The Effect Of Shortening The Light Time On The Production Performance And Pituitary MRNA Expression Of 817 Broilers

This article is studying the effect of shortening the light time on the growth performance,comb development,slaughter performance,meat quality,serum biochemical indicators and pituitary mRNA expression of 817 broilers.The experiment selected 600 817 broilers and randomly divided them into 2 groups with 10 replicates in each group and 30 chickens in each replicate.The two groups were exposed to 24 hours of light for 1 to 3 days,0.5 hours of light per day for 4 to 8 days,and a constant light duration of 21 hours after 9 days.Starting from the 21 st day,the test group(lunch break group)turned off the lights for 45 minutes at13:00-13:45 every day.On the 50 th day,according to the average weight of each group,20 roosters were selected for slaughter determination,meat quality determination and serum biochemical index determination.Four pituitary samples were taken from the control group and the test group respectively,and RNA was extracted to build a library for RNA-seq analysis.The results showed that there was no significant difference in weight between the 20-day-old control group and the test group(P>0.05);the 35-day-old and 49-day-old test groups had significantly higher body weights than the control group(P<0.05),and the feed-to-meat ratio and death rate were low in the control group.There was no significant difference in crown length,crown height and crown thickness between the control group and the test group(P>0.05).The total evisceration rate and half evisceration rate of the test group were significantly higher than those of the control group(P<0.05),while the liver index was extremely significantly lower than that of the control group(P<0.01).There was no significant difference in fat percentage index between the two groups(P>0.05).The b* value of pectoral muscle in the test group was extremely significantly higher than that of the control group(P<0.01),and the L* value and a* value were extremely significantly lower than the control group(P<0.01).As for p H,cooking loss,drip loss,and shear force,there was no significant difference between the test group and the control group(P>0.05).The serum glucose content of the control group was significantly higher than that of the test group(P<0.05);while the content of cholesterol,triglycerides,high-density lipoprotein,low-density lipoprotein,uric acid,total protein and albumin did not change significantly(P>0.05).Transcriptome sequencing studies showed that a total of 284 differentially expressed genes were screened with |log2foldchange|>1 and corrected P-value<0.05 as the threshold.The genes SST,SSTR3 and SSTR4 related to broiler growth and development were down-regulated in the pituitary of the test group.GO enrichment analysis found that these differentially expressed genes were significantly enriched in the "Somatostatin Receptor Pathway","Cell Response to Calcium","Negatively Regulate Photoreceptor Cell Differentiation","Central Nervous System Development" and other pathways.Based on the above,the use of the 45 min light time of turning off the lights at noon can promote the growth rate of 817 broilers,improve the quality of broilers and increase the economic benefits of breeding.