According to Rick Funston, Nebraska Extension Beef Cattle Reproductive Physiologist, transportation stress, heat stress, diagnosing pregnancy and nutrition at breeding are all factors that can lead to early pregnancy loss in cattle. From his recent BeefWatch article, here’s what to watch for and what to do to prevent loss.
Transportation Stress
When trailering cattle to pasture, timing is important. Funston notes that research at Colorado State University found that transporting cattle between days 5 and 42 after artificial insemination or breeding resulted in a 10% reduction in pregnancy. The reason? This is the period when the blastocyst is forming and adhering to the uterine wall. The simple act of loading cows on a trailer can cause stress which releases hormones that alter the uterine environment so that it can’t maintain pregnancy.
Funston writes, “Prior to day 5, the embryo is still in the oviduct and protected from changes in the uterine environment. After day 42, the embryo has implanted into the uterine wall and is less susceptible to changes in environment.” He recommends waiting to haul cows until a week or two after Day 42 to reduce embryo mortality and pregnancy loss.
Recommended time to haul: Days 1-4 or after Day 60.
Period where hauling risks pregnancy loss: Days 5 – 55 or 60.
Heat Stress
Last week we talked about how heat stress can cause long-term health issues for offspring after they’re born. But it can also impact a cow’s ability to maintain her pregnancy. Studies at Oklahoma State University showed that heat stress within 8 to 16 days after breeding resulted in reduced embryo weight.
As a result, Funston recommends avoiding trailering cows on hot days (90º – 110º and 40% or greater humidity). Hauling on cooler days can reduce heat stress and pregnancy loss.
Diagnosing Pregnancy
It’s common for cows to be preg-checked via transrectal palpation or ultrasound. Unfortunately, if done by inexperienced technicians between days 42 and 74, fetal losses increased more than when done by experienced tecnhicians (2.07 vs 1.06%) This same study, done at Colorado STate University, found that palpation had more impact on pregnancy loss than ultrasound (2.07 vs 1.06%) As a result, Funston says that, though we can determine pregnancy by palapation or ultrasound as early as 25 – 30 days, its better to wait until 40 to 50 days after breeding/insemination to reduce the risk of disturbing the embryo in the more fragile, early stages of development.
Nutrition at Breeding
Body condition scores of 5 for cows and 6 for first calf heifers provide the best results. Thin cows that are gaining weight can equal the pregnancy rates of these cows. But thin cows that are continuing to lose weight will have pregnancy rates as much as 30% lower. Funston says, “Having a sound nutritional program is key to optimizing reproductive function during the breeding season.”
Want More?
Here are three papers that provide the information summarized here:
Comparison of Fetal Losses from Diagnosis of Pregnancy Using Ultrasonography or Rectal Palpation in Beef Heifers by Novice or Experienced Technicians
Effects of Shipping and Heat Stress on Embryonic Mortality in Cattle
Effect of Heat Stress on Early Embryonic Development in the Beef Cow
Listen to a discussion of the content in this article on this episode of the BeefWatch podcast. You can subscribe to new episodes in iTunes or paste http://feeds.feedburner.com/unlbeefwatch into your podcast app.
