Abstract
The present study aimed to investigate the effect of the dietary levels of protein, methionine (Met), as well as probiotic on productive performance, feed utilization, and environmental pollution by N in Lohmann Brown laying hens. A total number of 160 Lohmann Brown laying hens at 20 weeks of age were randomly divided into 8 treatment groups using a 2 x 2 x 2 factorial design experiment. The experiment involved two levels of crude protein (16 and 18 %), two levels of Met (0.45 and 0.50 %), and two concentrations of probiotic (0 or 1 g/kg diet, with a concentration of 10(10) CFU/g of Lactobacillus acidophilus) within 20-42 weeks of age. Results revealed that egg production parameters were significantly (P < 0.01) improved for hens fed diets of 18 % CP comparing with that of 16 % protein within the period from 26 to 30 weeks of age. Protein utilization and feed efficiency values were enhanced with 0.67 and 0.72 % Met during the period of 26-30 weeks of the age. For the N pollution, results showed that increasing crude protein in the diet from 16 to 18 % caused significant (P < 0.01) increase in the excreted N from 0.349 to 0.492 g/d. The methionine level of 0.72 % recorded the highest values of total consumed N being 3.98 g/d and excreted N being 0.527 g/d comparing with the other levels. It could be concluded that the best productive performance could be given by using 0.72 % total sulfur amino acids (TSAA). Furthermore, the dietary level of 18 % CP with 0.72 % Met is preferred in feeding laying hens through the whole experimental period. Ecologically, reducing the level of crude protein in layer diets to be 16 % along with the supplementation of Met can play an important role in minimizing the pollution with N from poultry excretion.