Guests: Dr. Jimena Laporta, University of Wisconsin-Madison

Covering the topic of Fetal Hyperthermia, Dr. Jimena Laporta of the University of Wisconsin is the second podcast at the 2022 Tri-State Dairy Conference. This makes up part two of the conference series.

Heat stress is known to be a significant issue for dairy cattle with both global temperatures and sensitivity of dairy cattle to heat rising. Dr. Laporta adds that negative effects of heat stress last for multiple generations and lactations. 1:16

While heat stress affects all cattle, Dr. Laporta focuses on dry cows and their offspring, to provide a more holistic view of its effects. Beginning with the dry cow, she notes that heat stress lessens milk production, as it derails involution and redevelopment. 3:59

Epigenetics play a role in fetal development in the dry cow - fetal hyperthermia creates changes in the DNA of the fetus, altering the epigenome. 11:22

What are the effects of fetal hyperthermia short term and long term, as well as across generations?

Dr. Laporta details many short term hallmarks of prenatal heat stress: the dam experiences a reduction in gestation length leading to a premature calf that has organ alterations, less of an immune response, less feed intake, and a higher core body temperature. 16:31

Analyzing a large data set of cattle affected by fetal hyperthermia, Dr. Laporta finds long term effects. The daughters had lower survival rates and less production each lactation, which carried over to the next 2-3 generations. Heat stress effects cost the dairy industry $1.4 billion. 23:08

Turning her focus to the molecular signature of heat stress, Dr. Laporta discusses her findings from inspecting a mammary gland, concluding that heat stress causes a lower cell proliferative capacity and negatively impacts protein synthesis. Both lead to compromised milk storage and synthetic capacity. 29:28

Wrapping up, Dr. Laporta states that heat stress negatively affects growth, organ development, immune function, survival, longevity, and milk yield for multiple generations. However, she believes that management and nutritional intervention can reduce such effects. 36:58

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