Search

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.

An in vitro experiment was performed to evaluate the effect of quality and supplementation (CON-control, no supplement, DDG-dried distillers grains, 29.32% CP, LFD-liquid feed, 56.45% CP) on IVDMD, NDF disappearance (NDFD) and ruminal fermentation parameters of Tifton 85 Bermudagrass (Cynodon dactylon). Forage was harvested at 2, 4, 6, 8, and 10 wk over three growing seasons to simulate various forage management practices. Samples were analyzed by Near-infrared spectroscopy and stratified by relative forage quality (RFQ). Samples were selected to represent high (120), medium (100) and low (80) RFQ. The LFD was added at 5.4% of DMI, equivalent to 0.91 kg (as fed) per head per day. The DDG was included at equivalent of 16.99%, 14.36%, and 12.23% of total DM for the high, medium, and low low RFQ forages, respectively, to make the treatments isonitrogenous to the LFD treatments. Fermentations were carried out for 48 h on 3 d. The experiment was analyzed as a 3 x 3 factorial; arrangement with RFQ and type of supplement as factors. The IVDMD (46.9, 54.6, and 62.8%) and NDFD (41.7, 53.8, and 56.1%) increased (P < 0.001) as RFQ increased. Supplementation increased (P < 0.009) NDFD (39.7, 49.5, and 59.5%) but only the LFD increased IVDMD (52.7, 55.4 and 56.2%). An RFQ x supplement interaction was observed for IVDMD (P < 0.001) and NDFD (P < 0.007). No effects of supplementation were observed for high RFQ. For medium RFQ forage quality only LDF increased IVDMD and DDG was not different from CON or LDF; and no effect of supplementation was observed for NDFD. Supplementation increased IVDMD and NDFD for low RFQ forage. There was no effect of supplementation on total gas production or total VFA concentrations. Supplementation with LFD and DDG improves IVDMD and NDFD in low RFQ Bermudagrass, and LFD supplementation can enhance IVDMD in medium RFQ forage quality

Most of the research efforts involving the bovine gastrointestinal microbiota have focused on cattle's forestomach, particularly the rumen, so information concerning the bovine fecal microbiota is more scarce, especially in young beef cattle. The present study was performed to evaluate the ruminal and fecal microbiotas of beef calves as they reached the end of their nursing phase. A total of 18 Angus cow/calf pairs were selected and assigned to one of two treatment groups for the last 92 days of the calves' nursing period, as follows: 1) calves were supplemented with concentrate in a creep feeding system; or 2) control group with no supplementation of calves. After 92 days, ruminal and fecal samples were individually obtained from calves in both groups, and their microbiotas were evaluated using 16S rRNA gene sequencing. Ruminal samples were predominated by Prevotella (18 to 23% of the total bacterial abundance), regardless if calves received supplementation or not; however, in the feces, Prevotella was only the seventh most abundant genus (0.6 to 2.1% of total bacterial abundance). Both the rumen (P = 0.01) and the feces (P = 0.05) of calves that received supplementation had greater abundance of Firmicutes. In addition, calves that were supplemented had lower abundance of Fibrobacteres (P = 0.03) in their rumens. Regardless if the calves were supplemented or not, Faith's Phylogenetic Diversity index (P ≤ 0.007) and total concentration of short chain fatty acids (P < 0.001) were both greater in the rumen than in the feces of calves. In summary, the ruminal and fecal microbiotas of weanling beef calves were considerably distinct. Additionally, supplementation with creep feed caused some significant changes in the composition of the gastrointestinal microbiota of the calves, especially in the rumen, where supplementation caused an increase in Firmicutes and a decrease in abundance of Fibrobacteres.