Differences in gut bacterial community composition between modern and slower-growing broiler breeder lines: Implications of growth selection on microbiome composition

Abstract

In the last century broiler chicken lines have undergone an extensive breeding regime aimed primarily at growth and high meat yield. It is not known if breeding has also resulted in a change to the broiler breeder’s associated gut microbiota. Here we compared the gut microbiota of 37-week-old commercial Cobb breeding dams with dams from a broiler Legacy line which has not undergone selection since 1986. The dams from both lines were kept together in the same shed under the same management protocol from day of hatch to avoid additional confounders. We chose this age to allow significant bacterial exchange, thus avoiding exposure dependent artifacts and so that we could compare dams at the same developmental state of adulthood and peak laying performance. Significant differences in the composition of the cecum bacterial communities were found. Bacteria of the genus Akkermansia, implicated in mucin degradation and associated with host metabolic health, accounted for 4.98% ± 5.04% of the Cobb cecum community, but were mostly absent from the ceca of the Legacy line dams. Inversely, Legacy dams had higher levels of Clostridiales, Lactobacillales and Aeromonadales. These results show that breeding has resulted in a change in the gut microbiota composition, likely by changing the physiological conditions in the mucosa. It remains unclear if changes in gut microbiota composition are a part of the mechanism affecting growth or are a secondary result of other physiological changes accelerating growth. Therefore, the identification of these changes opens the door to further targeted research.

Comparative analysis of reproductive tract microbiomes in modern and slower-growing broiler breeder lines

“…Thus, it is possible that the differences in the reproductive tract microbiome between the Legacy and Cobb hens shown here are a result of physiological differences affecting the gut environment rather than the reproductive tract environment. However, differences in the orders Pseudomonadales, YS2 and RF32, reported in this work, were not found in previously reported cecum samples ( 13 ) and may imply additional differences also in the reproductive tract environment.…”

“…Indeed, the analysis described for both breeds analyzed here reaches the same conclusion. Here it was shown that the order Verrucomicrobiales was found to be significantly higher in the infundibulum and magnum of Cobb dams, and Lactobacillales was significantly lower in the infundibulum, mirroring the significant differences shown in the comparison of the cecum microbiota of the two breeds ( 13 ). Furthermore, Bacteroidales which was found to be significantly higher in the infundibulum of Cobb dams was also high in the cecum of Cobb dams, though not significantly so.…”

“…Because a previous analysis of cecum bacteria of these same birds showed associations of some of these orders ( 13 ) we tested whether the same associations can be identified in the reproductive tract microbiome. In the infundibulum, we found that the relative abundances of most of the differentially abundant orders were correlated ( Figure 6A ).…”

“…Two genetic lines were sampled: Cobb – the current modern breeder line; and Legacy – a local Israeli broiler line which has not been under selection pressure since 1986 ( 13 , 15 , 16 ).…”

“…Because the intestinal and reproductive tract microbiotas are connected, it is likely that breeding also modulates the reproductive tract microbiota. In this regard, we have previously compared the cecum microbiome of 37-week-old commercial Cobb breeding dams with dams from a broiler Legacy line which has not undergone selection since 1986 ( 13 ). This comparison showed that the two microbiomes were different.…”