The objective of this study was to evaluate the effect of coenzyme Q10 (CoQ10) and L-carnitine (LC) administration on litter size, ovarian characteristics and in vitro production of rabbit embryos. This study was carried out at the International Livestock Management Training Center (ILMTC), belonging to the Animal Production Research Institute, Agricultural Research Center, Ministry of Agriculture. Total of 36 mature NZW rabbit does (5-6 months of age, 3-3.5 kg LBW as well as 6 NZW bucks (7.5-8 months of age and 3.5-4.0 kg LBW) were used in this study. Does were divided into 3 similar groups, (n=12). The 1 group was control (G1), while does in the 2 and 3 groups were given daily oral dose of 10 mg CoQ10/kg LBW (G2) and 40 mg LC/kg LBW (G3) for 21 days prior to natural mating, respectively. Five does from each group were slaughtered post-mating as oocyte donors for studying the effect of treatments on ovarian characteristics and in vitro maturation and fertilization of oocytes. Immediately after slaughtering, ovaries were removed and oocytes were collected by slicing technique and evaluated, then only compact-cumulus oocytes (COCs) were matured and fertilized in vitro. For the rest number of does in each group (n=7), pregnancy was handy diagnosed by palpation 10-12 days post-mating. Also, litter size and weight at birth up to weaning were recorded. The obtained results showed that, ovarian weight and number of follicles increased (P<0.05) in G2 and G3. Number of bleeding follicles and recovered oocytes increased (P<0.05) only in G2 as compared to G1, however, oocyte recovery rate was not affected by treatment. Frequency distribution of compact and partial denuded oocytes was higher (P<0.05), while that of expanded and denuded oocytes was lower in G2 and G3 as compared to G1. Percentage of oocytes with full expansion (maturation rate) was 80.3 and 79.3% vs. 73.8% and fertilization rate was 67.4 and 66.7% vs. 64.5% in G2 and G3 vs. G ((P≥0.05). Percentage of embryos at morula stage was higher (P<0.05) in G2 and G3 than in G1 (30.3 and 3.1% vs. 20%), respectively. Percentage of embryos at blastocyst stage was 21.2 and 21.4% vs. 15% in G2 and G3 vs. G1, respectively. Litter size of rabbit does was higher (P<0.05) in G2 and G3 than in G1 at birth (7.29 and 6.71 vs. 5.43/doe), at 21 days of age (6.71 and 5.86 vs. 4.43/doe) and at weaning (6.43 and 5.43 vs. 4.14/doe). Mortality rate of kits at birth or weaning was not affected by treatment. Average kit weight at birth was higher (P<0.05) in G2 and G1. However, average kit weight at weaning, average litter weight from birth up to weaning and average litter daily gain from birth up to weaning were higher (P<0.05) in G2 and G3 than in G1.
In conclusion, treatment of rabbit does 21 days prior to insemination with CoQ10 at a level of 10 mg/kg LBW or L-carnitine at level 40 mg/kg LBW as daily oral dose is recommended to improve in vitro embryo production and also to increase litter characteristics (size and weight from birth up to weaning) of New Zealand White rabbit does.