Impact of Betaine Supplementation on Growth Performance, Nutrient Digestibility, Egg Quality, Gas Emissions, and Blood Profile in Laying Hens Under Heat Stress Conditions

A total of 216 Hy-Line brown laying hens (28 week old) were utilized for this experiment. The laying hens were randomly divided into three treatments. Each treatment had six replications, and there were 12 hens in each replication. The ambient temperature was 32 ± 1 °C from 9:00 am to 5:00 pm, and 26 ± 1 °C otherwise. Treatments included a basal diet (CON), basal diet +0.075% betaine (TRT1), and basal diet +0.15% betaine (TRT2). The results indicated that incorporating betaine into the diets of laying hens led to a significant improvement in egg production between weeks 6 and 8 (<i>p</i> < 0.05). HU height showed a linear improvement in week 8 alongside betaine supplementation. At week 8 of the experiment, there were significant increase in the digestibility of DM, nitrogen (<i>p</i> < 0.05). Moreover, there was a linear decrease in gas emission of NH_3, H₂S (<i>p</i> < 0.05), and Methyl mercaptans (<i>p</i> = 0.05) in week 8 in hens whose diet was supplemented with betaine. Betaine also linearly reduced blood cortisol (<i>p</i> < 0.01). In summary, increasing betaine supplementation in the diet of laying hens during the summer season enhanced egg production, egg quality, gas emission, and blood profile.