Cow-Calf Commentary for Iowa Cattleman Magazine
By Randie Culbertson, Cow-Calf Extension Specialist
June 2025
Hair shedding, does it matter?
As we start to feel the summer heat, it is a good time to consider how our cow herd handles it. Some breeds are more adapted to heat, such as Brahman, while others thrive in more moderate climates, such as our British and Continental breeds. Hair shedding is a trait of interest that has garnered a good deal of attention for heat tolerance. Seasonal hair shedding is a normal biological process for cattle. However, the retention of a winter coat during the spring and summer can indicate adaptation or health issues.
The ability of a cow to shed her hair coat earlier has economic impacts on cow-calf operations. Research has shown that calf weaning weights from cows that lose their coats earlier are heavier. A project from 2010 conducted by North Carolina State University reported that calves from cows that shed their coats by March were, on average, 57 pounds heavier than calves from cows that retained their coats until July. Cattle that keep their coats longer are susceptible to heat stress. Cows experiencing heat stress during the summer are less likely to get pregnant early in the breeding season, resulting in later calving and ultimately weaning a lighter calf. All this results in an economic loss for operations with decreased calf performance and potential loss in reproductive efficiency for cows retaining winter coats.
The process of cattle shedding their winter coat is essential to thermoregulation. Recent work at the University of Missouri investigated whether animals start shedding due to changes in day length or temperature. They found that daylight and longer days had a larger influence on cattle shedding winter coats than temperature, suggesting that an animal's ability to shed their winter coat earlier are more adaptable to their environment.
Several factors affect hair shedding, such as age, sex, nutritional status, and animal health. In a recent heifer development study conducted at the Iowa State University McNay Memorial Demonstration and Research Farm, heifers on a restricted diet retained their winter coat longer than heifers on a non-restricted diet on average. In general, younger animals (i.e., yearlings and first-calf heifers) tend to keep their winter coats longer than older cows. This is mainly attributed to younger animals still growing and more nutritionally stressed than mature cows. The effect of sex is seen in males, as they tend to shed out a few weeks earlier than females.
Tall Fescue toxicosis has long been associated with a rough hair coat in cattle. Delayed hair shedding can be a sign of fescue toxicosis as it limits the animal’s ability to shed its winter coat. The ergot alkaloids that cause fescue toxicosis will also disrupt the hair follicle growth, resulting in a rough coat and hair shedding interference. Retaining a winter coat can exacerbate heat stress during the summer months as a cow will have difficulty regulating their body temperature.
Hair shedding has been used as a tool for selecting cattle that are more adapted to the summer heat. Hair shedding has a moderate to high heritability of 0.35 to 0.42, meaning placing selection pressure on this trait will change within your herd over time. Some breed associations publish hair-shedding expected progeny differences (EPDs); therefore, selecting animals with lower hair-shedding EPDs will result in progeny that, on average, shed earlier in the season.
Collecting hair-shedding scores should be done once in late spring or early summer, depending on your geographical area. In Iowa, late May and early June are the ideal times to collect hair shedding scores based on our geographical location. The more humid and hotter the climate, the earlier in the spring scores should be collected. Scores are a visual appraisal of an animal and are reported on a scale of 1 to 5 (Table 1 and Figure 1). Cattle shed from head to tail and top to bottom. It is recommended that animals be scored on the same day, but keep in mind that males tend to begin shedding a few weeks before females. Scoring bulls separately should be considered.
In conclusion, hair shedding is a trait relevant to all cattle producers. There is an economic and physiological benefit for cows that shed earlier in the season, and it can be an indicator of overall herd well-being and productivity.
2025 Archives
2024 Archives
2023 Archives
