Minerals: Small Ruminant Series
Minerals: Small Ruminant Series
Minerals: Small Ruminant Series
Small
Ruminant
Series
Minerals
by Dr. Rick Machen
Associate Professor & Extension Livestock Specialist
Texas Agric ultur al Exte nsio n Service, Uvalde
As mentioned in previous articles, the nutrient requirements of goats are not well defined -
certainly not as well defined as those for beef and dairy cattle, sheep, swine or poultry. Much of
the research with goats has involved dairy goats in confinement-fed conditions. Very little work
has been done with free grazing goats.
Research projects of this type are quite expensive and time consuming. Consequentl y,
many of the mineral specifications used in the development of goats feeds are extrapolated from
other species or are the result of practical experience.
Plant content of mineral elements is dependent upon the interaction of a number of factors
including soil, plant species, stage of maturity, yield, pasture management and climate. Most
naturally occurring mineral deficiencies in herbivores are associated with specific regions and are
directly related to soil characteristics.
Young and alkaline geological formations are tend to be more abundant in most trace
elements than the older, more acid, coarse, sandy formations. Significant leaching and weathering
of soi ls i n tropical regions, under conditions of heavy rainfall and high temperature, accentuate
mineral deficiencies.
It is generally accepted that forbs (weeds) and legumes are richer in a number of minerals
than are grasses. For example, legumes contain over twice as much calcium as grasses and are
more than adequate to meet animal requirements.
As plants mature, mineral content declines due to the natural dilution processes and
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translocation of nutrients to the root system. Micromineral concentration of forages across
growing seasons is generally less variable than macromineral concentrations.
Mineral Nutrition
Minerals are divided into categories relative to the amount thought to be required in the
diet of ruminants. The seven major essential minerals (in addition to carbon, hydrogen, oxygen
and nitrogen; refer back to article on protein) and nine minor essential minerals are listed in
Table 1. Macromineral requirements are usually expressed as a percent of the diet while
micromineral requirements are typically quoted in parts per million (ppm) of the diet.
Other minerals which are possibly essential at very low levels include chromium, nickel,
vanadium, silicon, tin and arsenic.
Practical determination of animal s mineral status is often very difficult. Blood analysis is
a poor indication of mineral status for many of the minerals. The body has a significant storage
capability for many of the minerals (for example, the calcium in bone). Therefore, until body
reserves are depleted, symptoms of deficiency may not be apparent. More involved processes like
liver biopsy may be required to determine the mineral status of an animal.
Macrominerals
Following is a very brief list of some of the functi ons of macro- and microminerals in the
body. Obviously, space does not allow a detailed description of each mineral and its numerous
functions throughout the body.
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Calcium (Ca) Most abundant mineral in the body; 98% is found in the bones and teeth.
Functions in blood clotting, membrane permeability, muscle contraction,
nerve function, cardiac regulation and enzyme activation. Vitamin D is
required for active absorption. As dietary Ca intake increases, absorption
is reduced. Cereal grains (corn, oats, milo, wheat, barley) are low in Ca.
Phosphorus (P) The most deficient mineral throughout the world. Must be supplemented to
livestock grazing native forages in order to meet requirements. Eighty
percent of P in the body is found in the bones and teeth. Functions with Ca
in bone formation, is essential for cell growth, energy utilization,
maintaining acid:base balance, is a component of DNA and is required by
rumen microbes for optimal growth and activity. The greatest bang for the
buck in mineral supplementation is generally associated with providing P.
Oilseed meals are an excellent source of P. Palatability is low.
Potassium (K) The third most abundant mineral in the body. Essential for the maintenance
of osmotic and fluid balance in the body. Cereal grains and mature,
weathered forages have low K contents. Oilseed meals and green, growi ng
forages are an excellent source.
Magnesium (Mg) Sixty-five to 70% is found in the skeleton. Functi ons in carbohydrate and
fat metabolism and is a catalyst i n over 300 enzyme systems. Like
phosphorus, Mg is bitter and is sometimes used to limit consumption of
mineral supplements.
Sodium (Na) Usually considered with chlorine (Cl). Sodium chloride (NaCl) is salt.
Both are critical electrolytes in body fluids. Sodium functions in amino
acid and glucose transport and muscle contractions. Chlorine is a
component in hydrochloric acid formation and activation of amylase, a
starch digesting enzyme.
Sulfur (S) Two amino acids (methionine, cysteine) and two B- vitamins (biotin,
thiamin) contain S. Also functions in maintaining bone, cartilage, tendon
and blood vessel integrity (contained in chondroitin). Note: Rumen
microbes are capable of synthesizing all of the sulfur containing compounds
from inorganic S. High S levels in the diet antagonize the use of copper and
molybdenum.
Micr ominerals
Copper (Cu) Copper is second only to phosphorus in severity of deficiency throughout
the world. Copper is involved in hemoglobin formation, enzyme systems,
nervous and immune system function. Copper interacts with iron, zinc,
sulfur and molybdenum in antagonistic relationships. Sheep are very
susceptible to copper poisoning as dietary Cu levels approach or exceed 20
ppm.
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Iodine (I) Primarily involved in the thyroid
hormones that regulate rate of Table 2. Macrominerals
metabolism. Deficiency usually not and their requirements.
a problem except with goitrogenic
forages or feedstuffs like turnips, % of diet
kale, rape, white clovers.
Cottonseed and soybean meal have Calcium 0.20 - 0.80
some goitrogenic properties. Use of Phosphorus 0.20 - 0.40
iodized salt has eliminated I
deficiency problems. Potassium 0.50 - 0.80
Selenium (Se) Involved in the prevention of white muscle disease. The requirement for Se
is very close to its toxicity level.
Mineral Requirements
Mineral requirements for the macro- and microminerals are shown in Tables 2 and 3,
respectively. Notice the requir ements are presented as ranges and not absolute numbers. As
previously mentioned, mineral requirements are not well defined in the scientific literature and are
influenced by many factors. These tables are presented here only for reference purposes, not as
standards against which to hold those who develop mineral supplements.
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Mineral Supplementation
Direct methods of supplementation include adding deficient minerals to the drinking water,
oral drenching, injection, ruminal boluses, force-feeding in protein/energy feeds and free-choice
supplementation.
Of these, free-choice supplementation is the most w idely used method for grazing
ruminants. Development of a balanced, palatable, free-choice mineral with predictable
consumption by goats is difficult and requires significant practical experience.
Mineral consumption varies daily, across animals within the herd and across seasons of the
year. Forage quality, dry matter content, degree of hunger and level of boredom seem to influence
the amount of mineral consumed.
Observations
If it is not broken, do not attempt to fix it! If nutrient requirements are currently being
satisfied and the goat herd is performing (growth, reproduction, milk production, appearance) as
expected, changes in the nutrition program are not warranted.
Balanced fee ds & other supplements. Most commercially prepared goat feeds are
balanced for the entire mineral profile and do not require mineral supplementation. Goat s
mineral requirements can be met without feeding a mineral supplement. Mineral supplements are
most often warranted when goats are grazing, especiall y when forage is dormant, mature and/or
weathered.
Salt - both White and Yellow . Despite a popular opinion within the livestock industr y,
neither of these qualify as a mineral supplement. In most cases, the sodium and chlorine
requirements are met without feeding salt.
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Animals, like humans, like the taste of salt. Salt is
sometimes used to limit the consumption of free-choice Table 3. Microminerals
oil seed meal and/or ground cereal grain supplements. If a and their requirements.
mineral supplement is offered, do not offer free-choice salt.
ppm
Cost vs. consumption. On a $/50 lb sack basis,
mineral supplements are expensive when compared to other Copper 10 - 20
feeds or supplements. Remember, daily consumption Zinc 20 - 33
should be relatively low. A rule of thumb for daily mineral
consumption by mature goats on pasture is 0.75 -1.0 oz or Iron 30 - 50
25-30 g per day. Consumption may be excessive
Manganese 20 - 40
immediately after introduction to mineral, but will generally
level off after 10-14 days. Mineral must be consumed if it Iodine 0.10 - 0.80
is to benefit the goats.
Molybdenum 0.50 - 1.0
Soil sulfur. Areas near coal-fired power plants and Cobalt 0.10 - 0.20
pastures w ith a long history of fertilization with sulfate
fertilizers may have soils with unusually high sulfur content. Selenium 0.10 - 0.20
As previously mentioned, excessive dietary sulfur can
Source : Personal expe rience and
antagonize the availability of other minerals in the diet. experimental data.
If you have questions concerning mineral nutrition for your goats, consult a knowledgeable
professional nutritionist. Your commercial feed manufacturer or an Extension professional can
provide valuable assistance.
SRS-5
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