Q. I have a lot of downed corn ears in my field, I have heard of this rumen inoculant that I can give to avoid acidosis. Is this something I should use? (December 2017)
A. Putting cattle not adapted to corn-based diets out on fields with a lot of downed corn can cause acidosis, lameness and, if severe enough, death. Un-adapted cattle get acidotic when eating corn because the bacteria that use lactic-acid have not built up in the rumen.
Lactic acid is a strong acid ―10 times stronger than other acids in the rumen― produced by bacteria when digesting corn. In gain-adapted animals bacteria in the rumen, such as Megasphaera elsdenii, will digest lactic acid, producing weaker acids in the process. This helps the rumen maintain a higher pH. Essentially, the reason why the amount of grain consumed by cattle should be slowly increased is so the population of these lactic acid-using bacteria can build up. Inoculating cattle before turning them out on down corn is to boost the population of lactic acid-using bacteria.
To my knowledge no controlled research has been conducted using a ruminant inoculant when turning cows out to fields with downed corn. However, inoculating un-adapted yearlings with Megasphaera elsdenii and placing them directly on a finishing diet has been reasonably successful. (See Orally dosing steers with Lactipro (Megasphaera elsdenii) decreases the quantity of roughages fed during finishing, KSU, 2013.) Thus, this method may have promise for mitigating some of the risks of acidosis associated with grazing down corn. It should be noted though that in this trial 35% of their diet was not corn and a high dose (100 ml for 900 lb yearlings) of the inoculant was used.
Currently, the cost of dosing cows (100 ml) with Megasphaera elsdenii (Lactipro Advance, MS Biotec) is about $8 per cow. The product has a very short shelf life (14 days) and is manufactured after it is ordered. Thus, it's important to be prepared to dose animals and turn them out as soon as the product is delivered.
Given the extreme risk with cows going from no corn to essentially an all-corn diet, I would still suggest feeding corn gradually and working up to 7 lb/day before dosing and turning out into corn fields with high amounts of downed ears (10 plus bu/ac).
It should also be mentioned that if there is enough down corn for gestating spring-calving cows to eat as much as they want for a month or more, they are likely to become very fat. In this situation we would expect them to gain two to three of a body condition score per month. Thus calves, cull cows, or fall pairs are much better options for using this high energy resource.
For more information on dealing with down corn, please read "Down Corn: Problem or Opportunity for Cattle Producers?".
Mary Drewnoski, UNL Beef Systems Specialist
University of Nebraska–Lincoln