for adequacy and dietary mineral levelseither sufficient for one body function or insufficient for another. Generally, minerals play a role as catalytic (enzyme function), physiological (maintaining osmotic pressure), structural (bone strength), and regulatory processes (cell replication and differentiation).^27,28

The following Figures 1, 2 &3 are shownthat the relationship between mineral supply and animal production. It shows also marginal bands between adequate and inadequate or toxic dietary concentrations. The graph and marginal ranges move to the right as absorbability of the mineral source declines; thus “A” represents the more and “B” (dashed line) the lesser absorbable of two mineral sources.^29–32 ‘Requirements’ are variously set within the central adequate band from minimum requirements to safe allowances, depending on the extent to which absorbability and other variables are taken into consideration.

Figure 1 Dose-response curve for feeds A and B and A has a higher mineral absorption coefficient than B, (Suttle, 2010).

Figure 2 Trace minerals deficiencies on ruminant animal’s causes for body condition loss.

Figure 3 Trace minerals deficiencies on plants.

Different experiments were conducted in our country to quantify mineral availability in the soil, plants, and body of animals including its effect on those organisms. However, there is limited research on crop residue mineral content and its impact on livestock productivity improvement. Therefore, due to havingthe significant effect of minerals on livestock productivity should be analyzing the mineral contests of the crop residue at a time before feeding for our animals.^33–38

None.

None.

The authors declare that there was no conflict of interest.

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