Dr bob Scott was a veterinarian and animal nutritionist practising in the USA. He was able to relate health issues experienced in all species of cattle, including dairy to that we experience in New Zealand and Australia when grazing pasture. I personally received excellent advice from Bob which has enabled me to help many farmers with problems associated with grazing fresh pasture and nutritional information with both pasture and supplementary feeding.

Bob was a man ahead of his time when most here in NZ thought that the health issues we experience were peculiar to pastures. When in fact feedlot and barn feeding dairy herds had the same issues, the only difference is the way in which the problem is arrived at.

Bicarbonate of Soda

A good example is that based on his advice I introduced supplementing bicarbonate of soda into my clients herds with great success.

Vitamin A: to help prevent lameness was another of his suggestions. He pointed out that high pasture protein(Nitrogen) suppresses thyroid activity and reduces the conversion of plant protein to vitamin A resulting in foot scald. This preventative treatment is very successful but still not accepted in NZ or Australia

Here I have posted some of his lessons, although a little technical, they do provide valuable information

LESSON 1

Minerals

• -Minerals are all inorganic elements.

Not all elements are minerals (C, H, O and N).

Mineral elements cannot be decomposed or synthesized by ordinary reactions.

Total mineral or inorganic content of feed is total ash remaining after high temperature burning of organic matter.

Ash may not measure total inorganic matter, some S, Se, I, F and even Na, Cl may be lost during combustion.

Mineral classification:

• -Needed in large amounts - major or macrominerals:
• - Ca, P, K, Mg, Na, S and Cl.

Trace or micro-minerals:

a. Traditional, Cr, Co, Cu, I, Fe, Mn, Mo, Se and Zn

b. Discovered since 1970 - As, B, Pb, Li, Ni, Si, Sn, V and Rb.

c. Fluorine (F) included because of proven benefits for dental health and suggested role in bone integrity.

• -Humans and animals consuming typical diets concerned with only 16 minerals elements.

Required:

Ca, Cl, Cr, Mg, P, K, Na, S, Co, Cu, I, Fe, Mn, Mo, Se and Zn.

Toxic:

Cu, F, Mn, Mo and Se.

Newer Trace Elements:

Ni, Sn, Si, V, F, As, Al, Pb, and Rb.

Discovered since 1970 to the present using highly purified diets and clean environments.

• -The newer trace elements are essentially based on growth and other effects with animals using improved procedures for purified diets and raising animals in metal-free isolator systems.
• -An additional 20-30 trace elements found in feeds and animal tissue, are they merely contaminants?
• -One of the latest essential element is rubidium (Rb). Female goats fed < 280 g/kg Rb (vs 10 mg/kg), abortion lower birthweight and mortality among kids (Anke et al., 1997).
• -In human nutrition F considered a "beneficial element".
• -Skeletal abnormalities in female goats and poor growth in their offspring after 10 generations of low F diets (Anke et al. 1997).

Cations or anions (valance number grouping in periodic chart).

Minerals classified as cations:

Ca, Mg, K, Na, Fe, Mn, and Zn.

Anions or anionic groupings :

Cl, I, Phosphate (PO₄³), Molybdate (Mo O₄²); Sulphate (SO₄²)

Monovalent cations:

K and Na, high absorption rate with major interrelationships.

Divalent cations:

(e.g., Co, Mg, Zn) - much lower absorption

Buffers

• -Minerals sometimes fed to dairy and feedlot cattle beyond requirements act as buffers.
• -Buffers reported to improve feed intake, milk production, milk composition and animal health.
• -Buffers control excess hydrogen and rate or passage of liquids from the rumen.
• -Combat milk fat depression.
• A lot of farmers use (e.g., NaHCO₃ – sodium bicarbonate)
• -NaHCO₃ used to restore blood pH from metabolic acidosis.
• -Na propionate also effective.

Elemental Composition of the Body

Ca - 46% of total minerals

P - 29% of total minerals.

K, S, Na, Cl, and Mg - 25% of total minerals.

• -Essential trace elements < 0.3% of total.
• -80-85% of total minerals located in bone (mainly, Ca, P, Mg).
• -80% of I thyroid gland.

General Functions of Minerals

1. Constitutes bone.

2. Maintenance of regulation of viscosity, diffusion and osmotic pressure.

3. Regulating acid-base equilibrium.

4. Component or activator of enzymes and/or other biological units or systems.

Mineral Requirements and Tolerances

• -Two main sources of information for animals.

National Research Council's Nutrient Requirement Series.

British (ARC) Nutrient Requirements of Farm Livestock Series.

• -For humans, Recommended Dietary Allowances (RDA)
• -ARC 1980 Mineral Tolerance of Domestic Animals.

Requirements expressed as:

Amounts per day or per unit of product.

Proportions of dry matter of diet consumed.

• -There is no single requirement for a mineral or a single safe maximum tolerated level.
• -Instead, there is a series of required levels and also tolerance levels that vary from animal to animal and from day to day in the same animal.
• -Fortunately, it is unnecessary to determine the requirements and tolerance levels so precisely.
• -Homeostatic regulation protects against marginally deficient or excessive intake by changing efficiency of absorption and excretion.

For example:

An Fe-deficient animal absorbs more Fe than one with adequate status.

Most trace minerals reduced in milk when dietary intakes are low.

To conserve Ca, shell strength can be reduced.

• -Minimum intakes must maintain mineral reserves and amounts lost in products (meat, egg, milk).
• -Mineral requirements dependent on level of productivity.
• -Improved practices that lead to improved milk, egg and wool production, growth rates mineral needs.

Criteria of adequacy and priority:

e.g., pigmentation and keratinization of wool, first effect of Cu deficiency.

Therefore, wool quality higher requirement than growth.

Examples:

Zn requirement for spermatogenesis and testicular development in sheep than growth.

Mn requirements for fertility higher than growth.

Not all pigs had Se-vitamin E deficiency.

Goiter in calves and skin lesions (Zn) affected a small percentage of cattle.

Maximum Tolerance Levels

All substances can be toxic.

Examples:

Water consumed at toxic levels.

Oxygen destroys nutrients (e.g., vitamins A and E).

Maximum tolerable level - dietary level that will not impair animal performance and should not produce unsafe residues in human food derived from animals.

There are no toxic elements, per se, but there are toxic concentrations of elements.

Toxic level of most macro minerals is between 2-10 times the requirement.

Toxic level of trace minerals is high variable, and can range between 4 to 1500 times the requirement.

e.g., Co, a tolerance ratio of 100, requirement 0.1, toxicity 10.

Factors Influencing Mineral Tolerance

1. Physiological state, age and level of production.

2. Breed and adaptation.

3. Biological availability and interrelationships.

4. Intake and seasonal effects (e.g., drought conditions can increase Se toxicity).

Methods of Mineral Analyses

Atomic absorption spectrophotometry, emission spectrometry and neutron activation powerful analytical tools.

Less time and labor for analyses.

Sampling -- because of low levels of trace elements high potential for contamination (sampling, storage, handling and analysis).

Significant levels of trace elements in reagents, air, hair skin, clothing.

Want stainless-steel blades, but even these contain Cr, Ni, Mn, and Fe contamination.

Analytical Techniques

a. Atomic absorption spectrophotometry (AAS).

Good sensitivity, precision, low cost.

Lamps -- amount of light absorbed at wavelength proportional to element concentration.

Two types -- Flame (many elements) and Graphite furnace (Co, Mo, Mn).

Graphite furnace more sensitivity, e.g., Co 0.01 for flame 0.00004.

b. Neutron activation analysis

A multi-element technique.

Sample and standard bombarded and made radioactive.

Count radiation with multi-channel analyzer.

c. Inductively coupled plasma optical emission spectroscopy (ICP-OES).

d. Inductively coupled plasma mass spectrometry (ICP-MS).

e. Isotope dilution mass spectrometry

Sample treated with enriched isotope (e.g., 206P).

f. X-ray fluorescence spectrometry

Characteristic x-ray emission wavelength

g. Conventional Methods (AOAC)

Examples:

Colorimetric for P

Fluorometric for Se

Sample Digestion (remove organic matter)

a. Dry ashing - high temperature using muffle furnace.

b. Wet oxidation-digestion - small amounts of acid -- need acids and reagents of high purity.

Calibration Standards

• -Concentration in sample to series of standards.
• -Validated for accuracy with certified reference material.

e.g., National Bureau of Standards (Bovine liver, Orchard leaves).

ASPAC ACCREDITATION SAMPLES

Detection of Mineral Status

• -Clinical signs, soil, water, plant and animal tissue analyses.

• -Incidence of mineral deficiencies and toxicities.
• -Deficiencies and imbalances for livestock are reported from all world regions.

Methods for Estimating Mineral Bioavailability (Ammerman, 1995)

• -Absorption and chemical balance.
• -Absorption is not always related to bioavailability

Examples:

Iodine as 3,5-diiodosalicylic acid utilized by rats but not cattle. Cattle could not remove from organic molecule.

Picolinic acid Zn absorption in rats by 60%, but increased urinary excretion by same amount.

Very few absorption studies with micro-elements.

a. Need purified diets.

b. Even slight contamination a problem.

c. Endogenous sources.

• -Apparent absorption - limited for elements where feces is major pathway of excretion (Ca, P, Zn, Mn and Cu).

• True absorption to correct for portion of element that was previously absorbed then excreted back into GI tract designated as total endogenous fecal excretion or metabolic fecal excretion.

TFE = Total fecal excretion

TEFE = Total endogenous fecal excretion

• Urinary Excretion

Urine is major pathway for Mg, I and K, but minor for Mn, Fe, Zn and Cu.

d. Net retention (net availability) -- is total intake minus total excretion (fecal + urinary)

e. Growth and specific tissue response.

A growth trial - requires use of semi-purified diets.

Young chick is an ideal assay animal.

a. limited nutrient stores

b. lack of or minimal coprophagy

c. rapid rate of growth

d. high nutrient demand

f. Bone development

Bone ash in very young chickens for Ca and P bioavailability.

e.g., total tibia ash or tibia ash of dry fat-free bone. (tibia = shine-bone)

Breaking strength (force required to fracture).

g. Essential compounds or enzymes

Fe - haemoglobin

Co - vitamin B₁₂

Se - glutathione peroxidase

Cu - cytochrome c oxidase

h. Tissue accumulation

Accumulation of the mineral element in various target organs (e.g., liver, bone)

Biological availability of several micro-elements for ruminants and poultry have been estimated by tissue uptake following high dietary level, short-term supplementation (Henry et al., 1986).

Advantages -- fewer animals required to test, due to higher dietary levels. Don't need purified diets.

Disadvantage -- what about homeostasis, do sources respond differently at the physiological requirement vs near toxicity?

Use of Isotopes.

Accumulation of radioactive or stable isotopes in target organ used to estimate absorption.

History of Mineral Nutrition

• -Prior to the 20^th century, little attention was given to mineral nutrition of domestic animals.
• -Armsby (1880), in his book Manual of Cattle Feeding, concluded: "In practice, in feeding animals, a lack of necessary minerals is scarcely ever to be feared. They are indeed generally in excess. Only common salt is in certain respects an exception."
• -Mineral deficiencies must date from antiquity. Wars were fought, and children were sold into slavery to obtain salt.
• -Only when methods were devised to identify and measure mineral elements in tissues and feeds and to characterize responses to pure elements could essentiality be established.
• -Bone chewing by cattle recorded in Africa (1780) and in Paraguay (1838).

• -Phosphorus deficiency clarified by Theiler et al., (1924) in South Africa.

Chronological History

29 BC The Fall of Thebes was hastened by large livestock losses caused by unknown factors while grazing luxuriant pastures.

40-120 AD Salt fed to domestic livestock.

1295 Signs of selenium toxicity described by Marco Polo in China.

1680 Sydenham treated anaemia with iron filings.

1770 Scheele reported bones contain calcium phosphate.

1811-25 Courtois, Coindet and Boussingault found iodine cure for goitre.

1842 Chossat found pigeons required calcium for growth.

1880 Forster showed dogs fed only meat had deficiencies.

1905 Babcock studied salt requirement for cattle.

1919 Kendall isolated thyroxin and found it contained 65% iodine.

1920 The use of purified diets.

1922 McCollum found rickets caused by vitamin D in addition to calcium and phosphorus.

1924 Theiler demonstrated phosphorus deficiency in grazing cattle.

1928 Hart showed copper in addition to iron needed for haemoglobin.

1931 Neal, Becker and Shealy established copper as essential element for ruminants.

1935 Franke and Potter identified selenium as responsible for alkali disease.

1935 Underwood and Filmer - colbalt deficiency in sheep.

1937 Becker et al. established salt sick in Florida, deficiencies of cobalt, copper and iron.

1938 Ferguson et al. reported a severe diarrhea for grazing cattle due to excess molybdenum.

1938-42 The use of radioisotopes to study mineral metabolism.

1946 Moulton - fluorine in water prevented dental cavities.

1948 Rickes et al., Smith showed cobalt part of vitamin B₁₂.

1955 Tucker and Salmon discovered zinc prevented Para keratosis.

1957-59 Many workers - selenium prevents exudative diathesis and white muscle disease.

1959 Schwarz and Mertz - chromium essential.

1970- To present. Most recently discovered elements

Essentiality established with highly purified diets and metal-free isolator systems.