| To study the effect of photoperiod on the development of puberty Meishan boars and underlying molecular mechanism,16 Meishan male piglets 55 d old were paired in litter and body weight into two trials,each trial had 4 pair piglets,(1)constant photoperiod group(CP,14L:10D,lighting duration was 08:00 to 22:00)vs.increasing photoperiod group(IP,12L-15 L,the light turned on at 08:00,and the turn off time starting at 20:00 and then postponed gradually for 15 minutes every week).(2)CP vs.decreasing photoperiod group(DP,14L-10 L,lighting time started from 06:00 to 20:00,and then gradually shorted as 08:00 to 17:00within 14 weeks by turning on light 10 minutes late and turn off light 10 minutes earlier every week).The developmental changes of bodyweight,gonadal organs,melatonin and testosterone content in fecal,and the circadian clock gene expressions in the testis and colon,and the fecal microbiome were analyzed.1 Effects of photoperiod on boar growth developmentThere was no significant difference in the body weight gain,the size and the weight of testicular and epididymal,and the testicular indexes in the boars among CP,IP,and DP group.While the bodyweight significantly positive correlated with the testicular weight(r = 0.710,P = 0.048).DP treated boars had a larger diameter(P = 0.012)and lumen area(P = 0.037)of seminiferous tubules,but smaller the interstitial area(P = 0.021)of boar testes than that in the CP-treated boars.There was no significant difference in the diameter and lumen area of seminiferous tubules and the interstitial area between the CP group and the IP group.The content of T in the IP group was significantly higher than that in the CP group at 2w(P = 0.011)and was significantly lower than that in the CP group at 4 w,8 w and 10 w(P= 0.013,0.006,0.015);the content of T in the DP group was significantly higher than that of in the CP group at 10 w and 14w(P = 0.048,0.022).The content of melatonin(MLT)in the feces in the CP group was significantly lower than that in the IP group(P = 0.025)and the DP group(P = 0.038)at the 2 w.At the 12 w,there was no significant difference between the CP group and the IP group.However,the content of MLT in the DP group was significantly higher than that in the CP group(P = 0.004).There is no significant correlation between the content of T and MLT in the feces.The expression of CLOCK and Per3 m RNA in the testis of the CP treated boars group were significantly lower than those in the IP treated boars(P = 0.004,0.022).The expression of Per2 m RNA in the testis of the CP group was significantly higher than that in the IP group(P = 0.006).There was no significant difference among the expression of BMAL1,Cry1,Cry2,and Per1 m RNA in the testis of CP group and the IP group.The expression of BMAL1 and Cry1 m RNA in the testis of CP group were significantly lower than those in the DP group(P = 0.029,0.000).There was no significant difference in the expression of CLOCK,Cry2,Per1,Per2,and Per3 m RNA in the CP group and the DP group.The MLT content in the feces significantly positively correlated with testicular circadian clock gene BMAL1(r = 0.505,P = 0.046)but did not correlate with other circadian clock genes.No significant correlation was observed between the content of T in the feces and circadian clock genes of the testis.2 Effect of photoperiod on circadian clock genes in colon and bacterial fecal floraThe expressions of colonic clock genes BMAL1,CLOCK,and Per3 m RNA in the colonic of CP group were significantly lower than those in the IP group(P = 0.006,0.001,0.008),and the expressions of Cry1 and Cry2 m RNA in the CP group was were significantly higher than those in the IP group(P = 0.002,0.002).No difference of the Per1 and Per2 m RNA abundance in the colon was observed between the expression of in the CP group and in the IP group.The expressions of colonic clock genes BMAL1,CLOCK,Per2,and Per3 m RNA in the colonic of the CP group was were significantly higher than those in the DP group(P = 0.013,0.001,0.001,0.020).The expression of Per1 m RNA in the CP group was significantly lower than that in the DP group(P = 0.042).There was no significant difference between No difference of the expression of Cry1 and Cry2 m RNA in the colon were observed between in the CP group and in the DP group.There was no significant difference in the microbial Chao,Ace,Shannon-Wiener,and Simpson indexes in the feces among the CP group,IP group,and DP group at the 2 w and 12 w.The relative abundance of Spirochaetes,Fibrobacteres(P = 0.008,0.019),unclassified＿Prevotellaceae,Mucispirillum,Anaerovorax,Butyricicoccus,Bacillus,Paraprevotella,Erysipelotrichaceae＿UCG-004,and Solobacterium in the feces in the CP group were significantly higher than those in the IP group at the 2 w(P = 0.018,0.000,0.045,0.015,0.046,0.025,0.029,0.031).The relative abundance of Chloroflexi,Corynebacterium,Mycobacterium,Alistipes,Ruminococcaceae＿UCG-009,and Sutterella in the feces in the CP group were significantly lower than those in the DP group at the 2 w(P = 0.049,0.016,0.014,0.037,0.009,0.013).The relative abundances of Oscillospira and Treponema＿2 in the feces in the IP group were significantly higher than those in the DP group(P = 0.023,0.039).The relative abundance of Quinella in the feces in the CP group was significantly lower than that in the IP group at the 12 w(P = 0.017).The relative abundances of Streptococcus in the feces in the CP group was significantly higher than that in the IP group(P = 0.037).The relative abundance of Epsilonbacteraeota,Alistipes,Ruminococcaceae＿UCG-001 in the feces in the CP group was significantly lower than that in the DP group at 12 w(P = 0.018,0.010,0.012).The relative abundance of horsej-a03 in the feces in the CP group was significantly higher than that in the DP group at the 12 w(P = 0.046).The colonic BMAL1 m RNA was positively correlated with the contents of acetic acid,propionic acid and isovaleric acid in the feces(r = 0.527,0.528,0.550.P = 0.036,0.036,0.027).CLOCK m RNA was positively correlated with the contents of acetic acid,propionic acid,butyric acid and isovaleric acid in the feces(r = 0.624,0.666,0.703,0.667.P = 0.010,0.005,0.002,0.005).Cry2 m RNA was negatively correlated with the contents of acetic acid,propionic acid,butyric acid,isovaleric acid and valeric acid in the feces(r =-0.653,-0.757,-0.775,-0.784,-0.560.P = 0.006,0.001,0.000,0.000,0.024).Per1 m RNA was negatively correlated with acetic acid in the feces(r =-0.509,P = 0.044).Per3 m RNA was positively correlated with propionic acid,butyric acid,and isovaleric acid content in the feces(r = 0.643,0.584,0.702.P = 0.007,0.018,0.002).There was no significant correlation between Cry1,Per2 m RNA and SCFAs.There was no significant difference in the content of acetic acid,propionic acid,butyric acid,isovaleric acid and valeric acid in the feces among the CP group,the IP group and the DP group at the 2 w and 12 w.In conclusion:(1)Decreasing photoperiod can promote the sexual maturity of adolescent Meishan boars.(2)Photoperiod affects gut microbial diversity and expression of colon and testis circadian clock genes.(3)Intestinal microbial composition correlates with the circadian clock genes,T and MLT,but their interaction needs to be further studied. |
