The answer depends on the year, the cattle and a host of other factors. Yet selecting the proper stocking rates on endophyte-infected tall fescue pastures is arguably the most important management decision that producers face, says Eric Vanzant, beef cattle nutritionist in the Department of Animal and Food Sciences at the University of Kentucky.
While the many changing variables that confront a cattleman from one year to the next can make the stocking decision difficult, generally speaking, Vanzant says as stocking rate increases, average daily gain (ADG) decreases within ranges that are typical for an area.
In research he conducted last year, he found that for stocker cattle grazing endophyte-infected fescue for 50-70 days in the spring, each 1,000 lb./acre increase in stocking rate resulted in a decrease in ADG that ranged from 0.15 to 0.67 lb./day.
He cautions, though, because stocking rate-gain relationships are highly variable from year to year, it’s difficult to draw generalizations regarding optimal stocking rates. That said, and until models are available to help predict optimal stocking rate on a year-by-year basis, results from his study suggest that the average optimal stocking rate for stocker cattle in the upper mid-South region will be around 1,300 lbs./acre.
The range in stocking rate varied considerably during the four years of the study due to, among other things, the highly variable precipitation. With the conditions experienced during the four years of this study, optimal stocking rate would have varied from about 300 lbs./acre to about 1,700 lbs./acre, Vanzant says. However, the wide range of environmental conditions across those four years allows for a reasonably robust estimate of the average optimal stocking rate for early spring grazing, he adds.
Based on his research, he says four key concepts can be drawn:
- Optimum stocking rate, from an economic standpoint, is less than the stocking rate that yields maximum gain per acre.
- High stocking rate can catastrophically influence net profit, particularly when adverse conditions require destocking. Such effects will be compounded by maintaining high stocking rates over long periods of time.
- Market factors, particularly the buy-sell margin, substantially affect optimal stocking rate.
- The optimal stocking rate for generating net profit varies tremendously from year to year.
Given that last point, it’s clear the eye of the master is still critical when it comes to fattening the calf. Until computer models can be developed to help put some science behind the decision, cattlemen will continue to rely on their experience and knowledge of cattle and their pastures to make year-to-year decisions.