2nd trimester

As cattle head for lower ground in the fall, be mindful of their nutritional needs as they are in their second trimester of pregnancy. 

The backbone of the United States beef industry is the cow/calf sector. As step one in the whole beef production chain, equal importance must be placed on both the cow and her offspring – be it a live suckling calf or a growing fetus.

The gestational period of a cow is nine months (289 days), which can be conveniently broken up into three blocks of time known as pregnancy trimesters. Generally speaking, a calf spends more time inside its mom then it does beside her. That being said, fetal development and research pointed at better understanding what happens during a cow’s gestation is critical to the overall success of cow/calf production.

Montana State University’s Beef Cattle Extension program hosted a series of online lectures this fall. The final instalment of the series was on Oct. 8, featuring Dr. Carla Sanford, MSU Extension beef specialist. During her talk, Sanford discussed a very important, yet often overlooked section of gestation, the second trimester.

“We do know the importance of conception and we do know the importance of pre-calving, but looking at individual events that happen during that second trimester has become more popular for researchers,” Sanford stated in a follow-up interview.

Cattle across the Northern Plains and Rocky Mountains usually calve in early to mid-spring, which means the majority of cattle are in the tail end of their second trimester in October. 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.

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

That is what is going on inside the cow. Outside the cow, she probably has a 400-500 pound calf still nursing. The stressors of weaning and/or shipping from summer grass are ensuing and the cow is being forced to maintain herself on forage that is being depleted exponentially in quality.

Needless to say, there is a lot going on outside the womb, as well. Studies have been done looking at how feed related stress during the second trimester can affect the live calf later on. A study done at Washington State University in 2010 discovered that if a cow lacks the proper nutrients she 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. This can be detrimental to those in the beef industry because, simply put, muscle matters.

Another study done in 2016 at South Dakota State University looked at how a cow’s energy intake may affect the calf. In the 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. The feeding was done over a 91-day period. Results from this study showed that calves born to mothers whose energy intake had been restricted were more likely to have a weakened immune response later on in life at the receiving stage.

As a producer, healthy calves that can deliver pounds across the scale is the whole goal. A lot of emphasis has always been put on third trimester nutrition and how that equates to offspring, but research is now showing just how important mid-gestation is to the calf’s performance.

During her talk, Sanford emphasized that these studies indicate just how important body condition scoring (BCS) on cows can be. It is recommended to maintain a cow at a BCS of 5.5 to 6 and Sanford recommends checking BCS on cows at pre-breeding, over the winter, pre-calving and at weaning.

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

Sanford went on to say that if less than 80 percent of your herd is not at an ideal body score, nutritional management changes may need to happen. Separating young and old, thin cows from the main herd and providing them with their specified nutritional needs could be necessary, and early weaning is an option, as well, if it is conducive to the year and operation.

Studying the second trimester is an area that Sanford has focused her research on while at MSU. She hopes to look more at stimulating placental function and blood flow during the second trimester and at the impacts of mineral consumption during mid-gestation.