Effects Of Royal Jelly On Growth And Reproductive Performance In Japanese White Rabbits

A series of techniques including radioimmunoassay (RIA), real-time fluorescence quantitative PCR and estrous synchronization were used in conjunction with the biological characteristics of Japanese white rabbit to detect the effects of Royal Jelly (RJ) on the growth and reproductive performance in Japanese white rabbits, with the aim to give hints for the improvement of animal husbandry production the prevention and therapy of reproductive disease, and the protection of endangered animal species.1. Effects of royal jelly on growth and reproduction performance of male Japanese white rabbits:Fifty four two-month-old male Japanese white rabbits were randomly and equally divided into three treatment groups which received RJ or saline by intragastric administration once a day for 80 days. The high and low dose groups received RJ of 0.2% and 0.1% of body weight, respectively, while the control group was administered with 0.1% body weight of saline. The rabbits were weighted once a week and slaughtered after 80 days. Levels of circulating FSH, LH, E2, P, T and PRL in plasma were determined by RIA on days 0,40,60 and 80 of treatment. Sperm density, vitality and abnormality rate were determined by biopsy prior to slaughter. After slaughter, organs were separated and each organ coefficient was calculated. The right testis was embedded in paraffin for histological examination. The results were as follows.(1) Of the six tested reproductive hormones, no difference was detected among the three groups before treatment. On days 40,60 and 80 of treatment with RJ, the levels of FSH, T and LH in the control group were significantly lower than those in the high or low dose groups (P<0.01). No significant difference was found for P, E2 and PRL levels. All of the six reproductive hormones had no difference between high and low dose groups.(2) The density of sperm was significantly higher in the high dose and low dose treatment groups than in the control group (P<0.01), but there was no significant difference between high and low dose groups. With regard to sperm motility, the low dose group was significantly greater than the control group while the high dose group was significantly lower than the control group (P?0.01). There was no significant difference in the frequency of abnormal sperm among the three groups.(3) Prior to 8 weeks, body weight among the three groups did not differ significantly. Beginning on day 56, the body weights were significantly higher in the high and low dose groups than in the control group (P<0.01), but high and low dose groups were not significantly different from each other. After slaughter, the organ coefficients of the male rabbit testis, hypothalamus and spleen in the high and low dose group were significantly higher than in the control group (P<0.01), while the organ coefficients of brain, lung and bladder were not significantly different among the three groups. The organ coefficients were not significantly different between the high and low dose groups.(4) Following 80 days of RJ administration, the cell number of the testicular seminiferous tubule epithelium was significantly higher in both treated groups than in the control group. Compared to the histology of the testes in the control group, the following changes were observed in the RJ-treated groups:Characters of the testicular seminiferous tubule appeared to be thin seminiferous epithelium; seminiferous epithelium cells were loosely arranged with larger central lumen; most cells in the lumen were the primary spermatocytes and secondary spermatocytes in the control group; however the seminiferous tube cavity was relatively narrow and was enriched by the sperm cells and sperm. Cell layers were increased. spermatogonia attached base membrane. Primary spermatocytes, spermatids and sperm were packed closely and extended to the lumen, clear nuclear staining. A large number of sperms were observed in the lumen in the RJ given groups.Taken together, these results suggest that RJ can promote the development of hypothalamus, spleen and testis of male rabbits; sperm density and sperm motility were significantly increased in the low dose group, and serum levels of FSH, T and LH (but not of P, E2 and PRL) were significantly increased after 40 d of RJ administration.2. Effects of royal jelly on growth, development and expression of sex hormone receptor mRNA in prepubertal female Japanese white rabbits:Twelve 50-days-old fasting female rabbits were given fresh RJ (0.2% or 0.1% of body weight) or saline (0.1% of body weight) once a day for 40 days. Then the rabbits were sacrificed by femoral artery bleeding and the hypothalamus, the right side of ovary and the uterus were quickly dissected for RT-PCR analysis of hormone receptor mRNA expression. In addition the organs like heart, the left side of the uterus and ovaries were collected for organ coefficient analysis. The serum levels of FSH, LH, E2, P, T and PRL were determined by RIA. The results were as follows.(1) Moulting was observed after 12 d in 67% and 75% of rabbits treated with high and low doses of RJ, respectively, but was not observed in the control group.(2) Royal Jelly had no effect on body weight or the organ coefficients of heart, hypothalamus and ovaries.(3) The levels of serum E2 in high and low dose groups were significantly higher than that in the control group. No significant difference was found in other sex hormones.(4) Uterine ER?and ovary ERp mRNA levels were lower in high and low dose groups than in the control group. There was a significant difference between the high dose and control groups in the level (P<0.01). High and low dose groups, low dose and control group were not significantly different. Hypothalamic GnRH mRNA was lower in the high dose treatment group compared with the control and low dose groups (P<0.01). LHR and FSHR mRNA levels were significantly decreased in the high dose group (P<0.01) and low dose group (P<0.05) relative to the corresponding levels in the control group.Taken together, these results suggest that RJ can increase serum E2 levels in prepubertal female Japanese white rabbits, while suppress the mRNA expression of GnRH in hypothalamus, ER?in the uterus, and ERp, FSHR and LHR in ovary.3. Effects of royal jelly on reproductive performance of mature female Japanese white rabbits:The effect of PG on the homochronous of healthy and multiparous female rabbits was studied at first. After that, the rabbits were injected with PG (0.25mg per rabbit) and divided into three RJ treatment groups as described above. They were then mated after a complete estrous to investigate the effect of RJ on the reproductive performance. The results were as follows.(1) Injection of 0.25mg PG per rabbit caused the levels of LH, FSH and E2 reaching peak and trough at 9h and 48h, respectively; P came into trough and peaked at 9h and 48h, respectively. After PG treatment, the levels of LH, FSH and E2 reached peak at 19:00 each day, and P came into trough; the levels of LH, FSH and E2 on day 12 after PG treatment was higher than those on days 4,8 and 16, P was lower(P<0.05).(2) The peak of LH, FSH, E2 and the trough of P appeared earlier in RJ treatment groups than the control group, no difference was observed between high and low dose RJ teatement groups, neither peak nor trough was different among the three groups.(3) There was no significant effect of RJ on litter size and survival rate. However, the number of ovulation and follicle, individual birth weight, litter weight at birth, lactation ability, litter weight and individual weight at weaning were significantly lower in the control group compared with the high and low dose groups (P<0.01), and high and low dose groups were not significantly different.Taken together, these results suggest that the injection of 0.25mg PG per rabbit can make the female rabbits reach estrus peak at 9h and come into dioestrus at 48h after treatment; it started into the next estrous cycle at 12d; peak and trough of sex hormone mainly appeared at 19:00 each day. RJ can shorten the estrous cycle of female rabbits, but has no significant effect on hormone levels in the same estrous cycle. RJ can promote the development of follicular and ovulating, improve the litter weight at birth, individual birth weight, lactation ability, litter weight and individual weight at weaning, but has no effect on litter size.