Tanniniferous Feeds for Dairy Animals

Tannins are defined as naturally occurring water soluble polyphenol of varying molecular weight which differ from most other natural phenolic compounds in their ability to precipitate protein from solutions (Spencer et al., 1988). Tannins are considered as secondary substances as they don't involve in metabolic pathways, but they involve in plant defensive mechanisms. After lignin they are the second most abundant group of plant phenolics. The presence of large numbers of phenolic hydroxyl groups which enables them to form large complexes with protein and to lesser extent with cellulose, pectin and divalent metal cation (McLeod, 1974; Mueller-Harvey and McAllan 1992; Scalbert, 1991).

Based on the structural and chemical properties tannins are classified into two groups namely hydrolysable and condensed tannins. Structurally hydrolysable tannins are ester of gallic acid (gallotannins) or ellagic acid (ellagitannins) with a sugar molecule specially glucose and readily hydrolysed by enzymes or acid into monomeric products. Condensed tannins are polymers of flavonoid units and are more resistant to microbial attack.

Tannins are widely distributed to many tropical forages and shurbs (e.g. Leucaena leucocephala, Soghum sp., Acacia sp. etc.)  and many agroindustrial byproducts namely salseed meal, mangoseed kernel, Prosopis juliflora, mahua cake etc. Utilization of such tanniniferous feeds in animal ration is very less because of antinutrient action of tannins. In order to eliminate antinutrient action of tannins, various physical, chemical and biological treatments are employed.

• Effect of Tannins on Feed Intake and Digestibility of Nutrients
• Beneficial Effect of Tannins on Animal Production
• Adverse Effect of Tannins on Animal Health