Effects of different LED light colors on reproductive performance of rabbits and their molecular regulation mechanism

PAN Xiao-qing;WANG Xing-long;YANG Jie;QIN Feng;SHAO Le;LI Jian;ZHANG Xia;ZHAI Pin;College of Animal Science and Technology, Yangzhou University;Institute of Animal Science, Jiangsu Academy of Agricultural Sciences;

LED light color;;rabbit;;reproductive performance;;molecular regulation

To explore the molecular mechanism of different LED light colors affecting the reproductive efficiency of female rabbits, three hundred female rabbits reared in a single cage were randomly divided into five groups for different LED light colors treatments. LED red light(660 nm), LED green light(540 nm), LED blue light(480 nm) and LED white light(400-760 nm) were projected downwards at 60 cm above the rabbit cage. The control group was incandescent lamp(400-1 050 nm). Female rabbits received the treatment with supplementary light three times a week, the duration was 12 hours(12 D∶12 L), the pre-experiment was seven days, and the standard test was 90 days. The light intensity of LED lamp and incandescent lamp was set as 100 lx. Compared with incandescent lamp group and LED white light group, the estrus rate of female rabbits in LED red light group increased by 20.89 percentage points and 10.51 percentage points(P<0.05). Compared with LED green light group and LED blue light group, the estrus rate of female rabbits in LED red light group increased by 4.66 percentage points and 7.33 percentage points(P>0.05). The number of large red follicles in the ovaries of the female rabbits in the LED red light group increased, but there was no significant difference between the experimental groups(P>0.05). Compared with incondescent light, LED white light, LED green light and LED blue light, LED red light could promote the mRNA expression of GnRHR in the pituitary gland of female rabbits, but the difference was not significant(P>0.05). Compared with LED white light, LED green light and LED blue light, LED red light significantly increased the expression of FSHR and LHR in ovarian tissue(P<0.05). Compared with the incandescent light, LED red light could increase mRNA expression of FSHR and LHR gene in ovarian tissue, but the difference was not significant(P>0.05). In the primordial follicles(PrF) stage and the primary follicles(PF) stage, the effect of different LED light colors on the number of follicles was not significant(P>0.05). Compared with PrF and PF, the number of secondary follicles(SF) was significantly reduced due to the stepwise blocking of follicles, and differences began to appear between different groups. Compared with that in LED green light group and the LED blue light group, the number of SF in LED red light group, LED white light group and incandescent light group increased significantly(P<0.05). Due to further atresia of follicles, the number of tertiary follicles(TF) decreased significantly. Compared with that in the LED green light group, LED blue light group and incandescent light group, the number of TF in the LED red light group was significantly increased(P<0.05), but there was no significant difference in the number of TF between the LED red light group and the LED white light group(P>0.05). Compared with the LED green light, LED red light and incandescent light could significantly inhibit mRNA expression of FoxO1 in female rabbit ovaries(P<0.05). Compared with LED white light and LED blue light, LED red light and incandescent light could inhibit mRNA expression of FoxO1 in female rabbit ovary, but the difference was not significant(P>0.05). Both apoptosis-related genes of Bcl-2/Bax mRNA were expressed in rabbit ovary, but the relative expression levels of them were significantly different(P<0.05). The expression level of Bax mRNA was significantly higher than that of Bcl-2 mRNA. The effects of different LED light colors on Bcl-2/Bax mRNA expression in rabbit ovaries were also different. Compared with the LED green light, LED blue light and incandescent light, LED red light significantly increased the expression of Bcl-2 mRNA(P<0.05), but there was no significant difference in the expression of Bcl-2 mRNA between the LED red light group and LED white light group(P>0.05). The expression of Bcl-2 gene was affected by different light colors, showing a trend of red light> white light> incandescent light> green light> blue light. The effect of LED light color on Bax mRNA expression showed a trend of green light> blue light> white light> incandescent light> red light, but there was no significant difference(P>0.05). In conclusion, during the periodical breeding and production of large-scale rabbit farms in short-day season, the estrus rate of female rabbits can be improved by using 100 lx LED red light to supplement light from 18∶00 in the evening to 6∶00 in the morning of the next day for three days in a week. The transcription levels of key receptor genes on the HPG axis for regulation of reproduction, the number of secondary follicles, the number of tertiary follicles, and the transcription levels of genes related to follicular atresia and oxidative stress were affected by different LED light colors.