This episode “Impacts of Skeletal Muscle Depletion and Accretion Across Lactation” was recorded at the 2025 Tri-State Dairy Nutrition Conference in Fort Wayne, Indiana.
Episode 169: Impacts of Skeletal Muscle Depletion and Accretion Across Lactation
Timestamps:
Dr. Boerman notes we know cows experience a negative metabolizable protein balance in early lactation. This means they’re mobilizing skeletal muscle to make up for that. They focus on strategies to measure these dynamics. (3:51)
Cows are ultrasounded during the dry period to determine longissimus dorsi muscle reserves. Then they are divided into low vs high muscle groups. Weekly ultrasounds follow them through lactation. Animals with high muscle reserves during the dry period mobilized muscle before calving. This resulted in increased calf birth weights. Animals with less muscle during the dry period can gain muscle during that time. As a result, they have more muscle reserves at calving than they had in the middle of the dry period. Dr. Boerman discusses possible nutrition interventions to manage muscle depletion and accretion. These interventions, along with timing of muscle loss and gain, significantly influence skeletal muscle across lactation. (5:14)
The panel discusses how cows were assigned to high- and low-muscle groups. They also consider how representative those groups might be to the general population of dairy cows. Dr. Boerman mentions they’ve recently started evaluating primiparous cows as well. This evaluation is to see if they perform differently than multiparous cows. These distinctions help in understanding the impacts of variable muscle reserves. (10:33)
Dr. Boerman notes that cows are mobilizing between 30 and 35% of their longissimus dorsi depth during lactation. Muscle biopsies have shown a reduction in muscle fiber size. They also measure 3-methyl histidine and creatinine as biomarkers of muscle loss and gain. The panel discusses increased calf birth weights and impacts on colostrum for high-muscle groups. Body condition score is not a good predictor of muscle depth, especially when evaluating skeletal muscle depletion impacts. (16:52)
The group discusses how parity might impact protein loss and gain. They explore the influence of genetics on these muscle measurements. They also examine how health events might affect muscle mobilization. This exploration of various impacts provides insight into lactation dynamics. (23:41)
Dr. Weiss shares about a project from his group where muscle and fat losses were measured by dilution. They fed 20% protein diets using soy alone or with supplementation of rumen-protected amino acids. He emphasized the differences between heifers and cows, similar to what Dr. Boerman’s group has observed. These observations offer insights into the impacts skeletal muscle depletion could have across different stages of lactation. (29:54)
Dr. Boerman shares some ideas of what kind of experiments she’d like to conduct next to continue this line of research on skeletal muscle. (33:42)
Panelists share their take-home thoughts. (35:29)
Conclusion
Please subscribe and share with your industry friends. Invite more people to join us at the Real Science Exchange virtual pub table. Furthermore, please be sure to register for our upcoming Real Science Lecture Series webinars.
If you want one of our Real Science Exchange t-shirts, screenshot your rating, review, or subscription. Then, email a picture to anh.marketing@balchem.com. Include your size and mailing address, and we’ll mail you a shirt.
