Evaluation of the Fecal Bacterial Communities of Angus Steers With Divergent Feed Efficiencies Across the Lifespan From Weaning to Slaughter

Abstract

Numerous studies have examined the link between the presence of specific gastrointestinal bacteria and the feed efficiency of cattle. However, cattle undergo dietary changes during their productive life which can cause fluctuations in their microbial consortium. The objective of the present study was to assess changes in the fecal microbiome of beef steers genetically selected to be divergent in feedlot feed efficiency, to determine whether differences in their fecal microbiomes could be detected as early as weaning, and continued throughout the rearing process regardless of dietary changes. Fecal samples were collected at weaning, yearling age, and slaughter for a group of 63 steers. Based on their feedlot-finishing performance, the steers were selected and divided into two groups according to their residual feed intake (RFI): efficient steers (low-RFI; n = 7) and inefficient steers (high-RFI; n = 8). To ascertain the fecal microbial consortium and volatile fatty acid (VFA) content, 16S rRNA gene sequencing and VFA analysis were performed. Overall, bacterial evenness and diversity were greater at weaning compared to yearling and slaughter for both efficiency groups (P < 0.001). Feedlot RFI linearly decreased as both Shannon diversity and Ruminococcaceae abundance increased (R2 = 65.6 and 60.7%, respectively). Abundances of Ruminococcaceae, Rikenellaceae, and Christensenellaceae were higher at weaning vs. yearling age and slaughter (P < 0.001); moreover, these families were consistently more abundant in the feces of the low-RFI steers (for most of the timepoints evaluated; P ≤ 0.05), compared to the high-RFI steers. Conversely, abundances of Bifidobacteriaceae were numerically higher in the feces of the high-RFI steers throughout their lifespan. Total VFA concentrations increased at slaughter compared to weaning and yearling for both efficiency groups (P < 0.001). The acetate:propionate ratio decreased linearly (P < 0.001) throughout the life of the steers regardless of their efficiency, reflective of dietary changes. Our results indicate that despite fluctuations due to animal age and dietary changes, specific bacterial families may be correlated with feed efficiency of steers. Furthermore, such differences may be identifiable at earlier stages of the production cycle, potentially as early as weaning.

Stool and Ruminal Microbiome Components Associated With Methane Emission and Feed Efficiency in Nelore Beef Cattle

“…This taxon was also associated with methane emission in Holstein cows ( Ramayo-Caldas et al, 2020 ) a phenotype that can negatively influence feed efficiency ( Hegarty et al, 2007 ). Interestingly, contrary to our results with the rumen microbiome, the family Christensenellaceae was linked to Low-RFI in the stool microbiome of Angus steers ( Welch et al, 2021 ).…”

“…Besides, Welch et al (2021) hypothesized that the link between highly feed-efficient animals and stool bacteria belonging to the Rikenellaceae family resides in the abundance of glycosaminoglycans present in their hindgut, as individuals from this family can use mucin as carbon and energy sources ( Bomar et al, 2011 ), they could metabolize and have a competitive edge over other bacteria. Although this area is still in its infancy, recent studies have linked OTUs classified as belonging to this gut group, or to a lower taxonomic level such as the Rikenellaceae family.…”

“…Although this area is still in its infancy, recent studies have linked OTUs classified as belonging to this gut group, or to a lower taxonomic level such as the Rikenellaceae family. Species from this family have been linked to Low-RFI in the rumen of Nelore steers and in the stool microbiome of Angus steers, being also linked to Low-FCR in the stool microbiome of pigs ( Quan et al, 2018 ; Lopes et al, 2021 ; Welch et al, 2021 ). Altogether, these results indicate a role of this specific taxon on this phenotype and suggest it as an RFI biomarker for highly efficient animals.…”

Relationships of the Microbial Communities with Rumen Epithelium Development of Nellore Cattle Finished in Feedlot Differing in Phenotypic Residual Feed Intake

“…In addition, Myer et al [ 65 ] fed cattle a high-concentrate diet, and also did not find differences in Shannon diversity and Chao richness. However, Welch et al [ 21 ] evaluated the impact of RFI groups on the composition of the fecal microbial community and reported greater Shannon’s diversity in more efficient animals (6.99 vs. 7.81) fed high-concentrate diets, but this difference disappeared when animals were fed forage-based diets. Based on the fact just presented, it seems that the variation in feed efficiency across different RFI groups could not be attributed to the rumen microorganisms.…”

“…Therefore, studies associating RFI with the microbial community of the rumen may help to clarify some differences in microbial composition [ 18 , 19 ]. The microbial community of animals seems to be peculiarly intrinsic to each animal [ 20 ], in addition to what can be changed over the life of the animal according to changes in its diet [ 21 ]; therefore, this may help explain differences in animal feed efficiency [ 22 ]. The objective of this study was to examine the differences in the ruminal microbial communities between Nellore cattle groups differing in RFI, as well as the RFI effects on performance, carcass traits, ruminal traits and feeding behavior.…”