Oklahoma State University Emeritus Extension Animal Scientist, Dr. Glenn Selk, offers herd health advice as part of the weekly series known as the "Cow Calf Corner" published electronically by Dr. Peel and Dr. Glenn Selk. Today, Dr. Selk talks about matching inventory to available resources.

Mature weight and milk production of MANY commercial beef cows are both greater than they were 30 to 40 years ago. Many ranchers have not recently weighed the adult cows in their herd to know what average mature weight to expect. Therefore most commercial ranchers would underestimate the mature size of their cows. To expect large, heavy-milking cows to be in moderate body condition at calving and maintain condition through breeding, they must receive more feed than smaller lighter-milking cows. The graph below uses the 1996 National Research Council’s guidelines to show the energy needs of two different body types and levels of milk production. These energy requirements would be representative for cows calving in February and March and weaned in October. The top line represents the energy needs of 1250 pound heavy-milking beef cows versus the lower line which represents the needs of 1100 pound moderate-milking beef cows. The values graphed are the megacalories per day required to maintain body weight throughout the year.

The larger heavier-milking cow requires about 34% more energy on the average for an entire year. Consequently, an operation that was carrying 100 of the smaller cows must carry only 66 of the larger cows in order to utilize the same quantity of forage from that farm or ranch. She also will need 34% more winter hay and supplement to maintain body condition. In some commercial herds, there are cows much larger than the 1250 pounders depicted in this graph.