EFFECT OF DRINKING WATER SUPPLEMENTED WITH GAMMA-AMINOBUTYRIC ACID (GABA) ON LAYING PERFORMANCE AND EGG QUALITY PARAMETERS IN LAYING HENS

The laying performance and egg quality parameters were studied after Gamma-aminobutyric acid (GABA) supplementation in laying hens. One hundred and fifty Lohmann Brown laying hens (32 weeks old) were randomly allotted to 3 treatments: control (without drug), GABA (40 mg/kg b.wt) and GABA (80 mg/kg b.wt). Each group consisted of 5 replicates of 10 hens and given the medication orally, daily for 4 weeks. The laying performance parameters (egg production, egg weight, egg


ISSN: 2320-5407
Int. J. Adv. Res. 8(02), 312-318 313 Heat stress in laying hens (Zhang et al., 2011) and broilers (Dai et al., 2011;Wang et al., 2011) which leads to depression in the performance could be prevented by GABA. Furthermore, it has been reported that GABA had widely varying effects on animals, and played a great role in alleviating stress, improving nutrition utilization efficiency and regulating appetite (Cherubini et al., 1991). No available information on the effect of GABA supplemented as oral medication, thus the objective of our study was to investigate the effects of oral GABA supplementation on laying performance, external egg quality, and egg yolk and albumin quality in layers.

Materials and Methods:-Experimental birds and design:
One hundred and fifty commercial Lohmann Brown Lite laying hens at 32 weeks old were divided to 3 equal groups (each group with 5 replicate and 10 hens per replicate); control (without drug), GABA (40 mg/kg b.wt) and GABA (80 mg/kg b.wt), the chosen doses were according to Xie et al., (2013). The medication was given once daily for 4 weeks. All groups were given a corn-soybean-basal diet without any additives. The chemical composition and ingredients in the diet were illustrated in Table 1. Diet formulations were according to the breeder recommendations (Lohmann Brown Lite layers, Germany). Body weights of group 1 were (1500-1700 gm); Group 2 (1550-1750 gm) and group 3 (1600-1800 gm) at the time of experiment.
During the experiment, water was provided ad libitum. The experiment was carried out between 32 and 36 weeks of age (4 weeks experimental period). Hens were housed in battery cages supplied with feeders and nipple drinkers. Continuous light per day (16 h) from 6 AM to 10 PM. The temperature was 29 o c and relative humidity 72%. Laying hens were fed 115 gm per hen per day were according to the breeder recommendations (Lohmann Brown Lite layers, Germany). The GABA was provided by AMECO-BIOS (USA) under a trading name (GABA-L) ® as watersoluble solution and each ml contains 100 mg GABA. Ethics Committee of the Faculty of Veterinary Medicine, Benha University, approved the use of laying hens and study protocols.

Collection and egg quality parameters analyses:
All hens weighed individually at the 32 nd and 36 th week of age. Hen per day egg production (%) was measured. In 7d intervals, feed consumption and feed conversion ratio were recorded (Singh and Kumar, 1994). By multiplying egg weight by egg production, egg mass was obtained.
Internal and external egg quality parameters were studied after GABA supplying. Albumen and yolk weights, albumin and yolk indexes, and haugh unit were measured as internal egg quality parameters. Egg shape, egg yolk, and albumen indexes were recorded (Romanoff and Romanoff, 1949). Yolk index (%) = [Yolk height (cm)/ Yolk diameter(cm) ] x 100 & Albumen index (%) = Albumen height (mm)/ Average of albumen length and width) mm x100. Egg yolk color was determined and a tripod micrometer was used for the estimation of haugh units.
Egg shell thickness was determined by using a special micrometer and albumen height and yolk color were determined using an egg multi tester (Touhoku Rhythm Co., Tokyo, Japan). Egg quality determinator (NABEL Co., Ltd, Kyoto, Japan) was used for the determination of shell weight.
The cholesterol and triglycerides concentrations (mg /g) in the egg yolk were measured by an ultraviolet spectrophotometer (Unico Co., Dayton, USA) using commercial kits (Biodiagnostic, Egypt) (Rotenberg and Christensen ,1976).

Statistical analysis:
Data were subjected to One-way ANOVA using SPSS Statistics 22 statistical package (SPSS Inc., Chicago, IL, USA) and expressed as mean ± SE. Significant differences between groups were determined using Duncan's test at P ≤ 0.05.

Results:-
From the results in Table 2, layers orally administered GABA (80 mg/kg b.wt) during weeks 32 to 36 showed significant increases in egg production, egg mass, heavier egg weight, and better feed conversion ratio compared with the control treatment. However, there was no significant difference between the two groups administered GABA.

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The external egg quality parameters (egg shape index, shell weight, and shell thickness) were significantly increased by supplementation of the drinking water by GABA (80 mg/kg b.wt) as shown in table (3). The effect on egg yolk quality was presented in table (4); a significant increase in yolk weight, yolk color score, and higher yolk shape index were recorded in laying hens supplemented with oral GABA (80 mg/kg b.wt) compared with the control group. Also, egg yolk cholesterol and triglycerides were decreased in both GABA (40 mg/kg b.wt) and GABA (80 mg/kg b.wt). As shown in Table 5, the effects on albumen quality (albumen weight, albumin %, and albumen haugh unit) were improved by the addition of GABA (80 mg/kg b.wt) to drinking water.

Discussion:-
Eggs are the second widely consumed food all over the world (Surai and Sparks, 2001) and the economic income in the poultry industry was affected by egg quality (Hussein et al., 2018). Chicken's eggs contain minimum fat with high-quality protein.
Overall, production, egg weight, egg mass and, FCR were increased with the high dose of orally administered GABA in drinking water of laying hens. The increased laying performance evoked by GABA supplementation in this study might relate to neuroendocrine system-mediated effects on nutrient metabolism (Zhang et al., 2012). It was recorded that, the addition of GABA in the layer diet not only alleviated stress in hens but also played a major role in the improvement of nutrient utilization, appetite regulation and increasing the utilization of dietary calcium and phosphorus, resulting in improving egg laying performance and quality ( GABA had a direct beneficial effect on laying performance and egg quality, which manifested as a significant effect on egg production, egg mass, eggshell thickness, and egg weight and albumin height. The increase of nutrition utilization and antioxidant activities in response to GABA are likely the main cause of the improvements in laying performance and egg quality in layers (Park and Kim (2015). The diet supplemented with GABA improved the laying performance, egg quality and physical condition of hens, which had a significant effect on egg production, average egg weight, egg strength, hen immune activity, anti-oxidation activity and hormone levels (Zhang et al., 2012). GABA improved egg production and egg quality by increasing the total protein (TP) concentration (protein is the basic composition of the egg) and modulating the electrolyte balance (Calcium and phosphorus are very important for egg quality) (Zhang et al., 2012).
Cholesterol, triglycerides, phospholipids, lipoproteins are most of the lipids in eggs, which are concentrated in the yolk (Hussein et al., 2018). The cholesterol and triglycerides content of egg were reduced by the supplementation of GABA.
Environmental condition, management, nutrition, type and dosage of additive as well as birds' related factors (age, species and production stage) may be partly responsible for these contradictory results (Torki et al., 2018).   Values are means ± SE. Means within the same row of different letters are significantly different at (P ≤ 0.05).
317 Values are means ± SE. Means within the same row of different letters are significantly different at (P ≤ 0.05).

Conclusion:-
This study showed that GABA is a valuable supplementation for layers, and in particular, exerts beneficial effects concerning laying performance, egg quality, as well as a lowering of egg yolk cholesterol and triglycerides concentrations as demanded by health-conscious consumers. However, the action of oral GABA in laying hens still needs additional investigation to determine the effective treatment duration, perfect dosage, and mode of action.