Effects of dietary vitamin E and lysine supplementation on performance and egg shell quality parameters of heat stressed laying hens in early laying period [Si{dotless}cakli{dotless}k stresi alti{dotless}ndaki erken yumurtlama döneminde olan tavuklari{dotless}n rasyonlari{dotless}na e vitamini ve lizin katki{dotless}si{dotless}ni{dotless}n performans ve yumurta kabuk özellikleri üzerine etkisi]

This experiment was conducted to determine the effects of vitamin e and/or lysine supplementation over their requirement levels in layer ration on performance and some egg quality characteristics of hens raised under heat stress conditions at early laying period. a total of 160 20-week-old layers (nick chick) were used in the study. there were four treatment groups each containing 40 layers in the experiment. each treatment group was consisted of 10 replicates. treatment groups were formed by inclusion of 250 mg/kg vitamin e,0.15% lysine,and 250 mg/kg vitamin e plus 0.15% lysine into corn-soybean meal based control diet. the duration of the experiment was 17 weeks and it consisted of a heat stress from 20 to 27th week of age and optimal environmental temperature from 28 to 36th week of age periods. dietary vitamin e supplementation increased egg shell thickness (p<0.001) for both periods and egg shell weight (p<0.01) in heat stress period only and a numerical increase compared to control group and showed significance (p<0.01) as compared to rest of the dietary treatments throughout the experiment. dietary lysine supplementation increased egg production in both heat stress and optimal environmental temperature periods (p<0.05). this positive effect on egg production was not seen in group with dietary vitamin e plus lysine supplementation. in conclusion,vitamin e supplementation above the requirement levels in layer rations improved egg shell quality whereas neither vitamin e nor lysine supplementation had any positive impact on the parameters investigated in layers at early laying period raised during and post-heat stress periods.