Molecular aspects, blood parameters, bone mechanical properties, and performance of laying hens in response to various levels of methionine and protein

SUMMARY The effect of protein and methionine levels on jejunal and magnum molecular aspects, blood parameters, bone mechanical properties and performance of laying hens in 82 to 92 wk of age was studied. A completely randomized design with six treatments and four replicates in factorial arrangement by three levels of methionine (0.25, 0.30 and 0.35%) and two levels of crude protein (13 and 15%) was used. Hen day egg production (HDEP), egg weight (EW) and egg mas (EM) increased with increasing methionine level (P 0.05). The performance did not affected by protein levels (P>0.05). Jejunal deoxyribonucleic acid (DNA) concentration, blood parameters thyroxine, low density lipoprotein (LDL) and cholesterol were not significantly affected by different levels of methionine and protein (P>0.05). Ribonucleic acid (RNA) concentration and RNA:DNA ratio in jejunum, protein content in magnum, blood parameters (glucose, total protein, high density lipoprotein (HDL) and triidothyronine), egg production, egg weight, egg mass and tensile strength were increased by diet include 0.35% of methionine and 15% of protein levels but rupture force was higher in treatment include 0.25% of methionine and 13% of protein levels. In addition, plasma triglyceride decreased by 0.35% of methionine and 15% of protein treatments. Finally, it can be concluded that 0.35% of methionine and 13% of protein levels are better levels than others in laying hens feeding.