Bovine Science with BCI

BCI Cattle Chat
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Listen to veterinary professionals from the Beef Cattle Institute at Kansas State University talk about a variety of topics within cattle health, nutrition, reproduction, and science. New episodes of Bovine Science with BCI are posted each Monday.

  1. 2d ago

    Do Vaccines Affect Bull Fertility? Evaluating Breeding Soundness After Modified Live and Killed Vaccines

    This episode examines a 2025 study that investigated whether modified-live or killed viral vaccines influence bull breeding soundness exam (BSE) results. The research addressed a common practical question among producers and veterinarians who are concerned that vaccination before breeding season might negatively affect fertility. Researchers randomly assigned mature bulls to receive either a modified-live or killed vaccine and then evaluated semen quality and breeding soundness multiple times over a full spermatogenesis cycle. The study found no statistically significant differences between vaccine types for key fertility measures such as sperm morphology and motility. These findings suggest that neither vaccine type caused major detrimental effects on reproductive performance in the mature bulls that were tested. However, the discussion highlights an important limitation: the study included only 11 bulls, making it difficult to detect smaller but potentially meaningful differences between treatments. The authors and hosts note that while some bulls consistently passed breeding soundness exams and others consistently performed poorly, these differences appeared to reflect individual animal variation rather than vaccine effects. The episode also raises questions about whether results would be similar in yearling bulls, which may respond differently than mature animals. Overall, the study provides reassuring evidence that vaccinating mature bulls with either modified-live or killed viral vaccines does not appear to cause major fertility problems. At the same time, the discussion emphasizes that additional research with larger numbers of bulls is needed to rule out smaller effects and strengthen confidence in the conclusions.

  2. Aug 24

    Rethinking Vitamin A in Beef Cattle: Why Calves May Be Deficient Despite Green Grass

    This episode explores the role of vitamin A in beef cow-calf systems and examines why some calves develop low vitamin A levels and respiratory disease even while grazing alongside cows on green pasture. The discussion highlights that vitamin A nutrition is more complex than simply having access to lush forage, because cattle primarily consume beta-carotene from grass, which must be converted into usable vitamin A by the body. A major takeaway is the importance of colostrum as the primary source of vitamin A for newborn calves. Because very little vitamin A is transferred across the placenta, calves are born with limited reserves and depend heavily on colostrum intake during their first hours of life. Research cited in the review shows that delays in colostrum consumption can negatively affect vitamin A status for weeks after birth. The discussion also challenges long-standing assumptions about vitamin A requirements. Current beef cattle recommendations are largely based on research conducted decades ago, despite major changes in cattle genetics and productivity over time. Recent studies suggest that supplementation levels commonly considered adequate may not be sufficient to maintain optimal vitamin A status in modern cows or their calves. One particularly striking finding is that even when cows received vitamin A supplementation at nearly three times traditional recommended levels, about 20% of calves still failed to achieve adequate vitamin A status. The authors suggest that late gestation nutrition deserves greater attention because maternal vitamin A status strongly influences the amount transferred through colostrum. Overall, the episode emphasizes that vitamin A management remains an unresolved area in beef production and may play a larger role in calf health and disease resistance than previously recognized.

  3. Aug 17

    Can Coronavirus Vaccination Reduce Pre-Weaning Respiratory Disease in Beef Calves?

    This episode reviews a 2026 Canadian study that evaluated whether vaccinating beef calves against bovine coronavirus could reduce pre-weaning respiratory disease in a commercial cow-calf herd with a history of respiratory problems. The researchers compared vaccinated and non-vaccinated calves under real-world ranch conditions, making the findings especially relevant for producers facing similar challenges. Results showed that vaccinated calves had lower odds of requiring treatment for respiratory disease before turnout, and overall disease rates tended to be lower in vaccinated groups. The study also included an economic analysis that suggested vaccination provided a financial advantage of approximately $10 per calf through reduced treatment costs, lower mortality, and improved performance. Interestingly, one of the strongest factors associated with disease risk was not vaccination status but the calf’s birth cycle, with calves born during certain calving periods experiencing significantly different disease outcomes. The discussion highlights several strengths of the research, particularly that it was conducted in a commercial herd rather than a controlled challenge trial, providing valuable insight into how vaccines perform under field conditions. However, the hosts also note limitations, including questions about experimental independence, blinding, and the use of a coronavirus vaccine in a manner different from its labeled route of administration. A key takeaway is that while coronavirus vaccination may offer another tool for reducing pre-weaning respiratory disease, it should not be viewed as a complete solution. The larger lesson is that herd management systems, calving patterns, and other underlying risk factors may play an even greater role in disease occurrence than any individual vaccine. Ultimately, the episode encourages producers to combine disease-prevention tools with a broader systems-based approach when addressing respiratory disease in cow-calf herds.

  4. Aug 10

    A Deadly Holding Pen: Poisoning Causes Sudden Loss of 14 Heifers

    This case study examines a tragic incident in which 14 open heifers died within hours of being separated from a larger group following pregnancy testing. The heifers had been placed in a familiar holding pasture with a functioning water source and secure fencing, leading managers to initially believe the environment was safe. When all 14 animals were found dead later that day, investigators quickly ruled out infectious disease and focused on acute toxic causes due to the rapid onset and 100% mortality rate. Potential causes considered included nitrate toxicity, cyanide poisoning, urea exposure, toxic plants, and other fast-acting toxins. Necropsies revealed few significant lesions, a common finding in animals that die rapidly from certain toxic exposures. Diagnostic testing of ocular fluid showed highly elevated nitrate levels, providing strong evidence of nitrate poisoning. Further investigation of the holding area uncovered several nitrate-accumulating plants, including pigweed, kochia, and sorghum-type grasses, all containing nitrate concentrations high enough to cause acute death. Environmental conditions and plant stress likely contributed to dangerous nitrate accumulation, while the hungry heifers rapidly consumed the available vegetation after being placed in the pen. The discussion highlights that facilities used safely for years can become hazardous when weather patterns, forage conditions, or management circumstances change. A key takeaway is to carefully evaluate holding pens for potentially toxic weeds, especially during late summer, and avoid turning hungry cattle into unfamiliar areas with questionable forage. Providing supplemental hay before and during confinement may be one of the simplest and most effective strategies for preventing similar losses.

  5. Aug 3

    The Mystery Eye Disease Outbreak: Investigating a Point-Source Event in Stocker Cattle

    This case study follows the investigation of a puzzling eye disease outbreak affecting approximately 10% of a group of 1,200 stocker cattle shortly after processing and placement on pasture. The affected animals developed severe eye lesions, including corneal cloudiness, swollen eyelids, redness, and inflammation, but lacked many of the classic ulcers typically associated with pinkeye. Because cases appeared almost simultaneously across numerous pastures separated by up to 90 miles, investigators quickly determined the outbreak did not fit the pattern of a contagious, spreading disease. Instead, the timing and distribution suggested a point-source event linked to something the cattle experienced while gathered together during processing. Common causes such as pinkeye, infectious bovine rhinotracheitis (IBR), and mycoplasma infections were initially considered, but diagnostic testing failed to identify a clear infectious agent. Necropsies, histopathology, and laboratory testing revealed unusual eye lesions but provided no definitive diagnosis. The investigation expanded to include less common possibilities such as malignant catarrhal fever and even immune-mediated eye disease, although evidence remained inconclusive. Interestingly, the outbreak peaked about two weeks after processing and then rapidly subsided without continuing spread, further supporting the point-source theory. The discussion highlights the importance of using epidemiology, history, and case patterns to guide investigations when laboratory answers are unavailable. Ultimately, while the exact cause remained unknown, the case demonstrates how understanding disease patterns can help narrow possibilities and inform future management decisions.

  6. Jul 28

    Strategic Heifer Development: Can Stair-Step Nutrition Improve Puberty Rates and Reduce Feed Costs?

    This episode examines a study evaluating different nutritional strategies for developing replacement heifers and their impact on puberty attainment. Researchers compared traditional low-gain and high-gain feeding programs with two “stair-step” nutritional approaches that alternated periods of higher and lower energy intake. The goal was to determine whether strategic feeding could achieve the same reproductive outcomes as intensive feeding while using fewer resources. Results showed that the first stair-step program, which provided a higher plane of nutrition immediately after weaning followed by alternating periods of lower and higher gain, achieved puberty rates nearly identical to the continuously high-fed control group. In fact, 100% of the heifers in both groups reached puberty by approximately 13 months of age, while less than half of the low-control heifers achieved puberty during the study period. The stair-step strategy accomplished this while utilizing less feed and producing lower body condition scores than the continuously high-fed heifers. The findings suggest that the period immediately after weaning may be especially important for influencing reproductive development. Researchers also observed unique responses in leptin levels, indicating that strategic nutritional changes may affect hormonal pathways involved in puberty onset. While the results are promising, the discussion notes that implementing a stair-step program requires careful management and dietary transitions to achieve the desired outcomes. Overall, the study highlights how targeted nutrition can potentially improve heifer development efficiency while maintaining strong reproductive performance.

  7. Jul 20

    More Than Stocking Density: How Pen Size Influences Puberty in Replacement Heifers

    This episode examines a study investigating whether the physical size of dry lot pens affects the development of replacement heifers, even when animal density remains the same. Researchers compared heifers housed in a standard-sized dry lot, a larger dry lot with the same space per animal, and a pasture-based control group. While growth performance and weight gain were similar across treatments, important differences emerged in behavior, stress indicators, and reproductive development. Heifers housed in the smaller dry lot reached puberty approximately 20–30 days later than those in the larger pen or pasture groups. The larger dry lot group, despite having the same stocking density, performed similarly to the pasture group in many reproductive measures. Researchers also observed higher cortisol levels and increased expression of stress-related heat shock proteins in the heifers housed in the smaller pen, suggesting greater physiological stress. The findings indicate that total pen area—not just square footage per animal—may influence social interactions, stress levels, and the timing of puberty. The authors speculate that larger pens may allow animals more opportunity to avoid dominant pen mates and reduce social stress. Overall, the study suggests that facility design can have meaningful effects on replacement heifer development and that evaluating pen size may be just as important as considering stocking density alone.

  8. Jul 13

    A Deadly Feed Mixing Mistake: Investigating Sudden Cattle Deaths in a Dry Lot

    This case study examines a sudden and devastating loss in which five cows and two calves died shortly after being moved to a dry lot following the calving season. The affected group consisted of only six cow-calf pairs that had been separated because they were open or had calved late, making the rapid mortality highly suspicious for a toxic exposure rather than an infectious disease. Necropsies revealed few significant findings, while the only surviving cow showed severe neurological signs, including tremors, vocalization, and an inability to stand. Investigators focused on feed and water as the most likely sources of exposure and collected samples from the animals, feed, and environment for evaluation. During the investigation, foreign granules were discovered in the feed bunk and were ultimately traced back to agricultural pesticide residue left inside a skid steer bucket. The bucket had previously been used to handle granular pesticide from corn planting operations and was later used to deliver feed without being adequately cleaned. The pesticide contamination explained the rapid onset of deaths and neurological symptoms observed in the remaining cow. The discussion highlights how potent agricultural chemicals can become deadly when accidentally introduced into livestock feed, even in relatively small amounts. A key takeaway is the importance of maintaining dedicated equipment for feed handling whenever possible or thoroughly cleaning equipment used for agricultural chemicals before reusing it. The case also demonstrates the value of careful history-taking and field investigation, which often provide the answers before laboratory testing is even completed.

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Listen to veterinary professionals from the Beef Cattle Institute at Kansas State University talk about a variety of topics within cattle health, nutrition, reproduction, and science. New episodes of Bovine Science with BCI are posted each Monday.

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