Thé 6 th Inter. Con .on Rabbit Prod. in Hot Clim., Assuit, Egypt, 503 - 520 (2010) EFFECTS OF PHOTOPERIOD AND MATING OR SEMEN COLLECTION TIMES ON THE PERFORMANCE OF DOES AND BUCKS OF NEW ZEALAND WHITE RABBITS UNDER HOT CLIMATIC CONDITIONS OF EGYPT Kh. M. Mahrose*; U.M. Abd El-Monem** and S.I. Peris** * Poultry Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt. Email: ostrichkhalid@hotmail.com or ostrichkhalid@zu.edu.eg ** Animal Production Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt. ABSTRACT Sixty three does at 6 months of age and twenty seven bucks at 7 months of age of New Zealand White (NZW) were used in an experiment of 3 × 3 factorial design during the hot period of the year (from May to September). Does and bucks were divided randomly into 3 equal groups (21 does and 9 bucks). The groups were allotted to one of the following 3 experimental photoperiods: 12L: 12D (12 hrs lighting and 12 dark), 14L: 10D (14 hrs lighting and 10 dark) and 16L: 8D (16 hrs lighting and 8 dark). Within each photoperiod, does and bucks were randomly distributed to 3 groups of mating times or semen collection times (8 a.m., 2 p.m. and 8 p.m.) and there were 7 does and 3 bucks per each mating time or semen collection time. The results of the present work can be summarized as follows: Doe and their litter traits: Insignificant differences were observed in the physiological body reactions due to the effect of photoperiods. All of doe and litter productive traits studied were significantly (P≤0.01) improved with the short photoperiod (12L: 12D). The lowest (P≤0.05) value of respiration rate was observed in does mated at 8 p.m. AST and ALT were significantly (P≤0.05) differed due to mating time. Rectum temperature, plasma blood total protein, albumin and globulin were insignificantly affected by mating time. Doe and litter productive traits studied were significantly (P≤0.05 and 0.01) higher in does mated at 8 a.m. Insignificant differences were observed in all traits studied of doe due to the effect of the interaction between photoperiod and mating time. Buck traits: Each of the physiological body reactions and reaction time of bucks did not significantly affect by photoperiods or semen collection time. Most of semen characteristics studied was significantly (P≤0.01) improved with short photoperiod (12L: 12D), while dead spermatozoa (%) was significantly (P≤0.05) declined with increasing photoperiod to 16 hrs/ day. Reaction time and semen characteristics studied were better (P≤0.05 and 0.01) when semen collected at 8 a.m. The interaction between photoperiod and semen collection time had insignificant effects on all of buck traits studied.