The use of beef cattle semen to breed dairy cows to produce calves (beef-on-dairy crosses) for beef production has greatly increased within the past five years. Beef–on–dairy crosses have become an important pillar of the beef industry and plays a key role in contributing to the U.S. beef demand. According to the National Association of Animal Breeders (NAAB), units of beef semen sales from 2017-2021 increased by 260%, largely to inseminate dairy cows to produce beef-on-dairy crosses. The 2016 National Beef Quality Audit Report estimated that 16.3% of fed cattle supply included dairy-influenced cattle. Beef-on-dairy calves have exhibited better feedlot performance, carcass quality and meat attributes compared to traditional male dairy calves (calf-fed Holsteins). Beef from beef-on-dairy cattle possess similar meat quality attributes (tenderness, juiciness and flavor) as beef from native beef cattle. The lifecycle of beef-on-dairy cattle, although varied among calf ranches, typically includes three stages: Stage 1 is from birth to weaning, approximately 75 days, with calves housed individually in hutches and fed milk or milk replacer with access to dry feed, Stage 2 is group housing in pens and typically fed a diet with varying proportions of roughage and grain, and Stage 3 is cattle are transported to a feedlot and fed a finishing diet before shipment to harvest. Because these cattle are fed a grain-based diet for an extended duration. Interest in determining fecal shedding during these three stages of their life cycle and prevalence of Salmonella enterica in lymph nodes at slaughter is an emerging area of research. There are no studies on the prevalence of Salmonella and its public health implications to food safety in beef-on-dairy cross cattle, which is especially important to investigate in the unique stages of production for these cattle. The objective of the study was to conduct a comprehensive analysis of feeding and management practices, including data on morbidity and mortality, from birth to harvest to determine their associations with the Salmonella prevalence in feces and lymph nodes. Salmonella prevalence in lymph nodes and fecal samples, collected from two stages, will be based on culture dependent methods.
The study sampled at several calf ranches in five U.S. states—Kansas, Texas, Colorado, Indiana, and Nebraska—over the course of one year. The calf ranches housed beef-on-dairy calves and growers. Fecal samples were collected randomly from the pen floors using sterile spoons and stored in sealed plastic bags before being transported to the lab. In addition to fecal samples, lymph nodes from calves and growers were collected from fresh mortalities. The lymph nodes were sealed in tubes and kept on ice before lab processing. In the laboratory, standard methods were used to isolate and characterize Salmonella in both fecal and lymph node samples. For the fecal samples, a small portion was added to a broth, incubated, and processed. Similarly, lymph nodes were surface-sterilized and homogenized before being processed using broth cultures. The presence of Salmonella was identified by streaking the cultures into specialized agar plates. The presumptive Salmonella colonies were further subjected to a slide agglutination test. Colonies that tested positive were confirmed via PCR. Relationships between state location and Salmonella prevalence were analyzed using chi-square tests. A logistic regression model was used to explore how the different production stages and states affected Salmonella prevalence.
Out of 529 fecal samples collected, 14.55% tested positive for Salmonella, with higher prevalence among growers (24.33%) compared to calves (7.26%). The prevalence varied significantly by location, with Texas having the highest incidence, especially among growers (62.1%), while states like Nebraska and Colorado showed much lower prevalence. Only 4% of lymph nodes samples tested positive for Salmonella. Statistical analysis revealed that both location and production stage significantly influenced Salmonella prevalence, with a strong interaction between these factors. In particular, Texas and Colorado showed elevated Salmonella prevalence during the grower stage. Feeding and management practices also played a role, with feeding whole grains reducing the odds of Salmonella prevalence. Overall, the study highlighted marked geographical variation in Salmonella prevalence, suggesting that factors like climate, management practices, and biosecurity measures significantly impacted the distribution of the pathogen. These findings underscore the need for tailored control strategies that account for regional differences to effectively manage Salmonella in cattle populations.
The significant variation in Salmonella prevalence by state and production stage underscores the need for region-specific management strategies. Sampled calves from Texas exhibited the highest prevalence, especially among growers, suggesting that warmer climates and certain management practices (one-time capacity of bottle calves and one-time capacity for post-weaned calves) may increase the risk of Salmonella in cattle. Understanding these regional differences can help producers implement targeted biosecurity measures, adjust feeding practices, and optimize antibiotic use to reduce the risk of infection. Additionally, the identification of specific management factors, such as feeding practices and milk timing, that influence Salmonella prevalence provides actionable insights for the industry. The cattle industry's adoption of tailored control strategies, informed by these findings, could not only reduce disease burden but also could enhance consumer confidence in beef products, contributing to overall sustainability and profitability. Moreover, the results emphasize the importance of continuous monitoring and adjusting management practices to ensure both animal welfare and public health.