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Keywords
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Laying hens, methionine, protein, feed, egg, performance
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Abstract
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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)
but the main effect of protein was not significant in this respect. Treatment
containing 0.35% of methionine and 15% of protein have shown the highest
HDEP, EW and EM. Moreover, main and interaction effects on average
daily feed intake (ADFI) and feed conversion ratio FCR were not significant
(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
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