UNL webinar covers considerations for low pregnancy rates in young cows
A March 10 webinar hosted by University of Nebraska-Lincoln (UNL) Extension covered key things for producers to consider when exploring potential causes for low reproductive rates in young beef cows.
UNL Extension Educator Aaron Berger moderated the webinar which featured comments from a series of specialists across four important topics – heifer development, genetic selection, nutritional considerations and impacts of infectious disease on infertility.
Heifer development
To start, UNL Extension Beef Cow/Calf Specialist Dr. Kacie McCarthy offers some comments on heifer development and longevity.
McCarthy emphasizes achieving consistent breedup in young cow herds begins with early management practices and acknowledging development strategies vary based on operational goals but should ultimately focus on setting the stage for continued success.
“Management of fertility and longevity is not a single stage event,” McCarthy says. “How we manage heifers to become pregnant earlier in the breeding season can ultimately set them up later on.”
She shares research findings showing the influence of calving period length on herd longevity, explaining a greater percentage of females remained in the herd for more consecutive calving seasons when bred earlier in the calving period.
McCarthy also emphasizes the positive impacts of implementing a stairstep approach to developing beef heifers, which utilizes periods of low weight gain followed by periods of high weight gain, on increased longevity.
“A lot of research tells us lighter target body weight at breeding reduced development costs while not impairing reproductive performance,” she adds.
Further, McCarthy shares research reflecting the difference in retention rates between range-developed and feedlot-developed heifers, noting a greater proportion of range-developed females remained in herds for a period of more than five years.
“Fitting heifers to their environment improves pregnancy rates,” McCarthy emphasizes.
UNL Professor of Animal Science Dr. Rick Funston also underscores the importance of preparing young cows in the months before breeding and emphasizes proper nutrition can contribute to decreased levels of early embryonic mortality.
Genetic selection
Next, UNL Extension Beef Genetics Specialist Dr. Matt Spangler offers some considerations regarding genetic selection.
He explains genetics impact both reproductive ability and how well cows fit their production environment and encourages producers to keep an updated understanding of herd performance and breeding objectives.
“As your herd changes in performance, the emphasis you need to place on different traits in your selection program changes as well,” he states.
He also expresses his belief in the advantages of a structured crossbreeding program, noting this practice can help producers capitalize on expected progeny differences (EPDs) which promote sustained fertility.
On this topic, Spangler notes milk and mature cow weight EPDs have a significant impact on driving fertility and profitability.
“Milk is something where fitting genetics to environment becomes important,” Spangler says. “In environments with limited feed availability, cows that out milk their nutrient availability have a greater tendency of showing up open.”
Also, Spangler adds the largest path to profit is pushing cow weight down without sacrificing performance, noting incorporating breeds with lower mature cow weight EPDs can complement a crossbreeding program.
Nutritional considerations
Following Spangler’s presentation, UNL Extension Cow/Calf Stocker Management Specialist Dr. Karla Wilke shares some considerations on the relationship between nutrition and reproduction.
Wilke’s comments highlight the importance of body condition score (BCS) when it comes to conception and underscores the need for setting young cows up for success through adequate nutrition.
“BCS at calving is one of the biggest factors contributing to timely return of estrus in beef cattle,” Wilke says, highlighting research which shows breed-up rates of cows with a BCS of five or better being significantly higher than those with a BCS below five.
The research also shows a shorter postpartum interval for cows with a higher BCS at the time of calving, meaning it took less time for them to breed back and re-enter the calf production cycle.
She explains BCS is most critical for young cows because this age group still has growth requirements mature cows do not, as well as a shorter postpartum interval than heifers.
Additionally, she em-phasizes since young cows are still maturing, a greater amount of their energy reserves go towards things like developing basal metabolism and growth in addition to lactation and reproduction.
“We have to have a little more consideration for the nutrient requirements of the two- and three-year-olds because they have more going on than their mature cow counterparts,” Wilke states.
Infectious diseases
UNL Extension Veterinarian and Veterinary Pathologist Dr. Matt Hille then shares some thoughts about the impact of infectious diseases on infertility.
Hille gives an overview of some infectious disease threats including vesiculitis, campylobacter and trichomoniasis which contribute to lowers conception rates, early embryonic death and increased abortions in cow herds.
He emphasizes infectious causes of infertility and early fetal death are relatively uncommon. However, the results of contracting the disease can be catastrophic.
Additionally, he notes it is difficult to diagnose infectious causes of calf loss retrospectively and emphasizes the importance preg checking early to differentiate infertility from early embryonic loss or abortion.
For this reason, Hille’s take-home recommendations for producers focus on remaining educated about infectious disease threats and taking preventative protective measures through testing and vaccination.
Final considerations
In closing, UNL Associate Professor of Veterinary Epidemiology Dr. Brian Vander Ley outlines a systems approach to understanding the problem of young open cows.
He refers to reproduction as the “engine driving profitability in a cow herd” and warns producers to be cautious of sacrificing overall reproductive efficiency in favor of short-term positive outcomes.
Instead, Vander Ley discusses a “big picture” approach to understanding factors from heifer development and breeding strategies to breeding objectives.
The webinar concludes with a question-and-answer session where presenters weighed in on questions from producers.
Grace Skavdahl is the editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
