An experiment was conducted to determine the effects of different levels of methionine, protein and tallow on productive performance and egg quality of laying hens in the late phase of production. A completely randomized design with a 3×2×2 factorial arrangement, with three levels (0.34, 0.31, and 0.27%) of methionine (MET), two levels (12.8 and 14.7%) of protein (PRO) and two levels (1 and 3%) of tallow (TAL) with constant level of linoleic acid (1.55 ± 0.02%), was used. A number of 144 Hi-Line W-36 layers from 70 to 76 wk of age was randomly distributed into 12 treatment groups with 4 replicates of 3 hens each. Egg production and egg weight were daily recorded and feed intake and egg quality traits were recorded every 2 wk. There was a significant interaction between PRO levels and TAL for egg weight. Low levels of TAL and PRO decreased egg weight throughout the experiment. High levels of MET and TAL with concomitant reduced PRO, increased eggshell thickness, and a significant interaction between levels of MET, PRO and TAL was observed during the experiment (70 to 76 wk). Low level of protein (12.8%) significantly decreased albumen weight in the third 2-wk period. Yolk color increased when hens were fed low levels of PRO and TAL. Results of this experiment indicated that the simultaneous reduction of dietary PRO and MET in diets of Hi-Line W-36 laying hens in the late phase of production, reduced egg weight (P<0.05). Productive performance and egg quality were not affected by 12 and 20% reduction of PRO and MET, respectively. It seems that decreasing the levels of MET and PRO to lower than the recommended values can decrease egg weight without negative effects on productive performance and egg quality of laying hens in the late phase of production

This experiment evaluated the effects of Saccharomyces cerevisiae (S. cerevisiae) and citric acid on production performance, egg quality, intestine histomorphology, and avian β-defensin 1 and 2 (AvBD 1 and 2) gene expressions in laying Japanese quails. A total of 400 48-day-old quails were randomly assigned to a 2×2×2 factorial arrangement of treatments with 5 replicates (each containing 10 quails) for 7 weeks. Variable factors consisted of S. cerevisiae (0 and 100 mg/kg diet), citric acid (0 and 5 g/kg diet), and Virginiamycin (0 and 50 mg/kg diet). At the completion of the trial, one bird per replicate was randomly killed, and jejunal tissue samples were removed to evaluate intestinal morphometric characteristics. Samples were taken from the midpoint of the jejunum to measure the gene expression of AvBD 1 and 2. Dietary inclusion of both S. cerevisiae and citric acid resulted in increased egg weight, egg mass, reduced feed intake, and improved FCR (p<0.05). The addition of S. cerevisiae to diets containing citric acid reduced feed intake, increased egg weight, and improved FCR (p<0.05). Shell weight and shell thickness were increased in birds fed each of S. cerevisiae and citric acid supplements (p<0.05). Dietary S. cerevisiae and citric acid similarly increased intestinal villus height, width, surface area, and the villus height to crypt depth ratio (p<0.0001). Results showed that AvBD 1 and 2 genes expression were up-regulated on quails fed S. cerevisiaesupplemented diets (p<0.0001). In conclusion, these results suggest that supplementation of S. cerevisiae and citric acid as functional feed additives either alone or in combination could be a potential alternative to antibiotics in the diet of Japanese laying quails.