Linkage between the intestinal microbiota and residual feed intake in broiler chickens

Background:Intestinal microbiota plays a key role in nutrient digestion and utilization with a profound impact on feed efficiency of livestock animals.However,the intestinal microbes that are critically involved in feed efficiency remain elusive.Methods:To identify intestinal bacteria associated with residual feed intake(RFI)in chickens,male Cobb broiler chicks were individually housed from day 14 to day 35.Individual RFI values were calculated for 56 chickens.Luminal contents were collected from the ileum,cecum,and cloaca of each animal on day 35.Bacterial DNA was isolated and subjected to 16S rRNA gene sequencing.Intestinal microbiota was classified to the feature level using Deblur and QIIME 2.High and low RFI groups were formed by selecting 15 and 17 chickens with the most extreme RFI values for subsequent LEfSe comparison of the difference in the microbiota.Spearman correlation analysis was further performed to identify correlations between the intestinal microbiota composition and RFI.Results:No significant difference in evenness,richness,and overall diversity of the microbiota in the ileum,cecum,or cloaca was observed between high and low RFI chickens.However,LEfSe analysis revealed a number of bacterial features being differentially enriched in either high or low RFI chickens.Spearman correlation analysis further identified many differentially enriched bacterial features to be significantly correlated with RFI(P<0.05).Importantly,not all short-chain fatty acid(SCFA)producers showed a positive association with RFI.While two novel members of Oscillibacter and Butyricicoccus were more abundant in low-RFI,high-efficiency chickens,several other SCFA producers such as Subdoligranulum variabile and two related Peptostreptococcaceae members were negatively associated with feed efficiency.Moreover,a few closely-related Lachnospiraceae family members showed a positive correlation with feed efficiency,while others of the same family displayed an opposite relationship.Conclusions:Our results highlight the complexity of the intestinal microbiota and a need to differentiate the bacteria to the species,subspecies,and even strain levels in order to reveal their true association with feed efficiency.Identification of RFI-associated bacteria provides important leads to manipulate the intestinal microbiota for improving production efficiency,profitability,and sustainability of poultry production.

Early inoculation with caecal fermentation broth alters small intestine morphology,gene expression of tight junction proteins in the ileum,and the caecal metabolomic profiling of broilers

Background:The establishment of stable microbiota in early life is beneficial to the individual.Changes in the intestinal environment during early life play a crucial role in modulating the gut microbiota.Therefore,early intervention to change the intestinal environment can be regarded as a new regulation strategy for the growth and health of poultry.However,the effects of intestinal environmental changes on host physiology and metabolism are rarely reported.This study was conducted to investigate the effects of early inoculation with caecal fermentation broth on small intestine morphology,gene expression of tight junction proteins in the ileum,and cecum microbial metabolism of broilers.Results:Our data showed that early inoculation with caecal fermentation broth could improve intestine morphology.The small intestine villus height was significantly increased(P<0.05)in the intervened broilers compared to the control group,especially on day 28.A similar result was observed in the ratio of villus height to crypt depth(P<0.05).Meanwhile,we found early inoculation significantly increased(P<0.05)the expression levels of zonula occludens-1(ZO1)on days 14 and 28,claudin-1(CLDN1)on day 28,whereas the gene expression of claudin-2(CLDN2)was significantly decreased(P<0.05)on days 14 and 28.Gas chromatography time-of-flight/mass spectrometry(GC-TOF/MS)technology was further implemented to systematically evaluate the microbial metabolite profiles.Principal component analysis(PCA)and orthogonal partial least squares discriminant analysis(OPLS-DA)displayed a distinct trend towards separation between the fermentation broth group(F group)and the control group(C group).The differentially expressed metabolites were identified,and they were mainly functionally enriched in beta-alanine metabolism and biosynthesis of unsaturated fatty acids.In addition,1,3-diaminopropane was selected as a key biomarker that responded to early inoculation with caecal fermentation broth.Conclusions:These results provide insight into intestinal metabolomics and confirm that early inoculation with caecal fermentation broth can be used as a potential strategy to improve intestinal health of broilers.

Association of growth rate with hormone levels and myogenic gene expression profile in broilers

Background： The growth rate often varies among individual broilers of the same breed under a common management condition. To investigate whether a variation in the growth rate is associated with a difference in hormone levels and myogenic gene expression profile in broilers, a feeding trial was conducted with 10,000 newly hatched Ross 308 chicks in a commercial production facility under standard management. At 38 d of age,30 fast-, 30 medium-, and 30 slow-growing broilers were selected among 600 healthy male individuals. The levels of insulin-like growth factor-1（IGF-1）, triiodothyronine（T3）, thyroxine（T4）, and growth hormone in the serum or breast muscle were assayed by ELISA or RIA kits, and the expression levels of several representative pro-and anti-myogenic genes in the breast muscle were also measured by real-time PCR.Results： Results showed that both absolute and relative weights of the breast muscle were in linear positive correlations with the body weight of broilers（P 〈 0.001）. Fast-growing broilers had higher concentrations of IGF-1 than slow-growing broilers（P 〈 0.05） in both the serum and breast muscle. The serum concentration of T3 was significantly higher in fast-growing birds than in slow-growing birds（P 〈 0.05）. However, no difference was observed in growth hormone or T4 concentration among three groups of birds. Additionally, a decreased expression of an anti-myogenic gene（myostatin） and increased expressions of pro-myogenic genes such as myogenic differentiation factor 1, myogenin, muscle regulatory factor 4, myogenic factor 5, IGF-1, and myocyte enhancer factor 2B, C, and D were observed in fast-growing broilers（P 〈 0.05）, relative to slow-growing broilers.Conclusions： Collectively, these findings suggested that the growth rate is linked to the hormone and myogenic gene expression levels in broiler chickens. Some of these parameters such as serum concentrations of IGF-1 and T3 could be employed to breed for enhanced growth.