D- Biotine

What it is

Biotin is one of the more recently discovered vitamins. It was first reported as "co-enzyme R" in 1935, and its chemical structure was identified in 1942. It can be synthesised by microorganisms in the rumen, or in the caecum/colon of monogastric animals. For many years it was assumed that this synthesis was adequate, together with the contents of the feed ingredients, to provide livestock requirements. Research during the past two decades has revealed the inadequacy of these supplies. It is now known to be an essential co-enzyme in several enzymatic systems, where it has a specific function in carboxylations (transfer of enzymatically bound CO₂, or CO₂ fixation).

Although most feed components contain biotin, research has shown that a large proportion is organically bound and biologically unavailable. Only very small quantities are required daily, but the biologically available portion is often insufficient to meet the requirement without supplementation. Biotin is a very stable vitamin, normally unaffected by mill processing including pelleting. It is affected by oxidised fat and by alkaline pH.

Synonyms:

hexahydro-2-oxo-1H-thieno[3,4-d]imidazole-4-pentanoic acid

Molecular formula: C₁₀H₁₆N₂O₃S

Figure 1: Structure of biotin

Appearance: white crystalline powder

Melting point: 232 C

Stability: Stable, but light sensitive. Incompatible with strong oxidizing agents, strong bases, strong acids, formaldehyde, chloramine-T, nitrous acid.

What it does

The full biochemical role of biotin is still not fully understood. In practical terms it is essential for life, growth, food utilisation, maintenance of epidermal tissues, normal bone development and reproduction. Two important enzyme functions, which have been under investigation, are related, respectively, to gluconeogenesis and fatty acid synthesis. Pyruvate carboxylase is a biotin-dependent enzyme in the gluconeogenesis pathway, where it helps maintain normal blood sugar concentration by controlling the conversion of stored energy into glucose.

Then, in fatty acid synthesis, it controls the carboxylation of acetyl-coenzyme A to malonyl-coenzyme A (acetyl CoA carboxylase is biotin-dependent). It also affects protein synthesis through its influence on the nature and rate of formation of ribonucleic acid. This seems particularly important in controlling the rate of production and deposition of scleroproteins ("hard" proteins such as keratin). Thus, biotin is involved, directly or indirectly, with the metabolism of carbohydrates, fats and proteins.

Suggested levels of supplementation

The results of recent research suggest that the levels of biologically available biotin in compound feed stuffs are too low, and feeds may require supplementation in order to ensure optimum livestock health and production.

Suggested biotin supplementation of feeds for farm livestock

Species and age		Supplemention (mg/t)
Fish	trout, salmon	800-1000
	carp	500-1000
	eels	300-500
Shrimp	Penaeus monodon
	Macrobrachium rosenbergii