The objective of this study was to determine the impact of varying dietary manganese and selenium concentrations, antioxidant cofactors, on the growth performance and fecal microbial populations of nursery pigs. The piglets (N = 120) were blocked by weight (5.22 ± 0.7 kg) and sex. The pens (n = 5/treatment) within a block were randomly assigned to diets in a 2 × 3 factorial design to examine the effects of Se (0.1 and 0.3 mg/kg added Se) and Mn (0, 12, and 24 mg/kg added Mn) and were fed in three phases (P1 = d 1–7, P2 = d 8–21, P3 = d 22–35). The pigs and orts were weighed weekly. Fecal samples were collected d 0 and 35 for 16S rRNA bacterial gene sequencing and VFA analysis. The data were analyzed as factorial via GLM in SAS. There was a linear response (p < 0.05) in overall ADG across dietary Mn. Supplementing 24 mg/kg Mn tended to decrease (p < 0.10) the relative abundance of many bacteria possessing pathogenic traits relative to Mn controls. Meanwhile, increasing Mn concentration tended to foster the growth of bacteria correlated with gut health and improved growth (p < 0.10). The data from this study provide preliminary evidence on the positive effects of manganese on growth and gut health of nursery pigs.

The catabolic activity of the ruminal microbial community of cattle enables the conversion of low-quality feedstuffs into meat and milk. The rate at which this conversion occurs is termed feed efficiency, which is of crucial importance given that feed expenses account for up to 70% of the cost of animal production. The present study assessed the relationship between cattle feed efficiency and the composition of their ruminal microbial communities during the feedlot finishing period. Angus steers (n = 65) were fed a feedlot finishing diet for 82 days and their growth performance metrics were evaluated. These included the dry matter intake (DMI), average daily gain (ADG), and residual feed intake (RFI). Steers were rank-ordered based upon their RFI, and the five lowest RFI (most efficient) and five highest RFI (least efficient) steers were selected for evaluations. Ruminal fluid samples were collected on days 0 and 82 of the finishing period. Volatile fatty acids (VFA) were quantified, and microbial DNA was extracted and the 16S rRNA gene was sequenced. The results showed that the ADG was not different (p = 0.82) between efficiency groups during the 82-day feedlot period; however, the efficient steers had lower (p = 0.03) DMI and RFI (p = 0.003). Less-efficient (high RFI) steers developed higher (p = 0.01) ruminal Methanobrevibacter relative abundances (p = 0.01) and tended (p = 0.09) to have more Methanosphaera. In high-efficiency steers (low RFI), the relative abundances of Ruminococcaceae increased (p = 0.04) over the 82-day period. The molar proportions of VFA were not different between the two efficiency groups, but some changes in the concentration of specific VFA were observed over time. The results indicated that the ruminal microbial populations of the less-efficient steers contained a greater relative abundance of methanogens compared to the high-efficiency steers during the feedlot phase, likely resulting in more energetic waste in the form or methane and less dietary energy being harvested by the less-efficient animals.

Cattle feed efficiency can influence operating costs and revenues, and it is a complex phenotype that can be measured by different metrices. The objective of this study was to determine which microbial taxa in the ruminal and fecal microbiomes of Angus bulls are associated with residual feed intake (RFI), residual average daily gain (RADG), feed conversion ratio (FCR), and adjusted feed conversion ratio (AFCR) by using a large sample size. The metrics RFI and RADG are calculated from the difference between an animal’s actual feed intake and actual gain, to their predicted intake and gain, respectively, and AFCR is the FCR adjusted for the animal’s size. Rumen (n = 1176) and fecal (n = 1179) samples were collected from Angus bulls from 10 contemporary groups located across the continental U.S. Animals were assigned to three classifications (High, Medium, or Low) for each feed efficiency metric within each contemporary group, according to their individual performance data. To compare the feed efficiency metrics, a cost analysis scenario was performed, and bulls classified by RADG had the greatest correlation with predicted profit (r² = 0.98). For alpha diversity, only classification by FCR resulted in differences within both rumen and fecal samples. In the rumen environment, only ‘X112’ was significant (p = 0.02) by RFI classification, and Succinivibrionaceae was significant (p = 0.01) by FCR classification. In the fecal environment, a total of 19 families significantly differed, with bulls classified by RFI having the greatest number of different families. Bull feed efficiency status had greater impacts in the fecal microbiome compared to the rumen, but results should be taken in context since the animals were classified within each contemporary group. Still, differences detected within the fecal microbiome may allow for more assessable microbiome applications; however, the metric used to classify cattle as feed efficient will determine which microbial families are relevant.