Beef Operations Research Articles

Bacterial Communities of House Flies from Beef and Dairy Cattle Operations are Diverse and Contain Pathogens of Medical and Veterinary Importance.

Adult house flies (Musca domestica L.) are important reservoirs and mechanical vectors of bacteria in livestock operations. House fly bacterial communities are influenced by their local environment, yet a comprehensive understanding of bacterial diversity, pathogen prevalence, and bacterial source is not fully understood. We characterized bacterial communities from adult female house flies and associated manure samples from beef and dairy cattle farms in Kansas, Oklahoma, and Texas over four months (July-October). Bacterial community composition in flies and manure reflected the local environment, and house flies shared the majority (≥ 99%) of bacterial taxa with manure. The variability of bacterial diversity was greater among individual fly (species richness range: 48-1747) samples than manure (species richness range: 345-1162). Temporal variability of fly bacterial diversity was observed within each farm type. Bacterial taxa of veterinary and medical importance such as Corynebacterium, Turicibacter, Staphylococcus, Streptococcus, and Acinetobacter were highly prevalent in flies, constituting core bacterial communities. The prevalence of bacterial taxa associated with bovine keratoconjunctivitis (IBK) and bovine respiratory disease (BRD) was higher in flies than in manure and prevalence varied monthly. This study underscores the crucial role house flies play as carriers of cattle pathogens, contributing to their dissemination among animals and to off-site locations, where they pose a threat to surrounding communities and agricultural operations.

PSIV-26 Extent of use of supplemental feeding in beef cattle operations across the Southeast: A report of the regional survey

Abstract With input costs on the rise, researchers and producers, alike, are seeking alternative management strategies for profitable and sustainable beef production. Studies suggest that supplemental feed provided to grazing cattle may be used to offset some of the cost. However, there is a lack of knowledge on the extent of supplemental feeding programs in the southeastern US and which feeds may be used in these programs. Thus, the objective of this study was to better understand supplemental feeding practices and choices among beef producers in the southeastern US. To address this objective, a 24-question survey was distributed through Extension and commodity organizations to beef producers across the Southeast. This survey received 118 complete responses. The majority of respondents operated cow-calf production systems (65.6%) on either tall fescue or bermudagrass pastures (32.7 and 28.0%, respectively). Approximately 88% of these producers employed some type of supplemental feeding strategy, but there is no clear decision on whether commodity or byproduct feedstuffs were preferred. The leading commodity used was corn (61.4%), while common byproducts included whole cottonseed, corn gluten feed, and soybean hulls (17.1, 16.6, and 14.4%, respectively). At the end of the survey, the participants were asked to submit a sample of their byproduct supplements to have a nutritive analysis completed to better understand what nutritional components the products they are feeding contain and how they may vary from place to place. Some of the products that were sent in include whole cottonseed, cotton byproduct, corn gluten meal, distillers grain, chicken litter, and others. The nutritional test being run on these samples included crude protein and fiber analysis. The crude protein of the samples received ranged from 13.3% to 30.3% with an average of 21.5%. The fiber profile received ranged from 45.5% to 76.3% with an average of 59.9%. With the information recorded from these tests, recommendations can be provided on different feeding methods in both commercial settings as well as research settings.

PSI-1 Genetic and non-genetic factors influencing beef cattle attractiveness to horn fly

Abstract Horn flies are the most common summer pests of cattle, leading to substantial economic losses due to impaired production and decreased animal welfare. Genetic and non-genetic factors have been reported to influence cattle susceptibility to horn flies. However, the wide range of heritability estimates, and few identified genomic regions associated with cattle resistance to horn fly may be due to subjective assessment in collecting the fly load phenotype and the small size of the population assessed. Here, beef calves from the UF purebred Brahman (BRA) and Multibreed Angus-Brahman (MAB) populations were video recorded at weaning using a GoPro camera mounted on the top of the chute. Fly infestation was determined as the average fly count obtained from five longitudinal images of each animal using ImageJ software. A total of 748 crossbred and 415 purebred calves born from 2021 to 2023 were evaluated during summer (August or September). Analysis of variance (ANOVA) was performed within herd by fitting linear models that included collection date, age, skin color, coat color, and pre-weaning average daily gain (ADG) as fixed effects, and residual as a random effect. For MAB calves, breed groups (BG) determined based on the percentage of Brahman breed, with BG1 ranging from 0 to 19%, BG2 from 20 to 39%, BG3 from 40 to 59%, BG4 from 60 to 79%, BG5 from 80 to 100%, were also fit in the model. Fly count was transformed to a natural log value (log[count +1]) ensuring normally distribute residuals. As expected, darker colors were significantly more attractive to horn flies, while animals with greaterr percentage of Brahman were less susceptible than animals with greater percentage of Angus breed. Considerable variability in fly load was observed within purebred Brahmans, indicating that additional genetic factors, other than breed, influence cattle resistance to flies. Positive estimates were observed between horn fly load and average daily gain in both herds, which can be due to the fly load below the previously reported economic injury level of 200 flies (BRA: 28.78 ± 38.20, MAB: 19.31 ± 26.72). Variance components were estimated within herds by fitting the same aforementioned effects and a genomic-based relationship matrix (G) constructed with genotypes from the GeneSeek Genomic Profiler F250 SNP chip. The moderate heritability estimate demonstrates the feasibility of selecting cattle resistant to horn flies. Overall, our findings have the potential to contribute to reducing losses and costs in beef cattle operations, while reducing the impact on the environment of overuse of insecticides.

10 Awardee Talk: Pregnancy losses in Bos indicus-influenced cowherds

Abstract Pregnancy loss is recognized as a major reproductive challenge in beef cattle operations. Most pregnancy losses are associated with early embryonic mortality, but limited research evaluated pregnancy losses throughout the gestation period. Research is warranted to address this gap in knowledge, particularly fetal losses in Bos indicus-influenced females. This subspecies predominates in tropical regions of the planet, which contain more than 80% of the world’s cattle population and supply a major portion of the global demand for beef products. Our group recently evaluated pregnancy losses from d 30 of gestation to calving in 4,926 Nelore females assigned to an ovulation synchronization + fixed-time artificial insemination (FTAI) protocol. Pregnancy loss was greater (P < 0.01) from d 60 to 150 of gestation (10.2%) compared with d 30 to 60 of gestation (6.0%) and with d 150 of gestation to calving (7.4%) and differed (P = 0.04) between these latter two periods. Pregnancy loss from d 30 to 60 of gestation did not differ (P = 0.26) among cow parities (nulliparous, primiparous, and multiparous), whereas total pregnancy losses (d 30 to calving) were greater (P < 0.01) in precocious (28.4%) and conventional (27.1%) heifers compared with primiparous (16.4%) and multiparous (13.0%) cows. In a second experiment, pregnancy losses from fixed-time embryo transfer (FTET) to calving were evaluated in 4,366 FTET events using Nelore × Angus recipient heifers. Pregnancy losses were greater (P < 0.01) from FTET to d 32 of gestation compared with d 32 to 100 and with d 100 to calving (58.7, 39.5, and 36.7%, respectively), and did not differ (P = 0.56) between these latter periods. Recipients that lost the pregnancy from FTET to d 32 gained less (P < 0.01) body condition score after FTET compared with recipients that maintained the pregnancy. Pregnancy losses from d 32 to calving were greater (P < 0.01) in recipients reared in drylots and moved to pastures on d 32 compared with recipients reared on pasture. Collectively, these results provide novel information about pregnancy losses in Bos indicus females, with a substantial proportion of losses occurring as fetal mortality.

64 Effects of alternative finishing methods on performance and carcass quality of beef feeder steers

Abstract There has been an interest in directly locally marketing finished beef end products in Arkansas; however, most beef operations do not have the infrastructure to finish cattle conventionally. The objective of this study was to evaluate two non-traditional finishing methods (pasture-based with supplement) compared with a conventional finishing method on live performance and carcass quality of feeder steers. Crossbred beef steers (n = 63; 363.9 ± 28.7 kg) were blocked by body weight (BW) and assigned to pens (n = 3 steers/pen) with 7 pens randomly allocated to each treatment: conventional feedlot finishing diet with roughage included in the ration (FDLT); high starch supplement fed at 2 to 2.25% of BW with ad libitum access to bermudagrass pasture (STCH); or high by-product supplement fed at 2-2.25% of BW with ad libitum access to bermudagrass pasture (BYPD). Steers were fed their respective diets once daily and weighed on d 0, 28, 56, 84, 112, 140, and 161. Once cattle reached their targeted endpoint, they were transported to and harvested at a commercial slaughter facility in Arkansas City, Kansas. Carcass data were collected including hot carcass weight (HCW), preliminary yield grade (PYG), yield grade (YG), quality grade (QG), dressing percentage (DP), and final carcass value. Data were analyzed using PROC GLIMMIX and MIXED (SAS 9.4); pen was the experimental unit, treatment was a fixed effect, and block was considered a random effect. Cattle fed FDLT and BYPD had a greater BW on d 84, 112, and 140 (P ≤ 0.02) and greater overall carcass-adjusted BW (P = 0.03) compared with STCH. Average daily gain (ADG) was greater on d 84 (P = 0.03) for FDLT compared with STCH and BYPD. Overall carcass-adjusted ADG tended (P = 0.09) to be greater for FDLT and BYPD compared with STCH. As expected, cattle fed FDLT had greater dry matter intake (DMI) compared with STCH and BYPD for the entire study (P ≤ 0.0005). Both STCH and BYPD had a more efficient feed-only feed conversion on d 28, 56, 112, 140, and 0-161 (P ≤ 0.05) and were more economical (P < 0.0001) than FDLT. In this study, cattle fed BYPD were more profitable (P ≤ 0.04) compared with STCH and FDLT. Hot carcass weight tended (P = 0.13) to be greater and final carcass value (P = 0.01) was greater for BYPD and FDLT compared with STCH. No differences (P ≤ 0.78) were noted for PYG, YG, QG, or DP. Data from this study suggests feeding supplemental diets to beef cattle grazing pasture could successfully be used as an alternative finishing method without affecting carcass quality.

263 Public perspectives of calf handling: A survey of Canadians

Abstract In North American beef production handling and restraint of young calves is integral to animal welfare and management practices. This study used a mixed method approach to gather public perceptions of three handling and restraint methods common on beef operations in western Canada (RW - Roping and Wrestling, NF – roping and NordForks, and TT – Tilt Table). Canadian participants (n = 551) recruited by CloudResearch to represent the national demographics participated in an online survey that included videos of each handling method to ascertain preferences and acceptability. Prior to watching the videos, participants were given industry information about handling and restraint or generic information regarding hay as a control information statement within the topic of agriculture. The survey also collected information about knowledge of the beef industry, animal welfare, and empathy toward animals. The reasons for preferences were described as presence of a perceived positive attribute and absence of a perceived negative for most preferred methods, and inversely when explaining least preferred method. The findings focused on calf’s experience, perception of handler actions, and pragmatic balancing of handler needs and a good life for the calf. Methods were rated as more acceptable for participants that ate meat consistently, knew more about the beef industry, and, to a lesser extent, if the individual had a lower animal empathy score (Table 1). Acceptability was not affected by providing information about the practices; however, information about handling and restraint did elicit more pragmatic reasoning. Most participants preferred TT over NF and RW (P < 0.001) and found TT more acceptable as well (P < 0.001). The TT was the most preferred method due to calf experience and human handling, notably the absence of dragging a calf, which was predominant in why participants selected NF or RW as their least preferred method. Consistency of themes highlights that the Canadian public has a fundamental expectation of value for the quality of life of the calf, humane handling, and pragmatism which aligns with beef sustainability initiatives and represent points of connection for building trust between industry and the public.

451 Establishing producer research sites for the development of beef and bison climate-smart agriculture

Abstract Greenhouse gas (GHG) emissions and livestock production are topics that are increasingly intertwined. While livestock production is frequently presented as harmful to the environment, this perception fails to consider the carbon sequestration that takes place in livestock grazing systems and the role that grazing ruminants have in maintaining healthy grassland ecosystems. Grazing lands, which are often unsuited to row crop agriculture, are estimated to account for 25% of the global soil sequestration potential for soil carbon storage. Grazing livestock producers are often overlooked in the GHG reduction conversation, despite over 70% of beef GHG emissions being attributed to the cow-calf sector, which is primarily grazing. Furthermore, there is a relative lack of data surrounding the implementation of climate-smart agriculture practices on grazing operations and a lack of cost-effective methods to measure carbon/GHG sinks and sources on these landscapes. The potential climate benefits are considerable, with nearly 940 million acres of rangelands in the U.S. supporting forage-based livestock production. South Dakota State University recently received funding to support a large-scale climate-smart project focused on grazing beef and bison. For this project, we are utilizing the Cottonwood Field Station that has over 80 yr of historical grazing data, along with six grazing beef and bison ranching operations in the Northern Great Plains. The work on these ranches will focus on measuring and monitoring the impacts of climate-smart NRCS land practices, including cover crops, improved pasture and range seedings, prescribed grazing, and prescribed burning. A significant focus will be extensive, annual soil sampling across these operations to continuously monitor changes in soil organic carbon, bulk density, texture, pH, and soil microbiome community profiles. Each operation will have GreenFeed methane pasture units deployed for 5 yr to monitor changes in beef cattle and bison methane emissions in response to climate-smart practice adoption. We are also assessing biodiversity pre and post climate-smart practice adoption, as biodiversity improvements may be one of the most overlooked and yet most important responses to climate-smart land practice implementation. Over the duration of this project, a large-scale, comprehensive data collection will be achieved and used to refine GHG and carbon sequestration estimates associated with range livestock systems. Data resulting from this project will be used to inform research protocols and prediction models, fill knowledge gaps, and shape science-based discussions and marketing strategies for climate-smart agricultural commodities.

Evaluation of a voluntary passive surveillance component in cattle through notification of excess mortality

Passive surveillance can be most effective in the early detection of disease outbreaks given that farmers observe their animals daily. The European Animal Health Law states that unexplained excess mortality should be reported to the veterinary authorities. In the Netherlands, in addition to notifications to the competent authority, Royal GD is commissioned a passive surveillance component that consists of a veterinary helpdesk and postmortem examination for early detection of emerging diseases. The aim of this study was to evaluate this voluntary passive surveillance component through excess mortality in cattle.Weekly on-farm mortality was calculated using the cattle Identification and Registration records. Mortality was assessed on regional level for dairy, veal and other beef cattle using a Generalized Linear Model (GLM) (log-link, negative binomial). We used a cumulative sum of the model residuals to identify periods of excess mortality. The mortality was defined as excessive when above five times the standard error. The analysis was also conducted on herd level, but these models did not converge.We checked for an association between the two passive surveillance components elements and excess mortality. A GLM (log-link, negative binomial) with the number of contacts or submissions per region as the dependent variables and excess mortality per region and year as independent variables was carried out.Overall, the models showed significantly higher use of passive surveillance components in periods of excess mortality compared to non-excess periods. In dairy cattle the odds for contact or submission were between 1.72 (1.59–1.86) and 2.02 (1.82–2.25). For veal calves we found the odds of 2.19 (1.18–4.04) and 2.24 (1.78–2.83) relative to periods without excess mortality. Beef cattle operations, other than veal, showed only an increased odds for postmortem submissions in calves of 3.71 (2.74–5.01), submissions for cattle and contact in general was not increased for this farm type.In conclusion, the voluntary passive surveillance component in the Netherlands is used more often in periods of excess mortality in cattle. The chance of getting a timely response is highest for dairy farms. For veal calf operations the chance of receiving a timely response is more likely for postmortem submissions. A comparison with passive surveillance for excess mortality in other countries was not possible because no literature could be found. However, the method of this study can be used by other countries to evaluate their passive surveillance. This would make comparison of the performance of passive surveillance in different countries possible.

Genomic Profiling of Antimicrobial Resistance Genes in Clinical Salmonella Isolates from Cattle in the Texas Panhandle, USA.

Rising antimicrobial resistance (AMR) in Salmonella serotypes host-adapted to cattle is of increasing concern to the beef and dairy industry. The bulk of the existing literature focuses on AMR post-slaughter. In comparison, the understanding of AMR in Salmonella among pre-harvest cattle is still limited, particularly in Texas, which ranks top five in beef and dairy exports in the United States; inherently, the health of Texas cattle has nationwide implications for the health of the United States beef and dairy industry. In this study, long-read whole genome sequencing and bioinformatic methods were utilized to analyze antimicrobial resistance genes (ARGs) in 98 isolates from beef and dairy cattle in the Texas Panhandle. Fisher exact tests and elastic net models accounting for population structure were used to infer associations between genomic ARG profiles and antimicrobial phenotypic profiles and metadata. Gene mapping was also performed to assess the role of mobile genetic elements in harboring ARGs. Antimicrobial resistance genes were found to be statistically different between the type of cattle operation and Salmonella serotypes. Beef operations were statistically significantly associated with more ARGs compared to dairy operations. Salmonella Heidelberg, followed by Salmonella Dublin isolates, were associated with the most ARGs. Additionally, specific classes of ARGs were only present within mobile genetic elements.

State of the art of the cow-calf systems in beef and dairy cattle (Bos taurus) operations in EU, USA, and Brazil from 1998 to 2023

Cow-calf systems represent a significant research area in animal husbandry, with differences depending on the final product (meat or milk). This study aimed to apply text mining and topic analysis on literature describing cow-calf systems in European, American, and Brazilian beef and dairy sectors between 1998 and 2023. Additionally, cow-calf contact (CCC) literature data was manually extracted. Our findings revealed the presence of 11 research areas among literature on cow-calf systems, with different priorities identified in the beef and dairy sectors. Beef industry mainly focused on animal proficiency and nutrition, while dairy on animal welfare and CCC, which showed a growing trend as emerging research topic, mostly in the EU. Current debates around calf welfare and EU's planned animal welfare legislation revision appeared to be driving the increasing interest in this topic. Studies in the beef sector were mainly localized in Brazil, showing that research in different contexts and species is important for CCC implementation. Manual data extraction showed considerable variation in the retained CCC documents regarding sample size, type of contact, methods and CCC duration. Learning about the varied CCC approaches used in beef and dairy farms in different locations, concentrating on their strengths and weaknesses, will help to develop novel solutions to global challenges. Adopting validated and robust indicators would help scientists and policymakers to monitor the system's quality. To improve CCC feasibility, match consumer demands, and move towards One Welfare and One Health, future research should focus on a variety of situations to overcome the current shortcomings.

Vaccines for all stages

There are many vaccines to select from when developing proto­cols for beef cattle operations, and no single vaccine protocol is appropriate for all operations. Thus, vaccine protocol develop­ment requires understanding of the management of each op­eration. Unfortunately, current field trials confirming efficacy of vaccines to prevent disease in “real life” settings are not com­mon, and not all protocols have been tested. Thus, development of protocols for farm or ranch use often relies on experimental challenge studies or expert opinion. When vaccination of calves in the first 3 to 4 months of life is possible, vaccines for clostrid­ial infections and respiratory viral infections are most likely to be used to limit preweaning disease. On some operations, pre­weaning vaccination may be delayed until close to weaning if the aim is to limit postweaning disease. Vaccines likely appro­priate to limit postweaning disease include those for clostridial agents, agents that cause bovine respiratory disease, and agents likely to impact fertility in replacement heifers. Other vaccines may be appropriate on a case-by-case basis. Health records in­cluding vaccine timing and occurrence of disease in vaccinated animals can be a major help to confirm efficacy of vaccine pro­tocols. Veterinarians should periodically check for new sys­tematic reviews, meta-analyses, or randomized controlled field trials testing vaccines they used, to have the best information to use when planning vaccination protocols.

Synchronization of the bovine estrous cycle: Current and emerging opportunities

Controlling the bovine estrous cycle is a necessity if performing fixed-time artificial insemination or embryo transfer. Addition­ally, irrespective of the genetic objectives driving the decision to use reproductive technologies, the use of synchronization protocols often has beneficial effects on the overall reproduc­tive performance and commercial production output of a beef cattle operation. This proceedings paper provides a general review of the conceptual goals and challenges associated with synchronization of estrus, and directs readers to resources on current protocols and emerging opportunities in the field.

Factors associated with perceived Anaplasma marginale infection and clinical anaplasmosis cases on beef operations in California

Bovine anaplasmosis is a tick-borne disease caused by Anaplasma marginale in the United States. The objective of this study was to use a survey tool to generate information for beef operations in California on anaplasmosis prevention and control management, including to what extent management activities were informed by perceived herd-level exposure to A. marginale infection or occurrence of clinical anaplasmosis cases. We mailed 2,621 questionnaires with questions on Anaplasma status, herd demographics, anaplasmosis control and prevention measures, and environmental factors to beef ranchers in California in October 2020. Survey-weighted chi-square tests were used to compare management differences according to perceived Anaplasma infection status. Generalized estimating equations (GEEs) were used to analyze whether region of California, management practices, or environmental factors were associated with reported clinical cases of anaplasmosis in the previous five years. A total of 466 questionnaires describing 749 herds were obtained and used in this study. Use of management measures, including deliberate exposure of calves to ticks, vaccination for Anaplasma, infection control through antibiotics in feed, maintaining a completely closed herd, blood testing for Anaplasma on all herd additions, and taking no anaplasmosis control and prevention measures, were significantly different between herds with or without perceived A. marginale infection based on producers’ self-declared status. The overall perceived prevalence for Anaplasma infection and reported clinical cases of anaplasmosis at the herd level was 26.0 % (95 % CI: 24.3–27.7 %) and 17.1 % (95 % CI: 15.6–18.6 %) respectively, with the highest perceived infection and case numbers reported in the Central Coast region. In the GEE model, higher odds of reporting clinical cases of anaplasmosis in the previous five years were observed in cattle located in the Central Coast region, cattle within a large herd, cattle that are treated with tick/fly control, cattle in a completely closed herd, and cattle receiving Anaplasma vaccine. Anaplasma infection and bovine anaplasmosis status may be underestimated in beef herds in California based on previous study results. Changing needles between cattle after injections and conducting blood testing for Anaplasma on herd additions are important Anaplasma management measures that are infrequently implemented in beef herds in California. The results show a need for producer education to improve producers’ awareness of bovine anaplasmosis and implement proper measures for disease control and prevention.

Characterization of the Worthen Sparrow (Spizella wortheni)'s Nest Building Materials in Northeastern Mexico.

The study was conducted within a well-managed beef cattle operation in northeastern Mexico. Each nest was weighed and dissected to obtain the plant and animal material used to build the nests. The number of materials present per nest and relative frequency were determined. Twenty-one building materials were used. Over the years, Muhlenbergia torreyi represented 85.5% of the total biomass of the nests, and Aristida longiseta, Bouteloua gracilis, Brickellia canescens, Purshia mexicana and Cirsium ehrenbergii constituted 2.45, 2.80, 2.44, 1.34 and 1.11% of the total biomass, respectively. The above-mentioned grasses represented 95.62% of the total biomass. Material of animal origin was horse and cow hair, which represented 0.84 and 0.58% of the total biomass, respectively. It was concluded that, at the study site, Muhlenbergia torreyi was a key nest-building material for the Worthen sparrow nest.

Species composition of Culicoides (Diptera: Ceratopogonidae) in the Ridge and Valley region of Tennessee, USA.

Biting midges in the genus Culicoides Latreille (Diptera: Ceratopogonidae) are known to transmit many pathogens of veterinary and medical concern. Although much work has been done globally and in certain regions of North America, Culicoides spp. research in rural Appalachia is limited. To begin characterizing the distribution and community structure of Culicoides spp. in Appalachia, we surveyed 2 distinct sites in the Ridge and Valley ecoregion of northeastern Tennessee, USA, from April 2021-September 2021. Culicoides spp. were sampled using 2 methods: Centers for Disease Control ultraviolet LED light traps and potential larval habitat substrate collection (coupled with water chemistry values). Site 1 was dominated by natural features, and Site 2 was a beef cattle operation. During 96 trap nights, a total of 1,568 Culicoides were collected, representing 24 species. Site 1 yielded the highest diversity, with 24 species, while Site 2 yielded 12 species. Overall, the most abundant species in light traps were C. stellifer Coquillett (44%), C. bergi Cochrane (18%), C. haematopotus Malloch (12%), and C. debilipalpis Lutz (11%). From substrate sampling, 8 species were identified. Culicoides haematopotus was the most abundant and was collected during each sampling period. Water chemistry values taken at the time of substrate collection were not significantly related to which Culicoides spp. emerged from a given substrate. Our results indicate a diverse community of Culicoides spp. in our study area, however, further work is needed to identify Culicoides species composition across a variety of landscapes in Appalachia and inform research on vector presence and associated vector disease dynamics.

122 A retrospective analysis of gestational length and its influencers for Bos taurus beef cows

Abstract The gestational length of cows is commonly set at 283 d. The objective of this study was to perform a retrospective analysis to determine gestational length and evaluate cow and calf parameters that influence gestational length of Bos taurus beef cows. A total of 10,037 reproductive records were used in this study. Data evaluated were obtained from reproductive records collected from Fall of 2011 through Spring of 2018, from 14 herds from the Virginia Department of Corrections beef cattle operations and the Virginia Tech Beef Center research herd. Cows used to measure gestation length were all pregnant to artificial insemination (AI) to ensure accurate breeding dates, and only pregnancies that resulted in a live birth were included in the dataset. Data were analyzed using the MIXED and CORR procedures of SAS. The average age of cows in this study was 5.5 ± 0.03 yr, with a minimum of 2 yr and a maximum of 18 yr of age. The average gestation length was 280.2 ± 0.05 d. The shortest and longest gestation lengths recorded were 253 d and 300 d, respectively. Gestation length was affected by calving season (P < 0.0001), with a shorter gestation period for Fall (279.1 ± 0.08 d) than Spring born calves (281.1 ± 0.07 d). Calf sex also had an impact on gestation length (P = 0.0002), where male calves were on average gestated almost a day longer (280.8 ± 0.07 d) than females (279.6 ± 0.07 d). To evaluate whether a correlation exists between gestation length and selected variables, Pearson correlation coefficients were calculated. Cow age (r = 0.2136; P < 0.0001), calf birth weight (r = 0.3834; P < 0.0001), calf weaning weight (r = 0.1438; P = 0.01) and calf adjusted weaning weights (r = 0.0253; P < 0.0001) were correlated with gestation length of beef cows. In conclusion, the average gestation length of Bos taurus beef cows was 280 d, which is shorter than the commonly used 283 d, and it was affected by calving season (Fall and Spring) and calf sex. Further, while correlations exist among gestation length, cow age and calf traits, these correlations were weak to moderate.

An updated meta-analysis of the anti-methanogenic effects of monensin in beef cattle.

Meta-analyses were performed to quantitatively summarize the effects of monensin on in vivo methane (CH4) production in beef cattle, and differentiate these outcomes according to dietary management, dose of monensin, and length of monensin supplementation. Data from 11 manuscripts describing 20 individual studies were used, and CH4 was converted to g/d when required. Studies were classified according to dose of monensin (mg/kg of diet dry matter), length of monensin supplementation prior to the last CH4 measurement, feeding management (ad libitum vs. limited-fed), and diet profile (high-forage or high-concentrate diets). Variance among studies were assessed using a χ² test of heterogeneity and calculated using I² statistics. The inclusion of monensin decreased (P < 0.01) CH4 production by 17.5g/d when all studies were analyzed together. A moderate (P < 0.01) heterogeneity (I² = 55%) was detected for CH4 production estimates between studies; thus, meta-analyses were performed within classes. The reduction in CH4 differed (P < 0.01) according to dose of monensin, as it decreased (P < 0.01) by 25.6g/d when the high recommended dose range was used (32 to 44mg/kg), and tended to decrease (P ≤ 0.07) by 9.7 and 13.5g/d when the moderate (≤31mg/kg) and above recommended (≥45mg/kg) doses were used, respectively. The reduction in CH4 also differed (P < 0.01) according to the length of monensin supplementation. Monensin decreased (P ≤ 0.05) CH4 production by 24.3g/d when supplemented for <15 d, by 15.4g/d when supplemented from 23 to 33 d, by 24.3g/d when supplemented from 52 to 79 d, and tended to decrease (P = 0.06) CH4 production by 3.21g/d when supplemented from 94 to 161 d. The reduction in CH4 did not differ (P = 0.37) according to diet profile, despite a 30% difference in reduction when monensin was added to high-forage (20.89g/d) compared with high-concentrate diets (14.6g/d). The reduction in CH4 tended to differ according to feeding management (P = 0.08), decreasing by 22.9g/d (P < 0.01) when monensin was added to diets offered ad libitum, and by 11.5g/d (P = 0.05) in limit-fed diets. Collectively, this study provides novel insights and further corroborates monensin as CH4 mitigation strategy in beef cattle operations. The most effective responses were observed during the first 79 d of monensin supplementation, and when monensin was included between 32 to 44mg/kg of diet, was added to high-forage diets, and added to diets fed ad libitum.

Solutions to the fertility equation in beef embryo recipients.

In beef cattle operations that conduct embryo transfer, the overall success depends on the pregnancy outcome that results from every pregnancy opportunity. In this review, we dissected the main components that determine if a recipient will sustain the pregnancy after embryo transfer up to calving. Specifically, we describe the effect of the uterus on its ability to provide a receptive environment for embryo development. We then discuss the capacity of the embryo to thrive after transfer, and especially the contribution of the sire to embryo fitness. Finally, we review the interaction between the uterus and the embryo as an integrated unit that defines the pregnancy.

Evolution over the last 40 years of the assisted reproductive technologies in cattle - the Brazilian perspective for embryo transfer and resynchronization programs (part II).

The productivity of the beef and dairy industries depends directly on the reproductive efficiency and genetic gain of the herd, which are directly associated with the appropriate use of Assisted Reproductive Technologies (ARTs). The objective of this review is to show from a Brazilian perspective the evolution over the last 40 years of ARTs related to ovulation resynchronization programs and embryo transfer in cattle. Despite significant improvements and high fertility obtained in timed artificial insemination (TAI) protocols (Sales et al., 2024 - Part I), the improvement of the use of in vitro-produced embryos, development of resynchronization programs, and the advance in Doppler ultrasonography (Doppler-US) for reproductive assessments of bovine females were the ARTs that presented the greatest relevance on reproductive effectiveness in cattle. In the last seven years, the embryo transfer (ET) technology using in vitro-produced (IVP) embryos took over the conventional ET of in vivo produced embryos after donor's superovulation. Also, procedures and pregnancy rates after ET of IVP embryos were improved in dairy and beef operations. The Doppler-US allows the identification of non-pregnant females at an early stage based on the evaluation of blood perfusion of the corpus luteum. Recent studies in beef and dairy cows indicate satisfactory accuracy when Doppler-US is used at 20-22 days after TAI. Consequently, super-early resynchronization programs have been developed and are being implemented in commercial programs, thereby facilitating earlier conception through the use of semen from superior bulls, providing genetic and economic improvements in herds. Likewise, the assessment of luteal function by Doppler-US allows the selection of embryo recipients with greater receptivity, and consequently may increase the effectiveness of timed ET programs.

Validation of a Bacteriophage Hide Application to Reduce STEC in the Lairage Area of Commercial Beef Cattle Operations.

Finalyse, a T4 bacteriophage, is a pre-harvest intervention that utilizes a combination of bacteriophages to reduce incoming Escherichia coli O157:H7 prevalence by destroying the bacteria on the hides of harvest-ready cattle entering commercial abattoirs. The objective of this study was to evaluate the efficacy of Finalyse, as a pre-harvest intervention, on the reduction in pathogens, specifically E. coli O157:H7, on the cattle hides and lairage environment to overall reduce incoming pathogen loads. Over 5 sampling events, a total of 300 composite hide samples were taken using 25 mL pre-hydrated Buffered Peptone Water (BPW) swabs, collected before and after the hide wash intervention, throughout the beginning, middle, and end of the production day (n = 10 swabs/sampling point/timepoint). A total of 171 boot swab samples were also simultaneously taken at the end of the production day by walking from the front to the back of the pen in a pre-determined 'Z' pattern to monitor the pen floor environment from 3 different locations in the lairage area. The prevalence of pathogens was analyzed using the BAX® System Real-Time PCR Assay. There were no significant reductions observed for Salmonella and/or any Shiga toxin-producing E. coli (STEC) on the hides after the bacteriophage application (p > 0.05). Escherichia coli O157:H7 and O111 hide prevalence was very low throughout the study; therefore, no further analysis was conducted. However, boot swab monitoring showed a significant reduction in E. coli O157:H7, O26, and O45 in the pen floor environment (p < 0.05). While using Finalyse as a pre-harvest intervention in the lairage areas of commercial beef processing facilities, this bacteriophage failed to reduce E. coli O157:H7 on the hides of beef cattle, as prevalence was low; however, some STECs were reduced in the lairage environment, where the bacteriophage was applied. Overall, an absolute conclusion was not formed on the effectiveness of Finalyse and its ability to reduce E. coli O157:H7 on the hides of beef cattle, as prevalence on the hides was low.