Beef Production Systems Research Articles

Induction of puberty vs. induction of ovulation using steroid hormones in beef heifers: a comprehensive review.

This review elucidates the physiological and endocrinological processes intrinsic to puberty and ovulation induction protocols in Bos indicus and Bos taurus beef heifers. Puberty is a complex physiological event involving gonadotropic and metabolic changes that lead to sexual maturity, first ovulation, and regular reproductive cycles, enabling females to reproduce. Exposure to progesterone-based hormonal protocols, with or without additional hormones, can reduce the age at first ovulation and improve sexual maturity through stimuli in the hypothalamus-pituitary-gonadal (HPG) axis and uterine development. However, inducing puberty differs from inducing ovulation, as it does not ensure the heifer will continue cycling or be ready to establish and maintain pregnancy after hormonal exposure. Regardless of the pharmacological basis, studies consistently report that beef heifers that had a corpus luteum (CL) prior to the timed-artificial insemination (TAI) protocol, have greater expression of estrus in response to synchronization and greater pregnancy per AI compared to heifers without a CL. The combination of P4 and E2 significantly impacts uterine development, increasing reproductive efficiency. Exposure to P4 causes a positive effect on inducing ovulation. However, studies indicate that the addition of E2 esters at the time of P4 device removal increases the ovulation rate. In general, the studies showed that fertility varied according to the type of the ovulation induction protocol used, but with inconsistent results. Although ovulation induction protocols are strategic tools to accelerate sexual maturity, a holistic view of the entire system is extremely important, combining integration with genetics and nutrition to enhance the reproductive outcomes of beef heifers. Future research is needed to understand and refine these protocols, driving the efficiency of beef cattle production systems.

Sustainable intensification of grass-based beef production systems in alpine regions: How to increase economic efficiency while preserving biodiversity?

CONTEXTBeef production on grasslands has multiple positive impacts. In addition to the production of high-quality protein, marginal lands in particular enable high biodiversity and landscape quality. However, this type of production is perceived as less economical than more intensive meat production systems. OBJECTIVEThe aim of the study is to develop recommendations on how different grass-based production systems can be economically improved without endangering biodiversity. METHODSThirty-five suckler cow farms supplying into two different brand programmes (Natura-Veal: slaughter age at five months; Natura-Beef: slaughter age at 10 months) were grouped into four production systems across two production sites in Switzerland: Natura-Veal, mountain region, extensive (VMount); Natura-Beef, mountain region (BMount); Natura-Veal, hilly region, intensive (VHill) and Natura-Beef, lowlands (BLowla). On the farms, beef production was analysed in detail on the basis of technical production data as well as full cost accounting. The farms were grouped into one model farm (farm type) per production system. On each model farm, optimisation options were simulated and checked for practicability with farmer participation. The optimisation focused primarily on improving cow efficiency via the sale of more slaughter animals per cow, through lower animal losses, higher fertility or the additional purchase of calves suckled by a nurse cow. RESULTS AND CONCLUSIONSDescriptive statistics showed significant positive correlations between stocking rate and land productivity and significant negative correlations between stocking rate/land productivity and the share of biodiversity areas (SBA), confirming previous findings. These relationships were also reflected in the production site of the farms, as mountain farms with lower productivity had a significantly higher SBA, while farms in areas with better grass growth had fewer biodiversity areas but higher productivity. Accordingly, the optimisation options were adapted to the production site under the constraint of a constant stocking rate. In favourable forage-growing areas, further intensification via improving cow efficiency by buying foreign calves led to significant improvements in profitability (VHill and BLowla). In mountain areas, the optimisation potential is lower. Site-adapted, i.e., small-framed and robust, cow types lead to better cow efficiency, which also contributes to good profitability in extensive production with a high biodiversity share, although this is strongly determined by national direct payments (VMount and BMount). Both income and biodiversity can be optimised if cow efficiency is increased and production systems are adapted to the site as closely as possible. SIGNIFICANCEThe study shows practicable recommendations for sustainable intensification in grass-based meat production systems in the current discussion on maintaining or increasing biodiversity in agriculture.

Choice of metrics matters—Future scenarios on milk and beef production in Norway using an LCA approach

The consumption of dairy and beef products is expected to increase globally in the future, and at the same time, food must be produced in a more sustainable way, including reduced greenhouse gas (GHG) emissions, avoided feed-food competition, and reduced biodiversity loss. The purpose of the study was to a) provide an overall life cycle assessment (LCA) of these impacts for various future milk and beef production systems in Norway and b) determine how the choice of metrics for climate change affects the results. System boundaries were from cradle to farm gate and the temporal boundary was 2017 with future scenarios for 2040. The actual production and consumption in Norway in 2017 was used as a baseline (BL), and the sustainability of future Norwegian domestic production of milk and beef was assessed through three scenarios for 2040: 1) a trend yield scenario (TrendY) based on an expected increase in milk yield following the present trend, 2) a high yield scenario (HighY) with higher increase in the milk yield per cow per year than the trend, and 3) a low yield scenario (LowY) where the milk yield per cow per year was adjusted for covering the domestic demand for beef solely from dual-purpose production and no domestic specialized beef production. The beef production per dual-purpose cow was kept constant and the remaining domestic demand in scenario 1 and 2 were covered by specialized beef production. Climate change was assessed using both a GWP100 and a GWP* approach. The HighY scenario had the lowest impact on climate change using GWP100, but when taking the different behaviors of short- and long-term climate pollutants into account (GWP*), the ranking of the future scenarios changed and favored LowY. The potential biodiversity loss was lower for the LowY scenario because the proportion of concentrates in the dairy cow ration was decreased due to lower milk yield. Similarly, the feed-food competition was lower (land use ratio < 1) for the LowY. The results of our study suggest that the choice of metric for GWP and time frame highly affects the results and conclusions and strategies for climate smart and sustainable livestock production should therefore be made with caution.

Grass-based finishing of early- and late-maturing breed bulls within suckler beef systems: Performance, profitability, greenhouse gas emissions and feed-food competition

Demand for beef is increasing but concerns about the environmental impact of ruminant-protein production and food security are also increasing. Animal performance, profitability, greenhouse gas (GHG) emissions and feed-food competition within spring-calving suckler grass-based systems in which the males, progeny of either early- (EM) or late-maturing (LM) breed sires, were finished from pasture-alone or pasture-plus-concentrate supplementation, at 19.5 months-of-age, were evaluated. Sixty yearling bulls, previously offered grass silage ad libitum and supplementary concentrates during a first winter ‘store’ period, were assigned within breed type (EM or LM) to a pasture-finishing strategy of grass only (G-G) or grass + 3.2 kg dry matter of a barley-based concentrate daily (G-GC). Bulls rotationally grazed Lolium perenne-based swards over a 192 day grazing season. Concentrates were offered to G-GC treatments for the final 95 days following which all animals were slaughtered. The experimental data produced were used to populate a whole-farm systems economic and environmental model to determine beef output, profit, GHG emissions and feed-food competition of spring-calving suckler calf-to-beef systems. There were no finishing strategy × breed type interactions. Supplementation increased slaughter weight (+37 kg), carcass weight (+27 kg), carcass fat score (+1.1 units, 15-point scale), and resulted in more yellow subcutaneous fat. The LM bulls were heavier at slaughter (+65 kg), had a heavier carcass (+45 kg), greater kill-out proportion (+14 g/kg), a greater lean meat proportion in the carcass (+35 g/kg), superior carcass conformation score (+1.4 units, 15-point scale), lower carcass fat score (-1.2 units), and more yellow subcutaneous fat than EM bulls. Compared to G-GC suckler calf-to-beef systems, G-G systems had lower beef output, were less profitable, had higher GHG emission intensities (kg CO2 eq) per kg live- (10.2 v. 10.1), carcass- (18.6 v. 18.1) and meat- weight (26.1 v. 25.5), but superior human-edible protein (HEP) and energy efficiencies. The LM-sired systems were more profitable, had lower GHG emission intensities, and superior HEP and energy efficiency than EM systems. The HEP efficiency ratios exceeded 1.0 (i.e. were net producers of protein) for the G-G treatments and ranged from 0.9 to 1.0 for the G-GC treatments, when offered the ‘control’ barley-soyabean meal based concentrate: alternatively, using by-product concentrate feedstuffs increased the HEP ratios to 3.9 or greater. In conclusion, the existence of synergies and trade-offs between sustainability metrics makes the selection of a beef production system that optimises all performance metrics difficult.

Genome-wide association study for reproduction traits in Colombian Creole Blanco Orejinegro cattle.

The profitability of the beef cattle production system relies heavily on reproductive traits. Unfortunately, certain traits, such as age at first calving (AFC), calving interval (CI), and gestation length (GL), can pose challenges in traditional breeding programs because of their low heritability (0.01-0.12) and sex-limited characteristics. Another important aspect is the conservation of the genetic resources of animals adapted to the Colombian regions, which implies the preservation and rational use of the creole breeds in the country market. Therefore, this study aimed to identify genomic regions in the creole cattle breed Blanco Orejinegro (BON) that influence the reproductive traits in females. The dataset comprised 439 animals and 118,116 single-nucleotide polymorphisms' (SNPs) markers. The GS3 program was used to identify the SNP effects employing the BAYES Cπ methodology. The number of SNPs with effect for AFC was 25, 1527 for CI, and 23 for GL. Some of the genes found associated with reproductive and growth traits as well as immune response and environmental adaptation ECE1, EPH, EPHB2, SMARCAL1, IGFBP5, IGFBP2, FCGRT, EGFR, MUL1, PINK1, STPG1, CNGB1, TGFB1, OXTR, IL22RA1, MYOM3, OXTR, CNR2, HIVEP3, CTPS1, CXCL8, FCGRT, MREG, TMEM169, PECR, and MC1R. Our results evidenced a high contribution of the genetic architecture of the Colombian creole cattle breed Blanco Orejinegro that may impact should be included in implementing genetic improvement and conservation programs.

89 Physiological Mechanisms Related to Feed Efficiency of Beef Cattle

Abstract Improving feed efficiency is essential for the sustainability of the US beef production system. However, achieving this goal is challenging due to various factors such as diet types, genetics, environments, and industry segmentation. To address these difficulties, it is critical to have a fundamental understanding of what contributes to efficient nutrient utilization and feed resources, which can guide future genetic selection and production practices. Despite recent progress, the regulation of feed intake in growing and finishing cattle remains incompletely understood, hindering advances in feed efficiency. Recent research has aimed to advance the hepatic oxidation theory to growing and finishing cattle fed high-concentrate diets and explored the control of appetite by gut peptide hormones. Other factors contributing to variation in feed efficiency include nutrient metabolism and hormonal control of metabolism. Previous research is limited by a lack of in-depth analysis of metabolism due to the inability to time sample collection relative to feed consumption and account for correlations among metabolites. The role of fat metabolism in the rumen has been associated with epithelial inflammation, while inflammation of the gut has been identified as a contributing factor to inefficiencies in nutrient utilization. However, there is still a need to further understand the role of fatty acid metabolism in the induction of inflammation. An issue that limits the further understanding of efficiency is that a wide variety of feedstuffs are utilized by the industry and small changes in the nutrient composition of a diet can have large impacts on efficiency. Therefore, it is important to consider the utilization efficiency of specific nutrients rather than general feed efficiency. Nitrogen utilization efficiency is becoming increasingly important due to the significant economic and environmental ramifications of inefficiencies in nitrogen utilization. There is growing evidence that precision feeding of protein to match requirements can reduce nitrogen excretion without compromising growth and efficiency. In conclusion, a better understanding of the underlying biology contributing to nutrient utilization is crucial for improving feed utilization efficiency in the US beef production system, which will enhance the sustainability of the US beef production system.

PSIX-17 Preliminary Assessment of Preweaning Growth Performance of Dexter and Mashona X Dexter Calves

Abstract Non-traditional cattle breeds are often considered by managers for niche beef production and marketing systems. Some of these alternative breeds are small-framed and thus desired by small-farm operators but have received little research attention because they do not fit traditional commodity beef production systems. Very few of these small breeds also offer heat tolerance. This project was designed to evaluate preweaning performance of straightbred (n = 76) and F1 crossbred calves (n = 81) produced by mature Dexter cows across three years and two Tennessee State University research farms. Spring-born calves were sired by Dexter (n = 7; DD) and Mashona bulls (n = 6; MD) in single-sire, natural service breeding groups following 60-d breeding seasons. Breed of sire was balanced across cow age and farm locations. Calves were weighed within 24-h of birth, at 4 months (125 d of age) of age, and at weaning (227 d of age). Calves were not creep-fed and bull calves were not castrated until after weaning. No cases of dystocia were observed as a result of crossbreeding. Calf performance traits were evaluated using MIXED models of SAS. Fixed effects included sire breed, sex, farm location, and the interaction of sire breed and sex. Random effect terms were production year and sire nested within sire breed. For all the traits evaluated, models were consistent in that the sire breed x calf sex interaction was not significant (P &amp;gt; 0.1), whereas sire breed and calf sex were consistently important (P &amp;lt; 0.01) sources of variation. Bull calves had greater weight and ADG values than heifer calves from birth to weaning. Mean body weight was heavier for MD than DD calves at birth (28.4 ± 0.8 vs. 23.9 ± 0.7 kg), at 4 months of age (120.6 ± 9.7 vs. 96.7 ± 9.6 kg), and at weaning (154 ± 8.6 vs. 124.4 ± 8.6 kg). The MD calves had greater ADG than DD calves from birth to 4 months of age (715.8 ± 36.1 vs. 599.1 ± 36 g/d), from 4 months of age to weaning (334 ± 44.3 vs. 256.8 ± 44 g/d), and from birth to weaning (547 ± 35.7 vs. 447.1 ± 35.7 g/d). Mean 205-d adjusted body weight was heavier for MD than DD (140.2 ± 7.6 vs. 114.7 ± 7.6 kg). Preliminary results indicated that crossbreeding with Mashona bulls significantly increased preweaning growth of calves produced by Dexter cows, while the F1 calves maintained small statute. The spring-born MD F1 calves likely benefited from heat tolerance provided by the Mashona influence and heterosis generated by crossbreeding.

PSIV-9 Describing the Consumption of Chlortetracycline-Containing Supplement Offered Free-Choice to Commercial Beef Cows on Pasture

Abstract Extensive beef cattle production systems depend on forage as the predominant nutrient source. However, mineral requirements are not always met solely through forage consumption. To maintain optimum animal productivity, beef cattle producers must provide mineral supplementation and free-choice supplements are most common. Free-choice supplement intake by grazing cattle is highly variable and is dictated by season, individual animal preference, supplement palatability and other factors. Variation in supplement intake is problematic for delivering medication such as chlortetracycline (CTC), which is aimed to mitigate the risk of bovine anaplasmosis in beef herds. Research investigating the relationship between individual animal attributes and supplement consumption in extensive settings is limited. Recently, adoption of technology such as a portable, self-contained individual feeding unit (SmartFeed; C-Lock Inc.) into supplementation programs has facilitated unprecedented data collection in grazing cattle. The study objectives were to describe the consumption patterns of a granular CTC-containing supplement and to evaluate the factors contributing to consumption variability by gestating cows on pasture. A total of 103 nonlactating, pregnant, crossbred cows were assigned to this experiment on d -28 and allocated to 1 of 3 pastures equipped with a SmartFeed unit to record individual supplement intake. Cows were offered dried distillers grains for 27 d of acclimation to the units (mean intake of 0.29 kg of supplement/cow daily; 74% of cows) before transition to a commercially available granular mineral supplement containing CTC for 46 d. Supplement was formulated such that a 630 kg cow must consume 113 g/d to receive the label CTC dose (1.1 mg/kg). Cow intake and unit visit frequency data were analyzed using a general linear model (PROC GLM) and differences evaluated using Least Squared Means. The runs test for serial randomness was used to evaluate clustering of feeding and non-feeding events. Feeding and non-feeding events during the 46-d observation period were not randomly distributed (P &amp;lt; 0.01), and the mean number of consecutive days a cow did or did not consume mineral supplement were 1.8 and 5.6 days, respectively. As cow age increased, visits to the feeding unit decreased and total supplement consumption also decreased (P &amp;lt; 0.01). According to supplement label instructions, each cow was expected to consume 5.2 kg of supplement in total over 46 d to receive the total recommended 32.2 g CTC dose. Mean supplement consumption was 40.5 g· cow-1· d-1, providing 0.25 g CTC· cow-1· d-1, and only 1.9% (2/103 cows) consumed enough supplement to receive the recommended dose. Collectively, results indicate that providing a granular free-choice supplement containing CTC is not an effective method of ensuring cows consume an adequate amount of supplement to receive CTC at the label-directed dose and frequency.

42 Environmental Impacts of Improving Forage Use Efficiency in Beef Cattle

Abstract As population grows, so does the demand for high quality protein, and beef ranks among the greatest in terms of nutrient density per caloric intake. Maintaining the sustainability of beef cattle production systems has been one of the main priorities of researchers worldwide. Because the global demand for beef production is projected to increase, the contribution of beef production to greenhouse gas emissions will increase. One of the most useful tools available to researchers to reduce the carbon footprint of beef production is the selection for more feed efficient cattle. The use of residual feed intake as a criterion for selection has been demonstrated to have potential impact on the carbon footprint of beef systems, by reducing emissions intensity. Greenhouse gas emissions intensity involves the carbon footprint per unit of product (e.g., beef or milk produced) and it is the main metric to be considered when assessing the environmental impact of production systems. Great advances have been made in terms of improving the digestibility of forage resources. However, because of the impact that fiber digestion has on enteric methane production, these improvements in forage digestibility need to be considered in the context of emissions intensity. Advances in forage breeding such as the incorporation of brown mid-rib traits, have undoubtedly led to improvements in fiber digestion and animal productivity. Fewer studies have examined the impact of this technology on greenhouse gas emissions. A great opportunity exists to begin assessing the impact of new technologies such as the use or fibrolytic enzymes and prebiotics, with the potential of enhancing fiber digestibility. Global beef production will continue to rely heavily on high-forage diets for at least some segments of the production system. Assessing the impact of new technologies to enhance fiber digestion in the context of greenhouse gas emissions per unit of product will be essential to maintain the sustainability of beef production systems.

161 A System Dynamics Model of Bovine Respiratory Disease Epidemiology and Prevention Strategies in an Integrated Beef Production System

Abstract Bovine respiratory disease (BRD) is a complex multifactorial disease that results in more than $1 billion in economic losses for the United States beef cattle industry, accounting for approximately 30% of the total antimicrobial use (AMU) in food animal production systems. The prevalence and production losses due to BRD vary significantly between different production systems, and is influenced by the host, pathogen, and environmental risk factors. These multiple risk factors together have a cumulative effect and will increase the prevalence of the disease if no preventive strategies are implemented in the system. Moreover, the increased AMU to treat BRD results in antimicrobial resistance, further complicating the issue. A linear, event-based solution to address such a complex problem will fail to consider the feedback loops and time delays in the system and may cause unintended consequences that might make the problem even more complex. Hence, we propose a more comprehensive system dynamic model to simulate an integrated beef production system with respect to BRD and predict the dynamic behavior of the system under different preventive strategies currently available to the beef industry. Our conceptual model accounts for host risk factors (auxiliary variables in the model) like age, nutritional status, daily weight gain, prior exposure to pathogens, and genetics. The environmental risk factors such as air quality, transportation, temperature humidity index, overcrowding, and source of animals were also included in the model. The various preventative strategies to reduce the incidence of BRD, including vaccination, biosecurity, adequate colostrum, and nutrition, were also added to the model. The key outcome variables considered were net profitability and AMU. The model simulates multiple scenarios by leveraging the auxiliary variables and can provide information about the system’s net profitability and total AMU. The model explains the interconnected effect of various risk factors associated with BRD in multiple complex scenarios and helps understand the combined effect of adopting various preventive strategies and host-environmental factors in controlling BRD. The initial result from our dynamic model suggests that using a combination of preventive measures and avoiding the selected host-environmental risk factors can minimize AMU while improving profit. The long-term goal of our modeling effort is to enable the beef system stakeholders to make informed decisions and strategies to mitigate the impact of BRD, thereby contributing to improved profitability. Through a systems-thinking approach, our model can contribute to addressing the challenges in BRD management currently faced by the US-based integrated beef production systems.

415 Awardee Talk: Foraging for Collaboration: Beef-Forage System Strengths Unite Research and Extension Efforts in the Asas Southern Section

Abstract The American Society of Animal Science Southern Section has a rich history of collaboration and hosts an annual professional development meeting for ASAS members. The Section meeting includes scientific presentations, academic quadrathlon, undergraduate and graduate student competitions, symposia, and networking opportunities for its members. The Section has used strategic collaborations to foster multi-state projects and initiatives. One of the key discipline focus areas of the Section is forage-based beef production systems. The Section holds two symposia focused on research, Extension, and industry topics related to beef cattle management. The Bill E. Kunkle Interdisciplinary Symposium was started in 2014 to honor the impact of Dr. Kunkle, University of Florida, and fosters multi-disciplinary communication of beef cattle science. The SERA 41 Symposium is part of the regional NIMSS project focus-group on improving production efficiency of the beef cow herd in the Southeast US. The NIMSS group works collectively to create partnerships and common goal-oriented projects across the Southern Section states. The section is also home to the Randel Physiology Lecture series which was formed in 2016 to highlight Dr. Ron Randel’s commitment to the Southern Section physiology section, and to promote high-quality science for the next generation of physiologists and endocrinologists. More than 25 peer-reviewed publications and several webinars have resulted from these symposia and invited lectureships. This creates a referenceable resource for scientists on emerging topics and identifies potential priority areas of focus for scientists within the Southern region. Another highlight of the Section is the collaborative work of the Extension committee. The Extension committee collaboratively fosters Extension program development across the Southern region. The committee developed a regional webinar series in 2015 for regional training of Extension agents on livestock and forage management topics. Subsequent in-service training courses have emerged through both virtual and in-person delivery. Training is primarily focused on forage-based livestock management systems. Through these opportunities, the Southern Section has remained a gathering point for professional engagement and should continue to evolve to meet the needs of animal scientists.

PSVIII-A-3 Activity Behavior and Growth Performance During Summer of Grazing Beef Heifers with Divergent Residual Feed Intake

Abstract Concerns about sustainability of beef production systems generate an interest in improved feed efficiency; however, there is a lack of research evaluating cattle activity budgets in response to the interaction between residual feed intake (RFI) and environment while grazing. Lying behavior and activity can provide insight into how animals interact with the environment and serve as an indicator of animal comfort. Furthermore, exposure to severe environmental factors can change behavioral patterns and impair animal performance. Therefore, this study evaluated activity budgets and performance in grazing beef heifers with divergent residual feed intake (RFI) during the summer season. From July to August 2022, forty-four crossbred beef heifers [358 ± 4.78 kg of body weight (BW); approximately 14 months of age] previously tested for RFI in drylot and classified as more (n = 21; LOW-RFI = -0.9 ± 0.70) or less feed efficient (n = 23; HIGH-RFI = 1.3 ± 1.00) were grazed at 2.72 AUM/ha over 7 wk in Alberta, Canada. IceRoboticTM pedometers (IceQube+) were used to track 24-hr heifer activity budgets [n = 43; total steps and lying and standing time (min/d and min/h) for 36 d]. Full BW was obtained on d -1, 0, 14, 28, 42, and 43 while fat scan on rib and rump were measured by ultrasound (Aloka 500 V diagnostic real-time) on d 0 and 42. Air temperature, relative humidity, wind speed and solar radiation information were collected within 1 km of the grazed area to calculate the Comprehensive Climate Index (CCI). Based on CCI, weather conditions were considered to impose risk to cause mild, moderate, severe, and extreme stress for 5, 18, 7, and 1 days, respectively. For BW, average daily gain (ADG), rump (RF) and rib fat (RiF), the data were analyzed as a completely randomized design, while behavior activity included repeated measures. An RFI x day interaction was observed for lying and standing times (P = 0.02) and total steps (P = 0.001). Greater number of steps (P &amp;lt; 0.01) and an increased standing time (P &amp;lt; 0.01) were observed in HIGH-RFI heifers. RFI × hour interaction was observed for lying and standing times (P = 0.006), where LOW-RFI heifers spent more time lying at 10:00 am (P &amp;lt; 0.01). Furthermore, LOW-RFI heifers had decreased number of steps per hour throughout the study (P = 0.03; 178 vs 191 ± 4.1). No effects were observed for ADG, BW, RF, and RiF (P &amp;gt; 0.24). In summary, selected activity behaviors differed between beef heifers with divergent residual feed intake while summer grazing. Further studies are needed to investigate the effects of continuous changes in weather conditions to better understand the environmental impacts on animal behavior while selecting for more efficient beef cattle.

21 Intentionally Induced Barrier Dysfunction Causes Inflammation, Decreases Growth, and Alters Carcass Characteristics of Feedlot Cattle

Abstract There are a variety of acute and chronic psychological and physical stressors associated with management practices used in beef production systems. Primary challenges in feedlot cattle include heat stress, acute and subacute acidosis, weaning, transportation, feed deprivation/restriction, and social mixing/crowding. These stressors disturb the homeostatic state of the host and microbiome and cause acute or chronic inflammation resulting in damage to the gastrointestinal tract (GIT) epithelial barrier that leaves the animal vulnerable to enteric pathogens and toxins. A breach of the small intestinal barrier (leaky gut) allows unwanted pathogens and toxins to infiltrate into blood, causing infection, depressed feed intake, and diverts nutritional resources away from anabolic processes. We have demonstrated that intentionally inducing GIT inflammation in feedlot cattle with aspirin, which is known to cause mucosal injury and increase GIT barrier dysfunction, provides a model system to better understand the metabolic cost of leaky gut in grain-fed feedlot cattle. Indeed, aspirin increased leakage of chromium-EDTA into urine, raised serum concentrations of lipopolysaccharide binding protein (LBP), decreased growth by 4.5 to 8.5%, and re-partitioned carcass components from lean tissue (rib-eye area) into fat. Thus, the chronic inflammatory effects of leaky gut have the potential to create a significant economic loss. Our work also shows that in-feed administration of monensin and tylosin have offered a solution to the non-specific immune response observed in grain-fed cattle by increasing jejunal villus height to crypt depth ratio, diminishing leaky gut, and decreasing serum LBP. Finally, we have observed that molasses based liquid supplements increase ruminal butyrate concentration, resulting in improved gut barrier function, decreased serum inflammatory markers, and greater DMI and ADG in newly received feedlot cattle fed a 30% roughage diet.

Discovering Genomic Regions Associated with Reproductive Traits and Frame Score in Mexican Simmental and Simbrah Cattle Using Individual SNP and Haplotype Markers.

Reproductive efficiency stands as a critical determinant of profitability within beef production systems. The incorporation of molecular markers can expedite advancements in reproductive performance. While the use of SNPs in association analysis is prevalent, approaches centered on haplotypes can offer a more comprehensive insight. The study used registered Simmental and Simbrah cattle genotyped with the GGP Bovine 150 k panel. Phenotypes included scrotal circumference (SC), heifer fertility (HF), stayability (STAY), and frame score (FS). After quality control, 105,129 autosomal SNPs from 967 animals were used. Haplotype blocks were defined based on linkage disequilibrium. Comparison between haplotypes and SNPs for reproductive traits and FS was conducted using Bayesian and frequentist models. 23, 13, 7, and 2 SNPs exhibited associations with FS, SC, HF, and STAY, respectively. In addition, seven, eight, seven, and one haplotypes displayed associations with FS, SC, HF, and STAY, respectively. Within these delineated genomic segments, potential candidate genes were associated.

Association of Residual Feed Intake to Metrics of Tanganyika Shorthorn Zebu Cattle in Maswa and Misungwi Districts, Tanzania

Increasing competition for feed resources and greenhouse gases pollution have been compelling beef production systems to operate at higher feed utilization. These challenges imply the need to breed cattle for Residual Feed Intake (RFI) to lower feeding costs and enteric methane production per output. To explore relevant indicator traits of RFI, this study investigated the association of RFI to Tanganyika Shorthorn Zebu (TSZ) cattle metrics from the Misungwi and Maswa Districts of Tanzania, where Tarime and Sukuma ecotypes are common. A correlation study involving the fattening of twenty-eight TSZ bulls was conducted at Tanzania Livestock Research Institute -Mabuki. From the animals' body weight and feeding data, regression of daily feed intake on average daily gain and metabolic body weight was analyzed to estimate the animals' RFI. Subsequently, the correlation of RFI to metrics of belly, horn, hip, dewlap and body length was investigated. Residual Feed Intake and Belly Length (BeL) were highly positively correlated, while RFI and Dewlap Depth (DD) were moderately positively correlated. The results indicated prospects for using BeL and DD as indicator traits for RFI. Extensive studies are recommended to analyze the correlation of RFI to hump depth, ear length, muzzle circumference and kidney fat.

Influence of animal production systems on the presence of pathogenic strains of Escherichia coli in the bovine production chain

Among the main pathogens involved in food outbreaks worldwide is diarrheagenic Escherichia coli (DEC). Cattle are considered natural reservoirs of DEC, and, during the slaughter stages, they can be a source of contamination for the carcass and final product. The objective of this work was to evaluate the influence of beef cattle production systems in Southeast Brazil, in the presence of diarrheagenic strains of Escherichia coli. A total of 485 samples were collected at the following points: post-bleeding (A), post-evisceration (B), post-final washing (C), meat cuts (D), bovine feces (F), surfaces (S), feces human (H) and wastewater (AR), from a cattle slaughterhouse, analyzing animals from two production systems: intensive and extensive. The samples were characterized in terms of pathotypes, phylogroups, and serogroups and analyzed using the chi-square test (p < 0.05). 126 samples were positive for E. coli, with points F (100%) and H (80%) being the points with the highest positivity. Only at point F was DEC identified (n = 35), with 28% of the animals in the intensive system and 38% in the extensive system positive for STEC, and 4% of the animals in the extensive system positive for EIEC, with no statistical difference between the production systems. Regarding phylogroups, B1 was the most detected in both systems, with 24% positivity in the intensive system and 68% in the extensive system. Serogroups O113 and O104 were detected, both in 4% of animals raised in an intensive system and in 6% of those in an extensive system. In view of the results, even with the identification of STEC and EIEC in the animals' feces, there was no difference between the rearing systems, with regard to pathotypes, phylogroups, and serogroups.

Ag Lenders Offer Insight on Conditions for Nebraska Livestock Producers

In 2017, the University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources (IANR) and Nebraska Extension made a commitment to implement a multidisciplinary Beef Systems Initiative (BSI) to develop and support implementation of beef production systems in Nebraska. In addition to the BSI, a parallel project funded by the Foundation for Food and Agriculture Research (FFAR) implemented a study of the best practices for incorporating beef cattle onto cropping systems while improving ecosystem services to ensure sustainability. As a component of the FFAR project, an agricultural lenders panel was formed to provide input and feedback to UNL researchers on the financial considerations for producers implementing new or expanding existing operations. The lenders panel met for the first time in 2019.

Mitigation of greenhouse gas emissions in pasture-based dairy-beef production systems

CONTEXTAgriculture and food systems contribute significantly to climate change. Greenhouse gas (GHG) emissions intensity from beef production are high when compared to other livestock production systems and, therefore, mitigation of these emissions is urgently required. In many countries dairy-beef is making a large and growing contribution to total beef output thereby reducing net emissions given the lower emissions intensity of beef originating from the dairy herd when compared to specialized beef-cow systems. GHG emissions from dairy-beef systems can be further reduced by adopting best practice and mitigation technologies. OBJECTIVESThe objectives of this study were to (1) evaluate a range of management practices to reduce GHG emissions for pasture-based beef cattle production systems, (2) model the individual and combined impacts of these management practices on GHG emissions from dairy-beef systems, and (3) identify any trade-offs between GHG emissions mitigation, farm profitability, food security and land use. METHODSA farm level bioeconomic systems model was modified to evaluate spring-born, steer production systems finishing cattle at differing slaughter ages and from contrasting forage-based finishing diets (grazed grass or grass silage, each supplemented with concentrates). Mitigation measures included earlier slaughter age, optimal slurry management, urease inhibitors for nitrogen (N) fertilizers, replacing cereals with ‘by-products’ in concentrate feed rations and incorporating clover in grassland pastures. RESULTS AND CONCLUSIONSCombining mitigation strategies reduced dairy-beef systems GHG emissions intensity by an average of 21%. Incorporating clover in grassland pastures was found to be the most profitable stand-alone mitigation strategy increasing net margin by an average of 18%. Substituting by-products for barley in a concentrate ration converted all systems into net producers of human edible protein; otherwise, steer systems finishing at pasture during the third grazing season were the only net producers of human-edible protein. However, finishing at pasture during the third grazing season increased GHG emissions per animal and per kilogram of beef carcass. SIGNIFICANCEWithin a grass-based dairy-beef system, such as that modelled in this study, a number of complementary GHG emissions mitigation strategies can be implemented, without making substantive changes to the production system, while simultaneously improving farm profitability.

Genomic Characterization of Listeria innocua Isolates Recovered from Cattle Farms, Beef Abattoirs, and Retail Outlets in Gauteng Province, South Africa.

Whole-genome sequencing (WGS) was used for the genomic characterization of one hundred and ten strains of Listeria innocua (L. innocua) isolated from twenty-three cattle farms, eight beef abattoirs, and forty-eight retail outlets in Gauteng province, South Africa. In silico multilocus sequence typing (MLST) was used to identify the isolates' sequence types (STs). BLAST-based analyses were used to identify antimicrobial and virulence genes. The study also linked the detection of the genes to the origin (industries and types of samples) of the L. innocua isolates. The study detected 14 STs, 13 resistance genes, and 23 virulence genes. Of the 14 STs detected, ST637 (26.4%), ST448 (20%), 537 (13.6%), and 1085 (12.7%) were predominant, and the frequency varied significantly (p < 0.05). All 110 isolates of L. innocua were carriers of one or more antimicrobial resistance genes, with resistance genes lin (100%), fosX (100%), and tet(M) (30%) being the most frequently detected (p < 0.05). Of the 23 virulence genes recognized, 13 (clpC, clpE, clpP, hbp1, svpA, hbp2, iap/cwhA, lap, lpeA, lplA1, lspA, oatA, pdgA, and prsA2) were found in all 110 isolates of L. innocua. Overall, diversity and significant differences were detected in the frequencies of STs, resistance, and virulence genes according to the origins (source and sample type) of the L. innocua isolates. This, being the first genomic characterization of L. innocua recovered from the three levels/industries (farm, abattoir, and retail) of the beef production system in South Africa, provides data on the organism's distribution and potential food safety implications.

Comparison of multiple international metrics for benchmarking antibiotic usage (ABU) using UK beef and sheep data.

Accurate surveillance of livestock antibiotic usage (ABU) at the farm level is an increasingly important part of national antibiotic stewardship initiatives. Numerous ABU indicators or metrics have been developed in Europe and North America but the comparability of these metrics is poorly understood. For policymakers, understanding the relationship between metrics is important when considering the risks posed by ABU and how to regulate them, at the national level, and regulate international trade access in livestock products between countries who use different ABU metrics. To quantify the patterns of ABU among beef (cattle) and lamb (sheep) production systems. To explore ABU variation between farm types across seven ABU metrics developed in Europe and North America using a common dataset of sheep and beef farms' antibiotic purchases from the UK. A dataset of >16 200 antibiotic sales events to 686 farm enterprises of different types underwent quantitative analysis. Correlation matrixes were generated for seven international ABU metrics. ABU was significantly higher among calf-rearers. Across all farm types, tetracyclines and β-lactams were the predominant groups by mass, but represent a similar dose equivalent to macrolides across most farm types. Good agreement (>0.9) was observed between metrics. Reliable metrics to accurately benchmark farms are crucial for maintaining confidence of farmers in the fairness of any surveillance system, especially when the ranking of any given system may be linked to financial subsidies or penalties and also when negotiating import and export access for livestock products between countries.