This study evaluated the effects of feeding a probiotic-postbiotic blend on transcript abundance in circulating neutrophils following an intramammary (IMM) LPS challenge in lactating dairy cattle. Lactating Holstein cows (n = 16 at 57 ± 4 DIM) with a SCC <250,000 cells/mL received either 28 g/d of probiotic-postbiotic (PB; n = 8, Dairyman's Edge PRO, Papillon Agricultural Company) or no PB (NP; n = 8) for 27 d before intramammary infusion of 200 µg Escherichia coli O111:B4 LPS into both rear quarters. Blood PMN were isolated at 0 (30 min before the IMM LPS challenge), 24, and 72 h following the IMM LPS infusion for transcript abundance analysis using real-time reverse transcription quantitative PCR (RT-qPCR). PB had 32% less PMN in blood compared with NP, and IMM LPS resulted in a 59% and 63% reduction in blood PMN across both NP and PB at 24 and 72 h, respectively, relative to 0 h. Transcript abundance for SOD2, S100A8, and S100A9 increased 3.0, 7.0, and 5.0-fold, respectively, at 24 h relative to 0 h but no longer differed at 72 h. TLR4, STAT3, IL1β, and CXCR1 transcript abundance were downregulated at 24 h and 72 h compared with 0 h. CXCL8 expression was reduced at 24 h relative to 0 h, but not at 72 h relative to 0 or 24 h. There was no effect of diet, time, or the interaction on the expression of transcripts for TLR2, IL6, IL10, TNFα, and MPO. There was a diet × time interaction detected for NFκβ such that NP at 0 h tended to be greater than PB at 0 h (P = 0.061) and was greater than all other treatments at 24 and 72 h and PB at 0 h did not differ from PB or NP at 24 or 72 h. In conclusion, IMM inflammation coincided with decreased PMN count in blood and was associated with a downregulated proinflammatory transcript abundance profile in circulating PMN based on the genes analyzed. This attenuated molecular phenotype may reflect accelerated PMN turnover and an increased proportion of immature PMN in circulation or alternatively, a regulatory mechanism aimed at minimizing systemic inflammation and preserving peripheral tissue homeostasis during localized immune activation. Although PB reduced PMN abundance in blood there was no measurable effect on PMN transcript abundance for the genes measured.

The use of yeast products, phytogenics, and direct-fed microbials (DFM) have been shown to improve health and growth performance of dairy calves. More recently, combining nutrients and additives to optimize calf performance has become a growing interest area. The purpose of this study was to determine if feed additives in milk replacer (MR) and starter could improve health and growth of Holstein calves through 13 wk of age. Ninety male Holstein calves <4 d of age were assigned to 1 of 3 treatments. Calves were individually housed in outdoor hutches through d 56, then moved to group pens through d 92. Treatments were a control MR and pelleted starters with no additives (CON); a MR with phytogenics and yeast extract plus a starter with a blend of phytogenics and yeast products (CTP); and the same CTP MR with a starter containing an experimental blend of phytogenics, yeast products, and DFM (CEP). Diets were formulated as follows: MR contained 22% CP and 20% fat and starters contained at least 16% CP and 4% fat (as-fed basis). Average initial BW and SD were 42.1 (±5.9) kg for CON, 42.9 (±4.9) kg for CTP, and 43.3 (±5.5) kg for CEP. Calves were fed MR at a rate of 600 g/d (as fed), reconstituted to 13% solids. This amount was fed from d 0 to 42 when the single step-down weaning process started by discontinuing the evening MR feeding. After d 49, MR was completely discontinued but calves stayed in individual hutches through d 56 and then were moved to group housing. During the group-housed portion of the experiment, calves were provided with ad libitum pelleted starters and water. Health scores were collected twice daily from d 1 to 56, and once daily from d 57 to 70. Body weight and frame measurements were collected weekly. Average ME intake was consistently greater for CTP throughout the trial, and starter ME intake was greater compared with CON for wk 4 to 13. Final BW was greater for CTP and CEP for wk 1 to 13 relative to CON. Frame growth was improved for CTP and CEP during wk 1 to 8 in comparison to CON. Feed efficiency tended to be greater for CTP and CEP compared with CON during wk 9 to 13. There was a tendency for lower incidence of scours for calves fed CTP, and overall health and need for medication were improved for calves fed both CTP and CEP compared with CON. Results of this study indicate improvements in pre- and postweaning health and growth of calves fed blends of yeast products, phytogenics, and DFM in MR and pelleted starters.

This study evaluated the effects of feeding a probiotic-postbiotic blend on DMI, milk and milk component yields, systemic inflammation, and regional paracellular permeability of the gastrointestinal tract (GIT) before and after exposure to an intramammary (IMM) challenge of LPS or no infusion. Lactating Holstein cows (n = 34 at 57 ± 4 DIM) with a SCC <250,000 cells/mL were used, including 14 that were ruminally cannulated. Cows were fed either 28 g/d of a probiotic-postbiotic blend (PB; Dairyman's Edge PRO, Papillon Agricultural Company) or no PB (NP) for 21 d before obtaining 5 d of baseline measurements. On d 27, cows received a mammary treatment (MTrt) of either 200 µg of Escherichia coli O111:B4 LPS (IML) using sterile PBS as a carrier into both rear quarters or no infusion (CON; PB-IML, n = 8; PB-CON, n = 9; NP-IML, n = 8; NP-CON, n = 9). Milk and milk component yields and DMI were not affected by PB before the MTrt. The IML increased rectal temperature by 2.8°C 6 h after the MTrt application and tended to be 0.3°C lower for PB than NP at 12 h. Milk SCS was 11 units greater at 12 h for IML versus CON and remained 1 unit greater on d 12. Relative to CON, IML reduced DMI by 28%, 11%, and 10%, and milk yield by 44%, 22%, and 10% on d 1 to 3 after the MTrt application, respectively. Dry matter intake recovered after d 4, whereas milk yield was not different on d 5 and 6 but was 6% lower for IML than CON on d 7 and 8. Milk fat yield was reduced for IML from d 1 to 13 when compared with CON. The PB reduced ruminal pH by 0.11 units, increased total short-chain fatty acid concentrations by 6% compared with NP, and stabilized the proportions of propionate and acetate following MTrt application. Plasma haptoglobin (Hp) and serum amyloid A (SAA) were greatest on d 2 for IML (562- and 16-fold greater than CON, respectively). On d 7 and 12, Hp was 37- and 6-fold greater for IML versus CON, respectively. Serum amyloid A was reduced by 42% for PB versus NP. On d 1 after the MTrt application, plasma Cr and Co area under the curve (AUC) were 24% and 28% lower for IML than CON, respectively. On d 6, Co AUC was 33% lower for IML than CON but the Cr AUC did not differ on d 6 or 11, and Co AUC did not differ on d 11. In conclusion, the IML infusion induced local and systemic inflammation resulting in reduced milk and milk fat yields that persisted beyond the decline in DMI. The PB did not improve recovery of DMI or milk yield but altered ruminal fermentation, reduced SAA, and tended to accelerate recovery of normothermia. Total GIT and postruminal paracellular permeability may transiently decrease in response to mammary and systemic inflammation, at least based on the Cr and Co AUC in plasma. These findings highlight the limited understanding whereby inflammation in the mammary gland, and potentially other non-GIT organs, influence paracellular permeability of the GIT in ruminants.

The objective of this study was to evaluate the effects of calcium magnesium carbonate (CMC) and/or tylosin phosphate (TYL) supplementation on behavior, rumination activity, growth performance and carcass characteristics of yearling beef steers. Treatments were arranged in a 2 × 2 factorial including CMC and TYL. Beef steers (n = 156; 469 ± 18 kg) were randomly assigned to treatment pens (7 to 8 steers/pen) with pen (n = 20 pens total, 10 pens/main effect mean, and 5 pens/simple effect mean) as experimental unit. Cattle were transitioned from a 30% roughage diet to a 7% roughage finishing diet based on dry-rolled corn, dried distillers grains plus solubles, liquid supplement, and oat silage over the initial 20 d period. The CMC was included at 1.5% of the diet (DM basis) in replacement of dry-rolled corn and TYL was provided at 90 mg·animal·d-1. Behavior and rumination activity were monitored during a 24 h period on d 42. Data was collected on a pen-basis, every 10 min from 0800 h to 0750 h the next day and included minutes spent drinking (DR), eating (EA), active (AC), ruminating (RU), and resting (RE). Cattle were shipped for harvest on d 105 to a commercial beef abattoir. Growth performance was calculated on a carcass-adjusted basis (HCW/0.625). Data were analyzed as a randomized complete block design with fixed effects of CMC, TYL, or their interaction; block was a random effect. An interaction was observed between CMC and TYL for time spent DR (P = 0.03) and RU (P = 0.01). Control steers ruminated 28% longer compared with CMC/-TYL steers (P = 0.05) and 20% longer than -CMC/TYL steers (P = 0.05). The main effect of CMC tended to increase time spent EA by 19.3% (P = 0.06). Dry matter intake was decreased (P ≤ 0.02) by 4.57% when CMC was fed and increased by 1.96% when TYL was fed. However, no difference (P ≥ 0.26) was observed for G:F or gain efficiency in either treatment. No differences (P ≥ 0.28) were observed in any dietary net energy utilization outcomes in either main effect treatment. Carcass weight tended (P = 0.07) to be lighter with CMC supplementation compared with CON (432 vs 439 kg). Supplementation of TYL resulted in a 11.7% reduction (P = 0.04) in percentage of abscessed livers. No differences (P ≥ 0.12) were observed in DP, marbling, YG, or EBF in either main effect treatments. These results indicate that supplementation of CMC did not result in any appreciable improvements in growth, carcass or dietary net energy utilization performance, but TYL supplementation resulted in a positive effect on liver abscess prevalence.

The objective of this study was to evaluate the effects of a supplemental probiotic-prebiotic blend (P-PB) on newly received beef cattle during the first 21 and 42 d after feedlot arrival. Crossbred steers (n=258; BW = 250 +/- 11.4 kg) were received at the Texas A&M AgriLife Research Feedlot in Bushland, TX. Steers (n=240) were stratified by average initial BW (d-1, d-0) and allocated to 1 of 2 weight blocks and 1 of 3 dietary treatments. The control treatment (CON) received a pellet without P-PB. Treatment 2 received a pellet with P-PB from d 0 to 21 and then the CON pellet from d 22 to 42 (P-PB21). Treatment 3 received the P-PB pellet from d 0 to 42 (P-PB42). Following the 42-d receiving period, treatment pellets were removed and replaced with steam flaked corn for the remainder of the finishing period. If DMI was < 6.35 kg/steer daily, the P-PB pellet was included at 8.75% of the diet. If DMI was >= 6.35 kg/steer daily, the P-PB pellet was included at 6.25% of the diet. Body weight was measured on d 21 and d 42 of the feeding period. Statistical analysis for the randomized complete block design was analyzed using SAS 9.4. Pen was the experimental unit with 10 per treatment. There were no treatment effects between d 0 to 42 for body weight (BW), average daily gain (ADG), gain to feed (G:F), and dry matter intake (DMI) (P < 0.99). No differences were observed for percent morbidity or mortality (P < 0.65) from d 0 to 42. P-PB did not impact LM area, rib fat, marbling score, USDA QG or YG (P < 0.99), while CON had a greater DP (P < 0.05) and tended to have a greater hot carcass weight (P = 0.09). While results remained similar between treatments, there were no negative effects on cattle health and performance during the first 42 days after receiving.

Enteric methane emissions are the single largest source of direct greenhouse gas emissions (GHG) in beef and dairy value chains and a substantial contributor to anthropogenic methane emissions globally. In late 2019, the World Wildlife Fund (WWF), the Advanced Research Projects Agency-Energy (ARPA-E) and the Foundation for Food and Agriculture Research (FFAR) convened approximately 50 stakeholders representing research and production of seaweeds, animal feeds, dairy cattle, and beef and dairy foods to discuss challenges and opportunities associated with the use of seaweed-based ingredients to reduce enteric methane emissions. This Perspective article describes the considerations identified by the workshop participants and suggests next steps for the further development and evaluation of seaweed-based feed ingredients as enteric methane mitigants. Although numerous compounds derived from sources other than seaweed have been identified as having enteric methane mitigation potential, these mitigants are outside the scope of this article.

Thirty-five Holstein cows were utilized in a completely randomized design to evaluate the efficacy of 2 doses of an aluminosilicate clay at reducing aflatoxin M1 (AFM1) transfer into milk. Cows were stratified by parity, stage of lactation, and milk production. Cows were assigned to 1 of 5 dietary treatments for 13 days (n = 7): (1) control (CON), basal diet; (2) clay control (4C), CON plus 4 oz clay; (3) aflatoxin (AF) control (AF-CON), CON plus 113 ppb AF; (4) AF-CON diet with 4 oz clay (4C+AF); or (5) AF-CON diet with 8 oz clay (8C+AF). Data were analyzed using the GLM procedure of SAS, and significance was declared when P ≤ 0.05. Milk yield was greatest in 4C+AF and 8C+AF cows and least in CON. Milk AFM1concentration averaged < 0.01, N/D (< 0.04 ppb), 1.64, 1.26, and 0.90 ppb for CON, 4C, AF-CON, 4C+AF, and 8C+AF diets, respectively. A dose response was observed for AFM1 transfer with a 21.88 and 40.63% reduction in cows consuming 4C+AF and 8C+AF diets, respectively. Feeding aluminosilicate clay to AF challenged Holstein cows resulted in a dose response reduction in AFM1 secretion and improved milk production.

Abstract A study was conducted to determine the effects of two prebiotic blends on the acute phase response (APR) following lipopolysaccharide (LPS) challenge in steers. Crossbred steers (n = 36; 273±4 kg) were fed for 21d on three different treatments: 1) Control, fed a standard receiving ration; 2) Control ration supplemented with a Prebiotic/Probiotic blend (28.4 g/hd/d; PMI); and 3) Control ration supplemented with a DFM/Prebiotic blend (19.0 g/hd/d; PMI). On d20, calves were fitted with indwelling rectal temperature (RT) monitors and jugular catheters and moved into individual stanchions in a covered barn. On d21, blood samples were collected, and sickness behavior scores recorded at 0.5-h intervals from -2 to 8h and again at 24h relative to an i.v. challenge with 0.25 µg/kg BW LPS. Serum was isolated and stored until analyzed for pro-inflammatory cytokines, cortisol and glucose concentrations. Complete blood counts were measured every 2h from -2 to 8h and again at 24h. Pre-challenge RT measured for 18h prior to the challenge tended (P = 0.10) to be affected by treatment such that calves fed the Prebiotic/Probiotic blend had greater RT than Control and tended to be greater than calves fed the DFM/Prebiotic blend (38.9, 39.2, and 39.0±0.1oC, respectively). Post-challenge RT increased 0.8–1.0oC on average but did not differ between treatments (P = 0.53). Sickness behavior scores were not different between treatments (P = 0.14). There were no differences in white blood cell or differential counts between treatments (P ≥ 0.25). Serum concentrations of TNF-α, IL-6, and IFN-γ increased in response to the challenge (P < 0.01) but were not different between treatments (P ≥ 0.26). Serum cortisol and glucose concentrations were reduced in both supplemented groups compared to Control steers (P ≤ 0.006). Therefore, the data suggest that the effects of the prebiotic blends during an immune challenge were limited to alterations in metabolic biomarkers and energy utilization.

This study was realized to evaluate the effects of a yeast-based additive complex (AC) on animal performance, heat stress behaviors, and carcass characteristics of beef of finishing beef steers fed during a period of thermal heat stress. Black-hided beef steers (n = 192; initial live weight = 403 +/- 24.5 kg) were used in a randomized complete block design experiment with 2 treatments; a steam flaked corn-based diet with AC (fed at 0.14 kg.hd(-1).d(-1)) and a diet without AC (CON). Steers were stratified by live weight to 1 of 2 weight blocks and randomly allocated to an experimental treatment within block. Experimental supplementation was fed through d 75. Steers were fitted with an ear tag that recorded rumination and activity in 2-h intervals; whereas heat stress behaviors were recorded in 1-min intervals. Pen was used as the experimental unit for animal performance, carcass characteristics, and rumination, and animal was used for heat stress behaviors, while day was used as repeated measure for the analysis of heat stress behaviors and rumination. Data were analyzed using the MIXED procedure of SAS. Final live weight (LW), average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F) were not affected (P > 0.38) by treatment (d 1-76). Time spent ruminating (min/d) were not affected by AC supplementation (P >= 0.21). Treatment did not influence (P > 0.13) time spent panting, resting, or eating. Supplementation of AC did not impact (P >= 0.22) HCW, fat thickness, Longissimus area, or marbling score. Dressing percentage was decreased (P = 0.02) with AC addition (60.4% +/- 0.6) compared to CON (61.0% +/- 0.6) and calculated yield grade tended (P = 0.09) to increase with AC (2.51 +/- 0.16) compared to CON (2.37 +/- 0.16). Overall, feedlot performance, efficiency and carcass characteristics were not influenced by the supplementation of AC. Supplementing cattle exposed to thermal heat stress with AC did not impact rumination or panting behaviors.

The present study evaluated the effects of a feed additive (synthesized from Yucca schidigera) on some fermentation variables. In the first of two experiments, seven concentrations of the feed additive were evaluated using the in vitro batch culture technique to determine the optimum dose to use in the second experiment. The substrates used were a total mixed ration (TMR) and alfalfa hay. The levels of inclusion were 0 (control), 0.5, 1, 2, 4, 6, and 8 g/head/d. After this initial evaluation, 2 g/head/d was selected for the second experiment. For the second study, four dietary substrates (two corn silages and two TMR; collected from different dairy farms in the Piedmont, North Carolina, area) were used. Incubation times were 3, 6, and 24 h and treatments were 0 (control) and 2 g/head/d of the feed additive. Inclusion of the feed additive did not affect (p > 0.05) in vitro dry matter disappearance. Additionally, the feed additive had no effect (p > 0.05) on short-chain fatty acid concentrations, microbial mass, and efficiency of microbial production. Methane production was reduced by 22.7% with feed additive inclusion. Similarly, lower (p = 0.013; 18%) carbon dioxide concentration was observed in the feed additive treatment. Ammonia and hydrogen sulfite concentrations were similar (p > 0.05) for both treatments. Inclusion of the feed additive at 2 g/head/d decreased methane and carbon dioxide concentrations in most of the diets. The energy saved by reducing the amount of methane produced was not partitioned into valuable products such as short-chain fatty acids and microbial mass.

The objective of this experiment was to investigate the effects of a Saccharomyces cerevisiae-based direct-fed microbial product (SDM) and an exogenous enzyme product (ENZ) on enteric methane emission, milk yield and composition, total-tract digestibility of nutrients, ruminal fermentation, and nitrogen excretion and secretion in lactating dairy cows. Eighteen Holstein cows were used in a 3 × 3 Latin square design experiment with three 28-d periods. Treatments were (1) control (no additive), (2) 28 g of SDM/d per cow, or (3) 10 g of ENZ/d per cow. Treatments were top-dressed at the time of feeding. The basal diet consisted of (dry matter basis) 60% forage and 40% concentrates and contained 16.5% crude protein and 32.0% neutral detergent fiber. Treatments had no effect on enteric methane production, yield (methane per kg of dry matter intake, DMI), or intensity (methane per kg of energy-corrected milk yield). Carbon dioxide production was similar among treatments. Compared with control, SDM increased milk yield by 2 kg/d without affecting DMI or feed efficiency. Supplementation of the diet with ENZ did not affect DMI, milk yield, or feed efficiency. Concentrations and yields of milk fat, true protein, and lactose, and energy-corrected milk yield were not different among treatments. Neither SDM nor ENZ had an effect on total-tract digestibility of nutrients or nitrogen excretion and secretion. Concentration of total volatile fatty acids (VFA) in ruminal fluid was increased by both SDM and ENZ, and rumen pH was decreased by SDM compared with the control. At levels similar to the control DMI, the increased concentration of VFA in ruminal fluid of cows receiving SDM suggests an increased postruminal supply of energy and may partly explain the increased milk yield with that treatment. However, it is important to note that milk composition and energy-corrected milk yield were not affected by treatment.

Abstract Certain enzymes have improved fiber digestion of low-quality forages. Our objective was to determine the efficacy of a combination of a protease and Aspergillus oryzae and A. niger fermentation extracts on fiber digestion and rumen fermentation of bermudagrass hay supplemented with different energy concentrates. Bermudagrass hay was chopped and offered for ad libitum consumption to 20 ewes per study (33.1 ± 10.65 kg BW; Exp. 1; 36.0 ± 11.10 kg BW; Exp. 2) housed individually in 1 × 1.5-m pens (n = 5/trt). In Exp. 1, hay supplemented with DDGS at 0.25% BW, 1% BW, 1% BW + 2.3 g enzyme, or 1% BW + 3.5 g enzyme. In Exp. 2, hay was supplemented with cracked corn at the same levels as used in Exp. 1. Each experiment consisted of a 14-d dietary adaptation followed by 7 d of total fecal collection. On d 21, rumen samples were taken at 3 h intervals from each ewe for analysis of pH and VFA concentrations. Data were analyzed using PROC MIXED of SAS and orthogonal contrasts compared 0.25% vs. 1% BW, no enzyme vs. 2.3 g/d enzyme and 2.3 g/d vs. 3.5 g/d enzyme. In Exp. 1 NDF digestibility was greater (P < 0.05) from 1% vs. 0.25% BW supplement. Ruminal acetate and the acetate:propionate ratio were greatest (P < 0.05) from 0.25% BW vs. the other diets. Exp. 2, DM and OM intake were greater (P < 0.05) from the 1% BW diets and tended (P = 0.08) to be greater from 1% BW alone vs. 1% BW + 2.3 g enzyme. Ruminal acetate concentrations were greatest (P < 0.05) from 0.25% BW. Therefore, the blend of A. oryzae and A. niger fermentation extracts and a protease was not effective under the conditions of this study.

Certain enzymes may enhance fiber digestion, but the optimum dosage for ruminants consuming bermudagrass hay is not known. The objective of this study was to determine the optimal dosage of a combination of a protease with Aspergillus oryzae and A. niger fermentation extract blend on fiber digestion and rumen fermentation of bermudagrass hay by sheep. Twenty ewes (30.3 ± 5.29 kg BW) were allocated randomly to 1 of 5 diets (n = 4/treatment). Bermudagrass hay was chopped and offered for ad libitum consumption to ewes housed individually in 1 × 1.5-m pens with plastic-coated grate flooring. Diets were supplemented with 0.25% BW of soybean meal and either no enzyme or 1.5, 3, 4.5, or 6 g of a mixture of a protease with A. oryzae and A. niger fermentation extracts in a calcium carbonate carrier. A 14-d dietary adaptation was followed by 7 d of total fecal collection. On d 21, 3 rumen samples per ewe were taken at 4 h intervals for analysis of pH and VFA concentrations. Data were analyzed using the MIXED procedure of SAS and orthogonal linear and quadratic contrasts were used to assess enzyme dosage effects. Dry matter and ADF digestibility increased quadratically (P < 0.05), and NDF and OM digestibility tended (P ≤ 0.07) to increase quadratically across dosages. Ruminal acetate concentrations decreased quadratically and ruminal propionate increased quadratically (P < 0.05) with increasing enzyme dosage (P < 0.05). Total VFA concentrations were not affected by dosage (P = 0.71), but the acetate:propionate ratio decreased quadratically (P < 0.05) with increasing enzyme dosage. In conclusion, a protease and A. oryzae and A. niger fermentation extract blend increased fiber digestion, but dosages over 3 g of enzyme did not further enhance DMD or DMI.

Abstract Weaning and transit negatively affects DMI of newly received cattle. Restoring DMI is imperative to ensure rapid recovery and adequate response to immunological challenges. Eubiotics have the potential to increase DMI. The objective of this study was to evaluate effects of feeding a pre- and probiotic blend or a DFM-prebiotic blend on health and performance response by newly received crossbred cattle. Ninety-two Angus crossbred (Ranch 1) steers (n = 60; average BW 271 + 11 kg) and heifers (n = 32; Average BW 245 + 15 kg) and 89 Red Angus crossbred (Ranch 2) steers (average BW 264 + 11 kg), weaned immediately before trucking 1,520 km to the feedlot, were randomly allocated (5 to 7 hd/pen) within ranch and sex to one of 15 pens in each of two (north or south side) locations within a deep bedded confindment barn. Cattle were fed once daily for 49 d, orts were collected and weighed prior to feeding. Additives were incorporated daily into the total mixed ration as a premix using dried distillers grains. Performance data were analyzed using the MIXED procedure of SAS with pen and sex as random effects. Morbidity data were analyzed using PROC GLIMMIX of SAS. By day 7, cattle fed either additive tended (P < 0.10) to have greater DMI; this effect did not persist past 7 d. Cattle fed either microbial blend had heavier BW and ADG (P < 0.003) at day 28 and 49, which led to greater feed conversion efficiency (P < 0.03). Fewer (P = 0.001) cattle fed microbial blends were treated for BRD. Feeding either the prebiotic/probiotic blend or a DFM-prebiotic blend reduced morbidity and improved cattle performance during a 49-d receiving period.

We examined the effects of dietary supplementation of a Saccharomyces cerevisiae-based direct-fed microbial (DFM) on the growth performance, whole-blood immune gene expression, serum biochemistry, and plasma metabolome of newly weaned beef steers during a 42 d receiving period. Forty newly weaned Angus crossbred steers (7 d post-weaning; 210 ± 12 kg of BW; 180 ± 17 d of age) from a single source were stratified by BW and randomly assigned to 1 of 2 treatments: basal diet with no additive (CON; n = 20) or a basal diet top-dressed with 19 g of the DFM (PROB; n = 20). Daily DMI and weekly body weights were measured to calculate average daily gain (ADG) and feed efficiency (FE). Expression of 84 immune-related genes was analyzed on blood samples collected on days 21 and 42. Serum biochemical parameters and plasma metabolome were analyzed on days 0, 21, and 42. On day 40, fecal grab samples were collected for pH measurement. Compared with CON, dietary supplementation of PROB increased final body weight (P = 0.01) and ADG (1.42 vs. 1.23 kg; P = 0.04) over the 42 d feeding trial. There was a tendency for improved FE with PROB supplementation (P = 0.10). No treatment effect (P = 0.24) on DMI was observed. Supplementation with PROB increased (P ≤ 0.05) the concentrations of serum calcium, total protein, and albumin. Compared with CON, dietary supplementation with PROB increased (P ≤ 0.05) the expression of some immune-related genes involved in detecting pathogen-associated molecular patterns (such as TLR1, TLR2, and TLR6), T-cell differentiation (such as STAT6, ICAM1, RORC, TBX21, and CXCR3) and others such as TNF and CASP1, on day 21 and/or day 42. Conversely, IL-8 was upregulated (P = 0.01) in beef steers fed CON diet on day 21. Plasma untargeted plasma metabolome analysis revealed an increase (P ≤ 0.05) in the concentration of metabolites, 5-methylcytosine and indoleacrylic acid involved in protecting the animals against inflammation in steers fed PROB diet. There was a tendency for lower fecal pH in steers fed PROB diet (P = 0.08), a possible indication of increased hindgut fermentation. This study demonstrated that supplementation of PROB diet improved the performance, nutritional status, and health of newly weaned beef steers during a 42 d receiving period.