Don’t get blinded by spring green

Don’t quit feeding hay too soon in the spring. It will be tempting with dwindling hay supplies to skimp on the feeding program and hope that the cows can satisfy their nutritional needs from sprigs of grass. But don’t short your cows now. Research shows that cows that lost weight just prior to calving had weaker calves and lower conception rates later in the spring, especially those that lost weight before and after calving.

There are numerous studies that show thinner cows have lower pregnancy rates. It suffices to say that cows at BCS 4 or below need help; cows should be closer to BCS 6 for best results. If you start to graze animals too soon, they flash graze—just chasing around anything green rather than buckling down and gnawing on fescue stems.

Some producers will be prone to forget the herd’s mineral needs as pastures begin to open. But remember that cows undergoing the stress of a hard winter will utilize minerals faster than cows with little stress. To obtain optimum immune function and reproductive performance from your herds, make sure to provide sufficient levels of macro and trace minerals.
Speaking in defense of the pasture, in a spring following drought, grass roots are suffering from last growing season’s water shortage—this is the case in spite of the pastures starting to green up. To help pastures recover, grazing should be delayed by a couple weeks to let roots recover and the plant build up leaf area.

Drought weakens plant root systems, and heavy grazing on drought-stressed cool-season grasses (fescue, bromegrass, Orchardgrass) makes the situation worse. Cool-season grasses grazed heavily early in the year will lower the total forage yield, which translates directly to lower carrying capacity.
Usually the best time to begin grazing cool-season pastures is when the plants are 3 to 4 inches tall. If you start earlier than that, the subsequent yields will likely be lowered. Yet it’s a fine line: if the pastures are too wet, you might refrain from grazing until grass is 6 inches tall. But in most of Today’s Farmer country, if you wait longer than that, the pastures will rapidly “get away from you.”

Given that normal (I have the usual questions about what is “normal” weather) springs are wet, graze the best-drained areas first. Start grazing in a different pasture every year, to maintain stand persistence and control weeds.
Native warm-season pastures will be treated differently than cool-season pastures. If you have pastures of switchgrass or bluestem, the pastures should be grazed early to remove early season grasses and weeds. Getting rid of the weeds helps retain moisture and reduces competition for the warm-season species. Grazing early growth on native, warm-season pastures will not harm the warm-season grass as long as cattle finish grazing before new grass shoots get more than a couple inches tall. In northern Missouri this is the first week of May. The further south you go, the earlier this happens.

In my discussions with the MFA agronomists about when to start grazing, I jotted down the following points:
•    There is no right or wrong time. Much depends upon stand condition.
•    Many producers will be frost-seeding legumes into stressed pastures this winter. It is critically important that stressed pastures receive adequate fertility before grazing. Growers should apply their N, P and K late winter and let that take hold before aggressive grazing.
•    In areas where stands have become thin, grazing too early will stimulate weed problems. Some weeds graze well, others do not.
•    If the pasture is extremely stressed, it would be a good time to renovate. In this situation we recommend a kill-smother-kill program. No grazing should be done on those fields.
Dr. Jim White is ruminant nutritionist for MFA Incorporated.