| With the continuous improvement of the scale and intensive level of animal husbandry in China,more and more attention has been paid to the welfare and health of animals.Appropriate growing environment is one of the prerequisites to ensure the welfare of animals and healthy growth.Compared with the temperature,humidity and harmful gases in the piggery environment,less attention is paid to the light condition of the piggery.Infrared heat lamps are widely used for local heating of piglets in the farrowing house.Because of its heating principle,the heat preservation lamp warms up the environment through infrared ray,and at the same time,it is accompanied by the transmission of light.The effect of luminous environment on sows and piglets in the farrowing pens with heat lamps is unknown.In this study,the effects of light produced by two kinds of infrared heat lamps commonly used in production on the behavior of lactating sows,and circadian rhythm,health and fecal microflora of piglets were investigated by controlling the lighting in the farrowing house and the temperature under the same heat lamp.Experiment 1.Effects of light from heat lamps on posture of sows,and nursing and growth performance of pigletsIn this experiment,"Landrace × Large White" sows and their "Duroc × Landrace × Large White " offspring piglets were used as research subjects.24 primiparous sows with expected parturition dates were randomly divided into 3 groups: group C(piglets were heated by 250 W ceramic thermal lamps with no light radiation),group R(piglets were heated by 175 W infrared heat lamps with red surface)and group T(piglets were heated by 175 W transparent infrared heat lamps).Each group had 8 replicates,with 1 sow and her offspring piglets per replicate.The experiment lasted from the birth of the first piglet to weaning at 21 days.The temperature difference under the lamps was <1℃ by adjusting the hanging height of the heat lamps.The lighting in the piggery was turned on at 7:00 a.m.and off at 9:00 p.m.every day,and the heat lamps worked from the birth of the first piglet to the age of 14 days.Cameras were used to record diurnal posture changes and lactation behavior of sows on postpartum days 4,8 and 16.Piglets were weighed at 3 and 21 days of age.The result showed that there was no significant difference in the proportion of the duration of posture of sows in three groups on the same day(P>0.05);Compared with the other two groups,the frequency of posture change of sows in group T on the 8th postpartum day was increased(P<0.01).On the8 th postpartum day,the frequencies of posture changes of sows in the group R and group T were higher than that in the group C(P<0.05),while there was no difference between the three groups on the 16 th postpartum day(P>0.05).The nursing frequency in T group on the8 th postpartum day was higher than that in group C(P<0.05),but there was no significant difference in the nursing frequency at night.On the 4th and 16 th days,there was no significant difference in the nursing frequency during day or night among the three groups.There were no significant differences in duration per nursing,total nursing duration and total nursing duration at night among the three groups(P>0.05);The litter weight and ADG of piglets at 21 days in group T had a trend to be greater(P<0.1),while the RGR of piglets from3 days to 21 days was not different in three groups(P>0.05).In summary,under the conditions used in this study,the light from the two kinds of infrared heat lamps stimulated the posture change of sows to different degrees,and the effect of a transparent heat lamp was stronger than that of a red lamp,but both of them did not affect the total duration of each posture of sow.Nursing behavior in piglets was promoted by transparent heat lamps,and piglets heated by red lamps grew faster.Experiment 2.Effects of light from heat lamps on circadian rhythm and health status of pigletsOn the basis of experiment 1,the effects of light from heat lamps on circadian rhythm and health status of piglets were studied by measuring the concentrations of melatonin and cortisol in saliva samples at different times,as well as the concentrations of Cg A,HP,CRP,Ig A and ADA at different days.Six litters were randomly selected from each group,and a female piglet was selected from each litter.Salivary samples were collected at 8:00,14:00,20:00 and 2:00 of the age of 10 days and 20 days to determine the concentrations of melatonin and cortisol,and saliva samples were collected at 10:00 to determine the concentrations of Cg A,HP,CRP,Ig A and ADA.The concentration at 2:00 in group C was the same as that at8:00 and 20:00 in the daytime,and the concentration at three times was much higher than that at 14:00 in the afternoon(P<0.01).In group R,the concentration of melatonin at 2:00was much higher than that at three time in the daytime(P<0.01),while there was no difference in the melatonin concentration between the daytime(8:00,14:00,20:00)and the night(2:00)of group T(P>0.05).In the inter-group comparison,the content of melatonin in saliva of piglets in group R was higher than that in other groups at 8:00(P<0.05).At 20 days of age,the saliva melatonin concentration of piglets in group C at 8:00 and 20:00 had no difference,and both of them were extremely significantly higher than that at 14:00 and 20:00(P<0.01),and the concentration at 20:00 was higher than that at 14:00(P<0.05).The concentration at 2:00 in group R was much higher than that at 3 times in the daytime(P<0.01),and the concentration at 2:00 in group T was much higher than that at 8:00 and 20:00 in the daytime(P<0.05).In the comparison between groups,at 2:00,the concentration of group R was higher than that of group C,and there was no significant difference among the three groups at other moments(P>0.05).The results of cortisol showed that at 10 days,there was no difference between the three groups at different times or between groups(P>0.05).However,at 20 days of age,the cortisol concentration of piglets in group C at 8:00 was higher than that at 20:00(P<0.05),and there was no difference among different time periods in group R(P>0.05).The saliva cortisol concentration in group T at 8:00 was higher than that at 20:00 and 2:00(P<0.05).Cortisol concentration in group C at 8:00 was significantly higher than that in groups R(P<0.05).Significant differences were not found at other times(P>0.05).The results showed that at 10 days of age,HP levels were not different between the groups(P>0.05).At 20 days of age,the HP concentration in group T was higher than that in group C(P<0.05),but there was no difference between group C and group R,or between group T and group R(P>0.05).Compared with 10 days of age,HP concentration in group T was increased at 20 days of age(P<0.05),while there was no difference between group C and group R(P>0.05).The results showed that the levels of CRP and TP were not affected by different heat preservation lamp treatments,but the concentrations of CRP and TP were increased and decreased,respectively,compared with those at 10 days(P<0.05).The levels of Cg A,Ig A and ADA were not affected by different heat preservation lamp treatments and ages.In conclusion,transparent infrared heat preservation light changes the light environment in the farrowing pen,and reduces the melatonin level in the saliva of suckling piglets.Moreover,the change of light environment after the transparent heat preservation light is turned off increases the Hp level in the saliva of piglets.The red heat preservation light has no effect on the health status of piglets.Experiment 3.Effects of light from infrared heat lamps on fecal microbiota of pigletsRelated studies have shown that gut microbiota is susceptible to host circadian rhythms.Meanwhile,photoperiod is an important factor affecting body circadian rhythm,but few studies have reported the effect of photoperiod on gut microbiota of piglets.Therefore,this study was designed to assess the effect of light from infrared heat lamps on fecal microbiota of piglets.The experimental deign and animals grouping of this study were the same as in the previous chapter.The fecal samples were collected from piglets on days 10 and 21 of age for high-throughput sequencing metagenomics.Our results showed that light from infrared heat lamps had no effect on α-diversity index of fecal microbiota in piglets.Compared with group C,the distribution of gut microbiota community by using β-diversity in group R and T was more dispersed on day 10.Compared with other two groups,the relative abundance of Lactobacillus and Clostridium in feces of piglets in group T was the highest(P<0.05).In addition,melatonin and circadian rhythm related microorganisms were affected to some extent by photoperiod.For example,Parabacteroide and Lachnospira showed similar relative abundance in feces of piglets in R and T groups that received visible light sources.Taken together,light from infrared heat lamps can affect the microbiota composition in feces of piglets to some extent,but the overall effect on microbial structure is small.The effect of photoperiod on intestinal microbiota in piglets needs to be further explored. |
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