Third trimester cow nutrition: Examining critical calorie intake

For spring-calving herds, cows and heifers are either in or will soon be entering the third trimester of gestation. What changes occur during this latter part of pregnancy?


The holiday season is upon us and most of us certainly have a lot of things to be thankful for, including plentiful food, a warm place to take refuge, and the pleasure of working in an industry with the best people on Earth! Of course, it is also very easy to overindulge on many unnecessary calories during this time of year. Unfortunately, some of our cattle herds may have the opposite issue in the winter months, as they struggle to find the calories/energy necessary to fully sustain them in their homegrown forages, especially due to the challenging weather conditions experienced earlier in the year. For spring-calving herds, cows and heifers are either in or will soon be entering the third trimester of gestation, a period of increasing nutritional demands.

Late pregnancy nutritional needs

So, what changes occur during this latter part of pregnancy? You are probably aware that the fetus grows by 75% or more during the final three months of gestation, so the increased nutritional need for protein, energy, vitamins and minerals likewise goes up. These extra nutrients are needed as the fetus increases its weight as it builds vital internal organs, muscle, blood, and bone structure. Concurrently, the mama cow needs to increase blood flow to the fetus, so all of the structures vital to maintaining a healthy pregnancy are growing while also preparing for the onset of lactation and the related increase in mammary tissue. 

As we look at various nutritional phases for cows, here are some typical rules of thumb used by nutritionists, both during pregnancy and after calving:

  • Mid-pregnancy: 55% TDN; 7% CP

  • Late pregnancy: 60% TDN; 9%CP

  • After calving: 65% TDN; 11-12% CP

While these are average guidelines, we must not overlook the need to make adjustments during times of “weather stress.” In taking a look at a recent national weather forecast, it appeared that most areas of the country were expecting some sort of severe weather impact from either snow, rain or high winds. The lower critical temperature (LCT) — or the point at which cattle start to be affected by cold stress — is a bit variable due to body condition, hair length and acclimation to cold temperatures, but likely starts around 15-20 degrees Fahrenheit. Research from Colorado State indicates that first-calf heifers calving at a body condition score of 4 or less produce colostrum with reduced antibody levels. Calves from these undernourished heifers were more likely to become sick than calves from well-fed heifers.

Low-quality forage challenges

Cattle are very good at adjusting their intake to meet these needs for extra energy, but there are times when poor hay quality prevents them from doing so. Due to the extremely wet spring experienced by many parts of the country this year, late-cut hay significantly reduced both hay quality and quantity. With late-cut hay, fiber levels go up, which therefore reduces digestibility or available energy for maintenance and lactation. High fiber leads to “gut fill,” meaning cows can often not eat enough to meet their demands for energy in late gestation and while nursing. Supplementation with extra protein from a block can improve digestibility of the forage and allow the cow to satisfy her demands without pulling the extra weight off her body and losing condition. If you have not tested your hay this year to know what kind of energy and protein is in it, it is strongly advised that you do so.

In a recent conversation with two North Carolina producers, one recognized the challenge he was facing with poor quality hay, having started feeding earlier than normal due to abnormally dry conditions this summer and fall. The second producer, while having good grazing on some fall ryegrass pasture, had purchased a group of first-calf heifers in less than ideal body condition. Each cattleman recognized his cattle were in danger of losing body condition, so both chose to add a protein block to their feeding regimen. While temperatures in this location are still moderate—ranging from 30-60 degrees Fahrenheit—animals in more northern latitudes that are being fed low-quality forages are likely already adjusting their energy intake as cold, wet and windy weather sets in.

Which self-fed supplement product is right for you?

No matter your feeding situation, CRYSTALYX® Brand Supplements has a product that fits. One of our newer products called CrystalBlox™ is a hybrid combination of a low-moisture and compressed block that allows for a higher intake of nutrients when needs are greater. We see this situation more often during early lactation, but if forage quality is too poor for a group of cattle to maintain body condition, CrystalBlox is an excellent choice for improving forage digestibility and overall nutrient supplementation.

If your herd is already in good body condition and the primary need is for maintenance during late gestation, consider protein supplements such as CRYSTALYX BGF-20™, BGF-30™ or HP-40™.

For more information on products that will fit your needs this fall and winter, check out or visit with your local dealer.

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