The Effect of Different Levels of Monosodium Glutamate on Performance, Egg Quality Characteristics and Blood Parameters of Laying Hens

In the poultry industry, feed efficiency is of great importance in order to reduce the cost of feed by maximizing production efficiency. To achieve this result, the use of synthetic amino acids, such as the amino acids methionine, lysine, arginine, etc. in poultry nutrition can play an effective role in animal performance. Application of monosodium glutamate in animals cause to increased levels of triglycerides, total protein, cholesterol and blood glucose in rats. Addition of 1% monosodium glutamate in broiler diets increased feed intake compared to the control group and also in relation to weight gain at the level of 0.25 and 0.5% monosodium glutamate had a significant decrease compared to the control group. Therefore, considering the role and importance of laying hen performance during the production process and due to the very important role of monosodium glutamate in the occurrence of these changes, the effects of consumption of different levels of monosodium glutamate on performance, egg quality characteristics and blood parameters were investigated.

In this study, 60 laying hens of "Hy-Line W36" strain at the age of 68 to 74 weeks in 4 treatments and 5 replications and 3 hens per replication were used. The experiment was conducted as a completely randomized design in four periods 14-day for 8 weeks. Experimental treatments included 0, 0.4, 0.8 and 1.2% levels of monosodium glutamate per kg of feed. To better benefit from the data, all measurement factors except body weight gain were sampled and evaluated at the end of every two weeks. Egg mass was also obtained by multiplying the percentage of daily egg production by the average weight of eggs produced on the same day. Egg quality traits including height and diameter of albumin and yolk, relative weight of yolk and shell and albumin, shell thickness, shape and specific gravity were measured. Blood parameters were selected from two cages in each cage every two weeks and blood samples were taken from their wing veins and the concentrations of glucose, cholesterol, triglyceride, HDL and VLDL were measured using a Pars azmon kit and a spectrophotometer. Experimental data were statistically analyzed using statistical software (2002) SAS 9.1. Significant differences between treatments were compared with Duncan's multiple range test at a significance level (P<0.05).

The effect of adding treatments on the traits related to egg mass production and feed conversion ratio at the age of 72-74 weeks and feed consumption in all weeks of the experiment was significant. Today, several neurotransmitters have been identified to regulate feed intake, one of which is glutamate, which is most abundant in the central nervous system, which reduces feed intake in broilers. Feed intake is reduced by adding monosodium glutamate throughout the production period. Moreover of experimental treatments on Haugh unit, albumin and yolk height in the whole period was significant so that adding 0.4% of monosodium glutamate to the diet was able to increase the height of albumin and Haugh units and decrease yolk height compared to other treatments. Adding 0.8% monosodium glutamate increased the white diameter in the whole period compared to the control treatment and the treatment containing 0.4% monosodium glutamate. The data showed that adding 0.8% of monosodium glutamate to the diet could increase cholesterol, triglyceride and VLDL concentrations at 70-72 weeks of age compared to other treatments. Also, adding 1.2% of monosodium glutamate to the diet has been able to increase the concentration of HDL and VLDL at the age of 76-74 weeks.

In general, it can be concluded that the addition of monosodium glutamate to the diet has no significant effect on the percentage of production, the relative weight of yolk, albumin and egg weight despite the significant effect on blood parameters that was observed also it did not have qualitative parameters of the shell. On the other hand, the addition of 0.4% monosodium glutamate to the diet reduced feed consumption in the entire production period. Also, this treatment was able to increase the height of the albumin and Haugh unit and decrease the height of the yolk compared to other treatments in the entire production period.