Nutritional manipulations for value added egg and meat production
Consumers are always in search of newer products and never satisfied with the existing products. This consumers' attitude applies for the poultry products also. In case of poultry products, there are two types of value addition. One is, value addition before the product is produced, i.e."pre-slaughter or pre-oviposition value addition". Products like, organic / designer / functional eggs and meat will come under this category. The other category is "post-slaughter or post-oviposition value addition", which is usually referred as "post harvest technology".
Lots of work, literature and hundreds of products are already available regarding post harvest technology and further processed poultry products. Now the health conscious consumers are in need of safe poultry products, which are free from drug / pesticide residues and other harmful components. Moreover, the consumers are ready to pay a premium price for such products, which are safe and also promote their health; due to the presence of special health promoting components like n-3 fatty acids, anti-oxidants, extra vitamins, minerals and non-nutrient components. These types of value addition will be done mostly by combination of manage mental and nutritional manipulations. In this paper, the nutritional manipulations for value addition of eggs and chicken meat will be discussed.
Pre-Oviposition Value Added Eggs
Organic and cage-free eggs are the earliest pre-oviposition value added eggs. According to the American Egg Board (AEB), organic eggs are those obtained from hens fed rations having ingredients that were grown without pesticides, fungicides, herbicides or commercial fertilizers. Moreover, these hens are reared free from cages and fed organic feeds free from any performance enhancers like antibiotics, antimicrobials, coccidiostats and other drugs. The organic foods are usually free from residues of pesticides, drugs and other harmful chemicals. The chemical composition of cage reared and free-range hens' eggs are reported in Table 1.
Egg is the best vehicle to incorporate several health-promoting components in it. As early as 1934, Cruickshank has reported that the fatty acid composition of egg yolk could be modified by dietary manipulation. However, this technique was not utilized for more than 50 years. Dyerberg and Bang (1979) reported that n-3 fatty acids would protect the heart from Cardiovascular Diseases (CVD). In the late 80s, Sim, Jiang and their associates in the University of Alberta, Canada, have blended these ideas together and developed a Designer Egg, rich in n-3 fatty acids and antioxidants. They have patented this egg as Professor Sim'sDesigner Egg. They have incorporated the n-3 PUFA in the egg yolk at the expense of saturated fatty acids, by feeding hens with diets having flax seeds. Since n-3 PUFA is highly unsaturated and unstable, the yolk fat will undergo rancidity quickly; leading to off odours. To overcome this problem, they have incorporated natural antioxidants like vitamin E, selenium and carotenoid pigments.
Table 1. Chemical composition of cage and free-range (organic?) hens' eggs
* Significant (P<0.05); ** highly significant (P<0.01); NS Not significant (P>0.05)
Later in Australia, Farell (1998) enriched the eggs with folic acid and iron; which are good for anemic patients. In Canada, Leeson (2004) produced lutein-enriched eggs; which will act as a retinal tonic, by preventing Macular Degeneration and Retinitis Pigmentosa. In India, Narahari (2004) has developed Herbal Enriched Designer Eggs (HEDE), which are not only rich in n-3 PUFA, vitamin E, selenium, carotenoids, certain B complex vitamins and trace minerals; but also rich in herbal active principles like, Allicin, Betaine, Euginol, Lumiflavin, Lutein, Sulforaphane, Taurine and many more active principles of the herbs, depending upon the herbs fed to the hens (Table-2). Moreover, these eggs had about 25 % lesser cholesterol in their yolks, compared to ordinary eggs. Feeding such HEDE to human volunteers has resulted in significant reduction in their Triglycerides (TG) levels, increased the good HDL cholesterol (Table 4), improved immunity and haematocrit.
Table 2 Active principles present in herbs/ herbal enriched functional eggs and their role in human health
Pre-processing value added chicken meat
Organic chicken is the earliest pre-processing value added product introduced in to the market. They are produced from relatively slow growing birds, usually slaughtered after 82 days of age. They are reared under near natural conditions, with free access to range area. They are fed with organic feeds, free from drugs and pesticide residues.
The regulation for production of organic chicken varies from country to country. EC regulation, EC-2092/91 and its subsequent amendments, place restrictions on the ingredients that a manufacturer of organic food can use. Label Rouge is the largest brand of organic meat produced in France. Each bird bears a label, which serves as its individual identity card.
There will be certifying agencies in each country, to certify the product as organic. In India the APEDA (Agricultural Products Export Development Agency), in UK the UKROFS & OFF, in Europe the ECOCERT, Naturland & Skal and in USA the OCIA, OGBA, QAI and FVO are the prominent certifying agencies for organic foods.
For the last one or two decades, super markets in developed countries are dumping value added poultry products like, organic eggs and meat, functional eggs, designer eggs, lean meat, Pate-de-foie-Gros, Label Rouge chicken, lutein/ folic acid / iron / n-3 PUFA enriched eggs, in their racks. Moreover, many large value added egg producers are having their own direct retail outlets like farmers market, co-operatives etc., despite premium prices of 3 to 5 times the value of regular products, there is an ever-growing demand at the rate of about 10% per annum for designer foods.
Dietary manipulations to produce designer eggs /meat:
Dietary manipulation is the major step in producing the pre-oviposition/pre-slaughter value addedpoultry products. Various nutritional manipulations to the chicken diet will be done to produce different types of value added products.
W -3 Fatty Acids enrichment
The total fat content in the egg yolk cannot be altered; but its fatty acid composition can be altered, by changing the type of oil used in the hens' diet. Flax seed (linseed), marine algae, fish oil and rape seed oil are added to chicken feed to increase the omega - 3 fatty acid content in the egg yolk, at the expense of saturated fatty acids like palmitic and stearic acids. The fatty acid composition of oils rich in W -3 PUFA, regular eggs and W -3 PUFA enriched eggs (designer eggs) are shown in Table. 3
Table 3: Fatty acid composition of oils rich in W --3 PUFA, regular eggs
and W -3 PUFA enriched eggs
In designer eggs the N-6 / N-3 PUFA ratio is decreased to about 1.5, from as much as 20 in regular eggs. This favourable change in designer eggs, will supply about 50% of the daily requirement of N-3 PUFA to the consumers, without any change in the sensory quality of the egg. This n-3 PUFA in egg yolk has decreased the serum Triglycerides and increased the serum HDL-Cholesterol levels in human volunteers, when consumed for a period of two months at two eggs per day (Table-4).
Table - 4. Influence of Designer egg consumption on serum lipid profile in humans (mg/dl)
Source: Michael raj (2004) MVSc thesis, TANUVAS, Chennai.
Since the N-3 PUFA will undergo rancidity quickly, it is essential to prevent the rancidity of the designer egg yolk lipids, by incorporating anti-oxidants in the hens' diet.
Anti Oxidants in eggs and meat
Egg is a rich source of natural antioxidants like vitamin-E, selenium, carotenoid pigments, flavinoid compounds, lecithin and phosvitin. These compounds will protect the fat-soluble vitamins and other yolk lipids from oxidative rancidity. However, these levels are not sufficient to protect the designer eggs rich in N-3 PUFA. Hence it is essential to increase the anti-oxidant levels in the designer eggs. The designer egg and meat, not only contain high levels of the above anti-oxidants; but also contain synthetic anti-oxidants like Ethoxyquin and anti-oxidants of herbal origin such as Lycopene, Curcumin, Sulforaphene, Carnosine, Quercetin, depending upon the herbs used in hens' diet. Supplementation of these anti-oxidants in hens' diet will increase their levels in the egg and meat.
The advantages of enrichment of the egg and meat with anti oxidants include:
For designer egg/meat production, vitamin E and organic selenium (Selplex) are added as anti-oxidants at levels of 200-400mg/kg and 0.1-0.3ppm, respectively. Besides these, other anti-oxidants as chemicals and herbs may be added, to prevent oxidative rancidity. The vitamin E and Selenium levels, as well as the anti-oxidant properties of the regular and designer eggs are shown in Table 5.
Lowering Cholesterol Content
Even though the dietary cholesterol is insignificantly correlated with the serum cholesterol levels, the consumers are scared of high cholesterol foods, like eggs. A large egg contains about 200 mg of cholesterol and chicken meat contains about 60 mg per 100 g. Research towards lowering egg cholesterol has centered mostly on dietary and pharmacological interventions. Chromium, copper, nicotinic acid, statins, garlic, basil (tulasi), plant sterols, N-3 PUFA supplementation to chicken feed will reduce the yolk and carcass cholesterol levels significantly.
Similarly, dietary Linseed oil =2-4%, Fish oil (body oil and not liver oil)=1-2%, Garlic=0.5%, Basil=0.3%, Spirulina=0.2%, Bay leaves=0.5%, Nicotinic acid=200mg / kg, Neomycin=10ppm, Statins of yeast=0.5-1%, Guar Gum=1%, Grape seed pulp / Tomato pomace (lycopene)=2-5%, Citrus pulp (nirangenin)=2-5%, Chelated Copper=200ppm, Organic Chromium=2ppm, Roselle seeds=0.5% and many more herbs in chicken diets will reduce the yolk and chicken fat cholesterol levels by 10-25%. Dehydrated alfa alfa reduces cholesterol content and total lipids in chicken breast meat. Sunflower oil, soyabean oil, canola oil, linseed oil reduces fat and cholesterol content in cockerel thigh and breast meat. Moreover, these substances are having synergistic effect in reducing the cholesterol levels. Hence a combination of these supplements will be more beneficial, rather than a single substance. The yolk cholesterol levels in regular and herbal enriched designer eggs are shown in Table 5.
Lean Meat Production
Consumers prefer chicken meat with high protein, low fat and cholesterol. In fact, chicken and yolk fats are not fats, but oil; because their SFA content is only one third of TFA, nearly 45% is cardiac friendly MUFA and the remaining are PUFA. Lean meat with low carcass fat (<5%) and cholesterol (<50mg/100g) can be easily produced by dietary manipulations. However, the cost of production of such lean meat will be higher due to lower body weight and poor feed efficiency.
Chromium picolinate at 0.5 ppm had significantly lowered the carcass fat level. Neomycin sulphate at 5-10 ppm level also produced lean meat. Chromium enriched yeast at 1 g/kg diet improved the carcass quality. Organic chromium had increased the weight of pectoral muscles and the meat had less fat and cholesterol content. Narrowing the C: P ratio, either by increasing the protein level or decreasing the energy level also produces lean meat. Increasing the lysine level in the pre-starter diets and methionine level in the finisher diets will increase the lean breast meat yield in broilers. Addition of fish oil to broiler diet at > 2% level will reduce the abdominal fat pad thickness and cholesterol levels; but this technique is not advisable because, it will impart an undesirable fishy taint to the meat and also produce a condition called as oily bird syndrome.
Pigment Enrichment of Yolk and Skin
In many countries, deep yellow or orange colour yolks and yellow skin broilers are preferred over pale yolks and skin. Natural carotenoid pigments like carotenes, xanthophylls, cryptoxanthin, zeaxanthin, lutein present in alfalfa, corn gluten meal, blue green algae - spirulina, marigold petal meal and capsicum will impart rich yellow and orange colours to the yolk and skin. Besides providing attractive colour, they act as anti-oxidants and anti-carcinogenic agents. Some of the pigments are having vitamin A activity. The lutein will safeguard the retina.
Most of these natural pigment sources are used in feeds at 1-5 % levels to increase the yolk and skin colour. The active pigments extracted from these sources are sufficient at 0.05 - 0.1 % level, to give the same level of pigmentation. Turmeric powder at 0.5 kg along with red chilli powder at 1 kg / T of feed, not only improve the skin and yolk colour, but also act as anti-microbial agents and anti-oxidants. Fat soluble Azo dyes are also used for pigmentation, but this is banned in many countries.
Immunomodulating Egg Production
Chicken egg is abundant in antibodies like "IgY"; which is cheaper and better than mammalian immunoglobulin "IgG". In a 6-week period, a hen produces about 298mg of specific antibodies, compared with only 17mg from a rabbit. This "IgY" can be used to treat human rotavirus, E.coli, Streptococcus, Pseudomonas, Staphylococcus and Salmonella infections.
The lysozyme (G1-globulin), G2 and G3 globulins, ovomacroglobulin, antibody - "IgY" and other natural antimicrobials and immunostimulants in the egg, prolong the life of AIDS patients, by their high nutritional value, as well as immunostimulant and anti-viral properties.
The IgY level in the egg can be increased by dietary manipulations. The functional feed rich in omega - 3 fatty acids and anti-oxidants it self will increase the IgY level in the egg. Herbal supplementation will further boost the IgY level in the egg (Table-5). Among the herbs, Basil leaves (Tulasi) at 0.3-0.5 % dietary level is having the highest ability to boost the IgY level in the egg. Other herbs like Rosemary, Turmeric, Garlic, Fenugreek, Spirulina, Aswagantha, Arogyapacha etc., are also possessing immunomodulating properties.
By manipulating the diet of chicken with these feed supplements, value added and health promoting chicken egg, meat and their products can be made available to the consumers. All these value added products must be free from drug and pesticide residues. This value addition involves higher cost to the extent of 50-300 %of the conventional foods. Hence, the producers of these products must conduct a market survey or find out the export potential, before starting the venture.
Table 5: Health promoting properties of herbal enriched designer feeds and eggs
* Significant (P<0.05), ** Highly significant (P<0.01)
|Source : IPSACON-2005|