Over the past 60 years, mature cow body weight has increased at an annual average of 7.7 pounds per year, but it has not increased at a constant rate.
The chart shows the average annual estimated cow live weight estimated from USDA reports for monthly cow carcass weights. When we look at annual average live weight data, we see that the major structural shift in cow size began in the mid-1960s when selection for larger framed growthier cattle became popular.
Prior to that, mature cow weight was relatively stable and even slightly declining. After 1965, cow size began a steady upward climb increasing by approximately 6.5 lbs. per year until 1995. However, the rate of growth in cow size has not been uniform throughout the years.
During the 1960s and 1970s, cow size really changed very little. The increase in cow mature size began with the introduction of larger frame Continental genetics into the U.S. cow herd in the 1980s. This resulted in the rapid acceleration in cow weights of nearly 19 lbs. per year from 1995 to 2005.
During the ’80s, mature cow weight increased roughly 8 lbs. per year and 80 lbs. in 10 years. Along with the widespread adoption of larger framed genetics and Continental breed influence across commercial herds, the increased emphasis on growth EPDs has increased cow mature size but is also important to modern increases in post-weaning beef production and efficiency. Selection pressure for growth, heavier weaning weights and changing market signals all contributed to that trend.
After 2005, cow weights have shown a moderate increases of around 4 lbs. per year, which is essentially a plateau relative to the “acceleration decade” from 1995 to 2005. The recent moderation in the increase in cow size indicates our efforts to improve maternal efficiency have been fruitful. Cow size remains substantially larger than in the 1960s. Over the six decades, that translates to over 450 additional lbs. per cow.
That increase in cow size has consequences on ranch sustainability and risk tolerance. If stocking rates are not adjusted for the increased cow size, long term rangeland productivity will suffer from overgrazing and weather disruptions such as drought will have greater impacts.
Bigger cows require more forage, greater maintenance energy and influence stocking rates. While larger cows can wean heavier calves, they are often not as efficient. The cow efficiency question remains critical: are we adding pounds where they generate greater returns?
Understanding how cow size has changed can help producers evaluate whether their current cowherd aligns with forage resources and profitability goals. Bigger cows are not inherently good or bad—but cows must fit the production environment or we will be required to fit the environment to the cow by providing more supplemental feed from harvested forage and concentrates.
As always, the most efficient cow is the one that matches her environment and pays her own way. — Paul Beck, OSU Extension beef cattle nutrition specialist
