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The present study was carried out in Rabbit Research Unit at Sakha Research Station located in Kafr El-Shiekh governorate, Egypt to assess the impact of N-acetylecysteine (NAC) administration on the physiological, reproductive and productive performance of rabbit does. A total number of 21 pregnant, healthy, primiparous New Zealand White (NZW) rabbit does aged between 5-6 months with an average initial body weight (BW) of 3052 g were used. They were divided into three equal groups. The first group (G1) was served as control group without any administration. The second and third groups (G2 and G3) were injected subcutaneously with 50 and 100 mg NAC / kg BW, respectively. The injection with NAC doses started on day 14 of pregnancy and continued for seven consecutive days. The experiment lasted continuously for three months. The obtained results showed that, NAC treatment reduced the oxidative stress in pregnant rabbit does, G2 and G3 had the highest values of GST and the lowest values of both MDA and H 2 O 2 in comparison with those of G1.Total protein, albumin, globulin and A/G ratio did not significantly affected by NAC injection and tended to increase with pregnancy progress. In contrast, level of triglycerides decreased (P<0.05) in G2 and G3 than that of G1 and declined with progress of gestation till kindling. Treated groups decreased their blood urea nitrogen (BUN) values and increased their creatinine (CR) levels than those of G1. With progress of pregnancy, levels of BUN tended to decrease and CR levels tented to increase. Both transaminase enzymes (AST and ALT) activities decreased by NAC treatment and by pregnancy progress, particularly in G3. The changes in live BW of does in the three groups across the experimental period were insignificant. NAC injection achieved weaning day, G2 and G3 had heavier kits' weight than those in G1 by 26 and 20 %, respectively. Litter size increased obviously due to NAC treatment by 19 to 35 % in G2 and by 5.5 to 23.1 % in G3 than that in G1 during the all experimental days. Mortality rate reduced by NAC injection being the lowest in G2 (4.7 %) followed by G3 (11.2%) and the highest in G1 (23.6 %). Total milk yield was increased significantly in G3 and insignificantly in G2 compared to that of G1 by 17.5 and 4.5 %,respectively. The high dose was more effective in promoting milk production. The effect of NAC treatment on all milk components was insignificant, except milk lactose. From the first wk to the last wk, milk composition (%) of milk protein, milk lactose, milk total solids and milk solids not fats increased (P<0.05) whereas milk fat decreased. In conclusion, this study proved not only the effectiveness, but also the safety of NAC application and its capability to improve rabbit's performance particularly with high dose (100 mg/kg BW). Further studies are urgently needed to confirm our findings.

This study was carried out to improve the freezability of buck semen using two different types of cryoprotectants supplemented with melatonin as antioxidant in cold and hot temperature of breeding season. Ejaculates from four mature Egyptian baladi bucks were pooled after collection. Semen was extended with Tris-fructose-citric containing egg yolk using glycerol and dimethyl sulfoxide supplemented with two doses of melatonin (10-6 M and 10-3 M) in addition to control group. Types of motility as well as velocity, enzymatic activity and expression profile of selected genes were measured. The results revealed that the progressive motility percentage was significantly higher in samples supplemented with low dose of melatonin (10-6 M) compared to high dose (10-3 M) in glycerol (74.4 versus 64.4) and Dimethyl Sulfoxide (DMSO) based extender (35.5 versus 32.9) in cold temperature. The same trend was found in samples cryopreserved with glycerol (75.1 versus 53.5) and DMSO (32.1 versus 22) in hot temperature. The results also demonstrated that CASA parameters (VAP and VCL) were significantly increased in low compared to high melatonin dose in glycerol based extender during cold and hot temperature. The activity of total antioxidant capacity (TAC) was significantly higher in samples supplemented with low (0.49 mM/L) than high melatonin dose (0.16 mM/L) in DMSO extender. CPT2, ATP5F1A and SOD2 genes were up regulated in glycerol based extender groups in cold temperature compared to other groups of this study. On the other hand, NFE2L2 gene was upregulated in groups cryopreserved with DMSO in hot temperature compared with all other experimental groups. Therefore, it could be concluded that the glycerol based extender in cold season supplemented with low dose of melatonin improved semen quality, antioxidant defense capacity and transcriptional profile, which may maintain the post-thaw fertilizing ability of buck semen.

A total number of 24 mature New Zealand White (NZW) rabbits, was used in this work to determine some physiological reactions of rabbit does as affected by housing system (indoors versus outdoors housing) during Egyptian summer season conditions. Also, to ameliorate the adverse effects of stressful summer conditions by using highly concentrated nutritional supplement (Synertox® component). The animals were equally and randomly divided into two groups each of 12 does. In each group, 6 does received water plus Synertox and the other 6 does did not receive Synertox (control). Results showed that, the average values of rectal (RT) temperature was significantly lower in outdoors housing as compared to indoors one, and in the group received Synertox. The lowest and highest values of respiration rate (RR) were obtained in outdoors and indoors housing, respectively, for both control and treated groups. Synertox treatment caused significant (P≤0.01) decrease in RR in both housing models. The values of hematocrit, hemoglobin, red and white blood cells count, total proteins, albumin, aspartate and alanine aminotransferases, creatinine, urea-nitrogen and triiodothyronine, thyroxine hormone concentrations were significantly (P≤0.05) higher in does kept in outdoors housing than those kept in the indoors model. Treatment with Synertox caused significantly (P≤0.05) increase in most of these values under indoors housing condition. Conclusively, it can be concluded that, in spite of indoors housing "double iron sheets roof" accommodate and ideal house for raising rabbits but the good ventilation and absence of walls and its