News

Photo Credit: Shauna Rose Hermel

Protein’s Effect on Reproduction

By Kasey Brown   |   Angus Journal
2/24/2017

Nutrition and reproduction go hand in hand. Researchers have documented that excess protein has a negative impact on fertility in dairy cattle as increased concentrations of plasma urea nitrogen and milk urea nitrogen are associated with suppressed fertility. Patrick Gunn, assistant professor and beef cow-calf extension specialist from Iowa State University, explained how protein affects beef cow fertility at the 2016 Applied Reproductive Strategies in Beef Cattle (ARSBC) Symposium last fall.

He highlighted the relationship of nutrition and fertility in beef cattle, saying protein is a key nutrient that may be overlooked in rations, especially when cows are grazing low-quality forages.

Dietary crude protein is broken into rumen degradable and rumen undegradable protein. Gunn explained that degradable proteins are those that can be absorbed as amino acids for microbial protein synthesis. Undegradable protein is that which is left over and passes to the intestine.

“When metabolizable energy is not a limiting factor, excess dietary protein does not negatively impact reproductive processes and fertility in beef cattle,” said Patrick Gunn, extension beef specialist for Iowa State University.

Essentially, the goal of protein supplementation is to supply rumen degradable protein to feed the rumen’s microbial population to support production. While the Nutrient Requirements of Beef Cattle (NRC) was recently updated, he said protein requirements for reproduction have not been fully characterized, and the impacts of excess supplementation on reproduction have not been established in beef cows.

While data showed a poor relationship between dietary protein and fertility in dairy cattle, beef cattle research does not support the dairy data. Blood urea nitrogen concentrations don’t appear to be linked to fertility in beef cattle. He suggested that the relationship in dairy cattle has to do with metabolic stressors and negative energy balances during peak lactation, which often fall during breeding season.

“When metabolizable energy is not a limiting factor, excess dietary protein does not negatively impact reproductive processes and fertility in beef cattle,” he explained, adding that more research should be conducted.

Editor’s Note: The 2016 ARSBC was hosted in Des Moines, Iowa, Sept. 7-8. Gunn spoke during a session featuring nutritional effects on reproduction. Visit the Newsroom at www.appliedreprostrategies.com to view his PowerPoint, read the proceedings or listen to the presentation. Compiled by the Angus Media editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.