Cattle Fed Research Articles

Welfare and performance benefits of shade provision during summer for feedlot cattle in a temperate climatic zone.

There is increasing interest from cattle lot-feeders in the use of shade to mitigate the effects of a potential heat stress event, though it is unclear whether the reported benefits of shade in previous studies conducted in more high-risk heat stress zones are pertinent in cooler temperate zones. The objectives of this study were to measure the welfare and performance benefits of shade provision for lot-fed cattle at a commercial feedlot located in a mild heat-stress risk zone in Western Australia. Six blocks of black Angus (Bos taurus) steers were inducted into the feedlot over six time-windows across a southern hemisphere summer, with 80 cattle per block housed in a partially shaded pen (providing 3.125 m2 of shade per animal) and 80 in an unshaded pen. Parameters assessed in 960 cattle over the first 70 days in the feedlot included weight gain, feed intake, and physiological and behavioral indices of overall health and welfare. Over the months of October through to May in which the experiment was conducted, shaded cattle demonstrated a modest 0.13kg overall increase in average daily gain across the 70-day feedlot period (P = 0.13). There was no difference in dry matter intake between any block or treatment. The physiological and behavioral markers of health and welfare revealed that, even during to hottest times of the experiment, the cattle were quite able to thermoregulate, via increased panting and seeking shade (if available), to maintain physiological homeostasis. In addition, we measured the effect of heat stress and shade provision on the affective state of the cattle. Qualitative behavioral assessment was used to indicate that the cattle in the 'no stress' temperature humidity index (THI) category and the shaded cattle in the 'moderate stress' THI category displayed the most positive demeanor (P < 0.05), being described as more 'settled and sociable', while the unshaded cattle in the 'moderate stress' THI category and all cattle in the 'severe stress' THI category were described as more 'agitated/anxious' (P < 0.05). Overall, the findings from the present study suggest that there are definite welfare and modest performance benefits associated with providing cattle with shade in summer in a feedlot situated in a temperate climatic zone.

Thermal Stress as a Critical Factor in the Viability and Duration of Spittlebug Eggs

The spittlebug Mahanarva spectabilis (Distant, 1909) (Hemiptera: Cercopidae) is an important pest that causes significant losses in the production of forage crops for cattle feed. Information on the thermal requirements of this insect during the egg stage is crucial in assessing the interaction between insects and forage. The aim of this research was to evaluate the effects of constant and oscillating (diurnal/nocturnal) temperatures on the viability of M. spectabilis eggs and the duration of the egg stage. Temperatures of 20 °C to 30 °C were ideal for the development of this insect pest, resulting in greater viability and faster development of the embryos. In addition, it should be noted that a variation of up to 8 days is feasible for synchronizing the phenological stages of the forage plants and the eggs to be laid on these plants when subjected to 30 °C (16.6 days) or 20 °C (25.7 days) without significantly altering the viability of the eggs. Notably, a temperature oscillation of 25 °C during the day and 15 °C at night increased the viability of the eggs after exiting diapause. These results are essential for the rearing of M. spectabilis in the laboratory, allowing for the supply of eggs for experiments and contributing to advances in studies aimed at developing effective integrated management strategies for this pest.

Microwave Cooking of Some or All High Starch Ingredients of Cattle Feed Concentrate Improves Nutritional Value and In Vitro Bioavailability.

Microwaving has been used to qualitatively improve feed ingredients prior to including them in cattle feed. However, it is not known whether feed ingredients should be microwaved separately or in a mixture before being included in cattle feed concentrates. In the current study, the effects of the partial and full microwaving of high starch ingredients were investigated regarding their impact on the nutritional composition, physicochemical properties, and in vitro digestibility of feed concentrates. The cassava was microwave-irradiated before being mixed with other ingredients (MC, 35% of formulation). A microwave-cooked cassava-corn meal mixture (MCC, 45% of formulation) and a combination of all solid components (MSI, 96% of formulation) were also compared. A feed containing non-microwaved ingredients was formulated and served as the control (NM). Significantly altered proximate compositions and nutritive profiles were observed in all the microwaved components (p < 0.05). The observed modifications in pHs, water absorption capacities, thermal properties (differential scanning calorimetry), diffraction patterns (X-ray diffractometry), and microstructures (scanning electron microscopy) indicated enhanced enzymatic hydrolysis in vitro. A higher cellulase organic matter solubility and digestible organic matter were observed in the MCC and MSIs feeds relative to the control NM (p < 0.05). These findings indicate a combination of components could be added to feedstock before it is microwave processed to potentially include this pretreatment in the feed production process.

The Germination Performance After Dormancy Breaking of Leucaena diversifolia (Schltdl.) Benth. Seeds in a Thermal Gradient and Its Distribution Under Climate Change Scenarios.

Climate change models predict temperature increases, which may affect germination, an important stage in the recruitment of individuals in agroecosystems. Therefore, it is crucial to conduct research on how temperature will impact the germination of multipurpose native species. Leucaena diversifolia (Schltdl.) Benth. is native to America and is commonly cultivated around the world due to having a high protein content in seeds, and their trees are used in agrosilvopastoral systems because they fix nitrogen and provide shade and cattle feed. However, climate change affects the critical phases of its life cycle and influences its growth, reproduction, phenology, and distribution. To assess the germination performance of Leucaena diversifolia under different temperatures throughout thermal times, we estimated germination variables and determined cardinal temperatures and thermal time; we also analysed germination and potential distribution under two climate change scenarios. We found significant variations in seed germination (78-98%) and differences in cardinal temperatures (Tb = 5.17 and 7.6 °C, To = 29.42 and 29.54 °C, and Tc = 39.45 and 39.76 °C). On the other hand, the sub-optimal and supra-optimal temperature values showed little differences: 51.34 and 55.57 °Cd. The models used showed variations in germination time for the analysed scenarios and the potential distribution. We confirm that the populations and distribution of L. diversifolia will be altered due to climate changes, but the species retains the ability to germinate under warmer conditions.

Assessment of nutritionality and normative indicators of granulated vitamin-herbal four for agricultural animals, prepared in the conditions of the Vologda region

Feed analysis was carried out in a chemical laboratory using the equipment of the Center for Agricultural Research and Biotechnology at the Voluntary Research Center of the Russian Academy of Sciences. The testing procedure for most agricultural feeds is established by GOST 50817-95. To determine the crude protein content using the Kjeldahl method using a semi-automatic analyzer UDK 159 (VELP, Italy), GOST 13496.4-2019 was used, GOST 31675-2012 was used to determine the crude fiber content using an automatic analyzer FIBE-6, GOST 13496.15-2016 was used to determine crude fat content using the Soxhlet apparatus., GOST 32933-2014 is used to determine the crude ash content. An evaluation test of herbaceous unnaturally dried feed according to the quality class was carried out in the following sequence: when more characteristics were agreed upon for any one class, vitamin-grass meal (VHM) was assessed according to this class. When studying the energy nutritional value, the amount of dry matter in granulated vitamin-herbal flour was established within the range of 867.00–917.69 g, metabolic energy – 9.25–10.57 MJ/kg, digestible protein – 69.9–119.6 g/kg and feed units – 0.71–0.85 kg. Thus, checking the usefulness of the samples that were selected and sent to us showed that feed from alfalfa and clover helps to obtain high-quality nutritious feed that is easily absorbed by the body and corresponds to class II–III indicators. The quality of prepared flour from vetch-oat grass and a mixture of herbs leaves much to be desired. As a result of studying the quality of these artificially dried grass feeds, we can conclude that their nutritional value is not high enough, as a result of the low content of the main characteristics: such as metabolic energy (9.25–9.39 MJ/kg) and protein (11.69–12.83 %), which is necessary take into account when organizing proper feeding of cattle. The quality of feed is a fundamental condition on which productivity depends.

The Relationship between the Infrared Eye Temperature of Beef Cattle and Associated Biological Responses at High Environmental Temperatures.

Cattle in regions with high ambient temperatures are at risk of heat stress. Early detection is important to allow action to be taken to minimise the risks to cattle exposed to thermal stress. This study aimed to investigate the impact of heat stress on IRT-Eye temperature and its association with the behavioural and physiological responses of heat-stressed Angus steers (n = 24) on finisher and or substituted diets. Overall, 2 cohorts of 12 Angus steers were individually housed in a climate-controlled facility to examine responses to heat stress when fed on a standard finisher diet, based on a high percentage of cereal grains, and on a substituted diet in which 8% of the grains were replaced by an isoenergetic amount of lucerne hay. Exposing feedlot cattle to hot environmental conditions increased IRT-Eye temperature, which had a strong association with behaviour and physiology. There was no evidence of differences between the different dietary cohorts. The cattle with increased IRT-Eye temperature showed stress-related responses, including a downward-facing head, ears directed backwards, and other indicators of heat stress such as increased panting, standing, and increased rumen temperature. The strong association of IRT-Eye temperature with stress-related behaviours, as well as with rumen temperature and panting behaviour, highlights the potential for IRT-Eye to be utilised as a non-invasive tool to assess cattle responses in hot conditions.

Farmers’ Perceptions and Awareness of Cattle Feedlots as a Climate-Smart Approach to Enteric Methane Emissions

The perceptions of farmers regarding communal feedlots and their role in reducing enteric methane emissions have received limited attention in research. This study aims to examine farmers’ perceptions, assess awareness, and identify barriers to adopting feedlots as a climate-smart practice to enteric methane emissions in rural communities in the Eastern Cape Province, South Africa. 161 structured, paper-based questionnaires were distributed among smallholder cattle farmers around three feedlot locations. Most farmers had heard about feedlots (67.7%); however, only a few (19.9%) participated. The lack of knowledge about feedlot operations was the main factor influencing farmers’ participation in feedlots. Most farmers did not perceive feedlots as a climate-smart approach to reducing enteric methane output (53.8%), with few sure (9.6%) and others unsure (36.5%). When asked about the reasons for their perceptions of feedlots as a climate-smart approach to mitigating methane, many farmers were unsure of the reasons (86.5%), with the least believing it could be related to poor feed quality (1.9%). The availability of financial resources and level of education were the key factors influencing farmers’ willingness to adopt feedlots as a climate-smart practice. These findings emphasise the importance of targeted educational workshops and support systems to enhance farmers’ awareness and promote the adoption of cattle feedlots as a climate-smart approach. The findings can also inform policy and practice to address perceived feedlot drawbacks, such as feed provision and technical assistance, and improve their successful implementation. However, further research is needed to explore farmers’ perceptions of cattle feedlots as a climate-smart practice.

Programming and Setting Up the Object Detection Algorithm YOLO to Determine Feeding Activities of Beef Cattle: A Comparison between YOLOv8m and YOLOv10m.

This study highlights the importance of monitoring cattle feeding behavior using the YOLO algorithm for object detection. Videos of six Charolais bulls were recorded on a French farm, and three feeding behaviors (biting, chewing, visiting) were identified and labeled using Roboflow. YOLOv8 and YOLOv10 were compared for their performance in detecting these behaviors. YOLOv10 outperformed YOLOv8 with slightly higher precision, recall, mAP50, and mAP50-95 scores. Although both algorithms demonstrated similar overall accuracy (around 90%), YOLOv8 reached optimal training faster and exhibited less overfitting. Confusion matrices indicated similar patterns of prediction errors for both versions, but YOLOv10 showed better consistency. This study concludes that while both YOLOv8 and YOLOv10 are effective in detecting cattle feeding behaviors, YOLOv10 exhibited superior average performance, learning rate, and speed, making it more suitable for practical field applications.

Genome sequences of seven Mannheimia haemolytica isolates from feedlots in Oklahoma and California.

This report describes the genome sequences of seven Mannheimia haemolytica isolates recovered from feedlot cattle. These genome sequences will enhance our understanding of Mannheimia haemolytica evolution and antimicrobial resistance (AMR)-associated genes they carried over a two-decade span.

Aging increases lightness of grass-fed beef

Abstract Grass-fed beef is becoming increasingly popular and is expected to be a $14 billion industry by 2024. Even so, grass-fed beef is typically darker in appearance than that of conventional grain-fed beef. Aging has been shown to improve lean color (L*, a*) of dark-cutting beef however little work has focused on aging as it relates to improving lean color of grass-fed beef. Therefore, the aim of this study was to evaluate the effect of dry aging on grass-fed beef compared to varying length of grain-feeding hirty commercial Angus crossbred steers were randomly assigned to either pasture finishing (CON), short (SF), or long feeding (LF) programs. The SF and LF treatments ranged from 90 – 114 d (ave, 98 d) and 118 – 134 d (ave 125 d) on ad libitum high concentrate feeding, respectively. Cattle were randomly identified from each treatment group and harvested over a consecutive 3-week span. Carcass evaluation and longissimus lumborum (LL) samples were collected 24 h postmortem. Carcasses were aged for 21 d, and steaks were collected on 1-, 3-, 7-, 10-, 14-, and 21-days post-harvest and objective color was evaluated following 1 h bloom. Our data show color (L*, a*, b*) was improved with aging regardless of treatment. However grass-fed (CON) showed the greatest improvement in both lightness (L*) and redness (a*) ultimately making grass-fed comparable to that of grain-fed beef by day 21. These data argue dry aging grass-fed beef improves color development similar to that of grain-fed beef.

Measurement of the Direct Impact of Hematophagous Flies on Feeder Cattle: An Unexpectedly High Potential Economic Impact.

In addition to blood pathogen transmission, insects of the order Diptera affect livestock through visual and contact harassment; blood-feeders are responsible for painful bites and blood despoliation, generating behavioral modifications, anemia, and production losses. Knowledge of their economic impact is a basis for cost-effective control. Here, we measured the global impact of diptera insects by comparing two batches of six feeder cattle, one in the open air and the other protected by a mosquito net. The analytical data were insect density in the open air and, for feeder cattle, tail flick counts, hematocrit values (Ht), feed intake, feed conversion ratio (FCR), and live body weight gain (LBWG). Over a period of five months, the results showed significant losses in the LBWG of cattle exposed to insects, estimated at 8.0 ± 1.5 kg/month [2.7; 13.3], with a total loss reaching 40.0 ± 5.5 kg/head. Main diurnal insects were Stomoxys spp. and Musca crassirostris. There was a strong correlation between fly density and diurnal tail flicks. Night trapping and tail flicks showed a potentially important role of mosquitoes to be further explored. The Ht levels of exposed animals were 3-4% lower than those of controls. FCRs indicated that exposed animals needed 33% more dry matter intake/kg of LBWG. An economic assessment showed that dipterans were responsible for a 10-11% loss in LBWG during the main growing period of feeder cattle (10-15 months). A feedlot of 100 calves would register a total loss of USD 16,000 within 5 months, which appears to be an unexpectedly huge loss caused by dipterans. Investing part of this money into fly control would probably be beneficial.

Strategies, challenges, and outcomes of heat stress resilience in sub-Saharan African community-based cattle feedlots: a systematic review.

In sub-Saharan Africa, cattle feedlots face a significant challenge in dealing with heat stress. However, there is a lack of inclusive strategies for resilience in these situations. The aim of this systematic review is to investigate the strategies, challenges, and outcomes related to heat stress resilience in community-based cattle feedlots in sub-Saharan Africa. The PRISMA approach, which is a method for reporting systematic reviews and meta-analyses, was used to identify, screen, and analyze 30 peer-reviewed articles published over the last 20 years from Google Scholar and Scopus. The review found that key strategies to mitigate heat stress include providing shade through natural and artificial means, ensuring constant access to cool, clean water using water spraying systems and cooling ponds, and implementing nutritional adjustments such as high-energy feeds and electrolyte supplements. Additionally, genetic selection for heat-tolerant breeds and management practices like adjusting feeding times and improving ventilation were found to be effective in dealing with heat stress. In particular, local germplasm and genetic traits of cattle in sub-Saharan Africa play a crucial role in heat stress resilience. Indigenous breeds, which have adapted to the region's harsh climate over centuries, exhibit traits such as higher heat tolerance, better water-use efficiency, and improved feed conversion rates under heat stress conditions. This genetic resilience can be enhanced through targeted breeding programs aimed at amplifying these beneficial traits. Implementing these strategies resulted in improved cattle health and productivity, as evidenced by enhanced weight gain, better reproductive performance, and lower mortality rates. The socio-economic benefits of these strategies included reduced economic losses and increased farmer incomes, which in turn contributed to improved community health and nutrition. However, the review also identified significant challenges, including financial constraints, limited access to knowledge and training, and cultural resistance. To address these barriers, the review recommends increased investment in affordable cooling technologies, farmer education, and community-based initiatives. Additionally, leveraging the genetic strengths of local cattle breeds should be prioritized to maximize the effectiveness of heat stress resilience strategies.

PSLBII-27 Investigating the emergence of antimicrobial resistance in Mycoplasma bovis from feedlot cattle

Abstract Bovine respiratory disease (BRD) is the most significant disease affecting feedlot cattle in North America. Mycoplasma bovis is among the main BRD pathogenic bacteria. Infection control of M. bovis is hampered by a lack of effective vaccines and increasing antimicrobial resistance (AMR). Integrative and conjugative elements (ICEs) have been documented as a mechanism of horizontal gene transfer (HGT) in mycoplasmas. Mycoplasma ICEs (MICE) do not carry AMR genes but have been associated with the HGT of genes that confer AMR through point mutations. Hence, there is a need to gain a better understanding of the role of MICE in M. bovis AMR. Randomly selected M. bovis isolates (n = 54) collected from Western Canadian feedlot cattle (AB and SK) underwent whole-genome sequencing by short-reads (Illumina), with a subset (n = 6) selected based on AMR and ICE profiles for Oxford Nanopore long-read sequencing. Sequences were screened for the presence of MICE. MICE circularization (cMICE) is the first step of conjugation, and an in-house collection of 472 M. bovis field isolates (feedlot cattle just from AB) was screened by PCR for the presence of cMICE as a proxy for conjugation capabilities. Environmental conditions that could impact cMICE quantity, including growth phase, temperature, cell density, pH, starvation, UV light, CO2 concentration, and sub-inhibitory concentrations of mitomycin C were investigated by qPCR, followed by growth of M. bovis isolates under the most favorable conditions identified for cMICE-detection and screening by a high throughput qPCR method that eliminated the need for DNA extraction. Nineteen different mating pairs were carried out and 4 different environmental factors were tested for their possible impact on conjugation occurrence (incubation time, incubation volume, conjugation parent proportions, atmosphere). All isolates carried MICEs with 23/54 having a structure/sequence comparable to previously described functional MICE in mycoplasma, 43/54 possessing non-functional ICE, and 23 having &amp;gt;1 ICE. The presence of more than one MICE/genome suggests a lack of MICE (entry) exclusion systems in M. bovis, a trait that may promote the flow of genetic information among M. bovis isolates including AMR. Even though some factors including growth phase (early stationary phase) and pH (9.0) generated greater levels (≥1.5 fold) of cMICE, none of the examined parameters were statistically significant. However, as early stationary growth phase generated the greatest cMICE quantity (2.3 fold), M. bovis isolates were cMICE-screened at this growth stage for the expeditious identification of M. bovis conjugation candidates. A total of 25.7% M. bovis were cMICE-positive. Of 19 mating pairs tested, transconjugants were recovered from only 2 different mating pairs, possibly reflective of the need for further optimization of conjugation conditions.

PSXI-18 Effects of different fiber levels on rumination and inflammatory markers in feedlot cattle

Abstract Adding fiber to feedlot diets is essential to maximize performance, optimize feed conversion and maintain animal health. Monitoring blood inflammatory markers and rumination behavior can help to identify fiber levels that maximize performance and animal well-being. We aimed to evaluate the effect of fiber levels on inflammatory markers, lactate dehydrogenase and haptoglobin and rumination of Nellore cattle in confinement fed with diets containing 12% and 7% forage NDF, over a period of 50 d. Diets included corn silage as the source of forage fiber with 23.3% and 13.6% corn silage in the dry matter 64% and 73.5% ground corn, and 0.2 and 0.5% potassium chloride, respectively for the 12% and 7% fNDF. Soybean meal (1.5%); cottonseed (7%), urea (1.2%), and mineral mixture (2.7%) containing 25 ppm of monensin were present in both treatments. Average initial body weight (BW) was 460 ± 38 kg and average age was 20 mo. Bulls (n = 20) were randomly distributed for each treatment with animal being the experimental unit. The feeding behavior was monitored on d 21 and 42, with observations at each 10-min interval, over 24 h and data obtained were averaged for analysis and blood samples were collected immediately after behavior analysis. Blood samples were obtained by puncturing the jugular vein, centrifuged to separate the serum, stored at -20°C and subsequently analyzed. Lactate dehydrogenase was analyzed in an automatic biochemistry system using cattle specific cattle kits (LABTEST Diagnóstica SA). Haptoglobin analyses were carried out by ELISA (Vidavet-Veterinary Lab). Data were evaluated by PROC GLIMMIX from SAS. A significant interaction was observed between minutes of rumination and fNDF levels in relation to the concentration of lactate dehydrogenase (P &amp;lt; 0.0001), expressed by the solution: Lactate = 1,272.12 + 908.86 * (tract = 7) + 1,1427 -3.3170 * (treat = 7) * rumination. For animals receiving the 7% fNDF diet, the concentration of lactate dehydrogenase decreased as the minutes of rumination increased, with a significant linear effect (P &amp;lt; 0.001). On the other hand, for animals treated with 12% fNDF, no significant correlation was observed (P = 0.34) with increasing rumination time. There was also an interaction between minutes of rumination and fNDF levels for haptoglobin concentration (P &amp;lt; 0.01), expressed by the solution: Haptoglobin = 0.1901 + 0.4865 * (treat = 7) + 0.000828 - 0.00163 * (treat = 7) * rumination. In animals treated with 7% fNDF, haptoglobin concentration decreased with increasing minutes of rumination, with a significant linear effect (P = 0.02). Our data demonstrates that, for the low forage diet, as bulls increased rumination time there was an improvement (a decrease) in inflammatory markers concentrations.

PSXI-19 Effects of different forage levels on performance and feeding behavior of feedlot cattle

Abstract Body weight (BW) gain is highly correlated with profitability and positively associated with feed efficiency and reduced environmental impact of beef production. Fiber stimulates rumination which is essential for digestion, nutrient absorption, and maintenance of animal health. The quantity and quality of fiber in the diet affect BW gain and feeding and rumination patterns. Forage neutral detergent fiber (fNDF) has a key role in regulating intake and health. This study tested two levels of forage inclusion NDF on performance and feeding behavior of Nellore bulls. Corn silage was the source of forage fiber, diets had 12% or 7% fNDF [23.3% or 13.6% in the total dry matter (DM). Diets had 64% and 73.5% ground corn, and 0.2 and 0.5% potassium chloride respectively for 12% and 7% fNDF. Both treatments included soybean meal (1.5%); cottonseed (7%), urea (1.2%), mineral mixture (2.7%) and monensin (25 ppm). Diets were formulated to meet protein and mineral requirements with RLM model (rlm.app.br). Nellore bulls (n = 40; BW = 460 ± 38 kg and an average age of 20 mo) were fed for 50 d after 21 d adaptation. Each animal was considered as experimental unit in a completely randomized design. On d 21 and 42 behavior was evaluated every 10 min for 24 h. Feed intake was measured using Growsafe feeders. Average daily gain (ADG) was estimated by linear regression based on BW (without fast) obtained in real time scales at the water trough. Data were evaluated by SAS PROC GLM. Daily gain (1.71 vs. 1.43 kg/d, P = 0.0002), DM intake (10.97 vs. 10.00 kg/d, P &amp;lt; 0.001) and feed efficiency (0.154 vs. 0.139, P = 0.04) were greater for the 12% fNDF treatment. Likewise, rumination time was greater for the 12% fNDF compared with the 7% fNDF treatment; 356 and 275 min/d respectively (P = 0.0005). Animals fed 12% fNDF had longer rumination times and improved performance compared with those fed 7%. There were no differences in the number of visits to the troughs or in total feeding time (P &amp;gt; 0.05), with mean visits of 15.17 and 15.43, and feeding times of 145.6 and 146.8 minutes for the 12% and 7% fNDF diets, respectively. Linear correlation between ADG and rumination time was positive r = 0.49 (P &amp;lt; 0.03) and r = 0.28 (P &amp;lt; 0.23), indicating that rumination is associated with an increase in ADG. Coefficient of variation for ADG was 13.4 and 27.2% for 12 and 7% fNDF diets, with greater variability for the low fiber diets. The results highlight the importance of providing adequate forage to feedlot cattle. Results are consistent with previous work from our group demonstrating that the maximum performance is achieved at around 11 to 13% fNDF. Bulls fed 12% fNDF diets had greater BW gain, higher rumination and reduced ADG variation compared with those fed 7% fNDF diets.

PSIII-7 Effects of Saccharomyces cerevisiae fermentation product on total tract digestibility, ruminal fermentation, and plasma metabolome of beef steers fed a finishing diet

Abstract Saccharomyces cerevisiae fermentation product (SCFP) has been widely studied; however, its mode of action on high-concentrate diets has not been fully elucidated. This study evaluated the impact of SCFP on total tract digestibility, fecal excretions of N, P, Zn, and Cu, rumen fermentation, and plasma metabolome of finishing beef steers. Ruminally cannulated Holstein steers [n = 8; body weight (BW) = 580 ± 29.2 kg] were enrolled in a crossover design study with 25-d treatment periods and a 24-d washout period. Steers were fed ad libitum a finishing diet consisting of 20% corn silage and 80% concentrate (on DM basis). Steers were blocked based on initial BW and randomly assigned to two treatments in period 1 and switched to the other treatment in period 2. The treatments were CON (Control, basal diet only) and SCFP (basal diet top-dressed with 12 gּ steer-1ּ ּ d-1 SCFP, NaturSafe, Diamond V, Cedar Rapids, IA). Feed and fecal samples were collected during d 22 to 24 for determination of digestibility. Blood was collected before morning feeding on d 25. Plasma samples were analyzed for metabolome with liquid chromatography-mass spectrometry (LC-MS). Rumen fluid was collected via the rumen cannula at 0, 4, 8, and 12 h post-morning feeding on d 25 and analyzed for pH, volatile fatty acids (VFA), and NH3-N. Performance and ruminal fermentation characteristics data were analyzed using the GLIMMIX procedure of SAS 9.4. Metabolomic data analysis was conducted with Metaboanalyst 6.0. Supplementing steers with SCFP reduced DMI (10.6 vs. 11.4 kg/d, P = 0.05) without affecting (P &amp;gt; 0.05) average daily gain, feed efficiency, and digestibility of organic matter, crude protein, and neutral detergent fiber. Treatment did not affect (P &amp;gt; 0.10) fecal excretions of N, P, Cu, and Zn. Feeding SCFP increased ruminal pH (6.29 vs. 6.01, P = 0.01), numerically reduced concentrations of NH3-N (5.01 vs 6.25 mM, P = 0.16), and total VFA (96.8 vs. 102.5 mM, P = 0.15). SCFP also reduced the ruminal molar proportion of butyrate (11.2 vs. 12.8 molar %, P = 0.01) and tended to increase those of isobutyrate (1.03 vs. 0.90, molar %, P = 0.06) and isovalerate (2.62 vs. 2.29, molar %, P = 0.10). Supplementation of SCFP enriched (P ≤ 0.05) purine metabolism, amino sugar and nucleotide sugar metabolism, and lysine degradation pathways in the plasma. Additionally, tryptophan metabolism and pyrimidine metabolism pathways tended to be enriched (0.05 &amp;lt; P ≤ 0.10) by SCFP. Our findings indicate that feeding SCFP improved the ruminal pH of finishing cattle, which may be beneficial for preventing subacute ruminal acidosis in feedlot cattle. Additionally, SCFP enriched several important plasma nitrogen metabolism pathways, potentially associated with microbial nitrogen metabolism in the rumen, warranting further research.

PSXII-24 Use of a commercial blend of tannins as feed additive for feed lot cattle on large pen trial improves carcass weight and carcass feed conversion

Abstract The utilization of commercial tannin extracts as feed additives holds promise for enhancing animal performance and health within commercial feedlot settings. This study aimed to assess the impact of a commercial tannin blend, SilvaFeed BX (Indunor, Buenos Aires, Argentina), sourced from quebracho and chestnut extracts along with saponins, on the performance of beef cattle. Nelore bullocks (n = 1,198) were allocated to 12 pens in a completely randomized block design, stratified by initial date, at a commercial feedlot facility in Goias State, Brazil. Each pen served as an experimental unit, with 10 pens housing 100 animals each and 2 pens containing 99 animals each. The experimental treatments included a Control diet with monensin alone [25 ppm/kg dry matter (DM)] or treated with BX (0.7 g/kg DM) on top of the control diet. Individual body weights (BW) were recorded at processing (initial BW; IBW) and shipment (final BW; FBW), while DM intake (DMI) was averaged per pen throughout the study duration. Carcass weight (CW) was individually measured at the packing plant, and carcass gain was calculated as the discrepancy between carcass weight and the estimated initial carcass weight, set at 50% of the IBW, aligning with customary practices for negotiating feeder cattle in Brazil. Statistical analyses were conducted using Proc Glimmix in SAS, treating pens and treatments as fixed effects and blocks as random effects, with IBW considered as a covariate. Residuals were assessed for normality, identifying three outliers. Mean comparisons were facilitated using LSMEANS. The results indicated that BX-treated cattle exhibited increased FBW (502.17 vs. 493.64 kg, P = 0.0992), carcass weight (275.76 vs. 268.78 kg, P = 0.0343), total carcass gain (107.52 vs. 100.54 kg, P = 0.0343), and improved carcass feed conversion (10.46 vs. 11.45 kg DM/kg; Table). Despite numerical differences, the limited number of replications were not enough to detect significant differences between treatments in average daily gain (P = 0.2419), DMI (P = 0.5508), feed conversion (P = 0.2641), or dressing (P = 0.3757). In conclusion, BX, a blend of tannins, exhibits potential for enhancing carcass weight and feed conversion efficiency in Nelore bullocks. Further investigations employing larger sample sizes are warranted to comprehensively elucidate its effects on other performance parameters.

PSLBII-29 Effects of heat stress mitigation methods on growth performance, environmental, and economic outcomes of feedlot cattle raised in a hot climate

Abstract The increase in average global temperatures presents a challenge for the beef industry, especially in the feedlot sector where heat stress is a major animal welfare and economic concern. To combat this, shade stands out as one of the most practical methods to mitigate heat stress in feedlot cattle. An experiment was conducted as a completely randomized design with Bos indicus bulls (n = 1,560) with initial body weights (BW) of 287 kg. Three shade structure types were used to investigate the effects of different heat stress mitigation methods on cattle growth performance, environmental, and economic outcomes using live animal data, and a partial lifecycle assessment (LCA) using the Integrated Farm System Model (IFSM). The live animal portion of the experiment was done once a year over a 2-yr period with three pen replications per treatment per year (n = 6 per treatment). Four shade structures used were: conventional shade (SC; steel shade 1.8 m2 of shade/animal), double conventional shade (DS; steel shade 3.6 m2 of shade/animal), dome structures without fans (DSA; 8.5 m2/animal with 98% solar radiation blocked), and domes with fans (DCA; three large sized low-speed fans). Each pen held 65 bulls in an area of 570 m2. Live animal data were analyzed as a completely randomized design using the GLM procedure of SAS (version 9.4) with shade type as fixed effect, pen as the experimental unit, and repetition (year) considered a random effect. Cattle housed under DCA had 22 kg and 20 kg heavier final body BW (P &amp;lt; 0.05) compared with those housed under SC and DS, respectively. Final BW of DCA and DSA cattle were similar (P &amp;gt; 0.10). Average daily gain, feed efficiency, and hot carcass weight (HCW) were greater (P &amp;lt; 0.05) for cattle housed under DCA compared with the rest of the shade types. Dry matter intake was not affected (P &amp;gt; 0.10). When treatment results were extrapolated to the annual feedlot turnover of 209,700 animals, cattle in DSA and DCA versus SC and DS had 3 to 8 % reductions in greenhouse gas and ammonia emissions intensities. Compared with SC, DCA increased profitability by $29.66/animal, followed by DSA and DS with profit increases of $5.79 and $8.90/animal, respectively. Overall, the implementation of advanced shade structures improved cattle performance and profitability while reducing the environmental impact of beef production.

PSXI-7 Effects of selected feed additives on feedlot cattle performance when fed diets containing rehydrated corn grain silage

Abstract The use of additives makes it possible to improve body weight (BW) gain and muscle growth, the efficiency of nutrient use, in addition to reducing the incidence of metabolic disorders. The objective of the study was to evaluate the performance, feed intake and carcass production of feedlot Nelore cattle, fed with a high concentrate diet, using different feed additives. Nelore bulls [n = 48; initial BW (BWi = 378.1 kg ± 8.92 kg; 20 mo of age), were used. Bulls were allocated in a collective pen, randomly distributed in two treatments: 1) Sodium Monensin (MON), 26 mg/kg DM; and2) CRINA + RUMISTAR + Hy-D (CRD), blend of essential oils, 90 mg/kg DM + exogenous α-amylase, 560 mg/kg DM + 25 hydroxyvitamin D3, 1 mgּ animal-1ּ d-1 . The experiment lasted 101 d, the animals were weighed fasting (± 16 h) at the beginning and end of the experiment, at the end of the experiment the animals were subjected to carcass ultrasound, dry matter intake (DMI) was measured daily individually using electronic troughs with selector doors (Intergado, PONTA, Betim, MG-Brazil). The initial carcass weight (195.6 kg, P = 1.0) was estimated using the equation HCWi = 0.6587*BWi-53.44 (R² = 0.993), obtained through the reference slaughter of 9 animals, and the final carcass weight measured in the refrigerator. The “step-up” adaptation protocol lasted 15 d, followed by the finishing diet until the end of the experimental period, consisting of ground corn, rehydrated corn grain silage, cottonseed cake, whole cottonseed, sugarcane bagasse, urea and vitamin-mineral supplement. Data were analyzed by SAS PROC ANOVA, using BWi as a covariate when significant. Animals fed CRD had a greater final BW (534.0 vs 515.6 kg, P = 0.003) and increased average daily gain (ADG) by 0.180 kg/d (1.54 vs 1.36 kg/d, P = 0.003). DMI was greater (10.2 vs 9.3 kg/d, P &amp;lt; 0.001) as well as DMI:BW (2.24 vs 2.09 %BW/d, P &amp;lt; 0.001). The feed efficiency did not differ between treatments (P = 0.21). Animals fed CRD presented heavier HCW (305 vs 291 kg, P = 0.004) and ADG carcass (1.08 vs 0.95 kg/d, P = 0.004). The carcass conversion, calculated as kg DM/15 kg carcass produced (143.5 vs 152.6, P = 0.11), carcass yield (P = 0.15), 12th ribeye area (P = 0.52) and 12th rib fat (P = 0.12), were similar among the treatments. Feeding CRD tended to improve marbling (1.67 vs 1.45%, P = 0.08). These results underscore the potential of CRD as an effective alternative to traditional additives in enhancing the performance and carcass quality of feedlot cattle.

PSXII-29 Effect of tannins level and diet type on in vitro ruminal fermentation and methane production

Abstract The objective of the study was to evaluate the effect of four levels of a commercial product based on quebracho that contains tannins (Table 1) on three types of diets: Feedlot, Dairy Cattle, and Grazing, using the in vitro gas production technique on ruminal fermentation, dry matter digestibility and methane (CH4) production to determine its potential use as a greenhouse gas mitigation strategy in ruminants. An in vitro trial was carried out in a completely randomized block design with a factorial arrangement of 4 [dose: 0, 0.25, 0.50, and 0.75 % of Protein Enhancer (PE)] x 3 [diet types: low (LFD), medium (MFD) and high forage (HFD)]. The fermentation of each treatment was carried out in triplicate in 120 mL amber antibiotic bottles, containing 0.5 g of substrate previously deposited in nylon bags (24 µm pore size) and 60 mL of a mixture of medium and rumen fluid from three Holstein cows. Incubations were replicated in two independent runs (blocks). The gas pressure (PSI) was recorded at 1, 2, 3, 6, 9, 12, 18, 24, 30, 36, 48, 60 and 72 hours of incubation. Gas pressure data were converted to gas volume (y = mL of gas; x = gas pressure PSI). Subsequently, pH was measured, and subsamples for analysis of volatile fatty acids (VFA) by gas chromatography were collected. Methane was analyzed with a Crowcon Gas-Pro detector, while ammoniacal nitrogen with a hybrid multimodal microplate reader. The data were analyzed with the MIXED procedure of SAS, and the comparison of means was analyzed with Tukey and with orthogonal polynomials for doses. An interaction (P &amp;lt; 0.05) was observed between diets and PE levels for CH4 concentration (%), where the diet with a greater level of forage and the greatest level of PE (0.75%), showed the least concentration (30%, P &amp;lt; 0.05) compared with the control diet of dairy cattle. On average, CH4 production [mL CH4/g dry matter (DM)] were 83.3, 63.6, and 35.3 for LFD, MFD, and HFD, respectively (Table 2). As the dose of PE increased, rumen pH and N-NH3decreased (P &amp;lt; 0.05), and the total VFA concentration increased (linear effect, P &amp;lt; 0.05; Table 3). Methane production was less (30%) with the grass-based diet and the greatest level of quebracho-based product with condensed tannins, compared with the dairy cattle diet with 0% condensed tannins. The diet for feedlot cattle was more digestible and, therefore, produced more gas and a greater concentration of CH4, in contrast to the grass-based diet, which produces less CH4. It is necessary to carry out in vivo trials, particularly in grazing cattle, to evaluate the effect of the quebracho-based product on performance and in vivo methane emission. This study was partially funded by PAPIIT-DGAPA-UNAM (grant IN212523).