Most cattlemen realize the advantages of using a mineral supplement for grazing cattle in the summer. Most cattlemen are also aware that, in the fall, a protein supplement will greatly improve the utilization of mature grass.

So, at what point between summer and fall should one start using a protein supplement versus just a mineral supplement? The technical answer would be when the grass cannot supply adequate protein for the animal. For grazing yearlings this would be when crude protein of the grass falls under 12%. For the lactating cow, the level of crude protein required will be greatly impacted by her level of milk production, and will generally decrease over the summer months.

Roughly, it will drop from 11% at the beginning of the summer to 8% or lower prior to weaning. Unless you are able to sample grass, and test it for crude protein content, this still does not tell you when you could see a benefit from using a protein supplement on grass.

There is one thing you can easily do, and that is observe the maturity of the grass in your pastures. Once grass shoots a seed head, crude protein content and digestibility decline rapidly. We must remember that drought will further hasten this decline as well. As grass becomes mature and begins to lose its green color, you are most certainly in a satiation where protein supplements will provide a boost to cattle performance.  This is likely to be earlier in the summer with yearling cattle than with beef cows.

The table below will give you some idea how fast the forage quality will decline in just a months’ time.

Self-fed protein supplements can greatly increase forage utilization in late summer and fall. Depending on the form of supplement used, costs can range between 30 and 60 cents per head per day (including delivery costs).  They can also draw cattle into underutilized areas of a pasture to further “stretch” that pasture. Both of these attributes of self-fed supplements are very beneficial when drought conditions exist.