Effects Of Early Feeding On Yolk Absorption And Utilization,Gut Development And Growth Performance In Broilers

Aiming at the problem of the long time of feed deprivation caused by hatching window and posthatch treatments in broiler chicks,a new type of hatching management system and early feeding have been carried out to improve the production efficiency and benefits of broilers.Pervious studies in our lacoratory have shown that chicks can get the highest body weight and feed conversion ratio by having access to feed within 24 h posthatch.Based on the above background,the purpose of this paper is to explore effects of early feeding on yolk absorption and utilization,gut development,growth performance and dynamic changes of physiological and biochemical indexs in broilers.Moreover,microbiomics and metabolomics were use to elucidate its molecular mechanism of early feeding on broilers,which may provide a theoretical basis for the development and application of early feeding strategies in broilers.1.Effects of early feeding on yolk absorption and utilization in broiler chicks(1-7 d)In this experiment,720 healthy Lingnan yellow broiler chicks which emerged within 2 hours with similar body weight were chosen and transported to the farm within 1 hour.All chicks were randomly divided into three treatments:2 h group,24 h group,and 48 h group.Each treatment had 6 pens of 40 chicks.All chicks had access to water ad libitum and to feed ad libitum only after initial feeding.The whole trial lasted 168 h.Samples were taken at 0,24,48,72,120,and 168 h.The results are as followed:1)Early feeding significantly increased(P<0.05)body weight and the relative weights of liver,pancreas and spleen in chicks;2)Early feeding promoted(P<0.05)the absorption of yolk and its nutrients(protein,IgY,amino acids,fatty acids and mineral elements);3)Early feeding promoted(P<0.05)glycogen and protein synthesis in liver and pectoral muscle,but inhibited(P<0.05)the synthesis of acetyl-CoA carboxylase and triglycerides in liver;4)Early feeding improved(P<0.05)the level of IGF-I in plasma and liver.These results suggest that early feeding promotes the absorption and utilization of yolk and its nutrients,thereby improving micronutrients synthesis and organ development,finally accelerating the growth and development in broiler chicks.2.Effects of early feeding on gut development and hormone scretion in broiler chicks(1-7 d)The design and breeding management of experiment 2 was consistent with experiment 1.The results of are as followed:1)Early feeding increased(P<0.05)the absolute and relative weight of the small intestine,villus height and crypt depth of jejunum and ileum in broiler chicks;2)The microvilli of the duodenum in early fed chicks were more neatly and tightly arranged;3)Early feeding increased(P<0.05)the mRNA and protein expression of tight junction genes(Occludin and Claudin-1)in jejunum of broiler chicks;4)Early feeding increased(P<0.05)IGF-I level in plasma and liver,gastrin and insulin concentrations in plasma,and decreased(P<0.05)glucagon concentration in plasma.These results suggest that early feeding can regulate hormone screation and tight junction genes and protein expresseion,which has the effect of improving the morphological structure of the small intestine in broiler chicks.3.Effects of early feeding on growth performance,hormone secretion and material metabolism based on serum metabolomics in broilers(1-50 d)In this experiment,900 healthy Lingnan yellow broiler chicks which emerged within 2 hours with similar body weight were chosen and transported to the farm within 1 hour.All chicks were randomly divided into three treatments:2 h group,24 h group,and 48 h group.Each treatment had 6 pens of 50 chicks.All chicks had access to water ad libitum and to feed ad libitum only after initial feeding.The whole trial lasted 50 days.A metabolic experiment is conducted during 14-21 days of age.Samples were taken at 8,22,and 51 days of age.The results are as followed:1)Early feeding increased(P<0.05)average daily gain and average daily feed intake of broilers during 1-7 and 1-21 days,and decreased(P<0.05)feed/gain ratio of broilers during 1-21 days;2)Early feeding increased(P<0.05)the apparent metabolic rate of Ash and P,but decreased(P<0.05)the apparent metabolic rate of EE;3)Early feeding increased(P<0.05)the contents of glycogen and protein in breast muscle at 7 and 21 days of age,and decteased(P<0.05)the contents of triglycerides in liver at 7 days of age;4)Early feeding increased(P<0.05)the concentrations of T4,IGF-I,INS at 7 d and T3,T4,IGF-I at 21 d in serum;5)19 different metabolites were observed between group 2 h and group 48 h through serum metabolomics at 7 days of ages.Compared with group 48 h,chicks in group 2 h had higher(P<0.05)concentration of linoleic acid,palmitic acid,inosine,guanisine et al.in serum.These results further confirm that early feeding could regulate hormone secretion and material metabolism,improving the growth performance and feed utilization at growth prophase.4.Effects of early feeding on gut development based on cecal microbiomics in broilers(1-50 d)The design and breeding management of experiment 4 was consistent with experiment 3.The results of are as followed:1)Early feeding increased(P<0.05)villus height and V/C ratio of duodenum at 7,21 and 50 days of age,and decreased(P<0.05)crypt depths of duodenum in 50 days of age in broilers;2)The tight junction in jejunum epithelial cell was more complete,having higher density,and the microvilli were longer.These results further confirm that early feeding could promote gut development in broilers.The results of microbiome analysis showed that:1)Early feeding decreased(P<0.05)the relative abundance of Bacteroidetes,Proteobacteria and Actinobacteria and increased(P<0.05)Firmicutes at phylum level;2)Early feeding decreased(P<0.05)the relative abundance of Bacteroides,Escherichia and increased(P<0.05)Clostridium at genus level.These results suggested that early feeding optimized the structure of microbial flora by decreasing the relative abundance of Proteobacteria and Escherichia(both are harmful bacterias).The correlation analysis of microbiome analysis and metabolomics anslysis showed that the relative abundance of Bacteroides in cecum was positively correlated(P<0.05)with the concentration of lipid and lipid-like molecules in the serum.This suggested that Bacteroides may have been involved in regulating the lipid metabolism of host.In summary,early feeding could promote yolk absorption and utilization,regulating hormone secretion and material metabolism,promoting tissue and organ development,and optimizing the structure of microflora and intestinal morphology,finally accelerating growth performance in broilers.