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Gut microbiota play critical roles in host nutrition and metabolism. However, little is known about the genetic effects on the gut microbiota assemblages because a suitable model for investigation is lacking. In the present study, we established the reciprocal hybrid fish lineages derived from the parents with different feeding habits, namely, herbivorous blunt snout bream (Megalobrama amblycephala, BSB, 2n = 48) and carnivorous topmouth culter (Culter alburnus, TC, 2n = 48). We investigated the genetic effects on gut microbiota assemblages by using 16S rRNA gene sequencing. The results showed that the gut characteristics (structure, relative gut length, relative gut mass, and Zihler’s index) differed between the two types of hybrids and the two parents. In particular, a strong correlation between genotype and gut microbial assemblages indicated that host genetic (subgenome) significantly altered the gut microbial communities. In addition, the microbial structures (composition and abundance) in the two types of hybrids were more similar to those in BSB parent (P > 0.05) than to those in TC parent (P < 0.05), and the cellulase contents in the gut (produced by gut microbes) also showed the similar results. The results suggested that the host genomic interaction (mainly subgenome domination) had a sizeable effect on shaping the gut microbiota assemblages in reciprocal hybrid fish. This study enriches our understanding of the relationship between host genetic and gut microbiota assemblages, and provides insight into gut microbiota and metabonomics.

Intestinal microbiota plays a key role in modulating host growth. However, the effect of triploidization on intestinal microflora and fast growth has not been fully explored. Here, autotriploid Carassius auratus (3nRR, 3n = 150) derived from Carassius auratus red var. (♀, RCC, 2n = 100) × autotetraploid fish (♂, 4nRR, 4n = 200) was established. Intestinal microbial community analysis of RCC and 3nRR was performed by 16S rRNA gene sequencing. Gut characteristics, growth rate, and digestive enzyme activity of the two groups of fish were explored. Significant changes in gut assemblages were observed in 3nRR fish. Differences in intestinal characteristics (structure, relative gut density, relative gut length, relative gut mass, and Zihler's index) were observed between RCC and 3nRR groups. Associations between microbial assemblages and intestinal characteristics were evaluated. Growth rate and activities of intestinal digestive enzymes (cellulase, amylase and trypsin) were higher in 3nRR compared with that in RCC. Spearman's correlation analysis showed a positive correlation between bacteria orders (Clostridiales, Micrococcales and Lactobacillales) and fast growth in 3nRR. In summary, the findings indicated that triploidization caused changes in gut microbiota and characteristics, and digestive enzyme activity. The relative abundance of several bacteria species was positively correlated with fast growth in 3nRR. The present study provided new insights into the growth mechanism of 3nRR and its interaction with intestinal microorganisms. • Triploidization could alter intestinal flora and gut characteristics in autotriploid Carassius auratus. • Growth rate and activities of intestinal digestive enzymes (cellulase, amylase and trypsin) were higher in autotriploid Carassius auratus compared with that in Carassius auratus red var.. • Spearman's correlation analysis showed a positive correlation between bacteria orders (Clostridiales, Micrococcales and Lactobacillales) and fast growth in autotriploid Carassius auratus. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of four dietary levels of L-threonine (0, 2.5, 5 and 7.5 g/kg) with or without Saccharomyces cerevisiae (SC) on performance, carcass characteristics, intestinal morphology and immune system of broiler chickens. A total of 360 1-d-old male broiler chicks were randomly allocated to eight treatments with three replicates of 15 birds. The experiment was done at 0 to 3 weeks (as starter phase) and 3 to 6 weeks (as grower phase). Growth performance traits including weight gain, feed intake and feed conversion ratio were recorded at the end of each week. At the end of the experiment eight birds per treatment were killed and carcass analysis was done. Sampling for blood evaluation was done on 7, 28 and 42 days of age. Results of this study indicated that use of SC did not affect feed intake, weight gain and feed conversion ratio in chicks in contrast with the L-threonine. Use of L-threonine improved feed conversion ratio and gain of birds. Carcass traits were not influenced by dietary L-threonine and SC supplements. Use of L-threonine increased the intestinal morphology parameters such as crypt depth and villi height and width in both jejunum and ileum segments. On the other hand, villi height and width and crypt depth increased in both jejunum and ileum segments when dietary L-threonine increased. Effect of SC supplement on intestinal morphology was not significant. Results of CBC (cell blood counts) parameters, such as white blood cells, red blood cells, haematocrit and haemoglobin showed that these parameters were not affected by dietary treatments. Furthermore, the immune response (antibody titre) against Newcastle disease was not affected by SC on both 26 and 42 days of age. However, use of L-threonine influenced the chicks' immune response at 42 days of age. Our results have shown that the supplementation of L-threonine as a source of dietary-threonine in combination with SC improved growth performance and intestinal morphology traits in broilers. [ABSTRACT FROM AUTHOR]

Gut microbiota play critical roles in host nutrition and metabolism. However, little is known about the genetic effects on the gut microbiota assemblages because a suitable model for investigation is lacking. In the present study, we established the reciprocal hybrid fish lineages derived from the parents with different feeding habits, namely, herbivorous blunt snout bream ( Megalobrama amblycephala , BSB, 2n = 48) and carnivorous topmouth culter ( Culter alburnus , TC, 2n = 48). We investigated the genetic effects on gut microbiota assemblages by using 16S rRNA gene sequencing. The results showed that the gut characteristics (structure, relative gut length, relative gut mass, and Zihler's index) differed between the two types of hybrids and the two parents. In particular, a strong correlation between genotype and gut microbial assemblages indicated that host genetic (subgenome) significantly altered the gut microbial communities. In addition, the microbial structures (composition and abundance) in the two types of hybrids were more similar to those in BSB parent ( P > 0.05) than to those in TC parent ( P < 0.05), and the cellulase contents in the gut (produced by gut microbes) also showed the similar results. The results suggested that the host genomic interaction (mainly subgenome domination) had a sizeable effect on shaping the gut microbiota assemblages in reciprocal hybrid fish. This study enriches our understanding of the relationship between host genetic and gut microbiota assemblages, and provides insight into gut microbiota and metabonomics.