Ruminal Microbiome Differences in Angus Steers with Differing Feed Efficiencies during the Feedlot Finishing Phase.

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.

Bulls fed a high-gain diet decrease blastocyst formation after in vitro fertilization.

In brief: Paternal high-gain diet reduces blastocyst development following in vitro fertilization and embryo culture but does not affect gene expression or cellular allocation of resultant blastocysts. Abstract: Bulls used in cattle production are often overfed to induce rapid growth, early puberty, and increase sale price. While the negative consequences of undernutrition on bull sperm quality are known, it is unclear how a high-gain diet influences embryo development. We hypothesized that semen collected from bulls fed a high-gain diet would have a reduced capacity to produce blastocysts following in vitro fertilization. Eight mature bulls were stratified by body weight and fed the same diet for 67 days at either a maintenance level (0.5% body weight per day; n = 4) or a high-gain rate (1.25% body weight per day; n = 4). Semen was collected by electroejaculation at the end of the feeding regimen and subjected to sperm analysis, frozen, and used for in vitro fertilization. The high-gain diet increased body weight, average daily gain, and subcutaneous fat thickness compared to the maintenance diet. Sperm of high-gain bulls tended to have increased early necrosis and had increased post-thaw acrosome damage compared with maintenance bulls, but diet did not affect sperm motility or morphology. Semen of high-gain bulls reduced the percentage of cleaved oocytes that developed to blastocyst stage embryos. Paternal diet had no effect on the number of total or CDX2-positive cells of blastocysts, or blastocysts gene expression for markers associated with developmental capacity. Feeding bulls a high-gain diet did not affect sperm morphology or motility, but increased adiposity and reduced the ability of sperm to generate blastocyst-stage embryos.

Assessment of effectiveness of deworming options in recently weaned beef cattle utilizing different anthelmintic programs in the southeast.

This study evaluated the effects of three different anthelmintic strategies on animal performance and anthelmintic effectiveness in weaned calves during a 42-d preconditioning period. The study was conducted at four locations over 2 yr and included a total of 797 recently weaned spring-born calves (initial BW 260 ± 37.7 kg). At the start of each year, at each location, calves were weaned and randomly assigned to one of four treatments: 1) oxfendazole (ORAL); 2) transdermal eprinomectin (POUR); 3) both anthelmintic treatments (BOTH); and 4) the control (CONT) group who did not receive treatment. Anthelmintic was applied per the manufacturer recommendation, the transdermal eprinomectin was administered at 1 mL per 10 kg and oxfendazole was administered orally at 1 mL per 50 kg. Weights were measured at the start of the study (day 0) and again at the end of the preconditioning phase (day 42). Fecal samples were collected at the start of the study prior to treatment application (day 0) and again on day 14. Rumen fluid was collected at the start of the study prior to treatment (day 0) and again on day 6. There were treatment effects for all performance metrics (P < 0.001). All treatments had greater weight gain and value of weight gained (P < 0.024), and all three strategies did not differ from each other (P > 0.420). On day 0, there were no (P = 0.795) treatment effects detected for fecal eggs per gram (EPG) counts. On day 14, there were (P < 0.001) treatment effects for EPG counts with feces from CONT calves containing greater (P < 0.014) EPG than feces from treated calves. EPG in feces from BOTH calves did not differ (P > 0.123) from the other two treated groups and feces from POUR calves tended (P = 0.052) to contain greater EPG counts than feces from ORAL calves. Volatile fatty acids were similar across treatments on days 0 and 6 (P > 0.115). Butyrate tended (P = 0.063) to be lower in ORAL on day 6. These results suggest that using eprinomectin and oxfendazole in combination was an effective strategy for reducing EPG and improving performance during a 42-d preconditioning phase.

The impact of feed efficiency selection on the ruminal, cecal, and fecal microbiomes of Angus steers from a commercial feedlot.

Feed is the greatest cost of animal production, so reducing it is critical to increase producer profits. In ruminants, the microbial population within the gastrointestinal tract (GIT) is critical to nutrient digestion and absorption in both the rumen and the hindgut. The objective of this study was to determine the bacterial taxonomic profile of the rumen, cecum, and feces of feedlot steers at slaughter in order to link feed efficiency and the GIT bacterial populations from these three locations. Twenty commercial Angus steers were selected and divided into two groups according to their residual feed intake (RFI) classification determined during the feedlot-finishing period: high-RFI (n = 10) and low-RFI (n = 10). After the ruminal, cecal, and fecal samples were collected at slaughter, DNA extraction and 16S rRNA gene sequencing were performed on them to determine their bacterial composition. One-way ANOVA was performed on the animal performance data, alpha diversities, and bacterial abundances using RFI classification as the fixed effect. Overall, the ruminal bacterial population was the most different in terms of taxonomic profile compared with the cecal and fecal populations as revealed by beta diversity analysis (P < 0.001). Moreover, bacterial richness (Chao1) was greatest (P = 0.01) in the rumen of the high-RFI group compared with the low-RFI group. In contrast, bacterial richness and diversity in the intestinal environment showed that Chao1 was greater (P = 0.01) in the cecum, and the Shannon diversity index was greater in both the cecum and feces of low-RFI compared with high-RFI steers (P = 0.01 and P < 0.001, respectively). Ruminococcaceae was more abundant in the low-RFI group in the cecum and feces (P = 0.01); fecal Bifidobacteriaceae was more abundant in high-RFI steers (P = 0.03). No correlations (P ≥ 0.13) between any ruminal bacterial family and RFI were detected; however, Ruminococcaceae, Mogibacteriaceae, Christensenellaceae, and BS11 were negatively correlated with RFI (P < 0.05) in the cecum and feces. Succinivibrionaceae in the cecum was positively correlated with RFI (P = 0.05), and fecal Bifidobacteriaceae was positively correlated with RFI (P = 0.03). Results collectively indicate that in addition to the ruminal bacteria, the lower gut bacterial population has a significant impact on feed efficiency and nutrient utilization in feedlot steers; therefore, the intestinal bacteria should also be considered when examining the basis of ruminant feed efficiency.