Effect of a Low-Protein Diet with Different Levels of Amino Acid Mixture in Laying Hens on their Performance and Some Qualitative Characteristics of Eggs

Abstract

Abstract This study was conducted for the period from 1/1/2022 to 1/8/2022 (210 days), to study the effect of replacing the mixture of amino acids (methionine, lysine, and threonine) instead of the protein concentrate in the diets of laying hens that reduced crude protein by (1, 1.5, 2%) in some qualitative characteristics of eggs. In the study, (128) laying hens of the Lohmann Brown type were used, at the age of (21) weeks, preceded by two weeks of preparation for the herd. They were randomly distributed among 8 treatments, with 8 replications for each treatment, as each repetition includes (2) chickens (16 chickens/treatment). And the experimental treatments were as follows: T1 the control (standard diet), T2 (a treatment devoid of the protein concentrate), and the treatments T3, T4, and T5 (in which the percentage of crude protein was reduced by 1% and a mixture of amino acids consisting of methionine, lysine, and threonine was added by 1, 1.5, and 2%, respectively)., and treatments T6, T7, and T8 (in which the percentage of crude protein was reduced by 2% and a mixture of amino acids consisting of methionine, lysine, and threonine was added by 1, 1.5, and 2%, respectively). The results showed that there was a significant (P < 0.05) superiority for the treatments T1, T4, and T8 in yolk weight, yolk diameter, yolk relative weight, and yolk index at the middle of the experiment at the age of (21-32) weeks, while both were significantly superior (P < 0.05) From the coefficients T2, T9, T10 in the yolk weight, yolk height, yolk diameter, and the relative weight of the yolk in the last period of the experiment, The results showed a significant superiority (P < 0.05) for treatments T1, T8, and T10 when calculating the Albumin weight, Albumin height, Albumin diameter, and the relative weight of the egg, Treatments T2 and T3 were significantly (P<0.05) superior when measuring the weight of the eggshell, the relative weight of the eggshell, and the average thickness of the eggshell, compared with most of the experimental treatments. These results indicate that there is a qualitative improvement for some of the studied traits when adding the mixture of amino acids and reducing the percentage of total protein by 1.2% compared to the control group that does not contain amino acids.