Effect Of Tea Polyphenol Extract On Egg Quality Of Laying Hens

Experiments were conducted to evaluate the quality of fresh and stored eggs laid by laying hens fed Tea polyphenol extract (TPE).In total,360 laying hens (65-wk-old) were randomly allotted into 4 groups with 6 replicates of 15 hens each. Four diets((T1?T2?T3?T4)) containing 0 (control),0.3, 0.6 and 1.2% of TPE were used in a 8-wk study. Egg quality was measured at week 2,4, 6 and 8, and the eggs laid at week 8 were collected for the determination of albumen characteristics, yolk cholesterol level, and yolk fatty acids composition.Dietary TPE made no effect on yolk color, shell thickness, shell strength, yolk cholesterol level and yolk fatty acids composition (P>0.05). Albumen index and eggshell index were reduced (P?0.05) at week 4 in T2 group when compared to the control group. Egg yolk index and eggshell index were significantly reduced at 6th week in T3 and T4 group (P<0.05), T3 and T4 significantly increased albumen index at 6th week (P?0.05), Eggs from hens fed T2 and T4 diet had increased (P?0.05) Haugh unit and albumen height at 8th week when compared to eggs from control hens, Hens fed T2 diet had increased (P?0.05) egg white gel water retention when compared to hens fed T4 diet. When compared to the control hens, hens fed T3 diet had decreased (P?0.05) rate of egg white foam.Hens fed T2 diet had increased (P<0.05) foam stability and decreased (P?0.05) strength, gel gumminess and gel chewiness of egg white when compared to the control groupEggs laid on the last day of the laying hen trial were collected and stored at either 4 or 22 ? for 30 d. Egg quality and yolk malondialdehyde (MDA) content were measured on d 0,5,10 and 30 of the egg storage study. Albumen characters were analyzed on d 10 of storage.Dietary TPE had no effect (P>0.05) on yolk color, shell thickness and yolk index of stored eggs. After a 30-d storage at 4 ?, eggs from hens fed T2 and T4 diet had increased (P?0.05) Haugh unit and tended (P=0.070) to have increased albumen height when compared to eggs from control hens.At 4 ?, eggs from hens fed T2 diet tended to have increased (P= 0.075) shell strength after 5 days of storage and decreased (P= 0.075) yolk MDA level after 10 days of storage, After a 30-d storage at 4 ?, eggs from hens fed T2 diet had decreased (P<0.05) yolk MDA level when compared to eggs from hens fed T3 diet., At 4 ?, eggs from hens fed T4 diet had increased (P<0.05) the rate of egg white foam and foam stability, when compared to eggs from control hens. After a 5-d storage at 22 ?,eggs from hens fed T2 and T3 diet tended to have increased Haugh unit (P=0.065) and albumen height(P=0.070), when compared to eggs from control hens.T2, T3 and T4 significantly decreased (P<0.05) gel strength, gel gumminess, gel chewiness and gelation of water, and decreased (P?0.05) strength of eggshell and albumen index, and increased yolk MDA level (P?0.05) at the 5th day of storage. After a 5-d storage at 22 ?, eggs from hens fed T3 diet tended to have decreased (P=0.071)shell index and increased albumen gel gumminess (P=0.060) and gel chewiness (P=0.088) when compared to those from control hens, Eggs from hens fed T4 diet had increased (P<0.05)yolk MDA level after a 5-d storage at 22 ? when compared to those from control hens. Eggs from hens fed T3 and T4 diet had increased (P<0.05) the rate of egg white foam after a 10-d storage at 22 ? when compared to eggs from control hens.In conclusion, in laying hens under corn-soybean based diet, dietary inclusion of T2 improved (P?0.05) Haugh unit, albumen height, egg white gel water retention and foam stability; and decreased (P?0.05) egg white gel strength and gel chewiness;dietary inclusion of T3 remitted Haugh unit decreasing, and improved water retention gel egg white and egg white hair bubble rate during storage.