Hauling Pregnant Cows

Steve Boyles, OSU Beef Extension Specialist

Sarah Fields and George Perry from South Dakota State University published a paper presenting the effects of stress on embryonic mortality in cattle. Shipping cows between days 5 and 42 causes around a 10% decrease in pregnancy rates. Research has also demonstrated that shipping cattle 45 to 60 days after insemination can result in 6% of embryos being lost. The following table demonstrates how transporting cows at different days after insemination affected pregnancy rates.

Effect of time of transport after insemination on pregnancy rates

Days after insemination that transportation occurred
                                                                      1 to 4         8 to 12        29 to 33        45 to 60
Synchronized pregnancy rate                      74%            62%              65%
% pregnancy loss compared
to transportation on days 1 to 4                                        12%                9%               6%*
Breeding season pregnancy rate                 95%            94%              94%
*Loss compared to percent pregnant prior to transportation (pregnancy determined by transrectal ultrasonography)
Data adapted from Harrington et al, 1995 and Merrill et al., 2007

Blastocyst formation, hatching, maternal recognition of pregnancy and adhesion to the uterus take place during this early time of pregnancy. If any of these time points are disturbed, then the result leads to increased embryonic mortality and decreased pregnancy rates. So . . . . . . . . . . . . . . .

When to haul pregnant cows: Days 1 to 4 or days 45 to 60

When to NOT haul pregnant cows: Days 6 to 42

Here is a link to the factsheet: https://www.sdstate.edu/vs/extension/beef/upload/ExEx2063_Shipping-and-Heat-Stress-on-EM.pdf