Chapter 17

NATURAL SOURCES OF MINERALS

• Most minerals received from diets, but some from water and soil.

• Methods of processing, storage and different analyses methods result in variability in feed minerals.

• Variation in tabular values (Feed Tables)

a. Organic constituents (e.g., protein, fat, cell wall contents) ± 15%

b. Energy values ± 10%

c. Minerals ± 30%

• Inadequacy of TM in grains related to soils and soil factors.

• Mineral values (particularly trace minerals) in feed table almost useless.

• Mineral content of grains vary less than forages.

• Se in corn can vary 10-20 fold within a state and 200 fold between states, e.g., 0.40 ppm in South Dakota to 0.05 ppm in Wisconsin, Indiana, and Michigan.

• Lack of mineral analysis in feed Tables (i.e., I, F, Se, Mo, S, Cl).

• Prior to discovery of mineral deficiencies, animals transferred from "unhealthy" to "healthy" areas.

• Compensate for trace element deficiencies when ruminants receive greater grazing opportunities and monogastrics and humans have access to feeds produced from other regions.

• Forages often do not satisfy mineral requirements of grazing livestock (Underwood, 1981; McDowell, 1997).

• Plants do not require Se, Co, I and grow normally even though they contain less Ca, P, Fe, Zn, Mn and Cu than required by cattle. Thus, it is necessary to provide mineral supplements for optimum production.

Mineral Concentrations of 2615 Latin American Forages^a
Mineral	Requirement	Critical Concentration	Percent of Total < Critical Concentration
Ca (%)	.18 - .60	0 - .3	31
P (%)	.18 - .43	0 - .3	73
Mg (%)	.04 - .18	0 - .2	35
Na (%)	.1	0 - .1	60
Co (ppm)	.05 - .10	0 - .1	43
Cu (ppm)	10	0 - 10	47
Zn (ppm)	30 - 50	0 - 40	60
^aMcDowell et al., 1977.

• Plant mineral concentrations can be toxic due to soil factors and environmental contamination.

• Soil factors result in toxic forage concentrations of Se, Mo, Mn.

• Plants contaminated with Cd, Pb or F from industry.

• Cd, Hg, Pb and As frequently encountered in insecticides, fungicides, batteries, paints, gasoline additives, phosphate fertilizer, etc.

• Grasses generally higher in Se and Mn.

• Mn deficiency common in poultry for corn, sorghum and barley diets but not wheat or oats.

• Soybeans grown on same soils, tenfold Se difference due to varieties.

• Thirteen ryegrass plants from different strains in New Zealand ranged from 185 to 2,470 ppb I.

Mineral Concentration in Pasture Species
	Ca	P	K	Mg	Na	Fe	Mn	Cu	Co
	percent					ppm
Legumes	1.7	0.37	2.4	0.68	0.08	306	45	8.7	0.17
Grasses	0.4	0.24	2.0	0.24	0.14	264	29	8.2	0.15
Herbs	1.4	0.35	3.1	0.75	0.17	358	42	10.2	0.19
Concentration of Cu, Zn, Mo and Co generally higher in legumes. Concentration of Se and Mn generally higher in grasses.

Effect of Liming on Trace Element Content of Plants (ppm, dry basis)
Red Clover	Soil pH	Co	Mo	Mn
Unlimed	5.4	0.22	0.28	58
CaCO3 - 5,855 kg/acre	6.1	0.18	1.48	41
CaCO3 - 10,996 kg/acre	6.4	0.12	1.53	40
Mitchell (1957).

Nutrients in Brazil Molasses Grass (%)
Age (week)	P	K	Ca	Crude protein
4	0.30	1.58	0.45	18.7
12	0.18	0.82	0.45	10.1
20	0.15	0.40	0.39	7.9
28	0.12	0.34	0.40	6.3
36	0.10	0.31	0.51	6.0

Biological Availability of Minerals in Feed

Availability of feed minerals depends on:

a. age and species (and breed) of animal

b. intake

c. physiological need

d. chemical form

e. amounts and proportions of antagonist

• For some minerals (e.g., Na, K, Cl) availability unimportant since almost completely absorbed.

• For others (i.e., Mn, Fe, Zn, Cu) very low percent absorbed.

• Typically Mn absorption is 3-4%.

• Availability difficult to determine since absorption for many minerals (e.g., Ca, Zn, Se, Fe) controlled by homeostatic mechanisms.

• ⁶⁵Zn absorption from the same source varied from under 10 to over 80%, depending on Zn animal status (Miller, 1970).

• Swine deficient in Se utilize inorganic forms (i.e., Na selenate and Na selenite) as well as organic forms of Se (Cary et al., 1973).

• Beyond requirements not so.

• Mo from inorganic sources less toxic than from pastures.

• Cu more available from hay than grass.

• Mg less available from immature forage.

• Chelated minerals often more available.

• Phytates interfere with P, Ca, Fe, Mn and Zn.

• Ca more available from white vs brown bread (phytate).

Pig Diet	Zn Requirement
Corn-soybean	50
Casein-glucose	15

• Oxalates interfere with Ca absorption.

• Processing affects availability, grinding ↑ digestion.

• Grinding may add metals to feed.

• Grinding citrus pulp ↑ Fe, Zn, Cu, Mn and Na (Ammerman, 1970).

• Steam-pelleting ↑ P availability

Factors Affecting Mineral Intake

• Factors that reduce palatability (e.g., tannins in sorghum).

• Restricting FI practices or improved feed conversion.

• High-energy feeds (i.e., fats) ↓ FI and cold temperature ↑ FI.

Feed Consumption Broilers	Consumption
2800 kcal/kg	--
3550 kcal/kg	19.1% lower

Factors Which Reduce Forage Intake

a. Low protein (< 7.0% protein)

b. Increased degree of lignification

c. High stem to leaf ratio

Water as a mineral source

• Although highly variable all mineral elements essential as dietary nutrients occur to some extent in water.

• Public water supplies generally < 10% trace-element needs for humans.

• For livestock, water provides < 2% requirement for Fe, Zn, P, Cu and Se.

• Water is the principal source of F, resulting in fluorosis.

• F in water has little relationship to soil status or herbage content.

• In addition to F, wells and springs may contain high concentration of As, Li, B and Pb.

• H₂0 high in Mo and/or S can induce Cu deficiency.

• Cd in rivers from industrial sources in Japan, high rice Cd content.

• Atmosphere, a minor pathway of trace elements, except Pb.

• Areas close to sources of Pb emissions from manufacturing or auto exhaust result in high plant concentrations.

Saline Waters for Livestock and Poultry

• Ions most common in saline waters are Ca, Mg, Na, Cl, and sulfate.

NRC (1974) Guidelines for Saline Waters

Total Soluble Salts	Effect
1000 mg/liter	No problem
1000 - 2999 mg/liter	OK, maybe slight temporary diarrhea
10,000 mg/liter	Can not be used

• Hardness confused with salinity, but differences.

• Saline waters containing Na salts can be soft.

• High levels of Ca and Mg (divalent cations) are largely responsible for hardness.

Soil as Sources of Minerals

• Soil ingestion results in a direct soil-animal effect.

• Although highly variable, livestock obtain some minerals from soil.

• From New Zealand (Healy, 1974), annual soil ingestion:

a. sheep (75 kg)

b. dairy cattle (600 kg)

• Soil Mo, Zn, Fe and Cd can result in Cu deficiency (Suttle et al., 1975).

• Longhand et al. (1982) concluded that stocking rate and soil ingestion decreased Se and Cu concentrations in tissues.

Comparison of Element Intake by Sheep per Day from Clean and Contaminated Pasture^a
	Element Intake/day
Trace Elements (mg)	Clean Pasture	Contaminated Pasture (2% wet basis)
Iron	150	4150
Manganese	60	160
Zinc	18	24
Copper	4.2	6.2
Molybdenum	0.6	0.7
Cobalt	0.18	0.68
Selenium	0.06	0.21
Iodine	0.3	0.8
^aModified from Healy (1973)

Soil Characteristics

• Young alkaline geological formations higher in trace minerals vs old worn out leached soils.

• In tropical regions under conditions of heavy rainfall and high temperature, marked leaching and weathering of soil minerals.

• In weathered soils on well-drained sites, only a fraction of trace elements present are available to plants.

• Co content of plants on water-logged soils was 10 to 20 times greater than controls.

Effect of Soil Ingestion on Health

a. Providing a source of essential elements.

b. Acting as a physical conditioner, improving performance from various rations.

c. Affecting availability of dietary elements in the digestive tract.

d. Causing sand impaction in underfed livestock.

e. Having an abrasive effect, causing erosion of ruminal epithelium and tooth wear.

f. Supplying undesirable materials, such as pesticide residues or heavy metals that may be absorbed in surface soil particles.