A total number of 228 Domyati ducks (180 ducks and 48 drakes), 24-wks-old were randomly taken, weighed and divided into four treatments of equal three replicates each. The main objective of this study was to investigate the effect of supplementing betaine (B) at levels of 0 , 0.5 , 1.0 and 1.5 g/kg diet on laying performance, egg quality , hatchability traits, semen quality, serum constituents and nutrients digestibility coefficient as well as economical efficiency during the studied laying period (24-40 wks of age) under summer conditions.
Dietary betaine supplementation resulted in a decrease in body weight losses comparing to the control, whereas, viability was insignificantly improved during the whole experimental period (24-40 wks). Egg number and laying rate were insignificantly improved, whereas, egg mass was significantly increased by supplementing 1.5 g B/kg diet as compared to the control during the overall experimental period. Feed consumption was insignificantly increased by supplementing different betaine levels, also, feed conversion ratio was insignificantly improved by supplementing 0.5 and 1.5 g B/kg diet during the overall experimental period. Fertility percentage was insignificantly improved by supplementing 0.5 and 1.0 g B/kg diet, while, hatchability percentage of both total set and fertile eggs was significantly improved by supplementing 0.5 g B/kg diet as compared to the control. Early, late and total embryonic mortality were significantly decreased by supplementing 0.5 and 1.0 g B/kg diet as compared to the control.
Serum total cholesterol was significantly decreased, and HDL was significantly increased by supplementing different betaine levels as compared to the control, whereas, LDL cholesterol was significantly decreased by supplementing 1.0 g B/kg diet only. Both HDL/ total cholesterol and HDL/ LDL ratios were significantly increased compared to the control. Red blood cell and lymphocyte (L) count were significantly higher by feeding betaine diets, whereas, heterophils (H) and H/L ratio were significantly decreased compared to the control.