Acidosis in Feedlot Cattle

Fecal microbiota of diarrheic calves: Before, during, and after recovering from disease

BACKGROUND

It is unknown if gastrointestinal dysbiosis in diarrheic calves causes disease or is a consequence of the disease.

OBJECTIVES

Describe the fecal microbiota of calves before, during, and after recovering from diarrhea.

ANIMALS

Fifteen female Holstein calves of 0 to 21 days old from a single farm. Seven calves remained healthy throughout the study, and 8 developed diarrhea on Day 14.

METHODS

Longitudinal cohort study. Microbiota composition was characterized by amplifying the V4 region of the 16S rRNA gene.

RESULTS

Diversity (Shannon index) increased with age in healthy and diarrheic calves from Day 3 to 21, but diarrheic calves had a lower diversity on the day diarrhea was first observed (Day 14). By Day 21, diversity increased in calves that recovered from diarrhea and was not significantly different from that of their healthy counterparts (P > .05). Weighted UniFrac distance showed significant differences in the fecal microbiota between diarrheic and healthy calves at Day 14 of age (PERMANOVA, P < .05), but not before or after diarrhea (PERMANOVA, P > .05). Lactobacillus, Clostridium Sensu Stricto 1, and Collinsella were differentially abundant on Day 10 in calves that developed diarrhea on Day 14 (P < .05).

CONCLUSION AND CLINICAL IMPORTANCE

The fecal microbiota of healthy and diarrheic calves evolved similarly during the first 10 days of age but differed significantly on the day of onset of diarrhea. Enriching Lactobacillus, Clostridium Sensu Stricto 1, and Collinsella before diarrhea onset could have been contributed to the development of diarrhea.

Effects of monensin and a blend of magnesium oxide on performance, feeding behavior, and rumen morphometrics of Zebu beef cattle fed high-starch diets

This study aimed to evaluate the effects of a blend of different sources of magnesium oxide associated or not with monensin, on productive, ruminal, and nutritional parameters of steers. Eighty-four Nellore steers with an initial body weight (BW) of 367.3 ± 37.9 kg were allocated to one of 28 pens, with three steers per pen. Each pen was considered an experimental unit. Using a completely randomized design with a 2 × 2 factorial arrangement, the following treatments were assigned to each pen: 1) Control (CON)-a basal diet without additive inclusion; 2) Magnesium oxide blend (MG)-basal diet plus a magnesium-based product (pHix-up, Timab Magnesium, Dinard, France) provided at 0.50% of dry matter (DM); 3) Monensin (MON)-basal diet plus 25 mg/ kg of DM of sodium monensin (Rumensin, Elanco Animal Health, Greenfield, IN); and 4) MG association with MON-basal diet plus MG + MON, at the same doses of the individual treatments. The experimental period lasted 100 d. Blood samples were collected on days 0, 13, and 70 to determine d-lactate levels. Daily feed intake was recorded, and animal ingestive behavior was visually observed on days 66 and 67. On day 70, skeletal muscle tissue samples were obtained through biopsy for gene expression analysis. At the end of the experimental period, carcass ultrasonography was conducted. Subsequently, the steers were slaughtered, and rumen epithelium samples were collected for morphometric analysis. The use of monensin, of magnesium oxide blend, and their interactions, were treated as fixed effects, while the pens were considered as a random effect. Statistical differences were considered when P < 0.05. Steers-fed MG-containing diets consumed approximately 0.6 kg more DM per day than those fed diets without this additive (P = 0.01; 11.3 vs. 11.9 kg/d). The inclusion of MG in the diet increased (P = 0.02) the average daily gain. There was a greater Longissimus muscle area (LMA) and LMA per 100 kg of BW (P ≤ 0.03) for steers-fed diets with MG. Steers-fed MON exhibited reduced mRNA expression of the Atrogin-1 and mTOR compared to steers-fed MG + MON diets (MON × MG: P ≤ 0.04). Steers-fed MON had 6.9% greater feed efficiency (P = 0.02). Papillae width was lesser for CON than other treatments (MON × MG: P = 0.02). In conclusion, the magnesium oxide blend improved performance and carcass traits in high-energy feedlot diets, while monensin enhanced feed efficiency, suggesting potential for their use as alternatives or complements in beef cattle nutrition.

Epigallocatechin-3-gallate protects bovine ruminal epithelial cells against lipopolysaccharide-induced inflammatory damage by activating autophagy

BACKGROUND

Subacute ruminal acidosis (SARA) causes an increase in endotoxin, which can induce immune and inflammatory responses in the ruminal epithelium of dairy cows. In non-ruminants, epigallocatechin-3-gallate (EGCG), a major bioactive ingredient of green tea, is well-known to alleviate inflammation. Whether EGCG confers protection against SARA-induced inflammation and the underlying mechanisms are unknown.

RESULTS

In vivo, eight ruminally cannulated Holstein cows in mid-lactation were randomly assigned to either a low-concentrate (40%) diet (CON) or a high-concentrate (60%) diet (HC) for 3 weeks to induce SARA (n = 4). Cows with SARA had greater serum concentrations of tumor necrosis factor (TNF)-α and interleukin-6, and epithelium had histological signs of damage. In vitro, immortalized bovine ruminal epithelial cells (BREC) were treated with lipopolysaccharide (LPS) to imitate the inflammatory damage caused by SARA. Our data revealed that BREC treated with 10 µg/mL LPS for 6 h successfully induce a robust inflammatory response as indicated by increased phosphorylation of IκBα and nuclear factor kappa-B (NF-κB) p65. Pre-treatment of BREC with 50 µmol/L EGCG for 6 h before LPS challenge promoted the degradation of NLR family pyrin domain containing 3 (NLRP3) inflammasome through activation of autophagy, which further repressed activation of NF-κB pathway targeting Toll-like receptor 4 (TLR4). Analyses also revealed that the ECGG upregulated tight junction (TJ) protein expression upon incubation with LPS.

CONCLUSIONS

Subacute ruminal acidosis causes ruminal epithelium injury and systemic inflammation in dairy cows. However, the anti-inflammatory effects of EGCG help preserve the integrity of the epithelial barrier through activating autophagy when BREC are exposed to LPS. Thus, EGCG could potentially serve as an effective therapeutic agent for SARA-associated inflammation.

Postbiotics from Saccharomyces cerevisiae fermentation stabilize microbiota in rumen liquid digesta during grain-based subacute ruminal acidosis (SARA) in lactating dairy cows

BACKGROUND

Subacute ruminal acidosis (SARA) is a common metabolic disorder of high yielding dairy cows, and it is associated with dysbiosis of the rumen and gut microbiome and host inflammation. This study evaluated the impact of two postbiotics from Saccharomyces cerevisiae fermentation products (SCFP) on rumen liquid associated microbiota of lactating dairy cows subjected to repeated grain-based SARA challenges. A total of 32 rumen cannulated cows were randomly assigned to 4 treatments from 4 weeks before until 12 weeks after parturition. Treatment groups included a Control diet or diets supplemented with postbiotics (SCFPa, 14 g/d Original XPC; SCFPb-1X, 19 g/d NutriTek; SCFPb-2X, 38 g/d NutriTek, Diamond V, Cedar Rapids, IA, USA). Grain-based SARA challenges were conducted during week 5 (SARA1) and week 8 (SARA2) after parturition by replacing 20% DM of the base total mixed ration (TMR) with pellets containing 50% ground barley and 50% ground wheat. Total DNA from rumen liquid samples was subjected to V3-V4 16S rRNA gene amplicon sequencing. Characteristics of rumen microbiota were compared among treatments and SARA stages.

RESULTS

Both SARA challenges reduced the diversity and richness of rumen liquid microbiota, altered the overall composition (β-diversity), and its predicted functionality including carbohydrates and amino acids metabolic pathways. The SARA challenges also reduced the number of significant associations among different taxa, number of hub taxa and their composition in the microbial co-occurrence networks. Supplementation with SCFP postbiotics, in particular SCFPb-2X, enhanced the robustness of the rumen microbiota. The SCFP supplemented cows had less fluctuation in relative abundances of community members when exposed to SARA challenges. The SCFP supplementation promoted the populations of lactate utilizing and fibrolytic bacteria, including members of Ruminococcaceae and Lachnospiraceae, and also increased the numbers of hub taxa during non-SARA and SARA stages. Supplementation with SCFPb-2X prevented the fluctuations in the abundances of hub taxa that were positively correlated with the acetate concentration, and α- and β-diversity metrics in rumen liquid digesta.

CONCLUSIONS

Induction of SARA challenges reduced microbiota richness and diversity and caused fluctuations in major bacterial phyla in rumen liquid microbiota in lactating dairy cows. Supplementation of SCFP postbiotics could attenuate adverse effects of SARA on rumen liquid microbiota.

Evaluation of orally administered Megasphaera elsdenii in steer calves abruptly transitioned from a receiving diet with 4% dietary starch to a growing diet with 38% dietary starch

The objective of this experiment was to evaluate the effects of orally administered Megasphaera elsdenii NCIMB 41125 as a microbial supplement in steers abruptly transitioned from a receiving diet with 4% dietary starch (dry matter [DM] basis) to a growing diet with 38% dietary starch (DM basis). Steers (n = 192; initial shrunk body weight [SBW] = 309 ± 20.6 kg) were assigned to microbial supplement treatment in a randomized complete block design. Treatments were control (CON): no microbial supplement prior to diet transition, and (DFM): microbial supplement orally administered prior to diet transition (20 mL of microbial supplement [Lactipro NXT, Axiota Animal Health, Fort Collins, CO] containing 1 × 1010 colony forming units Megasphaera elsdenii NCIMB 41125). Steers were sourced from a previously conducted 49 d feedlot receiving period experiment and abruptly transitioned from a receiving diet including soybean hulls and wheatlage containing 4% dietary starch (DM basis) to a growing diet including high-moisture ear corn, dry-rolled corn, and wheatlage containing 38% dietary starch (DM basis). Diets were switched on an equal DM intake basis to achieve the abrupt change and steers were fed the 38% starch diet for 49 d until experiment completion. Prior to experiment initiation, steers (n = 72; n = 3/pen) were fitted with wireless rumination tags to track daily activity and rumination time. No differences (P ≥ 0.20) were observed between treatments for final SBW, average daily gain, DM intake, feed efficiency, calculated net energy (NE) for maintenance and gain, or observed-to-expected ratio of NE for maintenance and gain. Additionally, no treatment × day or treatment differences (P ≥ 0.12) were observed for activity or rumination measures. Minutes ruminating and active both differed (P < 0.01) for the main effect of day. Compared to non-supplemented steers, oral administration of Megasphaera elsdenii NCIMB 41125 did not improve growth performance or efficiency of dietary NE utilization in steers transitioned from a receiving diet containing 4% starch (DM basis) to a growing diet containing 38% starch (DM basis).

Abomasal lesions found in postmortem examination of fattening Holstein-Friesian bulls from central Poland

The health of the gastrointestinal tract in cattle is one of the factors influencing adequate nutrient absorption and body weight gain. This study aimed to evaluate the prevalence of lesions found in the abomasum of Polish fattening Holstein-Friesian bulls. A total of 149 abomasa from adult bulls from two voivodeships of central Poland were inspected for pathologicalanatomic position (displacement, volvulus), impaction, mucosal membrane lesions (inflammation, hyperplasia), and signs of parasite infestation(Moroccan leather, worm nodules) in one of the Polish abattoirs just after slaughter. Among all the examined males no lesions were observed in only 8 individuals. The most common findings were erosions (75.8%) and type 1 ulcerations (48.3%) of the body, pylorus, or both locations. Signs of parasite infestations were observed in 78.5% of the inspected animals. Significant differences correlated with age were found in the prevalence of healed ulcers, and between voivodeships in the prevalence of type 2 ulcers. The findings of this study indicate that most fattening bulls in Poland suffer from subclinical forms of abomasa inflammation (both diffuse and focal) and middle-large abomasum parasites invasions, which can influence the economics and profitability, as well as welfare, of livestock production.

The impacts of animal agriculture on One Health-Bacterial zoonosis, antimicrobial resistance, and beyond

The industrialization of animal agriculture has undoubtedly contributed to the improvement of human well-being by increasing the efficiency of food animal production. At the same time, it has also drastically impacted the natural environment and human society. The One Health initiative emphasizes the interdependency of the health of ecosystems, animals, and humans. In this paper, we discuss some of the most profound consequences of animal agriculture practices from a One Health perspective. More specifically, we focus on impacts to host-microbe interactions by elaborating on how modern animal agriculture affects zoonotic infections, specifically those of bacterial origin, and the concomitant emergence of antimicrobial resistance (AMR). A key question underlying these deeply interconnected issues is how to better prevent, monitor, and manage infections in animal agriculture. To address this, we outline approaches to mitigate the impacts of agricultural bacterial zoonoses and AMR, including the development of novel treatments as well as non-drug approaches comprising integrated surveillance programs and policy and education regarding agricultural practices and antimicrobial stewardship. Finally, we touch upon additional major environmental and health factors impacted by animal agriculture within the One Health context, including animal welfare, food security, food safety, and climate change. Charting how these issues are interwoven to comprise the complex web of animal agriculture's broad impacts on One Health will allow for the development of concerted, multidisciplinary interventions which are truly necessary to tackle these issues from a One Health perspective.

The welfare of ill and injured feedlot cattle: a review of the literature and implications for managing feedlot hospital and chronic pens

By definition, ill and injured animals are on the negative valence of animal welfare. For beef cattle kept in feedlot settings, advances in cattle health management have resulted in a greater understanding and prevention of illness and injury. However, the management of cattle once they become ill and injured is an understudied area, and there are gaps in knowledge that could inform evidence-based decision-making and strengthen welfare for this population. The aim of this review is to provide a comprehensive overview of the acquired knowledge regarding ill and injured feedlot cattle welfare, focusing on existing knowledge gaps and implications for hospital and chronic pen management and welfare assurance. Ill and injured feedlot cattle consist of acutely impaired animals with short-term health conditions that resolve with treatment and chronically impaired animals with long-term health conditions that may be difficult to treat. A literature search identified 110 articles that mentioned welfare and ill and injured feedlot cattle, but the population of interest in most of these articles was healthy cattle, not ill and injured cattle. Articles about managing ill and injured cattle in specialized hospital (n = 12) or chronic (n = 2) pens were even more sparse. Results from this literature search will be used to outline the understanding of acutely and chronically ill and injured feedlot cattle, including common dispositions and welfare considerations, behavior during convalescence, and strategies for identifying and managing ill and injured cattle. Finally, by working through specific ailments common in commercial feedlot environments, we illustrate how the Five Domains Model can be used to explore feelings and experiences and subsequent welfare state of individual ill or injured feedlot cattle. Using this approach and our knowledge of current industry practices, we identify relevant animal-based outcomes and critical research questions to strengthen knowledge in this area. A better understanding of this overlooked topic will inform future research and the development of evidence-based guidelines to help producers care for this vulnerable population.

Investigating the impact of feed-induced, subacute ruminal acidosis on rumen epimural transcriptome and metatranscriptome in young calves at 8- and 17-week of age

Introduction

With the goal to maximize intake of high-fermentable diet needed to meet energy needs during weaning period, calves are at risk for ruminal acidosis. Using the calves from previously established model of feed-induced, ruminal acidosis in young calves, we aimed to investigate the changes in rumen epimural transcriptome and its microbial metatranscriptome at weaning (8-week) and post-weaning (17-week) in canulated (first occurred at 3 weeks of age) Holstein bull calves with feed-induced subacute ruminal acidosis.

Methods

Eight bull calves were randomly assigned to acidosis-inducing diet (Treated, n = 4; pelleted, 42.7% starch, 15.1% neutral detergent fiber [NDF], and 57.8% nonfiber carbohydrates), while texturized starter was fed as a control (Control, n = 4; 35.3% starch, 25.3% NDF, and 48.1% nonfiber carbohydrates) starting at 1 week through 17 weeks. Calves fed acidosis-inducing diet showed significantly less (p < 0.01) body weight over the course of the experiment, in addition to lower ruminal pH (p < 0.01) compared to the control group. Rumen epithelial (RE) tissues were collected at both 8 weeks (via biopsy) and 17 weeks (via euthanasia) and followed for whole transcriptome RNA sequencing analysis. Differentially expressed genes (DEGs) analysis was done using cufflinks2 (fold-change ≥2 and p < 0.05) between treated and control groups at 8-week of age, and between 8- and 17-week for the treated group.

Results

At 8-week of age, DEGs between treatment groups showed an enrichment of genes related to the response to lipopolysaccharide (LPS) (p < 0.005). The impact of prolonged, feed-induced acidosis was reflected by the decreased expression (p < 0.005) in genes involved in cell proliferation related pathways in the RE at 17-week of age in the treated group. Unique sets of discriminant microbial taxa were identified between 8-and 17-week calves in the treated group and the treatment groups at 8-week, indicating that active microbial community changes in the RE are an integral part of the ruminal acidosis development and progression.

The influence of virginiamycin on digestion and ruminal parameters under feedlot conditions

This experiment aimed to assess the impact of virginiamycin on in vitro gas production dynamics, rumen kinetics, and nutrient digestibility in beef steers fed a grain-based diet. Nine ruminally cannulated British-crossbred steers (596 ± 49 kg) were assigned to this experiment. Animals were housed in three pens (n = 3/pen) equipped with a Calan gate feed system and water troughs. Pens were enrolled in a 3 × 3 Latin square design containing three periods of 16 d, and a 5-d washout interval between periods. Dietary treatments consisted of virginiamycin (VM) administration at 0 (VM0), 180 (VM180), or 240 mg/d (VM240). During days 15 and 16 of each period, about 600 mL of rumen fluid and urine samples were collected before (0 h), and at 4, 8, 12, and 16 h after the morning feed (0730 hours), rumen inoculum was used to take pH and redox potential measurements immediately after collection using a portable pH and redox meter, and subsamples were taken for volatile fatty acids (VFA) and NH3-N analyses, and urine samples were composited daily and analyzed for creatinine and purine derivatives (PD) content to estimate microbial crude protein flow. During the 4-h post-morning feed rumen collection, rumen inoculum was utilized to perform in vitro gas production measurements. Fecal samples were collected on day 16 of each period to estimate nutrient digestibility using acid detergent insoluble ash as an internal marker. Animals were considered the experimental unit for the statistical analyses, and periods and squares were included as random variables. The total and rate of gas production were similar among treatments (P ≥ 0.17). The second-pool (i.e., fiber) gas production increased linearly as VM inclusion increased (P = 0.01), with VM240 being greater compared to VM180 and VM0 (7.84, 6.94, and 6.89 mL, respectively). Ruminal pH linearly increased as VM increased, with VM240 being greater than VM0 and VM180 intermediate (5.90, 5.82, and 5.86, respectively; P = 0.03). The VFA concentrations did not differ (P ≥ 0.13), but the acetate-to-propionate ratio was the highest in VM240 (P = 0.005). Branched-chain VFA increased (P ≤ 0.03) while lactate concentrations decreased (P = 0.005) linearly with VM. The ruminal NH3-N concentration was the lowest in the VM0 (P = 0.006). The estimated absorbed PD, purine derivative to creatinine index, and microbial N flow increased linearly with VM (P ≤ 0.07). The provision of VM influenced rumen dynamics in a dose-dependent manner.

Can computerized rumen mucosal colorimetry serve as an effective field test for managing subacute ruminal acidosis in feedlot cattle?

Subacute ruminal acidosis (SARA) is one of the major nutritional disorders in the dairy and beef industries, leading to significant financial losses. Diagnosing SARA is challenging due to the need to evaluate multiple parameters, such as milk fat/protein ratio, ruminal lactate, and hemogram, instead of relying on a single definitive symptom or diagnostic method. This study aimed to evaluate the effectiveness of computerized rumen colorimetry in detecting SARA in beef cattle. Over one year, 75 cattle aged 8-10 months from five farms were periodically monitored for rumen pH prior to slaughter. Samples of rumen wall and rumen content were obtained at slaughter for analysis. The study found a positive correlation coefficient between rumen pH and color components, particularly for Red (0.853) and color lightness (L) (0.862). The darkening of the rumen epithelium's color was attributed to the effect of rumen pH on the keratinized layer of the epithelium. Furthermore, an increase in the thickness of ruminal epithelium layers, particularly non-keratinized and total epithelium, was observed in animals with a history of SARA. It is possible that the lower rumen pH increases the rate of replacement of the keratinized epithelium, and the non-keratinized epithelium overgrows to compensate for the need to of produce keratinized layers. In conclusion, computerized rumen colorimetry shows promise as a reliable method for managing SARA in bovine farms by monitoring the condition in the slaughterhouse. Further research is needed to evaluate its effectiveness in detecting SARA in live animals.

Cattle are more motivated for a high-concentrate diet than Sudan grass hay, despite low reticulorumen pH

Subacute ruminal acidosis (SARA) is characterized by chronic low ruminal pH, and occurs for feedlot cattle fed high-concentrate diets. Forages slow digestion and reduce acid production. We aimed to assess how motivated finishing cattle are to access forage (Sudan grass hay, SG) via their willingness to interact with an electrified barrier. Reticulorumen pH was measured to relate the results to digestive health. Twenty-eight animals fed a high-concentrate ration ad libitum had access to 4 L of one of two treatments (n = 14/treatment) fed 1×/d behind a barrier: 1) SG or 2) an additional offering of the normal ration (total mixed ration [TMR]). To access their treatment, the steer voluntarily pushed his muzzle against an electrified barrier. The electrical current was increased exponentially every 24 h (0, 156, 312, 625, 1,250, 2,500, 5,000 µA) until the animal ceased accessing it. Visits to the treatment were recorded continuously 24 h/d and reticulorumen pH was measured every 10 min. Time with a reticulorumen pH below 5.8 was 348 ± 101 and 280 ± 76 min/24 h for SG and TMR animals, respectively; these durations meet the criterion for SARA. However, animals with access to SG were less likely to advance to the next current than TMR animals (P < 0.01) and were approximately 3× less willing to interact with higher currents than TMR (mean maximum current touched: 469 ± 169 and 1,380 ± 254 μA, respectively, mean ± SE, P = 0.01). Lower motivation to access SG was further demonstrated through fewer visits to the SG (2.4 ± 0.4 vs. 5.3 ± 0.6 #/d, P < 0.01), and less SG consumed than TMR (32.0 ± 0.1 vs. 74.0 ± 0.0 %/d, P < 0.01, measured as % due to weight differences of SG and TMR). Overall, finishing cattle valued the TMR more than SG, likely because of differences in the quantity offered, palatability, and familiarity. When rumen health was considered, SG animals visited more often (r = 0.5, P = 0.09) and showed fewer failed attempts (r = -0.5, P = 0.06) to access forage as the severity and duration of pH depression below 5.6, for example, increased. No measures of treatment use were related to pH depression for TMR animals (P ≥ 0.31). These findings provide evidence that cattle are motivated for Sudan grass hay when experiencing chronic low reticulorumen pH. However, they also contribute to the mixed evidence about the motivation for forage in this life stage, because, overall TMR was valued more highly than SG. Despite widespread pH depression, TMR cattle contrafreeloaded for additional concentration, demonstrating unexpectedly high motivation for this resource.

Bioactive metabolites of Asparagopsis stabilized in canola oil completely suppress methane emissions in beef cattle fed a feedlot diet

Asparagopsis taxiformis (Asparagopsis) has been shown to be highly efficacious at inhibiting the production of methane (CH4) in ruminants. To date, Asparagopsis has been primarily produced as a dietary supplement by freeze-drying to retain the volatile bioactive compound bromoform (CHBr3) in the product. Steeping of Asparagopsis bioactive compounds into a vegetable oil carrier (Asp-Oil) is an alternative method of stabilizing Asparagopsis as a ruminant feed additive. A dose-response experimental design used 3 Asp-Oil-canola oil blends, low, medium, and high Asp-Oil which provided 17, 34, and 51 mg Asparagopsis derived CHBr3/kg dry matter intake (DMI), respectively (in addition to a zero CHBr3 canola oil control), in a tempered-barley based feedlot finisher diet, fed for 59 d to 20 Angus heifers (five replicates per treatment). On four occasions, live weight was measured and CH4 emissions were quantified in respiration chambers, and blood, rumen fluid, and fecal samples were collected. At the end of the experiment, all animals were slaughtered, with carcasses graded, and samples of meat and edible offal collected for testing of consumer sensory qualities and residues of CHBr3, bromide, and iodide. All Asp-Oil treatments reduced CH4 yield (g CH4/kg DMI, P = 0.008) from control levels, with the low, medium, and high Asp-Oil achieving 64%, 98%, and 99% reduction, respectively. Dissolved hydrogen increased linearly with increasing Asp-Oil inclusion, by more than 17-fold in the high Asp-Oil group (P = 0.017). There was no effect of Asp-Oil treatment on rumen temperature, pH, reduction potential, volatile fatty acid and ammonia production, rumen pathology, and histopathology (P > 0.10). There were no differences in animal production and carcass parameters (P > 0.10). There was no detectable CHBr3 in feces or any carcass samples (P > 0.10), and iodide and bromide residues in kidneys were at levels unlikely to lead to consumers exceeding recommended maximum intakes. Overall, Asp-Oil was found to be safe for animals and consumers of meat, and effective at reducing CH4 emissions and yield by up to 99% within the range of inclusion levels tested.

Soybean molasses increases subcutaneous fat deposition while reducing lipid oxidation in the meat of castrated lambs

This study aimed to evaluate the effect of including soybean molasses (SM) on performance, blood parameters, carcass traits, meat quality, fatty acid, and muscle (longissimus thoracis) transcriptomic profiles of castrated lambs. Twenty Dorper × Santa Inês lambs (20.06 ± 0.76 kg body weight [BW]) were assigned to a randomized block design, stratified by BW, with the following treatments: CON: 0 g/kg of SM and SM20: 200 g/kg of SM on dry matter basis, allocated in individual pens. The diet consisted of 840 g/kg concentrate and 160 g/kg corn silage for 76 d, with the first 12 d as an adaptation period and the remaining 64 d on the finishing diet. The SM20 diet increased blood urea concentration (P = 0.03) while reduced glucose concentration (P = 0.04). Lambs fed SM showed higher subcutaneous fat deposition (P = 0.04) and higher subcutaneous adipocyte diameter (P < 0.01), in addition to reduced meat lipid oxidation (P < 0.01). SM reduced the quantity of branched-chain fatty acids in longissimus thoracis (P = 0.05) and increased the quantity of saturated fatty acids (P = 0.01). In the transcriptomic analysis, 294 genes were identified as differentially expressed, which belong to pathways such as oxidative phosphorylation, citric acid cycle, and monosaccharide metabolic process. In conclusion, diet with SM increased carcass fat deposition, reduced lipid oxidation, and changed the energy metabolism, supporting its use in ruminant nutrition.

The effects of antibiotic-free supplementation on the ruminal pH variability and methane emissions of beef cattle under the challenge of subacute ruminal acidosis (SARA)

Subacute ruminal acidosis (SARA) in feedlot cattle during the feed transition to grain-based diets is a significant constraint to animal health and productivity. This experiment assessed an antibiotic-free supplement (ProTect®) effects on ruminal pH variability and methane (CH₄) emissions of cattle during the challenge of SARA. Ten 18-month-old Angus steers (472 ± 4.8 kg) were randomly allocated into monensin (n = 5) and ProTect® groups (n = 5) and progressively introduced to grain diets incorporating monensin or ProTect® for 36 days of the experiment [starter (7 days; 45% grain), T1 (7 days; 56% grain), T2 (7 days; 67% grain), finisher (15 days; 78% grain)]. The pH variability on the finisher period was reduced by the ProTect® supplement (6.6% vs. 5.2%; P < 0.01), with CH₄ emissions being significantly higher relative to the monensin group [88.2 g/day (9.3 g CH₄/kg DMI) vs. 133.7 g/day (14.1 g CH₄/kg DMI); P < 0.01]. There was no difference between treatments in the time spent on the ruminal pH < 5.6 or < 5.8 (P > 0.05). The model evaluation for the ruminal pH variation indicated that the mean absolute error (MAE) proportion for both groups was good within the same range [4.05% (monensin) vs. 4.25% (ProTect®)] with identical root mean square prediction error (RMSPE) (0.34). It is concluded that the ProTect® supplement is an effective alternative to monensin for preventing SARA in feedlot cattle by managing ruminal pH variation during the transition to high-grain diets. Both monensin and ProTect® supplemented cattle exhibited lower CH₄ yield compared to cattle fed forages and low-concentrate diets.

Metabolic Diseases in Beef Cattle

Beef cattle are less prone to metabolic diseases as compared with dairy cattle; however, there are disease entities of concern in feedlot and cow-calf beef cattle operations. In one study, a prevalence of 2% was found for ruminant acidosis in a feedlot; however, there is little prevalence information published with regard to metabolic diseases in beef cattle.1 Metabolic diseases covered in this article are hypomagnesemia, ruminal acidosis, and all of the common sequelae, polioencephalomalacia, manganese deficiency, and protein-energy malnutrition (PEM).

Disease Occurrence in- and the Transferal of Zoonotic Agents by North American Feedlot Cattle

North America is a large producer of beef and contains approximately 12% of the world's cattle inventory. Feedlots are an integral part of modern cattle production in North America, producing a high-quality, wholesome protein food for humans. Cattle, during their final stage, are fed readily digestible high-energy density rations in feedlots. Cattle in feedlots are susceptible to certain zoonotic diseases that impact cattle health, growth performance, and carcass characteristics, as well as human health. Diseases are often transferred amongst pen-mates, but they can also originate from the environment and be spread by vectors or fomites. Pathogen carriage in the gastrointestinal tract of cattle often leads to direct or indirect contamination of foods and the feedlot environment. This leads to the recirculation of these pathogens that have fecal-oral transmission within a feedlot cattle population for an extended time. Salmonella, Shiga toxin-producing Escherichia coli, and Campylobacter are commonly associated with animal-derived foods and can be transferred to humans through several routes such as contact with infected cattle and the consumption of contaminated meat. Brucellosis, anthrax, and leptospirosis, significant but neglected zoonotic diseases with debilitating impacts on human and animal health, are also discussed.

Disodium Fumarate Alleviates Endoplasmic Reticulum Stress, Mitochondrial Damage, and Oxidative Stress Induced by the High-Concentrate Diet in the Mammary Gland Tissue of Hu Sheep

The long-term feeding of the high-concentrate diet (HC) reduced rumen pH and induced subacute rumen acidosis (SARA), leading to mammary gland tissue damage among ruminants. Disodium fumarate enhanced rumen bufferation and alleviated a decrease in rumen pH induced by the HC diet. Therefore, the purpose of this study was to investigate whether disodium fumarate could alleviate endoplasmic reticulum (ER) stress, mitochondrial damage, and oxidative stress induced by the high-concentrate diet in the mammary gland tissue of Hu sheep. In this study, 18 Hu sheep in mid-lactation were randomly divided into three groups: one fed with a low-concentrate diet (LC) diet, one fed with a HC diet, and one fed with a HC diet with disodium fumarate (AHC). Each sheep was given an additional 10 g of disodium fumarate/day. The experiment lasted for eight weeks. After the experiment, rumen fluid, blood, and mammary gland tissue were collected. The results show that, compared with the LC diet, the HC diet could reduce rumen pH, and the pH below 5.6 was more than 3 h, and the LPS content of blood and rumen fluid in HC the diet was significantly higher than in the LC diet. This indicates that the HC diet induced SARA in Hu sheep. However, the supplementation of disodium fumarate in the HC diet increased the rumen pH and decreased the content of LPS in blood and rumen fluid. Compared with the LC diet, the HC diet increased Ca²⁺ content in mammary gland tissue. However, the AHC diet decreased Ca²⁺ content. The HC diet induced ER stress in mammary gland tissue by increasing the mRNA and protein expressions of GRP78, CHOP, PERK, ATF6, and IRE1α. The HC diet also activated the IP3R-VDAC1-MCU channel and lead to mitochondrial damage by inhibiting mitochondrial fusion and promoting mitochondrial division, while disodium fumarate could alleviate these changes. In addition, disodium fumarate alleviated oxidative stress induced by the HC diet by activating Nrf2 signaling and reducing ROS production in mammary gland tissue. In conclusion, the supplementation of disodium fumarate at a daily dose of 10 g/sheep enhanced rumen bufferation by maintaining the ruminal pH above 6 and reduced LPS concentration in ruminal fluid and blood. This reaction avoided the negative effect observed by non-supplemented sheep that were fed with a high-concentrate diet involving endoplasmic reticulum stress, oxidative stress, and mitochondrial damage in the mammary gland tissue of Hu sheep.

Using Expert Elicitation for ranking hazards, promoters and animal-based measures for on-farm welfare assessment of indoor reared beef cattle: an Italian experience

On-farm welfare assessment gives the opportunity to monitor and improve the quality of the animal life on the farm. In order to build the first Italian public standard for the welfare of indoor reared beef cattle, a list of 25 potential hazards and 22 potential promoters of beef cattle welfare was judged by a group of national experts by taking into account their negative or positive impacts on the welfare-state of the target population. In addition, the experts were asked to rank a list of 11 animal-based measures for identifying the most appropriate and important for measuring negative welfare outcomes in beef cattle. Based on experts' ratings, an "impact score" (IS_overall) was calculated for the proposed measures. Management hazards and promoters were ranked to have a greater impact on beef cattle welfare than housing factors. Keeping cattle in large (≥ 40 animals) and heterogeneous groups obtained the highest IS_overall among the proposed hazards (IS_overall = 5.54), followed by the presence of animals without free access to drinking water (IS_overall = 4.39) and the use of high-concentrate corn silage diets (concentrate > 80% and fiber < 6%) (IS_overall = 4.39). On the other hand, housing animals in small (≤ 20 animals) and homogeneous groups (IS_overall = 5.41), checking them at least twice a day (IS_overall = 4.62) and rearing cattle in loose housing systems with access to an outdoor area/pasture (IS_overall = 4.27) were ranked among the top 3 promoters. Concerning animal-based measures, experts scored lameness, severe respiratory diseases, body condition scoring and mortality rate to be measures most important for assessing serious welfare impairment.

Physicochemical Evaluations of Diets, Rumen Fluid, Blood and Faeces of Beef Cattle under Two Different Feedlot Systems

The physicochemical characteristics of diets and faeces were evaluated in combination with data of rumen fluid and blood lactate collected from two distinct feedlot systems in Brazil to understand the causes and correlations to digestive disorders in these production systems. The data were collected during two visits to a finishing system which fed about 80,000 head per year, and four visits to two properties that fed 150 to 180 straight bred Nellore bulls per year to be sold as stud cattle. The findings suggest that ruminal acidosis occurred when there was high intake of starch-rich concentrate, and that subacute rumen acidosis (SARA) most likely occurred in situations where more than 4% of faecal dry matter was excreted as particles larger than 4 mm. The latter were associated with diets having less than 15% of particles smaller than 8 mm and faecal pH under 6.30. It is concluded that ancillary tests, such as ruminal and faecal pH, and particle size distribution in the faeces, can potentially be used in combination with information on diet nutritional composition and a series of best practice management protocols to increase not only animal productivity but to reduce the risks of SARA and ensure the welfare of animals.

Effect of Yerba Mate Extract as Feed Additive on Ruminal Fermentation and Methane Emissions in Beef Cattle

The inclusion of plant extracts that contain secondary compounds with the potential to modulate rumen fermentation and improve animal performance has gained attention in recent years. The aim of this study was to evaluate the effect of the inclusion of yerba mate extract (Ilex paraguariensis ST. Hilaire) (YME) on the ruminal parameters. Eight castrated cattle were divided into four groups, a control without YME (0%) and three treatment groups with 0.5, 1 and 2% inclusion of YME in the dry matter. The inclusion of YME did not show differences in ruminal methane emissions (CH4), and total apparent digestibility (p = 0.54). Likewise, YME did not modify ruminal pH, but positively affected NH3-N, which decreased linearly as the extract level in the diet increased (p = 0.01). No short chain fatty acids (SCFA) were influenced by YME, except isovaleric acid (p = 0.01), which showed a lower concentration in the inclusion of 2% YME. Our results show that up to 2% YME does not affect digestibility, ruminal fermentation parameters, or the concentration of short-chain fatty acids in the rumen.

Whole or coarsely broken açai seed as a source of roughage in the diet of feedlot cattle: intake, digestibility, and ruminal parameters

This study was conducted to evaluate the effects of two methods of provision of açai seed (AS) as a fiber source (coarsely broken or whole) for feedlot beef cattle on the intake, digestibility, and ruminal parameters. Four bulls (male, non-castrated, and rumen fistulated), with an average body weight of 340 ± 31 kg, distributed in two simultaneous 2 × 2 Latin squares, were used. The treatments were two methods of processing of the açai seed, as follows: whole açai seed (WAS), and coarsely broken açai seed (CBAS). The dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF) intake were higher (P < 0.10) with the use of CBAS. The digestibility of DM and nutrients was not affected (P > 0.10) by AS processing. Acetate and total volatile fatty acids concentrations, and acetate:propionate ratio were higher with the CBAS diet, whereas the pH was higher with the WAS diet. The concentrations of propionate, butyrate, and ruminal ammonia nitrogen (NH₃) did not change with AS processing. Thus, coarsely broken açai seed increases the intake of DM and nutrients without altering the digestibility. Furthermore, it increases the concentrations of total fatty acids and acetate.

Siqueira MC, DiLorenzo N. Polyclonal antibody preparations from avian origin as a feed additive to beef cattle: Ruminal fermentation during the step-up transition diets

This study investigated the effects of feeding an avian-derived polyclonal antibody preparation (PAP; CAMAS, Inc.) against Streptococcus bovis, Fusobacterium necrophorum, and lipopolysaccharides (40%, 35%, and 25% of the preparation, respectively) on ruminal fermentation [pH, ammonia-N (NH₃-N), lactate, and volatile fatty acids (VFA)] of beef steers during a 21-d step-up diet adaptation. Eight ruminally cannulated Angus crossbred beef steers (658 ± 79 kg of body weight) were assigned in a crossover design to be transitioned from a diet containing ad libitum bermudagrass hay [Cynodon dactylon (L.) Pers.] plus 0.45 kg/d (as fed) of molasses with 0 (CON) or 3 g of PAP (PAP) to a high-grain diet. Transition consisted of three 7-d steps of increased inclusion of cracked corn (35%, 60%, and 82% of the diet DM for STEP1, STEP2, and STEP3, respectively). On each transition day and 7 d after STEP3 (STEP3-7d), ruminal fluid samples were obtained every 3 h for 24 h. Feeding 3 g of PAP daily increased (P < 0.01) average ruminal pH during STEP3 compared with CON steers (5.6 vs. 5.4 ± 0.05, respectively). During STEP1, NH₃-N concentration was greater (P < 0.01; 9.4 vs. 6.8 ± 0.74 mM, respectively), and time (min/d) and area (time × pH) of ruminal pH below or equal to 5.2 was lesser (P ≤ 0.03) for steers consuming PAP compared with steers assigned to CON treatment (33.4 vs. 73.3 ± 21.7 min/d and 187.4 vs. 406.3 ± 119.7 min × pH/d, respectively). Steers consuming PAP had greater acetate:propionate ratio at 0, 3, and 6 h relative to diet change compared with CON (2.42, 2.35, 2.29 vs. 1.66, 1.79, and 1.72 ± 0.17, respectively), whereas butyrate molar proportions increased (P = 0.02; 17.1 vs. 11 ± 1.58 mol/100 mol for CON and PAP, respectively) when PAP was not fed at STEP2. Total ruminal lactate concentrations were not affected by PAP feeding (P > 0.11). In conclusion, feeding 3 g/d of polyclonal antibody preparation against S. bovis, F. necrophorum, and lipopolysaccharides was effective in increasing ruminal pH, A:P ratio, and NH₃-N concentrations, possibly attenuating the risks of ruminal acidosis in steers during the step-up transition from forage to high-grain diets.

Ruminal bacteria lipopolysaccharides: an immunological and microbial outlook

Lipopolysaccharides (LPS) are outer membrane components of Gram-negative bacteria made of three regions: the O-antigen; the core oligosaccharide; and a glucosamine disaccharide linked to hydroxy fatty acids, which is named lipid A. The number phosphate groups, and hydroxy fatty acid chains is associated with the immunopotency and the immunomodulatory activity of LPS, where six-acyl chain lipid A with two phosphate groups is found in virulent strains and five- or four-acyl chain lipid A with one phosphate group are found in non-virulent bacteria strains. Ruminal bacteria are predominantly Gram-negative and their LPS have not been thoroughly investigated. In the rumen, LPS is comprised of mixed ruminal LPS. Drawing upon a body of theoretical and applied work, this paper aims to critically review the scientific literature regarding single-species and mixed ruminal bacteria LPS, highlighting the importance of ruminal LPS to the host. Lastly, future research directions are suggested in order to further our understanding of the roles of LPS in the rumen. Possible suggestions for further understanding ruminal LPS include (1) in silico evaluation of major bacteria contributing to ruminal LPS, (2) structural characterization of LPS from prominent ruminal bacteria species, such as ruminal selenomonads and Megasphaera elsdenii, and, (3) ruminal epithelial tissue immune response evaluation from single-species and mixed ruminal LPS. In conclusion, this review identifies numerous areas for future research, including setting the basis for future modeling and simulation of host microbiome interactions in ruminants.

Impacts of polyclonal antibody preparations from avian origin on nutrient digestibility and performance of backgrounding beef cattle

This study evaluated the effects of feeding an avian-derived polyclonal antibody preparation (PAP; CAMAS, Inc.) against Streptococcus bovis, Fusobacterium necrophorum, and lipopolysaccharides (LPS; 40%, 35%, and 25% of the preparation, respectively) on growth performance (Exp. 1) and apparent total tract digestibility of nutrients (Exp. 2) of beef cattle consuming a backgrounding diet. In Exp. 1, Angus crossbred heifers (n = 70; 360 ± 24 kg of initial body weight; BW) and steers (n = 20; 386 ± 24 kg of BW) were used in a generalized randomized block design. Heifers and steers were allocated to 1 of 18 concrete-surfaced pens (6 pens per treatment) to receive a common ad libitum diet (35% cottonseed hulls, 34% dry-rolled corn, and 20% corn gluten pellets; 15.9% crude protein on a dry matter [DM] basis, 1.58 Mcal/kg DM of net energy [NE] of maintenance, and 0.98 Mcal/kg DM of NE of gain) and 1 of the 3 treatments consisting of feeding 1 (PAP1), 3 (PAP3), or 0 g (CON) of PAP per day for 56 d. Feed intake was recorded daily and BW was obtained on days −1, 0, 14, 28, 42, 55, and 56 to assess average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F). Plasma concentrations of glucose and haptoglobin were measured on days 0, 14, 28, 42, and 56. In Exp. 2, 25 Angus crossbreed steers (390 ± 24 kg BW) were used in a completely randomized design to receive the same diet and treatments from Exp. 1 (CON: n = 8; PAP1: n = 9; and PAP3: n = 8). Following a 14-d adaptation to diets, feed and fecal samples were collected to determine apparent total tract nutrient digestibility. In Exp. 1, overall BW, DMI, ADG, G:F, and plasmatic measurements did not differ among treatments over the 56-d period (P ≥ 0.16). However, from days 0 to 14, a quadratic effect was observed for ADG, in which cattle receiving PAP1 had greater (P = 0.04) ADG compared with CON. In Exp. 2, no difference in DMI was observed (P = 0.88), yet DM, organic matter, neutral and acid detergent fiber, and starch digestibility were least (P ≤ 0.05) for PAP3, whereas digestibility of neutral detergent fiber was greatest (P < 0.01) for PAP1. In summary, feeding 1 g/d of a PAP against S. bovis, F. necrophorum, and LPS improved growth performance in the first 14 d and increased fiber digestibility of beef cattle consuming a backgrounding diet. Further research is needed to understand the impaired responses on nutrient digestibility when greater doses are provided.

The macroscopic and microscopic description of ruminal lesions in feedlot bovine

Abstract Administration of diets rich in highly fermentable carbohydrates and low fiber content can cause an imbalance between the microorganisms in the rumen with consequent ruminal acidosis. This problem can cause lesions in the rumen wall, often progressing to rumenitis. The purpose of the present was to characterize macroscopic and microscopic ruminal lesions observed in confined feedlot cattle with claw lesions or liver abscess. A total of 1060 bovines were evaluated via postmortem examination. Claw lesions were identified in 88, liver abscess in 10, and macroscopic rumen lesions in 230 bovines; furthermore, 178 rumens were characterized with hyperkeratosis, 41 with hyperemia, 9 with ulcer, and 2 with neoplasia. The 98 bovines with claw lesions and liver abscess were selected for histopathological examination. Of these, macroscopic lesions were noted in 23 and microscopic lesions in 23 animals. Of the 23 animals that presented macroscopic lesions, 10 showed the same changes observed under microscopy. Seven cases of hyperkeratosis were diagnosed in the macro and microscopic evaluation. Of the 5 cases of hyperemia verified on macroscopy, 2 cases were identified via microscopy, and 1 case of ulcer identified through macroscopy and microscopy. The microscopic evaluation of the rumens allowed the identification of lesions in animals with claw lesions that did not present macroscopic rumen alterations.

Descrição macroscópica e microscópica das lesões ruminais em bovinos confinados

Resumo O uso de dietas ricas em carboidratos altamente fermentáveis e com baixos teores de fibras pode ocasionar desequilíbrio entre os microrganismos do rúmen com consequente acidose ruminal. Esse problema pode resultar em lesões na parede do rúmen, evoluindo com frequência para formação de ruminite. O presente estudo objetivou caracterizar lesões ruminais macroscópicas e microscópicas, observadas em bovinos confinados que apresentavam lesões podais ou abscesso hepático. Avaliou-se 1060 bovinos pelo exame post mortem. Foram encontradas lesões podais em 88 animais, abscesso hepático em 10 e lesões ruminais macroscópicas em 230 bovinos, sendo caracterizado 178 rumens com hiperqueratose, 41 com hiperemia, 9 com úlcera e 2 com neoplasia. Os 98 bovinos com lesões podais e abscesso hepático foram selecionados para realização de exame histopatológico. Desses, foram encontradas lesões macroscópicas em 23 e, microscópicas, em 23 animais. Dos 23 animais que apresentaram lesões macroscópicas, 10 tiveram as mesmas alterações verificadas na microscopia. Foram diagnosticados 7 casos de hiperqueratose na avaliação macro e microscópica. Dos 5 casos de hiperemia verificados na macroscopia, 2 casos foram identificados na microscopia e um caso de úlcera identificado na macroscopia também foi identificado na microscopia. A avaliação microscópica dos rumens permitiu identificar lesões em animais com lesões podais que não apresentam alterações macroscópicas ruminais.

Impacts of polyclonal antibody preparations from avian origin as a feed additive to beef cattle: immune responses during the step-up transition diets

This study investigated the effects of feeding an avian-derived polyclonal antibody preparation (PAP; CAMAS, Inc.) against Streptococcus bovis, Fusobacterium necrophorum, and lipopolysaccharides (LPS; 40%, 35%, and 25% of the preparation, respectively) on immune responses (haptoglobin [Hp], serum amyloid A [SAA], rectal temperature [RT], leukocyte counts, and expression of cell adhesion molecules cluster of differentiation [CD] CD11b, CD14, and CD62L) of beef steers during a 21-d step-up adaptation to a high-grain diet. Eight ruminally cannulated Angus crossbred beef steers (658 ± 79 kg of BW) were assigned in a cross-over design and transitioned from a diet containing bermudagrass hay (Cynodon dactylon (L.) Pers.) ad libitum plus 0.45 kg/d of molasses with 0 (CON) or 3 g of PAP to a high-grain diet. Transition consisted of three 7-d steps of increased inclusion of cracked corn (35%, 60%, and 82% of the diet dry matter for STEP1, STEP2, and STEP3, respectively). On each transition day and 7 d after STEP3 (STEP3-7d), RT was obtained every 3 h for a total of 24 h, whereas blood was collected on days 0, 1, and 3, relative to diet transition. There were no effects of PAP inclusion in any of the blood parameters (P > 0.11). However, a tendency for day effect (P = 0.10) was observed for concentrations of Hp, which were greater on days 3 and 7 vs. day 0 relative to the second diet transition (STEP2). Plasma concentrations of SAA were greater on days 1, 3, and 7 compared to day 0 during STEP1 (P = 0.01), while during STEP2 and STEP3, SAA concentrations increased (P < 0.01) from day 0 to 3. During STEP2, PAP steers tended to have lower (P = 0.08) RT than CON steers. Neutrophil and monocyte counts were the least during STEP3 (P < 0.01), whereas expression of CD11b and CD62L was the least through forage feeding (P < 0.01). Concentration of starch in the diet was correlated to all the variables tested (P ≤ 0.01), except for the percentage of B cells (P = 0.22). Yet only ruminal pH, RT, monocyte, and neutrophil counts presented strong correlation coefficients. In conclusion, the step-up transition from forage to high-grain diets triggered systemic inflammation in beef steers as observed by increased plasma concentrations of Hp, SAA, and expression on adhesion molecules in leukocytes. However, feeding polyclonal antibody preparations against S. bovis, F. necrophorum, and LPS did not provide benefits to mitigate inflammation.

Effects of Megasphaera elsdenii administration on performance and carcass traits of finishing Bos indicus feedlot cattle

This study evaluated the effects of Megasphaera elsdenii administration at the beginning of the feedlot period on performance of Bos taurus indicus bulls. On d 0, 383 Nellore bulls (initial shrunk body weight 384 ± 29.2 kg; initial age = 24 ± 2 mo) were assigned to treatments in a randomized complete block design. Treatments consisted of 1) 14 d adaptation diet and transition to a finishing diet (CONT), 2) CONT plus oral administration of 20 mL of Lactipro-NXT (M. elsdenii) on d 0 of the study (MEG-14), 3) CONT diet, consisting of 6 d of adaptation diet plus oral administration of 20 mL of Lactipro-NXT on d 0 of the study (MEG-6), and 4) No adaptation diet and oral administration of 20 mL of Lactipro-NXT on d 0 of the study (MEG-0). Experimental period lasted 119 d. No treatment effects were observed for any of the performance parameters evaluated herein (P ≥ 0.15). Nonetheless, a treatment × wk interaction was observed for DM, NE_m, and NE_g intakes (P < 0.0001). For all these parameters, MEG-0 and MEG-6 had a reduced intake vs. MEG-14 and CONT in the first wk of the study (P ≤ 0.05). For the carcass traits, no effects were observed for HCW (P ≥ 0.24), whereas MEG-6 had a greater REA when compared with MEG-0 and MEG-14 (quadratic effect; P = 0.04) and MEG-administered bulls tended to have a greater BFT vs. CONT (P = 0.08). In summary, M. elsdenii administration at the beginning of the feedlot period did not improve performance, whereas reducing the length of the adaptation period for 6 d improved REA of finishing Bos taurus indicus bulls.

Ruminal Lipid A Analysis by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Lipopolysaccharides (LPS) are cell wall components from Gram-negative bacteria and are composed of three covalently linked regions: the O-antigen, the core oligosaccharide, and the lipid A moiety, which carries most of their endotoxic activity. The objective of this study was to isolate and compare the lipid A structures from ruminal LPS derived from total mixed ration (TMR)- and pasture-fed cows, by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Ruminal bacteria were collected from two rumen-cannulated Holstein cows; one fed a TMR (60:40, forage–concentrate) and the other pasture fed. The representativeness of each sample was validated by comparing the rumen microbiome from the cows in our study to the core rumen microbiome from the previous literature. Lipopolysaccharides from each respective sample were extracted with a phenol–water extraction procedure and purified via ultracentrifugation. To isolate lipid A from the core and O-antigen, pure ruminal LPS samples were hydrolyzed with acetic acid. Lipid A derived from the TMR-fed cow potentially exhibited a tetra-acylated structure, whereas lipid A derived from the pasture-fed cow potentially exhibited a penta-acylated lipid A structure. Both samples were quantified using limulus amebocyte lysate (LAL) assay and exhibited low endotoxic activity, consistent with the MALDI-TOF MS observations. Results indicate that the lipid A acylation pattern differs between diets, and that ruminal bacteria express solely under-acylated lipid A structures contrary to hexa-acylated lipid A, typically expressed by bacteria such as E. coli.

Effects of grain adaptation programs and antimicrobial feed additives on performance and nutrient digestibility of Bos indicus cattle fed whole shelled corn

Two experiments were conducted to evaluate the effects of feed additives [monensin (MON); 30 mg/kg of dry matter (DM), and virginiamycin (VM); 25 mg/kg DM] and grain adaptation programs [adding roughage (ROU; sugarcane bagasse) or not (NO-ROU) during the 20-d adaptation period] on performance, carcass characteristics, and nutrient digestibility of Bos indicus cattle fed finishing diets containing 85% whole shelled corn and 15% of a pelleted protein-mineral-vitamin supplement. In Exp.1, 105 Nellore bulls [initial body weight (BW) = 368 ± 25 kg] were used in a complete randomized block design with a 2 × 2 factorial arrangement of treatments, consisting of two feed additives (MON and VM) associated with two adaptation programs (ROU or NO-ROU during the 20-d adaptation period). Effects of feed additives × adaptation programs were not detected (P ≥ 0.13). Feed additives did not affect dry matter intake (DMI), average daily gain (ADG), and feed efficiency (G:F) during the 20-d adaptation period (P ≥ 0.35). During the total feeding period (105 d), feeding MON decreased DMI (P ≤ 0.03) compared to VM. Adding sugarcane bagasse to finishing diets during the 20-d adaptation period (ROU) increased ADG (P = 0.05) and G:F (P = 0.03), and tended to increase BW (P = 0.09) compared to NO-ROU. In Exp. 2, 10 ruminally cannulated Nellore steers (BW = 268 ± 38 kg) were used in a completely randomized design to evaluate the effects of the two feed additives used in the Exp. 1 (MON and VM; 5 steers/treatment) on DMI, total apparent digestibility of nutrients, and ruminal fermentation characteristics. No differences in DMI, total tract apparent digestibility of nutrients, and ruminal fermentation characteristics were observed between MON and VM (P ≥ 0.32). An effect of sampling day (P < 0.001) was observed for ruminal pH, which was greater on day 0 compared to day 7, 14, and 21 of the experimental period (P ≤ 0.05). In summary, supplementing monensin and virginiamycin for finishing Nellore bulls fed whole shelled corn diets, resulted in similar growth performance and carcass characteristics. Including sugarcane bagasse to adapt finishing bulls to no-roughage diets containing whole shelled corn is an alternative to increase growth performance.

Impact of Feeding Syngenta Enogen® Feed Corn Compared to Control Corn in Different Diet Scenarios to Finishing Beef Cattle

Simple Summary

A pooled statistical analysis of seven experiments and 200 pen observations was performed to determine the impact of feeding Enogen^® corn compared to conventional corn grain in beef cattle finishing diets. When the corn was compared as dry-rolled corn in diets with lower inclusion rates of distiller grains plus solubles (less than 20% of the diet), feeding Enogen^® corn improved the efficiency of beef production. That response was a 4.8% improvement due to feeding Enogen^® in a corn-based diet without distiller grains but was 1.8% in diets with 18 to 20% distiller grains. Feeding Enogen^® corn improved the efficiency by 4.5% in diets with another common byproduct, Sweet Bran^®. Cattle performance was similar for Enogen^® and conventional hybrids when processed and fed as high-moisture corn. Feeding Enogen^® corn improves the gain efficiency of finishing cattle compared with conventional corn when fed as dry-rolled corn in diets with less than 20% distillers or diets that include Sweet Bran^® feeds.

Abstract

The objective of this pooled statistical analysis was to evaluate Syngenta Enogen^® Feed Corn (EFC) versus conventional corn (CON) when fed as either dry-rolled corn (DRC) or high-moisture corn (HMC) for effects on finishing beef cattle performance and carcass characteristics. Corns were evaluated in diets with byproduct inclusion rates of 0, 15, 18, 20, and 30% distiller grains or 25 and 35% Sweet Bran^® (a commercial corn gluten feed product). Seven trials (n = 1856) consisting of 200 pen means comparing 26 diet treatments were analyzed using regression in a pooled analysis. When EFC was processed as DRC, the gain efficiency (G:F) improved compared with CON, but the response to feeding EFC decreased from a 4.8% improvement to no improvement compared to CON as distiller grains increased from 0 to 30%, but was significantly improved due to feeding EFC in diets with 0 to 18% distiller grains. Feeding cattle EFC as DRC increased the average daily gain (ADG) and G:F by 4.5% compared with CON corn in diets containing Sweet Bran^®. No improvements in animal performance were observed when cattle were fed EFC compared to CON when processed as HMC in any situation. Feeding Enogen^® corn improved the gain efficiency of finishing cattle compared with conventional corn when processed as dry-rolled corn and fed in diets with less than 20% distillers or diets that include Sweet Bran^®.

Technical Note: The comparison of pH and redox potential in different locations in the reticulo-rumen of growing beef steers supplemented with different levels of quebracho extract

Rumen acidosis is a common metabolic disorder occurring when organic acid production exceeds clearance capacity, reducing ruminal pH. The occurrence of acidosis has been directly correlated to the ratio of concentrate to forage in the diet. However, rates of substrate fermentation and acid absorption vary at different locations in the reticulo-rumen. The objective of this study was to determine the pH and redox potential (Eh) in different locations of the reticulo-rumen using 16 ruminally cannulated steers (309 ± 43 kg) receiving different supplementation levels of quebracho extract (QT; Schinopsis balansae) within a grower type diet (CP: 13.4%; total digestible nutrients [TDN]: 70.4%; and ME: 2.55 Mcal/kg, dry matter [DM] basis). Animals were randomly assigned to one of four dietary treatments: QT at 0%, 1%, 2%, and 3% of DM (QT0, QT1, QT2, and QT3, respectively), containing about 0%, 0.7%, 1.4%, and 2.1% of condensed tannins (CT), DM basis, respectively. Animals were adapted to the basal diet for 12 d before being introduced to predetermined treatments for 4 weeks (wk), with diets provided twice daily to allow ad libitum intake. Weekly measurements of ruminal fluid pH and Eh were taken 4 h post-feeding using a portable pH meter with two probes (pH and redox) in four locations of the reticulo-rumen (reticulum, cranial sac, dorsal sac, and ventral sac). Data were analyzed using a random coefficients model with the pen as a random effect and wk as repeated measures, with DM intake included as a covariate. There was no interaction among treatments, location, and wk (P ≥ 0.882) on reticulo-ruminal pH. Overall, ruminal pH was lower for QT0 and QT1 compared to QT3 (P < 0.001). The pH in the reticulum was greater than those of the ventral and dorsal sacs (6.05 vs. 5.94, 5.89, respectively; P ≤ 0.001) but similar to cranial sac (6.00). Reticular pH was positively correlated with the ruminal locations (≥0.78; P < 0.001). The linear equation to estimate ruminal mean pH using reticulum pH had an intercept and slope different from zero (P ≤ 0.04), but CT (% DM) was not different from zero (P = 0.15), root mean square error of 0.15, and R2 of 0.778: 0.723 (±0.36) + 0.857 (±0.059) × reticulum pH + 0.033 (±0.023) × CT. The Eh was lower for QT0 in week 1 than all other treatments (P < 0.001). We concluded that reticulo-ruminal pH differs among locations in the rumen regardless of QT supplementation level and days on feed, with reticular pH being the highest.

Effects of Ionophores on Ruminal Function of Beef Cattle

Ionophores have been widely used in the beef and dairy industry for decades to improve feed efficiency and performance by altering ruminal fermentation dynamics, increasing the level of propionate. Ionophores can also reduce ruminal proteolysis and ammonia synthesis, thus increasing the influx of protein into the small intestine in cattle, leading to improvements in performance and efficiency responses. Ionophores indirectly impact ruminal methanogenesis by decreasing the substrate used to produce methane. Despite the consistent benefits of using ionophores in cattle nutrition, their utilization is under public scrutiny due to concerns related to microbial adaptation. However, there is inconsistent evidence supporting these concerns, whereas ionophores are still an important dietary tool to enhance productivity and profitability in beef production systems.

Black oil sunflower seed ingestion associated with renal azotemia, gastroesophageal ulceration, and a high mortality rate in four alpacas and two llamas

CASE DESCRIPTION

4 alpacas and 2 llamas (11 months to 11 years old) from 2 properties were examined for lethargy (6/6), salivation and regurgitation (4/6), and recumbency (3/6). Signs developed approximately 48 to 72 hours after accidental access to black oil sunflower seeds.

CLINICAL FINDINGS

3 alpacas died suddenly prior to treatment and were necropsied. One llama survived, and 1 alpaca and 1 llama died after days of medical treatment. All 3 treated animals had systemic inflammatory signs including tachycardia, fever, and hematologic changes. Biochemical anomalies included azotemia, hyperglycemia, hyponatremia, hypochloremia, and hypoalbuminemia. Necropsy identified numerous sunflower seeds in the gastrointestinal tract of all 5 animals that died, with pulmonary congestion (5/5 animals), mild centrilobular vacuolar hepatic degeneration (4/5), and erosions of the esophagus (3/5) and first (3/5) and third (1/5) compartments of the forestomach. Renal tubular necrosis was found in the 2 animals that died on day 4 of treatment.

TREATMENT AND OUTCOME

One llama responded successfully to intensive medical management including supplemented IV fluid therapy, oral and partial parenteral nutrition, and administration of antimicrobials, furosemide, and insulin and was clinically normal with plasma biochemical analysis values within reference range 12 weeks later. Vitamin D, oxalates, heavy metals, and mycotoxins were excluded as the cause of clinical signs on the basis of screening of uneaten seeds and tissue samples and gastric content from the treated llama that died.

CLINICAL RELEVANCE

Inadvertent large volume black oil sunflower seed ingestion resulted in a high mortality rate in camelids. A specific toxic principle was not identified. Feeding this product to camelids is not recommended to avoid the risk of accidental overingestion and subsequent disease.

Specific inhibition of Streptococcus bovis by endolysin LyJH307 supplementation shifts the rumen microbiota and metabolic pathways related to carbohydrate metabolism

Background

Endolysins, the bacteriophage-originated peptidoglycan hydrolases, are a promising replacement for antibiotics due to immediate lytic activity and no antibiotic resistance. The objectives of this study were to investigate the lytic activity of endolysin LyJH307 against S. bovis and to explore changes in rumen fermentation and microbiota in an in vitro system. Two treatments were used: 1) control, corn grain without LyJH307; and 2) LyJH307, corn grain with LyJH307 (4 U/mL). An in vitro fermentation experiment was performed using mixture of rumen fluid collected from two cannulated Holstein steers (450 ± 30 kg) and artificial saliva buffer mixed as 1:3 ratio for 12 h incubation time. In vitro dry matter digestibility, pH, volatile fatty acids, and lactate concentration were estimated at 12 h, and the gas production was measured at 6, 9, and 12 h. The rumen bacterial community was analyzed using 16S rRNA amplicon sequencing.

Results

LyJH307 supplementation at 6 h incubation markedly decreased the absolute abundance of S. bovis (approximately 70% compared to control, P = 0.0289) and increased ruminal pH (P = 0.0335) at the 12 h incubation. The acetate proportion (P = 0.0362) was significantly increased after LyJH307 addition, whereas propionate (P = 0.0379) was decreased. LyJH307 supplementation increased D-lactate (P = 0.0340) without any change in L-lactate concentration (P > 0.10). There were no significant differences in Shannon’s index, Simpson’s index, Chao1 estimates, and evenness (P > 0.10). Based on Bray-Curtis dissimilarity matrices, the LyJH307 affected the overall shift in microbiota (P = 0.097). LyJH307 supplementation induced an increase of 11 genera containing Lachnoclostridium, WCHB1–41, unclassified genus Selenomonadaceae, Paraprevotella, vadinBE97, Ruminococcus gauvreauii group, Lactobacillus, Anaerorhabdus furcosa group, Victivallaceae, Desulfuromonadaceae, and Sediminispirochaeta. The predicted functional features represented by the Kyoto Encyclopedia of Genes and Genomes pathways were changed by LyJH307 toward a decrease of carbohydrate metabolism.

Conclusions

LyJH307 caused a reduction of S. bovis and an increase of pH with shifts in minor microbiota and its metabolic pathways related to carbohydrate metabolism. This study provides the first insight into the availability of endolysin as a specific modulator for rumen and shows the possibility of endolysin degradation by rumen microbiota.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00614-x.

Effects of wood kraft pulp feeding on feed digestibility and rumen fermentation of Japanese Black steer in the middle fattening stage

We investigated the effects of wood kraft pulp (KP) feeding on feed digestibility and rumen fermentation of Japanese Black (JB) steer in the middle fattening stage. The feeding experiment was carried out a replicated 3 × 3 Latin square design using six JB steers (16.2 ± 0.8 months of age). Steers were fed rice straw and three concentrated feeds: commercial formula feed (control), formula feed containing 7.5% KP on a dry matter (DM) basis (7.5% KP), and formula feed containing 15% KP on a DM basis (15% KP). Feed digestibility and rumen fermentation parameters were recorded for 3 days during the measurement period, after an adaptation phase of 11 days. There was no significant difference in DM intake per day among diets. A slightly higher digestibility of neutral detergent fiber was observed in steers fed 15% KP, compared with those fed other diets (P = 0.059). The butyric acid ratio in rumen fluid was higher in steers fed KP diets than in steers fed control (P = 0.083). The average ruminal pH was unaffected by KP diets. This study suggests that replacing 15% of concentrated feed with KP has little effect on feed digestibility and rumen fermentation in JB fattening steer.

Effect of biochanin A on the rumen microbial community of Holstein steers consuming a high fiber diet and subjected to a subacute acidosis challenge

Subacute rumen acidosis (SARA) occurs when highly fermentable carbohydrates are introduced into the diet, decreasing pH and disturbing the microbial ecology of the rumen. Rumen amylolytic bacteria rapidly catabolize starch, fermentation acids accumulate in the rumen and reduce environmental pH. Historically, antibiotics (e.g., monensin, MON) have been used in the prevention and treatment of SARA. Biochanin A (BCA), an isoflavone produced by red clover (Trifolium pratense), mitigates changes associated with starch fermentation ex vivo. The objective of the study was to determine the effect of BCA on amylolytic bacteria and rumen pH during a SARA challenge. Twelve rumen fistulated steers were assigned to 1 of 4 treatments: HF CON (high fiber control), SARA CON, MON (200 mg d^-1), or BCA (6 g d^-1). The basal diet consisted of corn silage and dried distiller’s grains ad libitum. The study consisted of a 2-wk adaptation, a 1-wk HF period, and an 8-d SARA challenge (d 1–4: 40% corn; d 5–8: 70% cracked corn). Samples for pH and enumeration were taken on the last day of each period (4 h). Amylolytic, cellulolytic, and amino acid/peptide-fermenting bacteria (APB) were enumerated. Enumeration data were normalized by log transformation and data were analyzed by repeated measures ANOVA using the MIXED procedure of SAS. The SARA challenge increased total amylolytics and APB, but decreased pH, cellulolytics, and in situ DMD of hay (P < 0.05). BCA treatment counteracted the pH, microbiological, and fermentative changes associated with SARA challenge (P < 0.05). Similar results were also observed with MON (P < 0.05). These results indicate that BCA may be an effective alternative to antibiotics for mitigating SARA in cattle production systems.

A method for assessing sustainability, with beef production as an example

A comprehensive approach to decisions about the use of land and other world resources, taking full account of biological and other scientific information, is crucial for good decisions to be made now and in future. The sustainability of systems for producing food and other products is sometimes assessed using too narrow a range of component factors. A production system might be unsustainable because of adverse effects on a wide range of aspects of human welfare, animal welfare, or the environment. All factors should be included in sustainability evaluation, otherwise products or actions might be avoided without adequate consideration of key factors or of the diversity of production systems. A scoring method that is based on scientific information and potentially of general relevance is presented here, using beef production as a example with a review of each of its sustainability components. This includes an overall combined score and specific factors that make the system unacceptable for some consumers. The results show that, in this example, the sustainability of the best systems is very much better than that of the worst systems. By taking account of scores for a wide range of components of sustainability in comparing beef-production systems, better quality policies about beef use can be formulated than when statements referring only to one system are considered. The least sustainable beef-production systems are extensive grazing that causes land degradation and the use of feedlots or indoor housing with grain feeding. Semi-intensive silvopastoral systems are the most sustainable beef-production systems, and well-managed pasture-fed beef from areas where crop production is uneconomic is also sustainable. This simple, scientifically based scoring system could be modified to use positive as well as negative scores and is of value for policy makers, researchers, producers, organisations aiming to improve sustainability, and the general public.

Influence of three microbial feed additives of Megasphaera elsdenii, Saccharomyces cerevisiae and Lactobacillus sp. on ruminal methane and carbon dioxide production, and biofermentation kinetics

AIMS

This study was performed to investigate the effects of Megasphaera elsdenii (Me), Saccharomyces cerevisiae (SC) and lactic acid bacteria (FP-Lactobacillus fermentum plus Lactobacillus plantarum) alone or in combination on biogas production and ruminal biofermentation parameter in a heterofermenter system.

METHODS AND RESULTS

Eight treatments were evaluated; (i) control (without additive; CON); (ii) Me; (iii) SC; (iv) FP; (v) Me plus SC (MSC); (vi) Me plus FP (MFP); (vii) SC plus FP (SCFP) and (viii) Me plus SC plus FP (MSCFP). Doses of FP, Me and SC were 1·5 × 10⁸ (CFU per ml), 1·5 × 10⁸ (CFU per ml) and 1·4 × 10⁷ (CFU 0·002^-1  g), respectively. Biogas production in all time increased (P < 0·05) by MSCFP than CON additive. The proportional methane (CH₄ ) decreased (P < 0·05) in MSCFP and FP, while carbon dioxide (CO₂ ) was decreased (P < 0·05) by SC compared MSCFP and MSC. The proportional CO₂ decreased (P < 0·05) by MSCFP and FP additive. The mean concentration of NH₃ -N was not affected by treatments. Concentration of total volatile fatty acids and the percent of acetate and propionate was not affected by treatments. The highest (P < 0·05) percent of butyrate and valerate were observed in MSCFP additive. The experiment showed that microbial additives of FP, SCFP and MSCFP reduced proportional CH₄ and CO₂ .

CONCLUSIONS

Microbial additives of MFP and MSCFP had a sustainable positive efficiency on pH and volatile fatty acids and mitigate CH₄ and CO₂ .

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of microbial additives control on the ruminal pH (MFP) and improve VFA such as butyrate (MSC, MSCFP) and valerate (MSCFP) and reduce the greenhouse gases production showed a reduced risk of ruminal acidosis.

Ruminal Lipopolysaccharides Analysis: Uncharted Waters with Promising Signs

Simple Summary

Lipopolysaccharide (LPS) is a component of the outer membranes of Gram-negative bacterial cell wall made of three covalently linked regions: the O-antigen, the core oligosaccharide, and the endotoxin lipid A moiety, which carries the endotoxic activity of LPS. Among Gram-negative bacteria there is significant structural diversity in the lipid A region. Specifically, the number of lipid A acyl chains directly correlates with the ability to induce cytokine production whereas the hexa-acylated forms usually are the most immunostimulant ones, contrary to penta- or tetra- acylated forms that result in weak inflammatory host responses. Ruminal bacteria are predominantly Gram-negative, and their respective LPS presence has been suggested to be associated with ruminal acidosis, a metabolic disorder of cattle with negative effects on health and production. In the rumen, the most predominant phylum is Bacteroidetes which exhibit weak host immunological response compared to widely used Escherichia coli LPS. This review aims to present accumulated knowledge regarding ruminal LPS, pointing out the differences in ruminal LPS compared to widely known LPS, and introduce hypotheses that could contribute to further understanding and planning strategies to tackle ruminal acidosis.

Abstract

The objective of this review is to present the need for the development of a comprehensive ruminal lipopolysaccharide (LPS) extraction, purification and analysis protocol and state hypotheses that could contribute to planning novel strategies against ruminal acidosis. Lipopolysaccharide is an immunostimulatory molecule of Gram-negative bacterial outer membranes and has been reported to contribute to ruminal acidosis in cattle. Bacterial death and lysis are normal processes, and thus LPS is normally present in ruminal fluid. However, ruminal LPS concentration is much greater during subacute ruminal acidosis (SARA). Contrary to the widely known LPSs, ruminal LPS seems to be composed of a variety of LPS chemotypes that may interact with each other resulting in an LPS “mixture”. Hypotheses regarding the influence of each specific ruminal bacterial specie to innate immunity during SARA, and the representativeness of the exclusive use of the Escherichia coli LPS to rumen epithelial tissue challenges, could expand our knowledge regarding SARA. In addition, possible correlation between the monomeric Toll-like Receptor 4 (TRL4) and the antagonistic penta-acylated lipid A of LPS could contribute to novel strategies to tackle this nutrition disorder.

Subacute Ruminal Acidosis in Zebu Cattle: Clinical and Behavioral Aspects

Simple Summary

Cattle that are fed high levels of concentrates may develop short-term rumen acidity that may occur frequently leading to necrosis of the rumen wall and reduced nutrient absorption, thereby decreasing animal productivity. This condition is known as subacute acidosis. Here, we evaluated an experimental model to induce such a condition in Nelore cattle, a Zebu breed widely used in Brazil, and assessed several clinical and feeding behavioral patterns of affected animals to better understand the disease pathogenesis and clinical outcomes. Subacute acidosis led to a reduction in food consumption and rumination time, and an increase was observed in the time spent in decubitus. Additionally, subacute acidosis caused different degrees of depression that was more pronounced with higher ruminal lactic acid concentrations.

Abstract

We evaluated the clinical aspects and feeding behavior of cattle with subacute ruminal acidosis (SARA) caused by short-chain fatty acids (SCFAs). Ten healthy Nelore heifers were subjected to an adjusted SARA induction protocol using citrus pulp (CP). Clinical examinations were performed at baseline and at 3, 6, 9, 12, 15, 18, and 24 h intervals after induction, with ruminal fluid, blood, and feces sampling. The animals’ feeding behavior was evaluated on, before, and for 3 days after SARA by observing the animals every 5 min for 24 h. The dry matter intake (DMI) was recorded daily. The ruminal pH during SARA was always lower than baseline, with an acidotic duration of 547 ± 215 min, a minimum pH of 5.38 ± 0.16, and an average pH of 5.62 ± 0.1. SARA was mainly caused by SCFAs (maximum 118.4 ± 9.3 mmol/L), with the production of l-lactic acids (7.17 mmol/L) and d-lactic acids (0.56 mmol/L) 6 h after the experiment began. The DMI was reduced by 66% and 48% on days 1 and 2, respectively, and returned to normal levels on day 3. SARA caused a reduction in feed intake and rumination time, as well as an increase in the time spent in decubitus on days 1 and 2. These results were influenced by the ruminal pH, ruminal movement, and osmolarity. Furthermore, SARA caused different degrees of depression, which became more pronounced with higher ruminal lactic acid concentrations.

D-Lactate Increases Cytokine Production in Bovine Fibroblast-Like Synoviocytes via MCT1 Uptake and the MAPK, PI3K/Akt, and NFκB Pathways

Acute ruminal acidosis (ARA) is caused by the excessive intake of highly fermentable carbohydrates, followed by the massive production of D-lactate and the appearance of neutrophilic aseptic polysynovitis. Bovines with ARA develop different lesions, such as ruminitis, polioencephalomalacia (calves), liver abscess and lameness. Lameness in cattle with ARA is closely associated with the presence of laminitis and polysynovitis. However, despite decades of research in bovine lameness as consequence of ruminal acidosis, the aetiology and pathogenesis remain unclear. Fibroblast-like synoviocytes (FLSs) are components of synovial tissue, and under pathological conditions, FLSs increase cytokine production, aggravating inflammatory responses. We hypothesized that D-lactate could induce cytokine production in bovine FLSs. Analysis by qRT-PCR and ELISA revealed that D-lactate, but not L-lactate, increased the expression of IL-6 and IL-8 in a monocarboxylate transporter-1-dependent manner. In addition, we observed that the inhibition of the p38, ERK1/2, PI3K/Akt, and NF-κB pathways reduced the production of IL-8 and IL-6. In conclusion, our results suggest that D-lactate induces an inflammatory response; this study contributes to the literature by revealing a potential key role of D-lactate in the polysynovitis of cattle with ARA.

Targeting the Hindgut to Improve Health and Performance in Cattle

An adequate gastrointestinal barrier function is essential to preserve animal health and well-being. Suboptimal gut health results in the translocation of contents from the gastrointestinal lumen across the epithelium, inducing local and systemic inflammatory responses. Inflammation is characterized by high energetic and nutrient requirements, which diverts resources away from production. Further, barrier function defects and inflammation have been both associated with several metabolic diseases in dairy cattle and liver abscesses in feedlots. The gastrointestinal tract is sensitive to several factors intrinsic to the productive cycles of dairy and beef cattle. Among them, high grain diets, commonly fed to support lactation and growth, are potentially detrimental for rumen health due to their increased fermentability, representing the main risk factor for the development of acidosis. Furthermore, the increase in dietary starch associated with such rations frequently results in an increase in the bypass fraction reaching distal sections of the intestine. The effects of high grain diets in the hindgut are comparable to those in the rumen and, thus, hindgut acidosis likely plays a role in grain overload syndrome. However, the relative contribution of the hindgut to this syndrome remains unknown. Nutritional strategies designed to support hindgut health might represent an opportunity to sustain health and performance in bovines.

Optimum roughage proportion in barley-based feedlot cattle diets: growth performance, feeding behavior, and carcass traits

High grain diets are fed to finishing beef cattle to maximize animal performance in a cost-effective manner. However, a small amount of roughage is incorporated in finishing diets to help prevent ruminal acidosis, although few studies have examined optimum roughage inclusion level in barley-based diets. The objective of the study was to evaluate the effects of roughage proportion in barley-based finishing diets on growth performance, feeding behavior, and carcass traits of feedlot cattle. Crossbred beef steers (n = 160; mean body weight ± SD, 349.7 ± 21.4 kg) were allocated to 20 pens that were assigned randomly to four dietary treatments (five pens of eight steers per treatment). The treatment diets contained barley silage at 0%, 4%, 8%, and 12% of dietary dry matter (DM). The remainder of the diets (DM basis) consisted of 80%, 76%, 72%, and 68% barley grain, respectively, 15% corn dried distiller's grains, 5% mineral and vitamin supplement, and 32 mg monensin/kg diet DM. The diets were fed as total mixed rations for ad libitum intake (minimum of 5% refusal) once per day. Cattle were weighed on 2 consecutive days at the start and end of the experiment and on 1 d every 3 wk throughout the experiment (124 d). Two pens for each treatment group were equipped with an electronic feeding system (GrowSafe Systems Ltd., Calgary, Alberta) to monitor feed intake and feeding behavior of individual cattle. The data for dry matter intake (DMI), average daily gain (ADG), gain:feed (G:F) ratio, and carcass traits were analyzed as a completely randomized design with fixed effect of barley silage proportion and pen replicate as experimental unit. Feeding behavior data were analyzed similarly, but with animal as experimental unit. Averaged over the study, DMI increased linearly (11.1, 11.3, 11.7, 11.8 kg/d; P = 0.001) as barley silage proportion increased from 0%, 4%, 8%, and 12% of DM, but ADG was not affected (carcass-adjusted,1.90, 1.85, 1.87, 1.89 kg/d; P ≥ 0.30). Consequently, G:F ratio decreased linearly (carcass-adjusted, 168.9, 163.8, 158.5, 160.6 g/kg DMI; P = 0.023). When averaged over the study, proportion of barley silage in the diet had no linear or quadratic effects (P > 0.10) on meal frequency, duration of meals, intermeal duration, or meal size, but eating rate decreased linearly with increasing silage proportion (P = 0.008). There was no diet effect on liver abscesses (P ≥ 0.92), and effects on carcass characteristics were minor or nonexistent. We conclude that increasing the proportion of barley silage in a feedlot finishing diet at the expense of barley grain to minimize the incidence of ruminal acidosis may decrease feed conversion efficiency.

Optimum roughage proportion in barley-based feedlot cattle diets: total tract nutrient digestibility, rumination, ruminal acidosis, short-chain fatty absorption, and gastrointestinal tract barrier function

Cattle need physically effective fiber to promote rumination and maintain rumen health, but economics favor the use of low-roughage feedlot diets. The study investigated the optimum barley silage proportion in barley-based finishing diets. Apparent total-tract digestibility (4-d total fecal collection), chewing behavior (6-d video recording), ruminal pH (6-d indwelling pH recording), and fermentation (1 day, sampling 0, 3, 6, 12, and 18 h postfeeding), short-chain fatty acid (SCFA) absorption (washed reticulo-rumen technique), gastrointestinal tract barrier function (marker infusion), and blood variables (catheters) were measured. Eight ruminally fistulated crossbred beef heifers (653 ± 44.2 kg; mean starting body weight [BW] ± SD) were used in a replicated 4 × 4 Latin square design with 28-d periods. Dietary treatments were 0%, 4%, 8%, and 12% of dietary dry matter (DM) as barley silage, with diets containing 80%, 76%, 72%, and 68% barley grain, respectively. Increasing silage proportion decreased dietary starch content from 49.0% to 43.1% DM, while neutral detergent content increased from 22.7% to 25.1% DM. Silage proportion had no effect on DM intake, but apparent DM digestibility decreased quadratically (86.0%, 82.1%, 81.1%, 79.5% for the four diets, respectively; P < 0.001). Although, silage proportion had no effect on eating activity, rumination time increased quadratically (246, 289, 302, 316 min/d; P = 0.04). Increased silage proportion increased minimum (5.07, 5.27, 5.29, 5.41; quadratic, P = 0.011) and mean (5.61, 5.87, 5.93, 5.95; quadratic, P = 0.007) ruminal pH, and there was a quadratic (P ≤ 0.047) decrease in duration and area under the pH acidosis threshold curves of 5.8, 5.5, and 5.2. Although increasing silage proportion decreased ruminal acidosis, it was not completely eliminated even with a diet containing 12% silage DM. SCFA concentration in ruminal fluid was not affected by diet, but silage proportion quadratically (P ≤ 0.088) increased ruminal acetate:propionate. There was no effect of diet on absolute or fractional rates of absorption of acetate, propionate, butyrate or total SCFA, and no effect on gastrointestinal barrier function or blood measurements. In conclusion, responses to roughage level were mostly quadratic with greatest improvements in acidosis variables between 0% and 4% barley silage, with incremental improvements with further increases in silage levels. The study showed a trade-off between maximizing digestibility and energy intake to promote animal performance and minimizing the risk of acidosis.