Nov 17,2021
The history of Vitamin D in animal nutrition dates back to
the early 20th century when a disease, now called rickets, used to be treated
with cod liver oil. In 1924 Steenbock demonstrated that antirachitic activity
could be generated by irradiation of foods with ultra-violet light. The
antirachitic component was named Vitamin D by McCollum in 1925.
Further studies in animal nutrition of Steenbock et al. and
Bethke et al. showed the inability of fowl to utilize irradiated ergosterol
from plant sources as effectively as cholecalciferol from fish oils. It was
found that Vitamin D in synthesis in plants is chemically different from its
synthesis in animal bodies.
Introduction
Vitamin D in animal nutrition is also known as the
"Sunshine Vitamin: as when skin is exposed to ample sunlight, Vitamin D is
synthesized by different molecules. Cholecalciferol (Vitamin D.). (occuring in
animals) and Ergocalciferol (Vitamin D.). (occurring in plants) are the two
main natural sources of Vitamin D in animal nutrition. As such Vitamin D would mean either Vitamin D, or Vitamin D, in
the absence of a subscript.
Physiologically Vitamin D in animal nutrition, metabolites
25 (OH) D₁, 1-a-(OH) D, and 1, 25 (OH), D, are more effective than
Cholecalciferol because all the Cholecalciferol entering the system is not
converted into active metabolites. Active metabolites may directly reach the
target tissue by bypassing hydroxylation in liver and kidney, hence have more
efficacy than Vitamin D, (Goodgame et al., 2011).
In animal nutrition when given through diet like all fat soluble
vitamins, Vitamin D in is absorbed from the digestive tract. Like the others,
it requires the presence of bile salts for absorption (Braun, 1986), and is
absorbed through chylomicron into the lymphatic system of animals along with
other lipids.
Sunlight and Vitamin D in animal nutrition
The 7-dehydrocholesterol present in the skin is converted
into Vitamin D, by irradiation. Ultraviolet light of 230 to 320 nm wavelength
affects the conversion by imparting a definite quantity of energy to the sterol
molecule.
Chemical Nature
Vitamin D comprises a
group of compounds with antirachitic activity that are closely related. It can
be administered through the diet or through irradiation in animal nutrition.
There are around 10 pro-vitamins with variable antirachitic activity after
irradiation. Ergocalciferol (Vitamin D₂) and cholecalciferol (Vitamin D.) are
the two most effective compounds of this group.
In animal nutrition The term D, was originally suggested for
activated sterol, which was later found to be impure and consisted primarily of
ergocalciferol, which had already been termed as Vitamin D The result of this
confusion was that the term Vitamin D, was abolished in the D vitamin group.
The D vitamins are insoluble in water but soluble in fats and fat solvents.
Vitamin D , and Vitamin D, are both more oxidation-resistant than Vitamin A,
whilst Vitamin D in, is more stable than Vitamin D₂.
Metabolism
Dietary Vitamins D₂ (Ergocalciferol) and D,
(Cholecalciferol) are absorbed from the small intestine and are transported by
the blood to the liver, where they are converted into 25
hydroxycholecalciferol.
In animal nutrition The vitamin, whether intestinally
absorbed or produced in the skin, is hydroxylated primarily in the liver by
25-hydroxylase to form 25 hydroxycholecalciferol (25-OH- D.). If elevations in
parathyroid hormone signal a need for increased circulating calcium levels,
25-OH-D₂-1 hydroxylase hydroxylates 25-OH-D, on carbon 1 to produce
1,25-dihydroxy Vitamin D, (1,25-(OH), D₂).
Supplemental Forms of Vitamin D
Vitamin D is an essential nutrient with a major role in the
regulation of a number of genes, many of which are involved in calcium
absorption and transport along with cell development. Vitamin D for animal
nutrition is normally supplemented as cholecalciferol. This form has to be
hydroxylated first in the liver as 25-hydroxy-cholecalciferol and subsequently,
in the kidney as 1,25-dihydroxy- cholecalciferol. This dihydroxy compound is
the main metabolically active form of Vitamin D and binds to the Vitamin D
receptor (VDR) which then binds to the Vitamin D in animal nutrition response
element in genes.
Vitamin D in animal nutrition
The role of Vitamin D in animal nutrition, and in supporting
production is well established. Vitamin D, is the most important molecule for
calcium absorption in the intestine.
In animal nutrition Vitamin D. (Cholecalciferol) is available
either by the conversion of 7-dehydrocholesterol to cholecalciferol in the skin
or from dietary sources. In modern animal nutrition production where animals
are kept in farms, the conversion of 7 dehydrocholesterol to cholecalciferol
does not ensure enough cholecalciferol. Hence, Vitamin D in is regularly
supplemented in through premixes in animal
nutrition.
25-Hydroxy Vitamin D
This metabolite is synthesized by hydroxylation of
cholecalciferol in the liver.
1,25-Dihydroxy Vitamin D
DeLuca (1974) concluded on the basis of many experiments
with 1,25(OH)₂D, that 1,25(OH), D₁ is a steroid hormone and is a biologically
active Vitamin D metabolite in animal nutrition. It is ten times more effective
in ricket prevention and cure than Vitamin D,.
Glycoside form of 1,25-dihydroxy Vitamin D
1,25-dihydroxy Vitamin D, glycoside is of plant origin and
is derived from the waxy-leaf nightshade (Solanumglaucophyllum). This plant
naturally contains 1,25 (OH), D, the metabolically active form of Vitamin D in
a glycosidic form. Several studies with different animal species have proved
its role in correcting problems associated with Vitamin D deficiency in animal
nutrition. The heat stability of the glycoside form is preferred over other
metabolic forms of Vitamin D, hence making it ideal for on top as animal
nutrition supplement.
Role of Vitamin D in supporting immunity in animal nutrition
When pathogens invade the body, the immune system first
activates the innate and then the acquired host defense systems. Antimicrobial
defences of the macrophages depend on the 10 hydroxylase activity in the
macrophages and the availability of Vitamin D for animal nutrition. If Vitamin
D is insufficient, the immune system is compromised, and the animal is at
greater risk of infectious diseases.
1a-hydroxylase activity in immune cells produces 1,25
dihydroxycholecalciferol which triggers innate defenses of the immune system by
stimulating production of defense proteins that kill pathogens. When there is a
deficiency of Vitamin D, immune system function may be impaired even if the
animal does not exhibit symptoms of conventional Vitamin D deficiency in animal
nutrition.
Deficiency Symptoms
In animal nutrition Vitamin D deficiency in causes
Osteomalacia in older animals, in which bone reabsorption has already
developed. Osteomalacia arising out of Vitamin D deficiency is not normal in
farm animals, although pregnant and lactating animals that need increased
amounts of calcium and phosphorus may experience a similar condition. Rickets
and Osteomalacia are not particular disorders that are exclusively caused by Vitamin
D deficiency but they may also be caused by a lack of or an imbalance of
calcium and phosphorus.
In Poultry
In poultry, Vitamin D deficiency in causes the bones and the
beak to become soft and rubbery. It also is the cause for retarded growth and
leg weaknesses. Egg production can reduce and eggshell quality may deteriorate.
Poultry feeds with the exception of fishmeal, contain little or no Vitamin D.This
vitamin is generally supplied in the form of fish-liver oils or synthetic
preparations.
Tibial dyschondroplasia (TD) is one of the most common
skeletal abnormalities observed due to Vitamin D deficiency in poultry. TD
represents deformed bones and lameness in birds. It is a disease common in
rapidly growing birds, especially broilers and turkeys. Comparisons between
fast growing and slow-growing strains have revealed less mineralization and
more porous cortical bone in fast growing birds.
Vitamin D supplementation in animal nutrition of breeder
birds impacts its content in egg yolks. Deficiency leads to marked reduction in
hatchability and frequent mortality of embryos. These embryos show a short
upper mandible or incomplete formation at the base of the beak.
In Ruminants
In animal nutrition Clinical signs of Vitamin D deficiency
in ruminants are decreased appetite, decreased growth rate, digestive
disturbances, stiffness in gait, labored breathing, irritability, weakness, and
occasionally tetany and convulsions. There is an enlargement of joints, slight
arching of the back, and bowing of legs, with an erosion of joint surfaces causing
difficulty in locomotion. Sometimes, young ruminants may be born weak, deformed
or dead.
Milk fever (parturient paresis) is a paralyzing metabolic
disease caused by hypocalcemia near parturition and initiation of lactation in
high milk- producing dairy cows. Milk fever is an impaired metabolic condition
that is related to Ca status, historical Ca intake, and malfunction of the
hormone form of Vitamin D in [1,25-(OH),D.] and the Parathyroid hormone
PTH. Animals that develop milk fever are unable to meet the sudden demand for
Ca that is brought about by the initiation of lactation.
In Swine
In swine, Vitamin D deficiency causes poor growth, stiffness, lameness,
stilted gait, posterior paralysis, fractures, softness of bones, bone
deformities, beading of the ribs and enlargement of joints. Bones may get
deformed by the weight of the animal and the pull of body muscles.
Conclusion
Fast growing and high performing birds and animals
frequently experience bone and health challenges due to poor absorption or
imbalance or deficiency of Calcium and Phosphorus, all of which lead to reduced
performance. In the modern animal farming industry, where the birds and animals
are mostly raised indoors, adequate availability of Vitamin D in animal
nutrition is essential to ensure proper turnover of calcium and phosphorus in
the body.
In practice, deficiency of Vitamin D in animal nutrition is
quite common and leads to several performance related issues. While regular supplementation
of Vitamin D, through premixes is common, there are more bioactive forms of
this vitamin which do not require liver and kidney level conversions. Often,
due to disease conditions, the liver and kidney do not work efficiently which
adversely affects the conversion of Vitamin D into its active form. To meet such challenges,
in the field of animal nutrition a biologically active form of Vitamin D represents
an answer in managing the gap between Vitamin D requirement and availability.