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Second trimester nutrition: MSU Extension Specialist explains the importance of nutrition during the second trimester

by Wyoming Livestock Roundup

During an online educational seminar hosted by Montana State University’s (MSU) Beef Cattle Extension Program, MSU Extension Beef Specialist Dr. Carla Sanford discusses the importance of nutrition during gestation, particularly during the second trimester, which she notes is often overlooked. 

“We know the importance of conception and importance of pre-calving, but looking at individual events that happen during that second trimester has become more popular,” Sanford states. 

The second trimester

The typical gestational period of a cow is nine months or 289 days, which is broken into three blocks of time known as trimesters. Since many producers across the West usually calve during spring months, the majority of beef cattle are currently in the second trimester of their pregnancy.

“Right now, the fetus developing inside the cow is starting to gain weight in pounds and length in inches. Also during this time, vascularization and blood flow is increasing to the entire placental unit,” explains Sanford. 

“Some other major things are going on at this time,” she adds. “We know nutrients are needed and waste exchange and oxygen are all very critical to the success of a pregnancy.”

In addition to the big changes happening inside the womb, the cow is most likely nursing a 400 to 500-pound calf as well as maintaining her own nutritional requirements on forage that is exponentially losing quality.

Studies on pregnancy and nutrition

Sanford notes several studies have looked at how nutrition related stress during the second trimester can affect a live calf later on. 

She points to a study done at Washington State University in 2010, which found if a cow lacks the proper nutrients it needs at any point from the end of the first trimester to the end of the second trimester, muscle fiber numbers and muscle mass can be decreased in the offspring. 

“Another study done in 2016 at South Dakota State University looked at how a cow’s energy intake may affect the calf. In this study, one set of cows was fed to maintain a body score of 5.5 to 6.5. The other group was fed only 80 percent of their required energy,” Sanford explains. 

According to Sanford, feeding in the study was done over a 91-day period, and results showed calves born to mothers whose energy intake had been restricted were more likely to have a weakened immune response later in its life.

Importance of BCS

During her talk, Sanford emphasizes how these studies demonstrate the importance of body condition scoring (BCS) in a cowherd. She recommends producers try to maintain a cow at a BCS of 5.5 to six. 

She also encourages producers to regularly check the BCS of their cows, especially during pre-breeding, over the winter, pre-calving and at weaning.

“I’ll always be a big proponent of using body condition scoring to determine what animals are not being able to maintain themselves in a herd,” Sanford says.

Sanford notes if less than 80 percent of a cowherd is not at an ideal body score, nutritional management changes may need to happen on the operation. 

She suggests separating young cows and old, thin cows from the rest of the herd and providing them with additional supplementation to meet their special nutrient requirements. She also notes if early weaning is conducive to the year and operation, it is also an option. 

Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to

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