Cows are what they eat just like we are. If they aren’t getting the right inputs, they won’t give the right outputs. For a cow, the most important “output” is a live calf.
While many factors influence a cow’s ability to conceive and carry a calf to term, nutrition is among the most obvious. Since artificial insemination (AI) still comes with lower pregnancy rates compared to those from natural service, it’s even more important that females to be bred via AI be on a good nutritional plane with no deficiencies.
“Nutritional status leading up to the breeding season plays a major role in the attainment of pregnancy,” wrote Carl Dahlen, beef cattle specialist at the North Dakota State University Extension, in a 2015 Extension fact sheet on maximizing AI success.
“The ideal situation is to have cows on an increasing plane of nutrition and gaining body condition leading up to the time of breeding.”
A cow’s body will prioritize milk production for her current calf and her own maintenance needs over reproductive functions. If she is not getting enough nutritional inputs for her current calf and herself, she is less likely to start cycling and become pregnant on time.
Since heifers do not have a calf to support in their first breeding season, they can have some conception rate advantages over cows. They are still growing, however, which means they have more than just maintenance needs.
Numerous academic and industry studies have also found that a cow’s body condition score (BCS) at breeding has a big impact on AI success. As can be seen in the chart at DIRECTION, AI pregnancy rates jumped about 16 percentage points between cattle bred at a BCS less than 4.5 and those over BCS 4.5. Generally, it is recommended that heifers be at a slightly higher BCS than older cows when bred.
Older cows that calve in BCS 5-6 also tend to begin cycling earlier as well, making them more likely to re-breed in that necessary 83 days post -calving to produce one calf per year.
Nutritional deficiencies
“Insufficient intake of energy, protein, vitamins, and micro- and macro-minerals have all been associated with suboptimal reproductive performance,” wrote Cliff Lamb, current head of the Department of Animal Science at Texas A&M University, in a University of Minnesota Extension factsheet.
It can be hard to tell what nutritional deficiency is in play, if at all, when AI servicing doesn’t stick. “Poor reproductive performance” is a general symptom of almost every deficiency out there. Plus, there are many other things in addition to nutritional deficiencies which can result in poor reproductive performance.
“Reproductive outcomes are always a combination of the animal status, environment, and nutrition—consult your veterinarian and nutritionist to thoroughly evaluate your operation,” suggested Neil Michael, DVM, manager of ruminant technical services with Arm and Hammer Animal Health. He told WLJ that nutritional deficiencies can occur in animals during times of stress, such as winter, or higher performance demands, such as nursing a young calf.
As covered recently in WLJ, some mineral deficiencies are more common in the U.S. cow herd than others. Copper deficiencies are especially widespread, according to research by Utah State University’s Dr. Jeff Hall, professor of veterinary diagnostics, and mineral nutrition.
Selenium deficiencies are also relatively widespread, but more regional than copper deficiencies given differing soil selenium concentrations across the U.S. The Pacific Northwest, the South, and the region stretching from the Corn Belt east to New England are areas known to have insufficient soil selenium levels to support cattle’s needs on range alone.
According to Extension resources, deficiencies in the following nutrients are associated with the corresponding reproductive problems:
- Calcium—retained placenta;
- Protein—continually open, anemia resulting in anestrus, extremely early embryonic loss/death;
- Iron—anemia resulting in anestrus;
- Phosphorous—anemia resulting in anestrus, retained placenta;
- Selenium—anemia resulting in anestrus, cystic ovaries, reproductive tract infections, early-term abortions, late-term abortions, retained placenta;
- Vitamin A—cystic ovaries, reproductive tract infections, late-term abortions, retained placenta;
- Vitamin E—anemia resulting in anestrus, cystic ovaries, reproductive tract infections, early-term abortions, late-term abortions, retained placenta.
Nutritional excesses can also cause problems, however. Many of the symptoms of deficiencies listed above are also displayed when cattle have an excess of those elements. Additionally, over-conditioned cows and heifers will have increased calving difficulties.
Consultation with your veterinarian on your cow herd’s nutritional needs is always important. It is even more important when preparing for AI. — WLJ
