Selenium, Choline, Vitamins, Minerals, and Proteins in Animal Nutrition

Posted on Feb 21, 2025 in Human Nutrition and Dietetics

Vitamin E and Selenium in Animal Nutrition

Vitamin E:

• Inhibits accumulation of damaging free radicals (Vitamin A, Beta-carotene, and Vitamin C are also antioxidants).
• Enhances the body’s immune response (defense against cancer).
• Protects Vitamin A and spares Selenium (Se).
• Inhibits conversion of nitrites (present in smoked, pickled, and cured food) to nitrosamines (strong tumor promoters) in the stomach.

Selenium (Se):

Types of Toxicity:

1. Blind staggers type (with as low as 2-5 ppm): Wandering aimlessly, stumbling, impaired vision, and signs of respiratory failure.
2. Alkali disease type (with as low as 2-5 ppm): Lameness, hoof malformation, loss of hair, and impaired reproduction.
3. High levels (over 40 ppm): Sudden death or severe distress (labored breathing, ataxia, abnormal posture, diarrhea, etc.).

As a Nutrient:

1. Established as an essential nutrient in the late 1950s:
   • Prevented liver necrosis in rats.
   • Prevented exudative diathesis in chicks.
   • Prevented white muscle disease in ruminants, etc.
2. In the early 1970s, Rotruck et al. (1973; Science 179:588) discovered that Se was an integral part of glutathione peroxidase.

Selenium Deficient Areas

Selenium deficient areas of the US are much larger than those areas that are Se-toxic.

Other Functions of Selenium

• May play a role in electron transport (e.g., isolated a selenoprotein that resembles cytochrome C) in heart and muscle, which was absent in Se-deficient animals.
• A specific selenoprotein in spermatozoa may serve as a structural protein for mitochondria, or as an enzyme.
• May play a role in RNA because Se can be incorporated into purine or pyrimidine bases.
• May have a role in prostaglandin synthesis and essential fatty acid (EFA) metabolism.
• May be involved in the immune response.

Selenium Absorption and Excretion

Dietary concentrations, Se status of animals, and the form affect the rate of absorption:

1. Greater absorption in a deficient state.
2. Organic compounds, selenide (-2), and elemental Se (0) are absorbed less efficiently.
3. Selenite (+4), selenate (+6), and selenomethionine are highly available sources.

Absorption Rate:

1. Swine: No absorption at the stomach and first part of the small intestine (SI), and the greatest absorption at the last part of the SI, cecum, and colon. About 77% of oral Se was retained in one study.
2. In rats, soluble Se compounds are efficiently absorbed from the GI tract (e.g., 92 and 91% for selenite and selenomethionine, respectively).
3. In humans, apparent absorption of dietary Se ranges from 55 to 70%.
4. Ruminants: Less efficient vs nonruminants (e.g., only 30% in sheep) because Se may be reduced to insoluble compounds in the rumen.

There seems to be no homeostatic control of Se absorption.

Excretion:

1. Via urine, feces, and exhalation (primary route in Se toxicity).
2. Urinary excretion: Primary route in nonruminants and humans (excretion rate is closely related to dietary intake).
3. Fecal excretions: Contain unabsorbed dietary Se, small amounts of Se excreted via bile, pancreatic, and intestinal secretions.
4. In general, ruminants excrete Se in the feces, possibly because rumen microbes reduce Se to an unavailable form, increasing excretion in the feces.

Selenium Deficiency

• Sudden death is a prominent feature of the deficiency.
• Based on necropsy: Massive hepatic necrosis, edema in lungs, stomach submucosa, etc., paleness and dystrophy of the skeletal muscle (white muscle), and mottling and dystrophy of the myocardium (mulberry heart).
• Impaired immune response.
• Impaired reproductive performance and milk production.

Assessing Selenium Status

• Analysis of plasma or serum Se.
• Analysis of whole blood Se.
• Assay of plasma or serum GSH-Px activity.
• Assay of whole blood GSH-Px activity.
• Measurement of urinary Se excretion.
• Analysis of Se in skeletal muscle.
• Se contents in animals (wet basis).

Selenium Requirements

• Must consider variations in the Se content of feedstuffs, antioxidant levels in the diet (including vitamin E).
• In swine and poultry, the Se status of the dam influences the requirement for nursing/weanling pigs and chicks.
• The amount of supplemental Se permissible is regulated in the US [maximum of 0.3ppm].
• Plasma glutathione peroxidase level is a reliable index of the Se status of pigs.

Amelioration of Selenium Toxicity

• L-Cysteine and its derivatives showed ameliorative activity.
• Arsenic (As) compounds totally corrected performance depressions, but did not lower liver Se.

Choline in Animal Nutrition

Functions of Choline

In Lipid Metabolism:

1. A component of phospholipids (important in the cell structure):
   • Phosphatidylcholine (lecithin): A part of the cell membrane, and also lipid transport moieties.
   • Sphingomyelin: Found in brain and nerve tissues.
2. Involved in phosphorylation and mobilization of long-chained fatty acids from the liver, and in oxidation of fatty acids in the liver.

Other Functions:

1. Involved in the formation of acetylcholine.
2. Serving as a source of labile methyl groups.

Is Choline a Vitamin?

• Tentatively classified as a B-complex vitamin.
• Choline is required by animals in greater amounts than others and functions as a structural constituent rather than as a coenzyme.

Choline Deficiency

Signs in Poultry:

1. Poor growth.
2. Perosis (slipped tendon).

Signs in Swine:

1. Poor growth and unthriftiness.
2. Poor conformation.
3. Lack of coordination.
4. Fatty infiltration of the liver.

Choline Requirements

• Requirements can be met by dietary supplemental choline or from typical feedstuffs, and choline synthesis in the body.
• Affected by dietary methionine level, folacin level, vitamin B12, and others.

Supplemental Dietary Lipids

Dietary Lipids in General

• High-energy diets for poultry.
• Energy density and energy intake.
• Dietary lipids in pigs.
• Extra caloric effect.

Supplemental Dietary Lipids in Pigs

• Baby pigs.
• Grower-finisher pigs.
• Gestating and lactating sows.

Feed Grade Lipids

Terminology

• Total fatty acids (TFA).
• Free fatty acids (FFA).
• Moisture.
• Insoluble impurities.
• Unsaponifiable matters.
• Iodine value.
• Fat stability.
• Titer.
• Color.

Feed Fat Categories

• Animal fat.
• Poultry fat.
• Blended feed grade animal fats.
• Blended animal and vegetable fats.
• Feed grade vegetable fat.

Rancidity

• Oxidative rancidity.
• Hydrolytic rancidity.
• Antioxidants.

Protein in Animal Nutrition

General

• Protein is a principal constituent of organs and soft structures of the animal body.
• Includes an enormous number of closely related, yet physiologically distinct groups of substances.
• For animals, a liberal and continuous supply of protein is needed throughout life.

Functions of Protein

• Enzymes.
• Hormones.
• Structural constituents.
• Transport.
• Protection.
• Coordination of motion.
• Storage of energy.
• Storage.

Determination of Protein – Kjeldahl Method

• Estimate the protein content based on the nitrogen content.
• Advantages and disadvantages.
• Calculation of the protein content from the N content.

Direct Determination – The Lowery Method

• Widely used for the analysis of proteins in tissue samples.
• Involves two steps: Biuret reaction and Folin-Ciocalteu phenol reagent.

Protein and Amino Acids

Protein Structure

• Primary structure.
• Secondary structure.
• Tertiary structure.
• Quaternary structure.

Classification of Protein

• Simple proteins.
• Conjugated proteins.
• Fibrous or globular proteins.
• Classifications by solubility.

Protein Digestion

Reasons for Protein Digestion

• To get through the membrane.
• To resynthesize necessary proteins.
• For the immune process/purpose.

Gastric Digestion

• HCl and pepsin.
• Importance of gastric digestion.

Intestinal Digestion

• General.
• Intraluminal digestion.
• Membrane and intracellular digestion.
• Digestion at the large intestine.

Digestibility

• Apparent digestibility.
• True digestibility.
• Apparent or true digestibility.
• Apparent fecal vs ileal digestibility.
• Some factors affecting protein digestibility.

Absorption of Amino Acids and Peptides

Digestion of Protein – Any Exception?

• Certain neonatal mammals.
• Closure.

Mechanisms of Absorption

• General.
• Four distinct amino acid transport systems.
• Absorption of peptides.
• Rate of absorption.
• Nutritional significance of peptide transport.

Protein Metabolism in General

Amino Acids

• Protein metabolism.
• Three major points.

Fate of Absorbed Amino Acids

• Anabolism.
• Catabolism.
• Specific functions of each individual amino acid.

Protein Synthesis and Turnover

Protein Synthesis

• General.
• Protein synthetic rate.

Protein Turnover

• Possible reasons.
• Factors influencing body protein turnover/metabolism.

Amino Acid as a Source of Energy

General

• Metabolic pathways.
• Classification of amino acids.

Transamination and Deamination

General

• These processes are necessary.
• Transamination.
• Deamination.

Vitamin B6

Chemical Structure

• Pyridoxine, pyridoxal, and pyridoxamine.
• Pyridoxal phosphate (PLP).

Functions of Vitamin B6

• PLP is a co-enzyme for many enzymes involved in amino acid metabolism.
• Also involved in carbohydrate and fatty acid metabolism.
• Essential for the formation of niacin from tryptophan.

Vitamin B6 Deficiency

• Swine.
• Poultry.
• Fish.

Requirements and Supplementation

• Widely distributed in feeds and food.
• Supplementation.

D-Isomers, Alpha-Keto, and Alpha-Hydroxy Analogs

• Inversion.
• Utilization.

Excretion of Nitrogen

• Mammals.
• Fowl.
• Urea Cycle.

Special Functions of Amino Acids

• Arginine.
• Aspartic acid.
• Cysteine.
• Glutamic acid.
• Glutamine.
• Glycine.
• Histidine.
• Serine.
• Tryptophan.
• Tyrosine.
• Methionine.

Folacin, Vitamin B12, Cobalt, and Sulfur

• Interrelationships in the metabolism of methyl groups.
• Folacin.
• Vitamin B12.
• Cobalt.
• Sulfur.

Essentiality of Amino Acids

• Essential or indispensable amino acids.
• Nonessential amino acids or nonessential N.

Amino Acid Disproportion

• Amino acid deficiency and imbalance.
• Amino acid toxicity.
• Amino acid antagonism.
• Amino acid interactions.
• Factors affecting amino acid disproportion.

Protein Quality

• Protein quality is not synonymous with the efficiency of utilization.
• Assessing protein quality for ruminants.
• Metabolizable protein or amino acids.

Protein and/or Amino Acid Requirements

• Protein requirements.
• The use of crude protein values.
• Ways to express the requirement.
• Estimating the requirement.
• Requirements.
• Protein/Amino Acid Sources.

Ideal Protein

• Definition of ideal protein.
• Should be the most efficient protein or diet.

Amino Acids and Energy

• Three possible N and energy relationships.

Amino Acids and Environment

• Adequate daily amino acid intake is the key.

Energy: Energy Metabolism and Vitamins/Minerals

Various Systems

• Energy.
• Gross Energy (GE).
• Digestible Energy (DE).
• Metabolizable Energy (ME).
• Net Energy (NE).
• Total Digestible Nutrients (TDN).
• DE, ME, and TDN systems.
• NE system.

Choosing the System

• The system should be precise, simple to apply, and easily estimated.
• TDN.
• DE or ME vs NE.
• Relationships between DE and ME.

Energy Requirement

• Energy requirement of growing animals.

Growing Animals and Energy

• Restricting energy intake or limit-feeding.
• Interaction of energy and amino acids.

Thiamin (Vitamin B1)

• Considered to be the oldest vitamin.

Riboflavin (Vitamin B2)

• Water-soluble factor or factors promoted growth and prevented beriberi.

Niacin

• Third vitamin to be discovered from the vitamin B complex.
• Pellagra.

Pantothenic Acid

• Previously called a chick anti-dermatitis factor.

Biotin

• Serves as a prosthetic group for a number of enzymes.

Chromium

• Chromium and Metabolism.

Bone and Vitamins/Minerals

• Bone Structure.
• Abnormal Bone Metabolism.
• Factors Affecting Bone Metabolism.

Calcium and Phosphorus

• Additional Functions.

Other Minerals in Bone

• Magnesium.
• Manganese.
• Zinc.
• Fluorine.
• Vitamin D.

Vitamin A

• Necessary for the support of growth, health, and life of higher animals.
• Defects in bone growth.

Vitamin C

• Scurvy is a disorder associated with inadequate vitamin C intake.
• Functions are probably related to its reversible oxidation and reduction characteristics.