Effect of Dietary Supplementation of Liquid Prebiotic and Antibiotic on Egg Production, Egg Quality, Blood Parameters, Immune System Response of Layer Hens at Post Molt Period

The inclusion of prebiotics in layer hen diets can act as a growth-promoting antibiotic replacer and have beneficial effects on egg production and egg quality. This study aimed to investigate the effects of liquid prebiotic on the post-molt laying performance, egg quality at different storage temperatures and times, immune system function, and blood biochemical parameters of laying hens.

A total of 144 White Leghorn Hy-Line W-36 laying hens at 83 wk of age were randomly assigned to 6 dietary treatments, 4 replicates, and 6 birds per each for 6 weeks in a complete randomized design experiment. Experimental diets were: 1- A corn-soybean meal-based diet without adding liquid prebiotic as a control, 2 to 5- Supplementing basal diets with 0.5, 1, 1.5, 2 ml of liquid prebiotic per Kg of diet, 6- basal diet with adding 500 mg of oxytetracycline as an antibiotic per kg of diet. Laying performance including egg production, egg weight, egg mass were recorded daily, and feed intake and feed conversion ratio were calculated weekly. In order to evaluate the egg quality traits at various storage temperatures (refrigerator temperature (4ºC) and room temperature (25ºC) and storage periods (0, 7, 14 days), two eggs were randomly selected from each replicate in the 2th, 4th and 6th weeks of the experiment and the egg quality traits were measured. To evaluate the effects of liquid prebiotic supplementation on humoral immunity, antibody production against sheep red blood cells (SRBC) was used. The data were subjected to statistical analysis using a completely randomized design by SAS 9.1 software (SAS, 2004). The egg quality traits data were subjected to analysis of variance in a completely randomized design as a 6×3×2 factorial arrangements (6 levels of liquid prebiotic and antibiotic supplementations, 2 different storage temperatures and 3 storage periods).

The results showed that by increasing the prebiotic supplementation, the daily egg production (p=0.0057) and egg mass (p=0.0013) were linearly increased, and feed conversion ratio (p=0.0016) were linearly decreased. The effect of adding liquid prebiotic on egg quality traits including egg shape index, shell percentage, and shell thickness was not significant (p>0.05), but the effect of storage period on egg shape index and the effect of storage temperature on shell thickness and egg shape index was significant (p<0.05). Supplementation of diets with liquid prebiotic was significantly influenced the cholesterol, glucose, calcium, and aspartate aminotransferase (AST) concentrations of laying hens (p<0.05). The total antibody titer (IgT) against SRBC was increased by increasing supplemental prebiotic.

In conclusion, supplementation of 2 ml/kg liquid prebiotic in the diet of layer hens at post-molt period can act as an alternative to antibiotic growth promoters, thus the laying performance was enhanced, and by augmentation of production the specific immunoglobulins, the immune status was improved.