An accurate estimate of feed intake is a critical element in determining a cow’s nutrient requirements at different stages of production. It is also necessary to establish appropriate stocking rate and carrying capacity for a given land base. The National Academy of Sciences, Engineering and Medicine developed and published an equation in 1996 to predict feed intake in beef cows (Nutrient Requirements of Beef Cattle, Seventh Revised Edition). 

This equation was recommended for use once again in the eighth revised edition, published in 2016. That equation predicts increasing feed intake as cow size increases and as diet digestibility (energy density) increases. This equation is used to estimate feed intake and nutrient requirements in many publications and beef cattle nutrition software programs. 

The 1996 equation was developed using beef cow intake data published between 1979 and 1993. Certainly the U.S. cattle population has changed since then. One of our graduate students, Megan Gross, searched more recent literature to find studies where cow intake was measured directly. She identified studies published or conducted between 2003 and 2022, providing 85 intake observations from gestating and lactating beef cows.  

Using this dataset, we evaluated the 1996 equation. In short, the old equation predicted feed intake reasonably well when diet digestibility was below about 55% total digestible nutrients (TDN). However, when diet digestibility was moderate to high, like grazing season conditions, feed intake was underestimated. Underprediction of feed intake was especially pronounced in lactating cows. For example, in lactating cows consuming a 60% TDN forage, the 1996 equation underestimated daily intake by 6 pounds (lb.). 

Another popular resource providing estimates for feed intake in beef cows was published by Hibberd and Thrift in 1982. In their guidelines, feed intake is expressed as a percentage of body weight and intake estimates are sensitive to diet quality, stage of production and cow body weight. 

Like the approach with the 1996 equation, the Hibberd and Thrift guidelines were evaluated. Briefly, feed intake of gestating cows was overestimated by about 3 lb. per day, while estimates for intake of lactating cows were reasonably accurate. Finally, we used the more recent data to update the intake guidelines, and those are provided in the table below.

These values assume the diet contains adequate protein to maintain optimal microbial growth, rumen fermentation and passage rate. They also assume the animals’ access to the diet is not restricted. In other words, the animals have the opportunity to consume grazed forage, hay or a total mixed ration on a free-choice basis. 

If you are interested in more details or if you need a more specific estimate of average daily feed intake, refer to the paper published in Translational Animal Science. Information to access that publication is provided at left.

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