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.