It may sound like I work for Elanco, and I don’t, but if ever there were a time for an additive like Rumensin, it is now.
One of my clients asked me yesterday what corn prices are going to do. I told him that my crystal ball has a crack in it, so I can’t always rely on it, but that all the experts think that high corn prices are here to stay. This is due to continually increasing world demand and our own government favoring ethanol production over dairy and livestock producers and people who have to eat.
So, what can we do? If you plug current corn and soybean meal prices into the University of Wisconsin FeedVal program, most of the byproducts are still competitively priced. They should be maximized in your rations. Other than this and good feed management, what else can we do?
Getting more milk per pound of feed will help offset increased feed costs. Rumensin has an FDA claim for “increased production of marketable solids corrected milk per unit of feed intake”, i.e., better feed efficiency. It may sound like I work for Elanco, and I don’t, but if ever there were a time for an additive like Rumensin, it is now.
Recent research indicates that higher Rumensin levels than have typically been fed to dairy cattle may result in more milk in fresh cows and greater feed efficiency in later lactation animals. The higher levels generally cost less than 2 cents more/cow/day. The FDA approved levels in complete feeds (TMRs) is 11 g to 22 g Rumensin per ton of feed dry matter.
I’ve always found this wording kind of confusing. For a cow eating 50 lb. of dry matter, it would result in Rumensin intakes between 275 and 550 mg/cow. Most dairies have been feeding on the low side of this range.
Issues with butterfat depression related to Rumensin, dietary starch and unsaturated fat levels have made dairy producers and nutritionists (myself included) reticent to try higher levels of Rumensin. This was especially true this past year when it seemed that butterfat was depressed in many herds due to some unknown reason (I have my theory). Now that we’re feeding corn and corn byproducts from the 2010 corn crop, it seems that butterfat is back.
Research indicates that feeding 450 mg of Rumensin/cow/day in early lactation resulted in significantly higher milk/cow when compared to zero and 300 mg. Fat test was lower on the higher dose, but due to the increase in milk, the fat yield was higher.
Rumensin reduces the relative proportions of gram-positive bacteria in the rumen in favor of gram-negative bacteria. Gram-positive bacteria produce acetic and butyric acid. Gram-negative bacteria produce propionic acid. Propionic acid is utilized more efficiently for glucose production, hence more efficient use of feed energy. In practical terms, the higher dose of Rumensin can replace the equivalent of up to 2 lb. of corn energy in the diet.
The response to Rumensin appears to differ with stage of lactation. In the dry period, cows consume less feed, but use the feed more efficiently. During the transition period and early lactation, cows tend to eat the same or more feed and derive more energy per pound of feed, reducing the period of negative energy balance and resulting in more milk. Once positive energy balance is achieved in mid and late lactation, dry matter intake may decrease and feed efficiency increases.
The rumen bacteria require time to adjust to feed changes. If you do increase the Rumensin level in your diets, do it in steps. Probably 50 mg/cow/day increments for two to three weeks would be sufficient. If dry cows consume 300-350 mg of Rumensin, they will be well adjusted by the time they freshen. However, increasing the level to 450 mg in the fresh cows would require that you ratchet up the feeding rate faster than I just suggested. If 450 mg per cow is the target level for the herd, then 400 mg per cow is probably appropriate for a fresh cow ration.