This episode examines whether feeding additional vitamin A to cows before calving can improve the vitamin A status of their calves. Reviewing two dairy research studies, the hosts explore how late-gestation supplementation affects vitamin A levels in colostrum, milk, and newborn calves. In the first study, cows received vitamin A at levels slightly above recommended requirements, but researchers found no increase in colostrum vitamin A content and no meaningful improvement in calf blood vitamin A concentrations.

The second study supplemented cows with much larger amounts of beta-carotene, a precursor to vitamin A. While this significantly increased beta-carotene levels in colostrum and resulted in more calves having detectable beta-carotene after birth, it still failed to increase retinol, the active form of vitamin A, in calf blood samples. The findings suggest that transferring additional vitamin A from cow to calf through maternal supplementation is more difficult than many producers might expect.

The discussion reinforces that newborn calves receive very little vitamin A through placental transfer and rely heavily on colostrum as their primary source after birth. However, even feeding cows three to four times the recommended vitamin A levels produced only modest changes in calf vitamin A status.

The hosts also compare these dairy studies to previous beef cattle research, noting that very large supplementation rates may be required before measurable improvements occur in calves. As a result, simply increasing vitamin A intake in pregnant cows may not be an efficient solution for improving calf vitamin A status. The episode concludes by raising important questions about whether calves born to cows consuming stored hay during late gestation may benefit from alternative strategies, such as direct vitamin A supplementation, and emphasizes the need for additional research to better understand vitamin A requirements in modern beef production systems.

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 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.

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 episode examines a 2026 study that explored whether pre-breeding behavior can predict which bulls will sire the most calves in multi-sire breeding pastures. Researchers fitted bulls with collars containing accelerometers and proximity sensors to objectively measure activity levels and social interactions before the breeding season. The goal was to determine whether behavioral traits such as activity, social connectedness, and interaction patterns were associated with a bull’s eventual siring capacity.

The study found that more active bulls tended to sire more calves, and bulls that were more socially connected within the group also appeared to have greater breeding success. Researchers used complex network-analysis measurements, including eigenvector centrality and relative strength, as indicators of social influence and interaction among bulls. Bulls with more diverse interactions across the bull group generally had higher siring capacity than bulls that spent most of their time with only a few herd mates.

The hosts found the concept particularly intriguing because previous efforts to predict breeding success often relied on subjective observations, while this study used objective monitoring technology. However, they also highlighted several limitations, including a relatively small sample size, missing sensor data, differences in bull grouping between years, and challenges associated with bulls entering or leaving breeding groups due to injury.

Another important finding was that some behavioral traits, especially activity level and social connectedness, showed moderate repeatability from year to year, suggesting they may reflect inherent characteristics of individual bulls rather than temporary conditions. The hosts emphasized that while the results are promising, the study should be viewed as an early step rather than definitive evidence. They concluded that larger studies across more herds and breeding environments will be necessary to determine whether wearable technology can reliably help producers identify the most effective breeding bulls before turnout.

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.