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4. Dietary manipulation for enhancing nutritional quality of eggs:

Cholesterol is not a fat. It is a waxy fat - like substance produced by all animals including man. Cholesterol is necessary for many bodily functions and serves to insulate nerve fibres, maintain cell walls, produce vitamin D, various hormones and digestive juices. There is little doubt that elevated blood cholesterol levels increase heart attack risk.

Cholesterol content of chicken egg has recently received far more attention than before due to increase in cardiovascular disease in man mainly arthrosclerosis, hypertension and coronary heart disease. Egg yolk is considered one of the richest sources of cholesterol in human diet Cholesterol content of eggs (about 200-250 mg) and blood (around 150mg%) in chickens has found to vary quite considerably. Various researches are presently going on to lower cholesterol content of chicken egg and meat either through the use of additives, dietary fiber, polyunsaturated fatty acid supplementation, etc.

After realizing the cardio protective and other beneficial effects of omega-3 fatty acids found in the eggs, the poultry nutritionists have started research to incorporate more of these fatty acids in the egg and have succeeded in developing such an egg called Omega 3 designer egg. They also call it the 'diet egg' or the 'functional egg'.

Diet eggs have a high percentage of Vitamin E, an antioxidant, which prevents oxidation of cholesterol and therefore its ill effects. Cholesterol by itself is not bad. It is harmful only when it is oxidized. These eggs contain 600 mg of Omega – 3 fatty acids. Omega – 3 fatty acids help to reduce cholesterol triglycerides, clog formation, tumor growth and improved immunity. Vitamin ‘E’ which is a fat-soluble vitamin and is effective antioxidant is enhanced to 100% in Designer Eggs. These eggs are already available in the markets in many countries, including India with good patronage. In order to improve the quality of these eggs further Vitamin E, selenium, and carotenoid pigments are also incorporated into these eggs.

‘Diet eggs’ produced by a local company M/s Kool Comestibles in Karnataka at Bangalore are priced at Rs.4 each, and come in packs of 12 and 24. World over, there are eleven licensed holders for the technology, who produce and market the diet eggs in 30 countries (source: internet).

Smart Eggs, which are low in cholesterol and fat. Produced by the Department of Zoology in Punjab University, The first 'diet eggs' in the region are the outcome of research conducted over a period of four years by Prof.S.K.Taneja, Head of PU's Zoology Department. Scoring over the average variety, these eggs have 30 per cent less cholesterol, 300 per cent more vitamin E and double the amount of 'omega3'. Another plus point is that these eggs do not have that marked "eggy" odor. The eggs, priced at Rs.21 for half-a-dozen would be available in leading stores (source: internet).

Most dietary cholesterol is associated with saturated fats. Dietary cholesterol (1%) and lard (10%) supplementation in Japanese quail was found to be more harmful with increased total serum cholesterol levels and also associated with increased LDL + VLDL cholesterol fractions. Serum cholesterol levels increased with increasing tallow (2-6%) incorporation.

Supplementation of polyunsaturated fatty acids (fish oil or sunflower seed oil, at 2% in diet of laying hens brought significant reduction in serum (20%) and yolk (9%) cholesterol as well as triglycerides (20%). Red palm oil and red palm oil + popped amaranth feeding resulted in a significant reduction in total lipids and cholesterol contents.

Dietary copper at 100 and 150 ppm in diet decreased both plasma and egg yolk cholesterol in laying hens and quails. The dietary guar gum at 0.5 and 1 per cent levels in diet did not alter cholesterol either plasma or egg yolk cholesterol in laying hens and quails.

Onion and garlic were effective as hypocholesterolaemic agents only to limited extent in Japanese quails. Supplementation of Cu at 150 and 250 ppm reduced the serum total cholesterol by about 14% and meat cholesterol by 20%, whereas, garlic at 1% level reduced serum cholesterol by 15% and meat cholesterol by 12% in broiler chicken. Garlic has been found to contain at least 400 constituent compounds of which more than 30 are known to influence the body function minerals such as selenium and germanium, amino-acids such as glutathione, methionine and cysteine, amino alkyl sulfoxides, allicin disulphide oxides, deoxidized supplied and sulphydryl bearing compounds, s-allyl cysteine and the oxide of trithio-doderiens ajoene. Substances like those have been shown to be effective in a wide variety of therapeutic applications.

Serum cholesterol was lower (P<0.01) in probiotic-supplemented birds (86.1 mg/100 ml) than in controls (118.4 mg/100 ml). A significant reduction on the total serum cholesterol concentration was observed, but no effect was found on HDL, VLDL, LDL and triglycerides. The addition of probiotic significantly increased the egg production, shell weight, shell thickness and serum calcium, and reduced the concentrations of cholesterol in the serum and yolk.

Choline chloride supplementation had no significant effect on blood glucose, protein and cholesterol levels.

Use of SBM or vegetable protein mixture (33.33% GNC + 33.33% SBM + 33.33% VPMA (VPMA: 37.5% mustard cake + 37.5% till cake + 12.5% cottonseed cake + 12.5% autoclaved linseed meal)) with added lysine and methionine resulted in significantly lower serum cholesterol but higher serum protein content in broiler chicken. No significant (P<0.05) differences in blood cholesterol levels were observed on feeding of soybean meal, rapeseed meal or sunflower seed meal in diet of Japanese quail.

A study on effects of diet on egg and serum lipid profile is given below for ready references. White Leghorn hens of 53-58 weeks of age in cages were fed ad libitum with designer egg production diet with or without 2g/kg Spirulina, 2g/kg Thulasi (ocimum sanctum) leaves or both; along with a control feed. All the four designer egg production diets had 10% linseed (flax), 10% full fat sardine fish having 22% oil and 200mg vitamin E per kg diet. The eggs were collected from 4th week onwards for estimation of their lipid profile. At 6th week, blood samples were drawn for estimation of the serum lipid profile. The results were as follows:

Traits

Control layer feed

Designer egg feed

Designer egg feed + Spirulina (S)

Designer egg feed + Thulasi (T)

Designer egg feed + S+T

Roche yolk colour*

8.0a

9.2b

11.8b

10.6c

12.4d

Yolk carotenoid pigments (μg/g) **

24.5a

36.8b

56.1c

44.8b

65.0c

Yolk cholesterol (mg/g) *

12.9a

11.4b

9.9c

9.5c

9.1c

Yolk fatty acids:

C16:0**

27.5a

20.1b

19.8b

19.6b

19.2b

C18:0NS

7.6a

7.9a

7.2a

7.3a

7.0a

C16:1NS

3.6a

1.9b

1.2b

1.4a

1.1b

C18:1NS

44.3a

43.2a

42.8a

42.4a

41.6a

C18:2*

15.7a

14.1ab

13.8a

13.4b

13.0b

C18:3**

0.16a

15.9b

6.1b

5.7b

6.2b

C20:5**

0.06a

0.58b

0.61b

0.60b

0.63b

C22:6**

0.17a

4.60b

5.1b

5.1b

5.3b

Yolk vitamin E (μg/g yolk)**

Serum cholesterol (mg/dl)

82.8a

290.5b

301.2b

292.4b

303.3b

Total C**

177.4a

164.7b

145.2c

140.0c

130.9c

VLDL C**

115.9a

97.5b

76.9c

69.5c

61.7c

LCL C**

30.4a

24.8b

20.5b

21.0b

19.0b

HDL C**

31.1a

42.4b

47.8b

49.5b

50.2b

Triglycerides**

840.9a

760.2b

718.7c

720.1c

708.2c

NS – Non-significant; *(P<0.05); **(P<0.01).

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