الفهرس 
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Abstract
Objectives : This study was undertaken to evaluate the effect of weaning age and dietary supplementation with β-Pro (a combined mixture of probiotics and enzymes) on growth performance, carcass traits and some blood plasma measurements of New Zealand White × Californian rabbits. Methods & Results : Seventy two unsexed rabbits were divided into two haves according to weaning age (4 or 5 weeks). Each half was randomly distributed into 3 experimental groups, of four replications each. Three pelleted experimental diets, fortified with 3 levels of β-Pro (0.0, 0.02 and 0.04%), were formulated and used from weaning to 12/13 weeks of age. Rabbit response was examined as growth performance, carcass traits, and some blood plasma measurements of growing rabbits. The most important results are: ☼ No mortality of rabbits occurred during the experimental period. ☼ Regardless of dietary β-pro supplementation, delaying weaning age to 5 weeks significantly increased (P≤0.01) total feed intake (FI) and final live body weight (LBW) of rabbits compared with those of rabbits that were weaned at 4 weeks old. ☼ Dietary supplementation with β-pro failed to significantly affect the final LBW of rabbits but caused a significant increase in total FI and when its level reached 0.04%, total weight gain improved significantly. ☼ Neither weaning age nor dietary β-pro supplementation could significantly alter feed conversion ratio, protein efficiency ratio, efficiency of energy utilization or economic efficiency of growth (EEG) during this study. ☼ The interactions between weaning age and dietary β-pro supplementation were not significant for all growth performance criteria, except for the total FI the interaction was significant. ☼ Carcass traits and blood plasma parameters of rabbits were not affected by weaning age, dietary β-pro supplementation or their interactions. Conclusion: Based on the present results, it is recommended to delay weaning age of rabbits to 5 weeks to obtain optimal growth performance. Diets of early weaned rabbits (4 weeks of age ) must be fortified with 0.04% β-pro to achieve optimal growth performance, with no adverse effects on carcass traits or the EEG under the conditions of this study.