Genetic Study to Re-Evaluate the Performance of Fayoumi Chickens • Means and Heritabilities of Growth Performance (Body Weight and Weight Gain) in Growth Line (Gg)

Twelve lactating Friesian cows with the average body weight of 490-560 kg were used in this study. All animals were in the second to fourth lactation season. Cows were randomly distributed into three similar groups (four for each group) to study the effect of the tested rations on milk production and its composition. All groups were individually fed according to NRC (2001) recommendations. The experimental period lasted for 140 days (20 weeks) after calving. The three experimental rations were formulated nearly as follows: (Control): 40 % concentrate feed mixture (CFM) + 32 % rice straw (RS) + 28 % corn silage (S), (Exp.1): 40 % concentrate feed mixture (CFM) + 32 % rice straw (RS) + 28 % berseem (B) and (Exp.2): 40 % concentrate feed mixture (CFM) + 32 % rice straw (RS) + 14 % corn silage (S) + 14 % berseem (B). The average daily milk yield was the highest (p < 0.05) with group fed exp.1 from W1 to W12 compared with the control ration, while there were no significant effect between exp.1 and exp.2 or exp.2 and control ration. The average milk yield were 12.69, 16.05 and 15.17 Kg/day with feeding on control, exp.1 and exp.2 respectively. The milk composition of protein% was higher (p < 0.05) with feeding on exp.2 (2.51%) than feeding on exp.1 (2.29%), but there was no significant effect between exp.1 and control ration (2.37%) or feeding on exp.2 and control ration. The net energy (NEL Mcal/kg milk) values were significantly (p < 0.05) higher with feeding on control or exp.2 (0.64 and 0.63 Mcal/kg milk respectively) than feeding on exp.1 (0.60 Mcal/kg milk). The protein yield and lactose yield (kg/day) were increased (p < 0.05) with feeding on exp.1 and exp.2 rations than feeding on control ration. The highest values of feed conversion (DMI kg/kg FCM) and net energy of the milk (Mcal/kg milk) were with feeding on rations containing corn silage (control) or corn silage with berseem (exp.2) than ration which containing berseem only (exp.1). The highest values (p<0.05) of feed cost were estimated with exp.1 (40.01 LE) and exp.2 (38.07 LE) than feeding on the control diet (36.09 LE), but there was no significant affect between the control and exp.2 or exp.1 and exp.2. With the same trend the profit (LE) values were higher (p<0.05) with feeding an exp.1 (21.63 LE) or feeding with exp.2 (18.69 LE) than feeding with the control (15.35 LE). Corn silage is an important source of digestible effective fibre and can be an economical source of CP in diets for lactating cows, but increased passage rate with feeding berseem which is more digestible forage NDF might increase efficiency of milk production and composition. So feeding on exp.1 or exp.2 resulted in improving milk production, feed conversion and economic efficiency.