Putting cows out on corn fields with a lot of corn is a recipe for acidosis (gain overload), abortion, and possibly death, if their rumen bacteria are not properly prepared. Cattle that become acidotic for even a short time can have reduced performance long term due to damage to the rumen wall. Therefore, taking the time to avoid acidosis is very important.
How do I know how much corn is in the field?
If corn is planted in 30-inch rows, count the total number of ears in three different 100-foot furrow strips and divide by two to give an approximate number of bushels per acre. Be sure to do this at multiple locations in the field as the amount of dropped ears may vary across the field. If the amount of dropped ears is above 8-10 bushels per acre, then proper precautions need to be taken.
Adapting cattle to grain to prevent acidosis
Before turn out, producers should start feeding grain and work them up to at least 7 to 10 lbs/hd of grain over period of a week to 10 days. Then give cattle access to the amount of acres to limit to 10 lbs/cow for 5 to 7 days then move to 15 lbs/cow for 5 to 7 days. After this point, they can have unlimited access to the field. These cows can be moved to the next field once the majority of the corn grain has been grazed. There is still risk of acidosis/founder but it will be less with this adaptation period.
| Quick guide to allocating corn residue with excessive ear drop to cows | ||||
|---|---|---|---|---|
| Ears in 300 ft | Grain, bu/ac | Grain, lb/ac | limit 10 lb/d | limit 15 lb/d |
Acres per 100 cows | ||||
20 | 10 | 560 | 1.8 | 2.7 |
30 | 15 | 840 | 1.2 | 1.8 |
40 | 20 | 1120 | 0.9 | 1.3 |
50 | 25 | 1400 | 0.7 | 1.1 |
60 | 30 | 1680 | 0.6 | 0.9 |
70 | 35 | 1960 | 0.5 | 0.8 |
80 | 40 | 2240 | 0.4 | 0.7 |
90 | 45 | 2520 | 0.4 | 0.6 |
100 | 50 | 2800 | 0.4 | 0.5 |
Grazing spring calving cows
In addition to the concern with having cows founder or get acidosis, we also have an issue with cows getting fat. Not weaning before turnout is an option to help increase the cow’s energy requirement.
The best option, regardless of whether you wean or not, is to limit access to corn by strip grazing daily. Allowing the pairs access to 10 lbs of corn and feeding 2 lbs of DM from distillers should allow the cows to maintain bodyweight and the calves to gain 1.0 to 1.5 lbs/d. If cows are weaned then limiting cows to no more than 10 lb/d of grain will allow them to gain about 0.5 to 1 BCS over the winter.
If daily allotment is just not an option, then the next best option is to work cows up to a full grain diet as suggested above. However, if you are going to need to move to a new field over the winter (based on stocking rate and the amount of residue in the field), then once again there is an issue; because they will likely have a period of time where all the grain had been grazed and the cows were eating only residue. Then when they are moved to a new field, they will have full access to grain again but their rumen is no longer adapted. Thus, there are two options: once cows are acclimated to full grain they could be split into groups on multiple fields that they will graze for the rest of the winter. Or move all the cows through all fields quickly allowing them to harvest most of the grain, once all fields have the majority of the grain gleaned then let them move back through the fields more to make use of the rest of the residue.
Capitalize on the grain (energy) by grazing calves
Calves do not initially seek out ears in the field as this is a learned behavior thus they are more likely to self-adapt by slowly increasing the amount of gain they consume each day. Although there is some risk of acidosis, feeding them corn and working them up to 5 lbs/calf of grain before turn out should help. Calves eating only corn grain and residue will not have enough protein in the diet to make full use of the energy available. Feeding 2 lbs of distillers can increase gain substantially and increase returns. Using the calves to glean the majority of grain and moving them from field to field before the cows may be a great way to reduce risk and make money at the same time.
Using cull cows to glean the fields?
Putting weight on cull cows can increase revenue Using them ahead of the rest of the cow herd can reduce risk long term negative effects of founder/acidosis in the cows that will remain in the herd. It might even be worth buying thin cull cows, grazing them through and selling fat cull cows at the end.
Can’t I just add some sodium bicarbonate to the mineral or water?
Research in beef cattle consistently shows that buffers like sodium bicarbonate do not prevent acidosis when cattle consume too much grain too quickly. Studies in finishing systems, indicate that adding bicarb to the diet does not protect the rumen when cattle overeat starch. These intake equated to 4 to 8 oz per day of sodium bicarbonate. This is why feedyards do not rely on buffers for acidosis control and instead use step-up rations to gradually adapt cattle to grain. The same principle applies in down-corn fields: if cattle suddenly consume large amounts of grain, no amount of sodium bicarbonate in the mineral or water can offset the rapid production of lactic acids that drive rumen pH down. Instead we suggest adapting the rumen bacteria to grain before turnout or strip-grazing to limit the amount of corn grain consumed.