Cow-calf Operations Research Articles

NAHMS 2021 Feedlot study


 The National Animal Health Monitoring System (NAHMS) con­ducts national studies on the health and health management of U.S. domestic livestock populations. In the NAHMS Feedlot 2021 study, for feedlots that placed cattle not born and raised on the operation slightly over half of cattle placed (51.1%) came direct­ly from a cow-calf operation or a stocker or backgrounder oper­ation, while 41.2% came from a sale barn. Of the cattle placed in 2020, 85.1% were placed with the intention of meeting no specif­ic marketing claims, 0.5% of cattle were placed to meet certified organic claims, 8.4% were placed to meet no or limited antibi­otic use claims, and 10.2% were placed to meet no hormone use claims. About three-fourths (73.1%) of feedlots used antibiotics in any form in 2020. Of these feedlots: 22.4% gave injectable an­tibiotics to cattle as a group; 67.6% gave injectable antibiotics to sick cattle; 42.8% gave antibiotics in feed; and 4.5% gave antibi­otics in water. Most feedlots (85.1%) used a veterinarian in 2020. About two-thirds of feedlots (64.2%) felt that on January 1, 2017, they had all the resources necessary to manage the Veterinary Feed Directive (VFD) rule change.

Effects of subclinical Theileria orientalis Ikeda genotype infection on average daily gain ratios and a satisfactory rating in the breeding soundness exam in bull test stations in Virginia

Theileria orientalis Ikeda genotype is a tick borne hemoprotozo­an that typically causes economic losses in dairy and beef cattle in Australia, New Zealand and Japan. Acute clinical infections from T. orientalis Ikeda include anemia, icterus, ill-thrift and death. The acute phase of the infection has been associated with decreased libido in dairy bulls, decreased live weight gain in beef bulls and increased mortality in naïve adults and calves. A sequela to acute infections within a herd is persistent sub­clinical infections, which have been associated with decreased mean daily gain in suckling beef calves. In late 2017, T. orienta­lis Ikeda was detected in beef cattle from multiple counties in Virginia and was associated with anemia, weakness, late term abortions and death. As of 2022, T. orientalis Ikeda has been identified in beef cattle in 31 of 95 Virginia counties. Beef pro­duction, typically in naturally bred cow-calf operations, is the second largest agricultural commodity in Virginia. Central bull testing programs for performance evaluation and marketing of beef bulls has existed for over 60 years in Virginia. T. orienta­lis Ikeda was first detected at the Southwest bull test station in 2020 when screened at conclusion of the test. The objective of this study was to determine if subclinical infection with T. ori­entalis Ikeda affected the average daily gain (ADG) ratios of all bulls on test and the achievement of a satisfactory rating of the breeding soundness exam (BSE) for senior bulls.

180 Assessment of Weaning and Backgrounding Management Practices Used by Alabama Cattle Producers

Abstract Weaning is one of the most critical and stressful stages of a beef calf’s life. Management strategies practiced during the post-weaning period can have a large impact on calf performance, quality, and economic viability. With the number of different practices that producers can utilize during these stages of production, it is important for Extension educators to understand which management strategies are most commonly used and the potential successes of those practices. In spring 2022, an online survey was conducted to examine beef calf weaning and backgrounding management practices used by Alabama cattle producers. The survey was distributed through Qualtrics software and contained 24 total questions. There were 214 responses received by the end of the survey deadline. A total of 94% of respondents considered their operation to be a cow-calf operation with 52% of respondents identifying as a commercial cow-calf operation. Most participants (46%) indicated they had a smaller size herd of 50 head or less. Almost one-half of respondents (47%) had a calving season in the fall, 23% had a winter calving season, and 19% had a spring calving season. There was an 11% response of producers not having a defined calving season. Participants were asked to describe their method of calf weaning and of the methods listed, 55% said they abruptly wean and 38% reported that they utilize fenceline weaning. Over one-half (61%) of producers indicated that they background or precondition their calves and another 25% stated that they do in some years, but not always. For respondents that do not background, market unpredictability is the main concern when choosing to not precondition calves. Producers who responded that they do background calves indicated that they wean for at least 60 days before sale. These respondents also followed other important management strategies such as a vaccination program (83%), castration (81%) and use of implants (37%). Methods for marketing backgrounded calves differed across respondents with 49% of survey respondents using local livestock auctions as one method of selling their calves and 13% of producers retaining ownership of their calves through the feedyard finishing phase. With these data, potential educational gaps for cow-calf operations, such as marketing knowledge and opportunities have been identified. Extension educators in Alabama will be able to use these data to create resources and programs centered around backgrounding cattle to improve overall understanding related to calf management post-weaning.

2 Challenges in Breeding and Genetics

Abstract Over the past 50 years tremendous advances were made in reproductive and genetic technologies that are available for beef cow-calf producers. In addition, extensive research has been done to establish the efficacy and economic advantages of adoption of such technologies. Nonetheless, adoption of reproductive and genetic technologies in beef cow-calf operations remain poor, especially when compared with dairy production. The USDA – National Animal Health Monitoring System (NAHMS) performs a survey of cow-calf management practices, with the latest survey performed in 2017. According to the NAHMS survey the majority (58.7%) of cow-calf operations in the U.S. do not have a defined breeding season, with 69.5% of operations in the southeast (SE) failing to adopt a defined breeding season. Reproductive technology adoption is poor, with only 37.5% of all operations utilizing at least one reproductive technology, with 78.1% of larger operations (>200 cows) utilizing at least one reproductive technology, compared with 30.4% of small operations (< 50 cows). Semen evaluation was the leading technology with 19.7% overall adoption, followed by palpation for pregnancy with 19.3%, artificial insemination with 11.6% and estrus synchronization with only 7.3%. The SE is behind the rest of the country on adoption of technology with only 22.1% of the operations adopting at least one reproductive technology, with the North-Central region leading the country with 58.3% of operations adopting at least one reproductive technology. Nationally, most heifers and nearly all cows were exposed only to bulls (76.8 and 92.9 %, respectively), with a greater percentage of heifers (15.1 %) than cows (5.5 %) being artificially inseminated and followed by natural service breeding. A total of 90.7% of all beef females were exposed to natural service only, clearly demonstrating that artificial insemination is not widely adopted by U.S. beef operations. Veterinary consultation also remains below expectations, with only 52.8% of operations consulting a veterinarian every year, and disease diagnosis and treatment being the most common reason (37.3%). The East U.S. remains behind the rest of the country with only 41% of beef operations consulting a veterinarian on a yearly basis. When making decisions about breeding and genetics, 21.5% of producers rated Extension services as slightly useful and 22.6% rated Veterinarians as very useful, with most (23.6) producers consulting other producers. Adoption of reproductive and genetic technologies remains below expectations for the entire U.S. with the East and SE regions lagging behind the rest of the country. Perhaps the fact that the vast majority (84.2% in the U.S., and 89.9% in East) of beef cow-calf producers list their operations as a supplemental source of income remains the most difficult challenge to increase adoption of technologies.

74 Ovulatory Follicle and Corpus Luteum Development ofBos Taurus Cows Under Nutrient Restriction

Abstract Establishment and maintenance of pregnancy is a central concern to the cattle industry, as it strongly impacts efficiency and profitability of beef cow-calf operations. The objective of this study was to determine if nutrient restriction impacts ovulatory follicle size and corpus luteum (CL) volume of Angus cows enrolled in estrous synchronization. A total of 26 Angus cows were housed at the Virginia Tech – Shenandoah Valley Agricultural Research and Education Center (SVAREC) equipped with a Calan gate system for individual animal intake, stratified by body weight (BW) and randomly assigned to one of two treatments: 1) a maintenance diet that provided 100% of nutrient requirements (MTN; n = 13) or 2) a diet providing 70% of nutrient requirements (REST; n = 13). Nutrient requirements were calculated and adjusted weekly based on BW using the 2016 NRC version of Beef Cattle Nutrient Requirements Model Software. Cattle underwent an acclimation period of4 days and were exposed to nutritional treatments for 30 days before estrous synchronization. Body weight was measured daily using an automated scale, and a conventional livestock scale at the beginning and end of the experiment. Cows were synchronized using a 7-day CO-synch + CIDR protocol beginning on day -10. An estrus alert patch was applied on day -3 and read on day 0 to assess expression of estrus. Ultrasonography of the ovaries was performed at each event of the estrous synchronization protocol. Data were analyzed using the MIXED procedure of SAS. Initial BW was similar between treatments (P = 0.07; 600 ± 32 kg), but MTN compared with REST cows had greater final BW (P < 0.01; 687 ± 24 and 556 ± 27 kg, respectively) and greater average daily gain (1.35 ± 0.18 and -0.72 ± 0.21 kg/d, respectively). Estrus expression was numerically greater (P = 0.185) MTN (84.62%) than REST (61.54%) cows. Diameter of the largest follicle was similar (P = 0.851) between treatments at the CIDR insertion (12.6 ± 0.6 mm) and CIDR removal (12.9 ± 0.4 mm), but were greater for MTN than REST cows at 60 hours after CIDR removal (14.01 ± 0.6 and 12.37 ± 0.5 mm, respectively). Volume of CL was similar (P > 0.01) at 5 (3211 ±13 mm3) and 7 (5280.3 ± 212 mm3) days after ovulation. In conclusion, nutrient restriction during estrous synchronization negatively affects diameter of the ovulatory follicle, but it did not affect subsequent CL volume in mature Angus cows.

58 Reproductive Performance of Beef Cow-Calf Operations in VA with a Fall or Spring Breeding Season

Abstract Establishing two breeding seasons (Fall and Spring) is a common practice in the southeast USA, including VA. We performed a retrospective analysis of data from 11 years, 22 breeding seasons and 14 locations in VA to compare reproductive performance between Fall and Spring breeding seasons. A total of 30,191 breeding records (24,032 for cows and 6,259 for heifers) from the VA Department of Corrections beef cattle operations were analyzed. Every year, each cow and heifer were enrolled in estrous synchronization protocols and received fixed-time artificial insemination (TAI) and were then exposed to natural service bulls for an approximately 65-day breeding season. Fall breeding occurred from November until January, and Spring breeding from March until May. Body condition score (BCS; 1 to 9, scale) was determined at the initiation of the TAI protocol. Estrus detection before TAI was performed by scoring an estrus detection aid prior to insemination. Pregnancy rate was determined by ultrasonography between days 55-65 post-TAI and 40-50 after the end of the breeding season. Data were analyzed using the SAS GLIMMIX procedure for binary data and MIXED procedure for continuous data. Average BCS was greater (P < 0.001) for Fall cattle than Spring cattle (5.7 ± 0.02 and 5.1 ± 0.02, respectively); however, days postpartum at TAI was similar between Fall and Spring (P = 0.645; 77.8 and 76.2 ± 0.5 days, respectively). Pregnancy rate to TAI differed (P < 0.0001) between Fall and Spring, 53.0 ± 0.03% and 48.6 ± 0.05%, respectively. Interestingly, estrus expression was greater (P < 0.001) for Spring than Fall (58.4 ± 0.05% and 50.4 ± 0.06%, respectively) and also was greater for cows that became pregnant to TAI compared with cows that failed to become pregnant to TAI (P < 0.001; 61.7 ± 0.03% and 46.9 ± 0.04%, respectively). End of breeding season pregnancy rate differed between season and was greater for Fall than Spring (P < 0.001; 90.7 ± 0.04% and 87.9 ± 0.04%, respectively). Calf birth weight was similar between seasons (P = 0.478; 34.1 and 34.4 ± 0.09 kg, for Fall and Spring, respectively). However, 205-day adjusted weaning weights differed (P < 0.001) between seasons with Spring calves being heavier than Fall calves (246.3 ± 0.12 kg and 227.8 ± 0.21 kg, respectively). In conclusion, for beef cow-calf operations in VA reproductive performance is enhanced for Fall breeding seasons; however, weaning weights were greater for calves born during the Spring seasons.

13 Stockpiling Bahiagrass to Extend the Grazing Season and decrease Winter Supplementation Costs for South Alabama Cattle Producers

Abstract Stockpiling forage is a management practice that can be used to decrease the cost of winter cow supplementation and is defined as the process of accumulating forage late in a growing season for grazing at a later date. The purpose of this study was to explore the effectiveness of bahiagrass as a potential stockpiled forage in lower Alabama by developing a better understanding of its forage accumulation, nutritive value and persistent characteristics during the stockpiling period (6 to 10 weeks). A small-plot stockpiling trial was conducted at three locations in south Alabama (Troy, Headland, and Goodway). Nine, 6.5 m x 2.0 m plots were cut to a 7.5 cm stubble height with a buffer of 0.9 m between plots at each location beginning on September 16, 2021. Nitrogen fertilization strategy was the main plot [0 N fertilizer, split N application (33.6 kg N/ha at initiation and again 30 d later), or 67.2 kg N/ha; 3 replications/treatment; N source = urea (46-0-0)]. Stockpiling period length was the split-plot (6, 8 or 10 weeks of forage accumulation; n = 9 subplots/treatment). Response variables were measured including forage mass and nutritive value at 6, 8 and 10 weeks, and nutritive value of standing forage 30 days after the stockpiling period. Data were analyzed using the PROC MIXED procedure of SAS 9.3. As the accumulation period length increased, average forage mass increased across all treatments with 1,312.6 kg DM/ha at 6 weeks, 1,270.1 kg DM/ha at 8 weeks and 1,585.9 kg DM/ha at 10 weeks. With respect to the fertilization treatments, the split N application (1,621.8 kg DM/ha) and 67.2 kg N/ha fertilization strategies (1,606.1 kg DM/ha) did not differ in forage accumulation but were greater (P < 0.05) than bahiagrass not receiving N fertilizer (1,377.6 kg DM/ha). For nutritive value, nitrogen application strategy impacted bahiagrass crude protein (CP), with both the split N application (14%) and 67.2 kg N/ha (13.8%) treatments having a greater CP (P < 0.05) than the 0 N fertilization approach (11.7%). Average total digestible nutrients across stockpiling periods were 62.5%. Year one results study indicate that bahiagrass may support forage production and nutritive value for cow-calf operations wanting to extend grazing into the fall and early winter months in the Southeast US. Based on year one results for forage mass measured at 6, 8 and 10 weeks, stockpiled bahiagrass could provide an estimated 45 to 55 days of grazing depending on mature cow weight, pasture stocking strategy and accumulation period length.

Quantifying biodiversity impacts of livestock using life‐cycle perspectives

Biodiversity impacts are rarely included in systems analyses of livestock production. We piloted two approaches toward quantifying biodiversity impacts, pressure‐state‐response (PSR) and potential species loss (PSL), at a cow–calf operation in Florida for which extensive environmental data were available. Using these approaches, we compared livestock production on two vegetation types, semi‐native pasture (SNP) and improved pasture (IMP), and we found fewer deleterious effects on biodiversity associated with SNP (characterized by low stocking rates and no fertilizer) than with IMP, as evidenced by a lower PSL and greater biotic integrity under PSR. Both approaches agreed in the direction of the outcome, but we argue that, when possible, they should be applied complementarily to inform both absolute and per‐unit product biodiversity impacts of livestock production. This research demonstrates how to incorporate biodiversity into life‐cycle perspectives of livestock sustainability assessments when data availability varies, supporting the expansion of multi‐metric, holistic evaluations that are absent from most livestock system analyses.

Forest Transition and Fuzzy Environments in Neoliberal Mexico

Although deforestation remains a continuing threat to both the natural world and its resident human populations, a countervailing land cover dynamic has been observed in many nations. This process of landscape turnaround, the so-called forest transition, holds the potential of regenerating ecosystem services by sparing land from agricultural activities and abandoning it to forest succession. Here, we present a case study of a long-term process of forest transition that is ongoing in the Patzcuaro watershed of the state of Michoacán, Mexico. The research to be discussed comprises a remote sensing analysis designed to (1) capture the land cover impacts of a multidecadal process of trade liberalization (1996–2018); (2) ascertain the role that land tenure plays in land use dynamics affecting forest cover, and (3) resolve forest cover types into native forest, secondary vegetation, and “commodity” covers of fruit trees, in this case, avocado. Mexico presents a useful case for addressing these three design elements. Our analysis, undertaken for both private property and collective modes of resource management in five communities, reveals a forest transition annualized at 20 ha-yr−1, or a gain of eight percent for the period. This translates into a relative rate of forest transition of 0.39%-yr−1 which is three times faster than what is occurring in the temperate biome on a national scale (0.07%-yr−1). Most of the forest transition is occurring on private holdings and stems from field abandonment as farming systems intensify production with avocado plantations and cow–calf operations. As this study demonstrates, forest transitions are not occurring ubiquitously across nations but instead are highly localized occurrences driven by a myriad of distal and proximate factors involving disparate sets of stakeholders. Consequently, policy makers who are keen to expand forest transitions to fulfill their national climate action commitments under the Paris Agreement must first promote research into the complexity of landscapes and drivers of land change at regional and local scales.

To Retain or Not to Retain: A Heifer Dilemma

Replacing females in the beef cow herd plays a pivotal role in a sustainable and profitable cow-calf operation. Analyzing the cost of raising replacements versus purchasing them can help make informed decisions. If retaining replacements, cattle producers must consider both the costs and potential returns associated with raising and integrating these heifers into the breeding herd. This article discusses some key financial considerations.

Prevalence of antimicrobial resistance in fecal Escherichia coli and Enterococcus spp. isolates from beef cow-calf operations in northern California and associations with farm practices.

Antimicrobials are necessary for the treatment of bacterial infections in animals, but increased antimicrobial resistance (AMR) is becoming a concern for veterinarians and livestock producers. This cross-sectional study was conducted on cow-calf operations in northern California to assess prevalence of AMR in Escherichia coli and Enterococcus spp. shed in feces of beef cattle of different life stages, breeds, and past antimicrobial exposures and to evaluate if any significant factors could be identified that are associated with AMR status of the isolates. A total of 244 E. coli and 238 Enterococcus isolates were obtained from cow and calf fecal samples, tested for susceptibility to 19 antimicrobials, and classified as resistant or non-susceptible to the antimicrobials for which breakpoints were available. For E. coli, percent of resistant isolates by antimicrobial were as follows: ampicillin 100% (244/244), sulfadimethoxine 25.4% (62/244), trimethoprim-sulfamethoxazole 4.9% (12/244), and ceftiofur 0.4% (1/244) while percent of non-susceptible isolates by antimicrobial were: tetracycline 13.1% (32/244), and florfenicol 19.3% (47/244). For Enterococcus spp., percent of resistant isolates by antimicrobial were as follows: ampicillin 0.4% (1/238) while percent of non-susceptible isolates by antimicrobial were tetracycline 12.6% (30/238) and penicillin 1.7% (4/238). No animal level or farm level management practices, including antimicrobial exposures, were significantly associated with differences in isolate resistant or non-susceptible status for either E. coli or Enterococcus isolates. This is contrary to the suggestion that administration of antibiotics is solely responsible for development of AMR in exposed bacteria and demonstrates that there are other factors involved, either not captured in this study or not currently well understood. In addition, the overall use of antimicrobials in this cow-calf study was lower than other sectors of the livestock industry. Limited information is available on cow-calf AMR from fecal bacteria, and the results of this study serve as a reference for future studies to support a better understanding and estimation of drivers and trends for AMR in cow-calf operations.

Bacterial culture and susceptibility of samples taken from septic foot lesions of adult beef cattle.

Lameness is an economically important and common disease of cattle, and foot disease is the most common cause of lameness in cattle. Limited data is available regarding lameness in cow-calf operations. Describe the bacteria most commonly isolated from septic lesions of the feet of adult beef cattle and the antimicrobial susceptibility patterns of the isolated bacteria. Fifty-four adult cattle from cow-calf operations and diagnosed with a sole abscess or distal interphalangeal joint sepsis were enrolled. Prospective observational study. Abscess fluid from a convenience sample of clinical cases was cultured. Isolated bacteria were identified using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry or 16s rRNA gene sequencing. Antimicrobial susceptibility profiling was performed on isolates when a bacterial species was identified from ≥5 samples. Fifty of the 54 samples were polymicrobial. Trueperella pyogenes (22/54), Streptococcus uberis (16/54), and Bacteroides pyogenes (14/54) were the most commonly isolated bacteria. Eighty-one of 96 tested isolates were resistant to at least 1 antimicrobial; multidrug resistance was identified in 37/96 isolates. Oxytetracycline (50/96), tylosin (40/96), and florfenicol (37/96) resistance was commonly identified. Resistance to ceftiofur (5/96) was rare. Septic processes of the foot in these adult beef cattle frequently were polymicrobial. Most of the isolated bacteria were resistant to at least 1 antimicrobial with over one-third being multidrug resistant. Although simple sole abscesses do not require antimicrobial treatment, deep septic processes of the foot often are treated with antimicrobials. Culture and susceptibility of deep septic lesions may guide judicious antimicrobial usage.

Assessing pregnancy outcomes in cow-calf operations after administration of modified-live or killed virus vaccinations at the initiation of synchronization for fixed-time AI

The objective of this study was to compare the reproductive outcomes (artificial insemination [AI] pregnancy rates, season pregnancy rates, AI pregnancy losses) and calf traits (birth and weaning weights) after vaccination of suckled beef cows against bovine herpesvirus 1 and bovine viral diarrhea virus using commercially-available modified-live virus (MLV) or killed virus (KV) vaccine at the initiation of a fixed-time AI program. Previously-vaccinated cows (n = 2138) on 14 farms throughout Virginia were enrolled in the study during the Fall 2017 and Spring 2018 breeding seasons. Animals received a single vaccination injection at 10 d pre-breeding, corresponding with time of CIDR insertion at initiation of the 7-d CO-Synch + CIDR synchronization protocol. Cows were inseminated at a fixed time (60–66 h after removal of the CIDR insert) and subsequently turned out with bulls approximately 1 wk after insemination for a natural service. Cows treated with the MLV vaccine had greater AI pregnancy rates than cows treated with the KV vaccine during the fall (P = 0.008; 54% vs. 46%, respectively), but not during the spring breeding season (P = 0.62; 48 vs. 49%). Season pregnancy rates were greater (P = 0.01) in the fall (95–96%) than in the spring breeding season (89–90%), but were not affected by vaccine treatment (P = 0.49) or treatment by season (P = 0.30) interactions. Percentage of AI pregnancy losses was not affected by season (P = 0.85), vaccine treatment (P = 0.83), or treatment by season interactions (P = 0.68). The number of cycles it took for cows to become pregnant by natural service differed by season (P = 0.006) but not treatment (P = 0.87) or treatment by season interaction (P = 0.997). Cows treated with the MLV vaccine gave birth earlier in the calving season (8.36 ± 0.6 d) than those treated with the KV vaccine (10.31 ± 0.6 d; P = 0.02). There was a main effect of season on birth weights (P = 0.008), weaning weights (P < 0.001), and ADG at weaning (P < 0.001), but no effects of treatment (P ≥ 0.26) or treatment by season interaction (P ≥ 0.10) on any of these parameters. Overall, this study demonstrated that the administration of an MLV vaccine at 10 d before fixed-time AI did not have any adverse effects on pregnancy or calf outcomes compared with KV vaccine administration.

Does grazing winter cereal rye in Iowa, USA, make it profitable?

Unproven economic returns at the farm level are a major barrier to large-scale adoption of cover crops. The objective of this study was to evaluate the short-run private net returns to producers implementing a cereal rye (Secale cereale L.) cover crop preceding the no-till corn (Zea mays L.) phase of a US Midwest corn–soybean (Glycine max [L.] Merr.) rotation in an integrated crop and cow–calf operation. We used experimental agronomic data from six location-years in Iowa to estimate private net returns to cereal rye across alternative scenarios in a partial budget framework. Net returns in the absence of grazing averaged −$123.74 ha−1 and were negative for 82.2% of the treatments, while net returns under partial grazing averaged −$15.24 ha−1 and were negative for 54.8% of the treatments. Early-broadcast cereal rye produced higher biomass and larger net cost savings in the livestock enterprise than late-drilled cereal rye, but it also resulted in higher corn yield penalties. In the no-grazing scenario, net losses for early-broadcast cereal rye were $165.97 ha−1 larger, on average, than for late-drilled cereal rye. Our findings should raise awareness about the low probability of obtaining positive annual private net returns to cereal rye in Iowa in the absence of sizable targeted financial incentives, and inform the policy discussion on the cost-effectiveness of government-sponsored conservation programs.

Assisted Reproductive Technologies (ART) and genome editing to support a sustainable livestock.

This article provides an overview of assisted reproductive technologies (ART) and genome engineering to improve livestock production systems for the contribution of global sustainability. Most ruminant production systems are conducted on grassland conditions, as is the case of South American countries that are leaders in meat and milk production worldwide with a well-established grass-feed livestock. These systems have many strengths from an environmental perspective and consumer preferences but requires certain improvements to enhance resource efficiency. Reproductive performance is one of the main challenges particularly in cow-calf operations that usually are conducted under adverse conditions and thus ART can make a great contribution. Fixed-time artificial insemination is applied in South America in large scale programs as 20 to 30% of cows receive this technology every year in each country, with greater calving rate and significant herd genetic gain occurred in this region. Sexed semen has also been increasingly implemented, enhancing resource efficiency by a) obtaining desired female replacement and improving animal welfare by avoiding newborn male sacrifice in dairy industry, or b) alternatively producing male calves for beef industry. In vitro embryo production has been massively applied, with this region showing the greatest number of embryos produced worldwide leading to significant improvement in herd genetics and productivity. Although the contribution of these technologies is considerable, further improvements will be required for a significant livestock transformation and novel biotechnologies such as genome editing are already available. Through the CRISPR/Cas-based system it is possible to enhance food yield and quality, avoid animal welfare concerns, overcome animal health threats, and control pests and invasive species harming food production. In summary, a significant enhancement in livestock productivity and resource efficiency can be made through reproductive technologies and genome editing, improving at the same time profitability for farmers, and global food security and sustainability.

Maternal Behavior in Beef Cattle: The Physiology, Assessment and Future Directions-A Review.

Bovine maternal behavior is known to be influenced by a variety of factors including hormonal mediation, breed, age, parity, host genetics and general management practices. Following centuries of varying levels of domestication processes, the behavior of the bovine cow has altered from that of her original wild ungulate ancestors, although many maternal instincts have remained unchanged. The influence of maternal behavior on calf health and performance is of interest to cow-calf beef production operations, as in most instances, the cow is solely responsible for rearing the calf until weaning. However, investigating the magnitude of this influence is challenging, in part because objective measurement of behavioral traits is difficult, particularly in extensive settings. In recent years, while a number of remote monitoring devices have been developed that afford opportunities for objective measurement of behavioral traits in livestock, characterization of physiological mechanisms that underlie superior maternal behavior, including identification of potential biomarkers remains elusive in cattle. Hormonal profiles during the periparturient period have been shown to influence behavioral patterns in both current and future generations in other mammalian species and may provide insights into the physiology of bovine maternal behavior. Therefore, the aim of this review is to describe general characteristics of bovine maternal behavior and the factors known to influence it, including hormonal drivers, through which cross-reference to other species is made. Current methods of measuring and assessing behavior that may also be applicable to most production settings have also been reviewed. At present, there is no known hormonal assay that can be used to measure and/or reliably predict bovine maternal behavior post-calving or across generations. Being able to objectively assess superior maternal behavior, whether that be through remote monitoring, hormonal profiling or indirectly through measuring calf performance will be beneficial to livestock industries in the future.

Beef nutrition 101: What a veterinarian needs to know to work with a nutritionist

The disunion between veterinarians and nutritionists sup­porting the cattle industry is not new, albeit there are plentiful opportunities to improve. Successful operations need the per­spective and technical knowledge of both professionals to op­timize productivity. The need for improvement is magnified by the inability of the cattle industry to make strides in improving mortality rates that is most likely a reflection of management x health x nutrition interactions. Opportunity for veterinarians to support producers nutritionally is most prevalent among cattle segments not traditionally supported by trained nutri­tionists. These include cow-calf operations and confinement feeding operations with less than 500 head capacity. To facili­tate nutritional conversations with the nutritionists, a basic un­derstanding of the 6 classes of nutrients is critical. These class­es include water, carbohydrates, lipids, protein, vitamins and minerals. A base level understanding of each nutrient paired with a broad idea of applied concepts associated with feeding will make for constructive two-sided conversations about nutri­tion between technical professionals.

Investigating effective testing strategies for the control of Johne's disease in western Canadian cow-calf herds using an agent-based simulation model.

Johne's disease is an insidious infectious disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Johne's disease can have important implications for animal welfare and risks causing economic losses in affected herds due to reduced productivity, premature culling and replacement, and veterinary costs. Despite the limited accuracy of diagnostic tools, testing and culling is the primary option for controlling Johne's disease in beef herds. However, evidence to inform specific test and cull strategies is lacking. In this study, a stochastic, continuous-time agent-based model was developed to investigate Johne's disease and potential control options in a typical western Canadian cow-calf herd. The objective of this study was to compare different testing and culling scenarios that included varying the testing method and frequency as well as the number and risk profile of animals targeted for testing using the model. The relative effectiveness of each testing scenario was determined by the simulated prevalence of cattle shedding MAP after a 10-year testing period. A second objective was to compare the direct testing costs of each scenario to identify least-cost options that are the most effective at reducing within-herd disease prevalence. Whole herd testing with individual PCR at frequencies of 6 or 12 months were the most effective options for reducing disease prevalence. Scenarios that were also effective at reducing prevalence but with the lowest total testing costs included testing the whole herd with individual PCR every 24 months and testing the whole herd with pooled PCR every 12 months. The most effective method with the lowest annual testing cost per unit of prevalence reduction was individual PCR on the whole herd every 24 months. Individual PCR testing only cows that had not already been tested 4 times also ranked well when considering both final estimated prevalence at 10 years and cost per unit of gain. A more in-depth economic analysis is needed to compare the cost of testing to the cost of disease, taking into account costs of culling, replacements and impacts on calf crops, and to determine if testing is an economically attractive option for commercial cow-calf operations.

Seminal and vagino-uterine microbiome and their individual and interactive effects on cattle fertility.

Reproductive failure is a major economical drain on cow-calf operations across the globe. It can occur in both males and females and stem from prenatal and postnatal influences. Therefore, the cattle industry has been making efforts to improve fertility and the pregnancy rate in cattle herds as an attempt to maintain sustainability and profitability of cattle production. Despite the advancements made in genetic selection, nutrition, and the implementation of various reproductive technologies, fertility rates have not significantly improved in the past 50 years. This signifies a missing factor or factors in current reproductive management practices that influence successful fertilization and pregnancy. Emerging lines of evidence derived from human and other animals including cattle suggest that the microbial continuum along the male and female reproductive tracts are associated with male and female fertility-that is, fertilization, implantation, and pregnancy success-highlighting the potential for harnessing the male and female reproductive microbiome to improve fertility in cattle. The objective of this narrative review is to provide an overview of the recent studies on the bovine seminal and vagino-uterine microbiome and discuss individual and interactive roles of these microbial communities in defining cattle fertility.

Effects of age and pasture type on the concentration and prevalence of tetracycline and macrolide resistant Enterococcus species in beef cow-calf production system

Enterococci are a normal flora of the gastrointestinal tracts of humans and animals. Enterococci can also cause life-threatening nosocomial infections. Antimicrobial-resistant Enterococcus species have been reported in the feedlot and dairy cattle productions and in meat and milk products, suggesting their foodborne importance. Cow-calf operations represent a significant segment in the beef production system by producing weaned calves. Weaned calves are brought into the feedlot to be finished for meat, and culled cows are also slaughtered for beef, primarily for ground beef products. Infection dynamics in the cow-calf operation can contribute to meat contamination. This study evaluated the effects of age and wheat grazing on the concentration and prevalence of a macrolide antibiotic erythromycin (ERYr) and tetracycline (TETr) resistant enterococci, associated resistance genes and species distribution in a cow-calf production system. In 2017 and 2018, 32 Angus breed cow-calf pairs were randomly assigned to feed on tall fescue or wheat pasture in two independent field experiments. During the grazing experiments of 2-3 weeks, fecal samples were collected weekly and cultured to enumerate, isolate and identify ERYr, TETr, and generic enterococci, using media supplemented with erythromycin, tetracycline or non-supplemented media, respectively. The two main species frequently associated with human illnesses, Enterococcus faecium and E. faecalis, were widely distributed in the cow-calf groups. Generic and TETr- enterococci were prevalent (96-100% prevalence) and abundant (3.2-4.9 log10 CFU/g) in the cow-calf population; however, ERYr enterococci were enumerable by direct plating only from a single cow despite being detected in at least 40% of the fecal samples after enrichment, showing their low abundance. TET- and ERY-resistance were mainly conferred by tet(M) and erm(B), respectively. Wheat grazing reduced the concentration of TETr enterococci and modified enterococcal species and resistance gene distributions. Hence, it is necessary to further investigate wheat grazing in cow-calf production as a potential strategy to mitigate antimicrobial resistance.