| To elucidate the effect of photoperiod on the growth development and sexual maturation of Meishan boars,we observed the effects of constant light on the development of body weight,body size,sexual organs,behavior,steroid hormones and the fecal bacterial flora of Meishan boars in present study.In addition,the interaction of photoperiod and temperature on the growth and steroid hormone secretions were analyzed by Two-way ANOVA.1.Effects of constant photoperiod on growth and steroid hormones in growing boarsFourteen Meishan piglets aged 70 d were divided into constant short photoperiod group(CSP,lighting time:08:00-18:00,10L:14D)and constant long-lighting group(CLP,lighting time:08:00-22:00,14L:10D),paired in same litter and bodyweight,the experiment duration was 14 weeksCLP treated boars had higher body weight gain(P=0.036)and lower feed conversion rate(P=0.030)than that of the CSP treated boars.CLP treated boars had higher height at 6w,8w,10w,and 12w(P=0.008,0.050,0.020,0.011)and longer chest circumference at 10w and 12w(P=0.009,0.049)than that in the CSP treated boars.There was no significant difference in testicular size between the two groups at 6w,8w,10w,and 12w.The length of testis in the CLP group at 14w was significantly larger than that in the CSP group(P=0.042).There was a significant correlation between body weight,body size,and developmental changes in the testis(r=0.423～0.912,P=0.000).Behavior observation data showed that the CLP group had fewer frequency and duration of explore behavior than the CSP group at the 50th,70th,and 80th day of treatment(P=0.033,0.025,0031),accordingly the CLP boars spent more time on lying than the CSP boars at 50d,60d,70d,90d respectively(P=0.011,0.012,0.021,0.01),there were no significant differences in the frequency and the duration of mounting and feed intake.In the first 11 weeks of treatment,the level of testosterone(T)in the feces of Meishan pigs increased gradually,and reached the peak level at 11w,afterwards it decreased.The fecal T levels of the CLP group were significantly higher than that in the CSP group(P=0.015,0.020)at 11w and 13w.During the first 5 weeks of the experiment,there were no changes of the fecal cortisol(Cor)level,whereas the fecal Cor level gradually increased from 5w and reached a peak level at 11w and then decreased.The fecal Cor level of the CLP group was significantly higher than that in the CSP at 11w(P=0.035).There was a significant positive correlation between T and Cor(r=0.693,P=0.000).2.Effect of constant photoperiod on the fecal bacterial flora of Meishan boarsThe pyrosequencing analysis of fecal microbiome indicated that there was no difference of Chao and Ace between the two treatments.CLP group had higher Shannon index(P=0.045)and lower Simpson value(P=0.044)than that of the CSP group.CLP group had higher relative abundance of Fibrobacteres(P=0.049),Mollicutes_RF9(P=0.043)and Fibrobacterales(P=0.049)than that of the CSP in the fecal microbiota.In addition,CLP treated boars had increased levels of fecal isovaleric acid and total short-chain fatty acids than that in the CSP(P=0.027,0.037),and no difference of acetic acid,propionic acid,butyric acid and valeric acid between the groups was found.3.Interaction of temperature and photoperiod on the adult Meishan boarsSix Meishan adult boars were divided into three pairs according same litter and similar weight,each pair of boars was treated with normal temperature and short light(NS,10L:14D,light time 08:00-18:00,temperature:15～20℃),normal temperature and long light(NL,14L:10D,light time 08:00-22:00,temperature:15～20℃),and high temperature and long light(HL,14L:10D,light time 08:00-22:00,temperature:21.5～32℃)for 2 weeks respectively,boars were weighed individually before and after each treatment.Boar was kept in individual pen,ad libitum to feed and drink.50 Lux were provided by LED Two-way ANOVA analysis indicated that,there was a significant interaction between photoperiod and temperature on daily weight gain(P=0.004),photoperiod did not have main effective influence on the daily body weight gain,whereas temperature had main effective influence on the daily body weight gain(P=0.000).The NL treatment increased daily body weight gain than that of HL treatment(P=0.001).Both temperature and photoperiod did not have main effective influence on the apparent digestibility of crude protein and dry matter.There was a significant interaction between photoperiod and temperature on exploring behavior and lying time(P=0.020,0.050).Photoperiod had main effective influence on the exploring frequency,the NL treated boars spent less time in exploring and more time in lying than that of NS treated boars(P=0.037,0.05).Temperature had main effective influence on the exploring behavior,the NL treatment had more exploring behavior than that of HL treatment at the 2d,6d and 14d of treatment(P=0.012,0.036,0.047).Photoperiod had main effective influence on lying,HL treated boars spent more time in lying on the 2nd and 6th day of treatment than that of HL treated boars(P=0.019,0.05).The NS treated boars had less time in lying than HL treated boars during the two week treatment(P=0.009,0.001,0.001,0.038,0.013,0.004,0.005,0.030,0.004,0.016,0.040,0.004).In summary,present date illustrate that CLP can promote the growth,sexual maturation and fecal microbiota diversity in growing boars.The temperature and photoperiod can interact influence the weight gain and the secretion of steroid hormones in adult boars. |
