Naturally occurring toxicants in feeds in animal nutrition and their deactivation methods
Naturally occurring toxins in plants are the nature's defensive agents for the plants and produce deleterious effects in livestock, and known as Antinutritional factors (ANFs). Certain enzymes are also used to supplement the naturally occurring enzymes (e.g. lipase).
A description of ANFs and methods to eliminate /minimize these in certain feed ingredients are given. In poultry nutrition, the feed ingredients are also supplemented with feed supplements such as toxin binders, antioxidants. Emulsifiers, vitamins, trace minerals etc.
SOYBEAN (Glycine max) MEAL
In animal nutrition Soybean meal (SBM) is the principle protein source for monogastrics. Soybeans contain a high quality protein with a good amino acid profile, but for methionine, and are highly digestible in the small intestine. It is also an important constituent of Poultry nutrition.
Antinutritional factors (ANFS) in SBM
Soybeans contain several ANFs.. Some ANFs are of nutritional significance and can be destroyed/inactivated by proper heat.
Tests to estimate the destruction/ inactivation of ANFs
Within animal nutrition, several tests are available in the feed additive and feed supplement industry to estimate the destruction or inactiveness of ANFs. These may be the ones to determine the ANFs directly or involve the estimation of other enzymes or solubility property of protein, nitrogen in water, or KOH solution. The latter are commonly employed to determine the ANFs in commercial channels
Trypsin inhibitors - The principle trypsin inhibitors are the Kunitz factor and the Bowman-Birk factor. The residual trypsin inhibitor in soy products combines with the trypsin in the small intestine and forms an inactive complex thus reducing digestibility of
Lectins – Lectin is a protein with a specific binding affinity for sugar residues. The lectin sugar interaction is important at the level of the membrane receptors in the gut where it is thought to be responsible for agglutination and mitosis. Lectins are heat sensitive and are therefore only present at residual levels in soybean products.
COTTONSEED (Gossypium Spp) MEAL
Generally for poultry nutrition, the cottonseed contains: hull 23%, oil 17%, linters 8%, and general meal 52%.
2. Cyclopropenoid fatty acids (CPFA)
The cyclopropenoid fatty acids (given as poultry feed supplement) are the components of residual oil (0.01% in meal obtained by commercial practices of extraction), increase the permeability of the vitelline membrane for iron of yolk to diffuse into the albumen, resulting in the formation of red iron-albumen complex accounting for pink white in stored eggs.
Toxic effects of feeding cottonseed meal - The signs of gossypol toxicity in poultry are decreased appetite, weight loss, leg weakness, decreased egg size, egg yolk discoloration, reduced hatchability, lowering of hemoglobin, total erythrocytic count. FG acts by reducing oxygen carrying capacity of the blood (Alford et al., 1996), may adversely affect male reproductive function (testicular damage) (Randel et al. , 1996).
Mustard meal is a fairly good source of crude protein (36%), lysine, methionine and energy in the feed additive industry. The ANFs in mustard meal are: (i) glucosinolates, (ii) erucic acid, (iii) high fibre, (iv) NSPs. Besides these orgemone seed is a frequent contaminant in mustard cake.
Broilers - Many workers in animal nutrition industry come across increase in weight of thyroid gland, liver and fat content of liver fat due to feeding 20 - 30% MC, attributed to the erucic acid content of MC The toxic effects of intrinsic principles present in mustard cake decreased with age of the bird. Expellermeal (25%) on protein basis in WL chick (1d to 15 weeks) diet without affecting body weight gain, feed efficiency and hematological parameters
Layers - In layers, inclusion of MC in place of groundnut meal and fishmeal ( as used along with poultry feed supplements) at 10% level in iso caloric and iso-nitrogenous diets significantly reduced the egg production and feed efficiency Iodine supplementation failed to improve egg production in birds fed MC based poultry nutrition diet. Contrary to these findings several workers (found no adverse effect on egg production, egg weight, feed efficiency, and body weight in layers fed with diets containing 10-16% expeller or solvent extracted MC.
Castor Seed (Ricinus communis) Meal
Castor seed meal contains 30-40% protein. Castor seed meal contains the ANF "Ricin". Ricin was found to have high haemoagglutinating and proteolytic activity. Castor seed meal contains ricin to an extent of 0.22- 1.0%. The Castor seed meal also has allergen, ricinine and chlorogenic acid but toxicity is only due to the presence of ricin. The type of solvent used for oil extraction has influence on level of toxins and toxicity
Mahua (Madhuca indica, M. longifolia) seed meal used is a moderate source of protein (15-24%). Mahua seed meal contains saponins: Madlongiside A, B, C, D; Mi-saponin A The saponins are having hemolytic effect. These have to be supplemented with feed additives. Mahua cake in chick mash at about 12% in feed caused mortality of all chicks within five hours. Even at 5%, mahua seed meal depressed the performance of chicks. Ethanol treatment of mahua seed meal reduced 86.46% saponins and 31.77% tannins (Singh and Agarwala, 1989).
Guar (Cyamopsis tetragonaloba L.) Meal
Guar meal, although a protein source in poultry nutrition, causes deleterious effects in poultry, because of residual gum. Guar meal can be incorporated up to 8% in commercial broiler (1 to 6 weeks) diet. The higher levels of inclusion (16 and 32%) of guar meal caused depression in growth and feed efficiency, and sticky diarrhea and high mortality (25 to 70%) Residual gum (18 to 21%) present in guar meal may be responsible for deleterious effects in broilers. Trypsin inhibitors, and saponins may be the contributing factors for guar meal toxicity. guar meal can be incorporated in WL grower diet and layer diets up to 10 and 11%, respectively The depression in egg production may be corrected by increasing the dietary protein
ANFs occurring in animal nutrition are the natural protective substances for the plant. It is possible that at a very low substitution, the ANFs of the vegetable protein sources such as guar meal, castor seed meal, and mahua meal, etc might have a nutraceutical function or immunological function.
