Equine Nutrition - Proteins, Amino Acids, Lipids, Minerals

Proteins

major component of tissue, second to water

Indispensable amino acids

required, cannot be synthesized to meet metabolic demands

10 indispensable AA in horses

Arginine

Histidine

Isoleucine

Leucine

Lysine

Methionine

Phenylalanine

Threonine

Tryptophan

Valine

Lysine

first limiting amino acid (runs out first), present in diet in the lowest amount

Midgut

auto digestion and absorption of CHO-H, AA, and lipids. rate of digestion transit is influenced here. By pass

Ionophores: Monensin, Lasalocid

Lethal for horses

Dietary essential fatty acids

Fatty acids needed because horse cannot synthesize themselves; Linoleic Acid, Linolenic Acid

Linoleic Acid

18:2, n-6 , Omega-6 , immune support , oil

Linolenic Acid

18:3, n-3 , Omega-3 , anti-inflammatory, fish

Why is high concentrations of soybean oil not appropriate to feed hindgut fermenters?

High amounts disrupts microbial fermentation in the cecum and colon by physically blocking microbial access to fiber

Concentrates formula

Smallest, as ADF increases, DE decreases

Forages Formula

Longest formula

Fats/Oils

Only formula with division

Lysine requirement

CP x 4.3%

Protein

made of individual subunits called AA

Crude protein is calculated as

N concentration of the feed x 6.25

Coprophagy

Intentional consumption of feces, essential for hindgut fermenters in order to digest and absorb microbial crude protein

Indication of a dietary fatty acid deficiency

If clinically diagnosed fat soluble vitamin deficiencies present

Digestible

amount of energy a species can take

Sources of minerals

forages, concentrations, supplements, water

Kinds of dietary levels of minerals

requirement, recommendation, max tolerable, toxicI

Influence

total intake to meet but not exceed, ratios and interactions between minerals, form affecting bioavailability

Antagonism

negative interactions between minerals (ex. high iron interferes with zinc and copper absorption)

Synergism

positive interaction between minerals (ex. vitamin D enhances Calcium absorption)

Inorganic

Less bioavailable, ex. oxides, sulfates

Organic

More and better absorption, ex. chelates

Assessments

blood, soft tissue, hair

Blood

somewhat useful but not reliable due to tight homeostatic regulation

Tight Homeostatic regulation

horses ability to maintain a stable level of certain substances, even if total body supply is too high or low, ex. Ca and P control

Soft tissue

very good indicator of long term and trace minerals, ex. liver via biopsy

Hair

not reliable due to external substances possibly messing with results

Macrominerals

Calcium

Phosphorus

Potassium

Sodium

Magnesium

Chloride

Sulfur

Calcium

Function: structural, muscle contraction, blood clotting, enzymatic regulation, recommended: 0.20% DM

Calcium homeostasis

Vit D (Ca-binding), Parathyroid hormone (bone resorption, decrease Ca excretion), Calcitonin (blocks bone resorption)

Phytic Acid

binds to P, reduced absorption

Bioavailability

measure of mineral utilization to support physiological functions

Factors affecting bioavailability

species, genetics, sex, age, metabolic function (growth, lact, maintenance), nutritional status, intestinal, physiological stress

Trace Minerals

Chromium
Cobalt

Copper

Iodine

Iron

Manganese

Selenium

Zinc

Fe:Zn:Cu

4:4:1

Iron

fourth most common element, essential

Iron functions

Oxygen transport, cellular respiration, component of hemoglobin, enzyme cofactors, erythropoiesis (red blood cell production)

Iron - Ferrous form

readily absorbed and bioavailable

Iron - Ferric form

less absorbed

Distribution of iron

Hemoglobin - 65%, storage - 25%, myoglobin - 5%, transferrin - 0.1%

Iron Homeostasis

tightly controlled at the point of absorption in the SI, relies on regulating uptake rather than elimination, controlled hepcidin

Nutritional Secondary Hyperparathyroidism

metabolic bone disease, hypocalcemia a/w diets providing deficient Ca and excess P

Entreolithiasis

a condition where intestinal stones from in the GI tract caused by high magnesium diets, low gut motility

Selenium

originally recognized as toxic, functions include component of glutathione peroxidase and protecting lipids from oxidative damage