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New research suggests a correlation between a bull’s breeding condition and calf health

by Wyoming Livestock Roundup

Recently, during the 2023 Montana Nutrition Conference and Livestock Forum held in Bozeman, Mont., co-hosted by the Montana State University College of Agriculture and Montana Feed Association, North Dakota State University (NDSU) Animal Science Professor Carl Dahlen discussed recent research findings exploring livestock epigenetics.

Dahlen and the NDSU research team are studying reproductive efficiency in livestock with a focus on implications of maternal nutritional management on offspring characteristics through multiple generations and addressing if paternal nutrition and management are implicit in offspring outcomes.

Dahlen’s epigenetics research suggests bulls may have a more substantial influence on herd genetics than previously thought.

Pushing the boundaries

In a Jan. 7 AgUpdate article featuring Dahlen’s presentation at the conference, he states the condition of a bull nine months before the breeding season might significantly influence calf health, based on studies in humans and mice. 

“We are all familiar with fetal programming or that maternal nutrition plays a role in the development of calves,” says Dahlen. “For instance, we all know we like a good, long cold streak in the winter when cows eat more because it generally results in bigger calves. But, we are also looking at the impact a bull’s condition can have immediately before breeding season.”

Dahlen’s research revealed sire age, fertility level, plane of nutrition and heat stress can induce alterations in the epigenetic profile of sperm.

The research team has been trying to understand the effects of common management scenarios of nutrition and growth rates in bull mechanisms resulting in paternal programming and subsequent offspring outcomes. 

“Understanding the implication of paternal programming is imperative as short-term feeding and management decisions have the potential to impact productivity and profitability of our herds for generations to come,” he states.

Bull calf nutrition

“Most of the research has been focused on bull calf gains in the pre-weaning stage when the body is supporting the development of sperm for the lifetime of the bull,” Dahlen explains.

“A lot is happening in a bull calf during the time some of us don’t even consider him being a bull,” he adds. “He’s out there with mom, but his nutrition at the time will affect his performance later.”

Dahlen reiterates most research from the 1980s focused on the weight gain of a bull calf as it matured, stating the target gain should be 3.9 pounds per day.

However, recent research has revealed this could contribute to scrotal fat accumulation, foot problems and liver abscesses.

To be effective herd sires, bulls must develop properly after weaning, and if nutrient intake is below acceptable requirements, growth weights are reduced and puberty can be delayed, which can permanently impair sperm production.

“Right now, we don’t know anything about cattle sire nutrition before the breeding season and how it relates to offspring, but it is interesting to consider,” he says. “As research continues, it will help determine the effects of bull nutrition on their offspring which is an important area to research.”

Nutrition alters hormones and metabolites

According to the 2021 North Dakota Livestock report, released by NDSU, the plane of nutrition in mature bulls fluctuates over the course of a year due to the demands of the breeding season.

Some bulls will lose weight only at the beginning of the breeding season and then manage to gain weight after, reaching the targeted optimal weight just before the subsequent breeding season.

The research further notes some bulls might begin losing weight before the breeding season, as they may have experienced a change in environment or diet after purchase or were being managed to gain weight over the winter and needed to be conditioned to be back in breeding shape or placed on pastures to graze ahead of the breeding season. 

In either instance, these bulls would be on a negative plane of nutrition leading up to the breeding season.

In the NDSU experiment, fluctuations in body weight and plane of nutrition of breeding bulls lead to changes in blood hormone and metabolite profiles. 

Increased hormone and metabolite concentrations in bulls on a positive plane of nutrition were a product of the enhanced plane of nutrition. Elevated non-esterified fatty acids in bulls on a negative plane of nutrition were indicative of bulls mobilizing body reserves and a source of energy.

The research team observed alterations in blood profiles likely resulted in alterations of nutrients available for developing sperm.

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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