Effects Of Different LED Light Colors On Reproductive Performance Of Rabbits And Their Molecular Regulation Mechanism

With the further expansion of the rabbit industry,improving the efficiency of breeding has become the key to the efficient production of the rabbit industry in China.Production efficiency in rabbit farms can only rely on exogenous hormones to maintain periodic production.Light is an important signal for animals to sense changes in the environment and can cause changes in animal reproduction rhythms.If artificial light can be used to induce intervention in the female rabbit’s own reproduction rhythm,it can achieve a cycle-free reproduction mode without artificial hormones and reduce the tolerance of the female rabbits to exogenous hormones.Affected to improve the efficiency of periodic reproduction.At present,rabbits have gradually started using mixed light sources such as incandescent lamps and energy-saving lamps to regulate the reproductive rhythm of female rabbits,related research results have also focused on the reproductive performance of rabbits with different photoperiods.The reason may be that the previous research is limited by the type of light source.With the popularization of energy-saving and environmentally friendly LED monochromatic light source products,it is different.The effect of monochromatic light on the behavior and reproductive performance of female rabbits provides research conditions.Therefore,this article first explores the effec different LED light colors on female rabbits ’selective staying behavior,emotional substances,and estrus rate during the same period.The effect of light color on the transcription of the opsin synthesis gene in retinal ganglion cells(ipRGCs)was explored.This difference caused the change of melatonin(MLT)and its synthetic rate-limiting enzyme gene expression,and combined with the classical HPG axis reproduction regulation Changes in the expression of major key receptor genes and key genes for follicular atresia and granulocytic apoptosis.The molecular mechanism of the effect of ED light color on the reproductive performance of female rabbits provides a reference for obtaining light demand parameters produced by rabbit industry.The specific research results are as follows:1.An experiment was conducted on the effect of different LED light colors on behavior of female rabbits.5 month old New Zealand female rabbits(n=40)were placed on a 6m*6m square slotted wood floor platform in an artificial light control room,and the surrounding area was exposed.The rabbit cage is enclosed,and conventional nipple drinkers and troughs are evenly placed in the cage.The female rabbit can freely enter and exit any rabbit cage on the platform.The LED red light(660 nm)and green light(60 nm)above each rabbit cage are downward 540 nm),blue light(480 nm),and white light(400-760 nm),the light intensity and light time are set to 100lux/12D:12L.Observation data of female rabbits’ selective staying behavior in the activity space under different LED white,red,blue,and green light environments were obtained by continuous camera.The LED red light environment is more easily accepted and stayed by the mother rabbit,and its staying frequency is 13.1%and 11.6%higher than the LED green light and LED blue light,respectively,with significant differences(P<0.05).The selective retention rate of female rabbits was 6.8%higher,and the difference was not significant(P>0.05).2.Based on behavioral experiment,a single cage feeding experiment of 300 reserve female rabbits under different LED light color environments was carried out,and they were randomly divided into 5 groups at random,with 3 replicates in each group and 20 in each.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 60cm above the rabbit cage.The control group was incandescent group C(400-1050nm).The female rabbit receives 3 times of supplementary light every week,that is,from Friday to Sunday evening from 18:00 to 6am of the next day in the formal experiment,the duration is 12h(12D:12L).Incandescent group C’s light intensity and light time are set to 100lux/12D:12L,Serum emotional substance concentrations in reserve female rabbits under different LED light color environments were measured,and the results showed that different LED light color environments had an effect on emotional substance concentrations in young female rabbits.The concentrations of β-endorphin(β-EP)and serotonin(5-HT)in the serum of reserve young female rabbits in LED red light and incandescent lamp groups were significantly higher than those in LED green light group and LED blue light group(P<0.05),But compared with the LED white light group,the difference was not significant(P>0.05);the serum acetylcholine(Ach)concentration was not significantly different between the experimental groups(P>0.05);the cortisol concentration in the LED red light environment Significantly higher than the LED green light group(P<0.05),compared with the incandescent lamp,LED white light group and LED blue light group,the concentration increased,but the difference was not significant(P>0.05).3.Compared with incandescent lamp and LED white light group,the estrus rate of female rabbits in LED red light group increased by 20.89%and 10.51%,respectively,with significant differences(P<0.05);Compared with blue light,it increased by 4.66%and 7.33%respectively,the difference was not significant(P>0.05);the number of large red follicles on the surface of ovary of female rabbits in the LED red light group increased,but the number of large red follicles on the ovary between the experimental groups The difference was not significant(P>0.05).4.Different LED light colors have an effect on the serum MLT content of female rabbits in a specific time period(11:30 pm-12:30 pm).Compared with the LED green light group,the female rabbit serum MLT content in the LED red light environment is 10.32%lower,The difference is it(P<0.05),and the difference is not significant compared with the control incandescent lamp group,LED white light and LED blue light group(P>0.05).The expression of the rate-limiting enzyme Aanat mRNA of MLT in pine cones is affected by different LED light colors.Compared with LED white light,LED red light can significantly inhibit the expression of Aanat mRNA in pine cones(P<0.05).Compared with the LED green light and blue light groups,LED red light had a tendency to inhibit the expression of Aanat mRNA in pineal cones,but the difference was not significant(P>0.05).The expression of MLT receptor Mel1a/b mRNA is different in different parts.The MLT receptor Mel1a mRNA is expressed in the retina,SCN nucleus,pineal gland,hypothalamus,pituitary gland,and ovary of female rabbits,and it is similar to other tissues.The expression level in the pineal gland is very significant(P<0.01);Mel1b mRNA is expressed in the retina,SCN nucleus,pineal gland,hypothalamus,ovary of the female rabbit,and suspected expression in the pituitary;LED the expression level of Mel1a mRNA in pineal gland of red light group was significantly higher than that of LED green light group and blue light group(P<0.05),but compared with incandescent light group and LED white light group,the difference was not significant(P>0.05);There was no significant difference in the expression of Mel1a gene in the retina,SCN,and hypothalamus of female rabbits under different light colors(P>0.05);the expression of Mel1b gene in the retina,SCN,pineal gland,and hypothalamus of female rabbits under different light colors The difference was not significant(P>0.05).The transcription of the Opn4 gene in the retina of female rabbits was affected by different LED light colors.The expression of Opn4 gene in the retina of female rabbits in the LED red light group was significantly higher than that of the incandescent light group and the LED green light group(P<0.05).Compared with the blue light group,the expression difference was not significant(P>0.05).5.Compared with incandescent lamp group,LED white light,green light and blue light,LED red light can promote the expression of GnRHR mRNA in the pituitary gland of female rabbits,but the difference is not significant(P>0.05);compared with LED white light,green light and blue light In comparison,LED red light significantly increased FSHR and LHR gene mRNA expression in ovarian tissue(P<0.05).Compared with the incandescent lamp group,LED red light had a tendency to increase FSHR and LHR gene mRNA expression in ovarian tissue.But the difference was not significant(P>0.05).6.There is no significant difference in the number of different LED light colors at the primary follicular(PrF)stage and the primary follicular(PF)stage(P>0.05).Compared with the LED green light group and the LED blue light group,the LED red light group The number of secondary follicles(SF)in the LED white light group and the incandescent light control group increased icantly(P<0.05);as the follicles were further blocked,the number of tertiary follicles(TF)decreased significantly,and the LED green light,LED blue light and incandescent light groups In comparison,the LED red light group significantly increased the number of tertiary follicles(TF)(P<0.05),but compared with the LED white light group,the difference was not significant(P>0.05).Compared with the LED green light group,LED red light and incandescent light can significantly inhibit FoxO1 mRNA expression in female ovaries(P<0.05);compared with LED white light and LED blue light,LED red light and incandescent light can inhibit female rabbit ovarian FoxO1 mRNA expression trend,but the difference was not significant(P>0.05).Both apoptosis-related genes of Bcl-2/Bax mRNA were expressed in rabbit ovaries,and the relative expression levels of the two were significantly different(P<0.05).The expression of Bax mRNA was significantly higher than that of Bcl-2 mRNA.The effect of different LED light colors on the expression of Bcl-2/Bax mRNA in rabbit ovaries also differed.Compared with the LED green,blue and incandescent control groups,LED red light significantly increased the expression of Bcl-2 mRNA(P<0.05).),But compared with the LED white light group,the difference between the two is not significant(P>0.05).The expression of Bcl-2 gene is affected by different light colors,showing red light>white light>incandescent light>green light>blue light Trend;the effect of LED light color on Bax mRNA expression in different groups showed a trend of green light>blue light>white light>incandescent light>red light,but there was no significant difference between groups(P>0.05).7.Analysis of the SCN nuclear transcriptome of female rabbits found that there were 263 shared differentially expressed genes(DEGs)in the LED red light group(R),LED white light group(W),and incandescent lamp(N)in the control group.Compared with the LED white light group and the incandescent lamp group,LED red light can significantly increase the number of differentially expressed genes in the SCN nucleus of rabbits.The GO analysis found the differential genes in molecular function are mainly G protein-coupled receptors.Related genes are dominant,among which the transporter activity has the largest proportion in molecular functions.The results of KEGG Pathway enrichment analysis of differential genes produced in different groups show that the common KEGG Pathway enrichment characteristics of different groups are mainly neuroactive ligands.Receptor interaction pathways are dominant;qPCR was used to verify Pathway enrichment of the NPY gene,BMP6 gene,and HTR4 gene in the cAMP signaling pathway of the NPY gene in the smallest top 10 steroid synthesis pathway(Ovarian steroidogenesis),AGTR1 gene in Neuroactive ligand-receptor interactio pathway,CD36 gene in extracellular matrix receptor interaction(ECM-receptor interaction)pathway,phosphatidylinositol 3 kinase(PI3K)/AKT(protein kinase B)(PI3K-Akt signaling pathway)signal pathway,IGF1 gene in the verification results showed poor The expression trend of heterologous genes in transcriptome sequencing was consistent with the expression trend verified by qPCR.In this paper,SCN nuclear transcriptome analysis was used to obtain the regulatory pathways of the effects of different LED light colors on the SCN of rabbit reproductive rhythm.In order to clarify the molecular signaling pathways and their mechanisms of regulating rabbit reproduction by different LED light colors.