Bovine Science with BCI

This episode explores how vitamin A nutrition in late-gestation cows affects both maternal health and the vitamin A status of newborn calves. The discussion builds on previous conversations about calf vitamin A deficiencies, emphasizing that colostrum is the primary source of vitamin A for newborn calves and that deficiencies early in life can persist for weeks or months.

The hosts review two research studies examining how vitamin A and its precursors are affected by rumen fermentation. The first study found that beta-carotene, the precursor to vitamin A found in green forages such as alfalfa, remains relatively stable during rumen fermentation, suggesting that high-quality green hay can be an excellent source of vitamin A for pregnant cows. They note that protecting hay from sunlight is important because ultraviolet light accelerates degradation of carotenoids, reducing the vitamin A value of stored forage.

The second study evaluated supplemental vitamin A and found that degradation of common vitamin A supplements increased substantially in higher-concentrate diets. In some cases, only about 30% of the supplemented vitamin A remained after 24 hours of fermentation in rumen fluid from cattle fed more concentrate-heavy diets. Interestingly, the form of the supplement had little effect on degradation, while diet composition had a much larger influence.

The practical takeaway is that producers should focus first on preserving and feeding high-quality green forage during late gestation, while also considering whether additional vitamin A supplementation may be necessary when hay quality is poor or concentrate feeding levels increase. The episode reinforces that thoughtful forage management and nutrition planning before calving can improve vitamin A delivery to cows, support colostrum quality, and help set calves up for better health after birth.

This case study examines a situation where a producer attempted to control a heavy fly burden by spraying cattle with a topical insecticide, only to have several cows develop severe toxic signs within hours. Affected animals became recumbent, excessively salivated, developed diarrhea, experienced respiratory distress, and showed muscle tremors and weakness, raising immediate concerns about insecticide toxicity.

The investigation focused on two common groups of insecticides used in cattle: organophosphates and pyrethroids. Because the cattle exhibited the classic “SLUD” syndrome of excessive salivation, lacrimation, urination, and defecation, the evidence pointed strongly toward organophosphate poisoning. Review of the product label revealed that the insecticide had been mixed at a dramatically higher concentration than recommended. Instead of being diluted according to animal-use directions, the concentrate was mixed at a strength far closer to premise-spray concentrations, resulting in massive overdosing.

The discussion highlights how many insecticide products contain multiple sets of directions depending on whether they are being used on facilities, back rubbers, or directly on animals, making careful label review essential. Once toxicity was identified, treatment focused on immediately washing cattle with detergent and water to remove residual insecticide from the skin and administering atropine to reduce secretions and support breathing.

Fortunately, the affected cattle recovered after treatment, demonstrating the importance of rapid recognition and intervention. The case serves as a reminder that insecticides are highly potent compounds designed to affect nervous system function and must be handled with extreme care. Proper dilution, careful reading of product labels, and attention to species-specific application instructions are critical to preventing potentially fatal mistakes during fly control programs.

In this episode of Bovine Science, we examine a 2024 Journal of Animal Science study that used hundreds of thousands of cattle records to investigate the genetic and environmental influences on fertility in beef cattle. The study evaluated traits including calving date, calving interval, first-calf interval, early calving, and heifer pregnancy.

The discussion highlights that most fertility traits have very low heritability, meaning management decisions such as nutrition, body condition, breeding-season length, and bull fertility have a much greater influence on reproductive performance. Heifer pregnancy was the exception, showing moderate heritability and providing a potential opportunity for genetic selection. The study also found no evidence that selecting for greater weaning or yearling weight negatively affects fertility, with yearling weight actually showing a positive association with heifer pregnancy.

This episode reviews a 2026 study investigating whether a modified-live Mycoplasma bovis vaccine can help protect young calves from one of the most frustrating respiratory disease pathogens in the cattle industry. The researchers conducted a controlled challenge trial in neonatal calves, comparing vaccinated and non-vaccinated groups after exposure to Mycoplasma bovis.

The results showed several encouraging outcomes for vaccinated calves. They experienced fewer lung lesions, fewer days with fever, and a shorter duration of clinical illness compared with non-vaccinated controls. In addition, vaccinated calves developed higher antibody levels both before and after challenge, suggesting that the vaccine stimulated a meaningful immune response.

The discussion also highlights important statistical considerations. While the study found positive effects on lung lesions and fever duration, some clinical disease measures showed less dramatic differences, emphasizing the need to carefully interpret challenge-study data. The hosts point out that challenge trials measure vaccine efficacy under controlled conditions, which differs from vaccine effectiveness in real-world ranch environments.

Another key point is that the study was funded and conducted by researchers affiliated with the vaccine manufacturer, making critical evaluation of study design and interpretation especially important. Despite those limitations, the trial was well designed, with randomization, blinding, and strong biosecurity controls. Overall, the paper provides promising evidence that a modified-live Mycoplasma bovis vaccine may become a useful tool for respiratory disease management, while also underscoring the need for larger field studies to determine how well those results translate to commercial cattle operations.

This episode focuses on some of the most challenging cases veterinarians encounter: cattle with vague signs such as weight loss, poor condition, or an unexplained death where no obvious cause is apparent. Dr. Scott Fritz explains that these situations are often far more difficult than classic acute poisonings because there is rarely a clear syndrome, exposure event, or obvious diagnostic clue. Instead, investigations must begin with a thorough history, careful necropsy, and a detailed evaluation of management changes, environmental conditions, forage availability, and grazing patterns.

The discussion highlights the importance of considering toxic plants while recognizing that simply finding a toxic plant in a pasture does not prove it caused disease. Weather conditions, grazing pressure, herbicide use, mowing, drought stress, and seasonal plant growth can all influence the likelihood that cattle consume potentially toxic species. The speakers also emphasize the value of examining rumen contents, collecting representative samples, and working closely with diagnostic laboratories to choose appropriate tests rather than ordering broad, unfocused toxicology screens.

Special attention is given to ocular fluid sampling, which can serve as a useful substitute for blood testing after death and help diagnose conditions such as nitrate poisoning. The episode explains that successful toxicology investigations rarely rely on a single laboratory result. Instead, diagnosis usually comes from combining clinical signs, animal history, environmental observations, necropsy findings, pathology results, and targeted laboratory testing.

A key takeaway is that toxicology cases are often diagnoses of exclusion, requiring patience and collaboration among veterinarians, diagnosticians, toxicologists, botanists, and producers. By taking a systematic approach and preserving high-quality samples early in the investigation, producers and veterinarians improve their chances of identifying the true cause and preventing future losses.

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.

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.

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.

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.

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.