Achieving essential nutrients is necessary for healthy life in human. Chicken’s egg are considered as most feasible source for getting protein and essential nutrients.
But major limiting factor for the service of yolk is high cholesterol concentration. Recommended level of cholesterol per day is less than 300 mg to prevent high blood cholesterol level. High cholesterol cause elevation of blood cholesterol, which tends to increase risk of coronary heart disease.
Cardiovascular disease remains the leading cause of death and disability worldwide, generally because of ischaemic heart disease and stroke (including both haemorrhagic and ischaemic stroke). Therefore, reducing egg cholesterol concentration is meaningful in the primary and secondary prevention of heart disease.
In recent years, a lot of “natural” additives have been used not only to increase bird’s productivity, but also to decrease the antibiotic load and to diminish the risk of potential human pathogens. Number of compounds have been used for reducing egg cholesterol level in layer hen diet.
Previously grape seed extract (GSE) has been used as natural antioxidant. Grape (Vitis vinifera) is one of the worlds’ largest fruit crop. Grape seed contains approximately 11% proteins, 16% oil, 40% fiber and 7% complex phenols including tannins, in addition to sugars, mineral salts, etc.
Grape seeds are considered as a good source of polyphenolic compounds. These compounds have various valuable pharmacological effects, including anti-hyperlipidemic, antibacterial activities and anti-inflammatory. Mainly gallic acid and the catechin are polyphenols of grape seed. These polyphenolic compounds have produced an incredible level of interest based on their defensive effects in dyslipidemia and cardiovascular diseases.
Blood lipids metabolism in mice, rabbits and other animal bodies can be regulated by addition of GSE, as its function of lowering cholesterol level. The lipid-lowering properties and antioxidants of the grape seed are beneficial in atherosclerosis prevention. Mostly GSE was used in human for lowering cholesterol level and getting other health benefits.
However, recent studies showed the evidence of reducing egg yolk cholesterol level due to supplementation of GSE in layer diet. A reduction of 18% has been shown in egg yolk cholesterol concentration because of GSE supplementation (Fig.1).
The decline in yolk cholesterol could be described by the limited absorption or synthesis of cholesterol in the gastrointestinal tract. First, 3-hydroxy-3-methylgluteryl CoA (HMG-CoA) reductase “rate-limiting enzyme in cholesterol biosynthesis” catalyzes the conversion of HMG-CoA to mevalonate, polyphenols in grape seed have presented inhibited HMG-CoA synthesis in hens and reduction of plasma and egg cholesterol.
Secondly, cholesterol is chiefly removed from the body via conversion of cholesterol to bile acids. Reverse transport of endogenous cholesterol might be improved by GSE and ultimately increased bile acid excretion.
7-alpha hydroxylase is a key enzyme in cholesterol-converting bile acids in the liver and proanthocyanidins can enhance the transcription and translation of 7-alpha hydroxylase. Hence, GSE was able to increase the excretion of bile acids and decrease the cholesterol content. Another advantage of GSE supplementation is that, it had no effect on laying performance (rate).
Authors: Muhammad Adeel Arshad1, Shaukat Ali Bhatti1, Hammad Ur Rehman Bajwa2, Nauman Iftikhar2, Uzair Asghar2
- Institute of Animal and Dairy Sciences, University of Agriculture, Faisalabad
- Department of Parasitology, University of Agriculture, Faisalabad