Effects of Shipping and Heat Stress on Embryonic Mortality in Cattle

By Robin Salverson

Embryonic loss is the greatest economic loss in the cow/calf industry, affecting number of cows carrying to term and percent calf crop weaned.

Fertilization rates are usually between 90% and 100% when semen is present at ovulation. Fertilization usually takes place, but conception rates (number of animals that conceive divided by number of animals inseminated) are usually around 70% for natural service or artificial insemination.

Although nature (poor oocyte quality, disease, chromosomal abnormalities, etc.) contributes much of this loss, management practices can also increase embryonic mortality. Stress, particularly heat and shipping stress, can be detrimental to embryos and decrease pregnancy rates.