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Know the Score: Improved Body Condition in Beef Cows Increases Conception Rates, Decreases Postpartum Intervals

GREENFIELD, Ind., — Cow-calf operators constantly struggle to find the right balance between optimal body condition scores — which improve conception rates — and keeping feed costs as low as possible.

Research has shown the body condition of cows at breeding and calving plays a major role in the length of the postpartum interval and conception rates. It is generally accepted that a minimum body condition score of five must be achieved and maintained to have good conception rates.1

“A body condition score of five on the one-to-nine scale is described as a moderate to thin animal whose last two or three ribs cannot be seen unless the animal has been shrunk,” explains Doug Hufstedler, PhD, technical consultant with Elanco. “There is little evidence of fat in the brisket, over the ribs or around the tailhead in such an animal.”

Adding Rumensin®, the only ionophore approved for reproducing beef cows, to supplemental feed can lower forage needs while helping maintain cow performance which aids producers as they strive to reach that critical balance point.5

Rumensin has been widely used in the beef cattle industry since 1976 as a feed additive to improve feed efficiency in feedlot cattle, improve average daily gain in stocker cattle and replacement heifers and to prevent and control coccidiosis in all stages of cattle production.2,3 In beef replacement heifers, Rumensin consistently improves weight gain that results in fewer days to first estrus4, a valuable benefit because a heifer that breeds earlier in its first breeding season generally breeds earlier throughout its lifetime. In 2005, Rumensin was cleared for use in mature reproducing beef cows. It has proven to be an effective forage management tool for mature cows by decreasing the amount of supplemental forage required or increasing the carrying capacity of the forage base, all while maintaining body weight and reproduction.

“Optimizing forage utilization can pay big dividends by reducing the amount of forage required to maintain desired body condition scores in the herd,” says Hufstedler. Rumensin works by increasing the amount of energy available to cows for growth and reproductive purposes. This effect is seen with both forage- and grain-based diets. Adequate energy is needed to achieve short postpartum intervals and high conception rates. “The increase in available energy that Rumensin provides is an added benefit for replacement heifers in purebred and commercial herds,” said Hufstedler. “Replacement heifers reach puberty earlier when fed higher-energy diets compared to those fed lower-energy diets, particularly when diets consist largely of low-quality forages.”

According to previous research5,6, Rumensin provides additional energy available to the animal through manipulation of rumen fermentation. In growth trials, it was calculated that the additional energy derived from feeding 200 mg of Rumensin daily to growing heifers was equivalent to feeding at least one pound of corn grain.5 In other studies6, feeding 50 mg to 200 mg of Rumensin daily reduced the feed requirement by five percent to ten percent while maintaining cow body weight and reproductive performance.

Rumensin is available for beef cows as a component of your supplemental feeding program. Ask your Elanco sales representative, animal-health distributor, nutritional supplier or veterinarian to help you increase your cow herd’s profitability with Rumensin.

Elanco is a global innovation-driven company that develops and markets products to improve animal health and efficient food animal production in more than 100 countries. Elanco employs more than 2,000 people worldwide, with offices in more than 30 countries, and is a division of Eli Lilly and Company, a leading global pharmaceutical corporation. Additional information about Elanco is available at

Consumption by unapproved species or feeding undiluted may be toxic or fatal. Do not feed to veal calves. The label contains complete use information, including cautions and warnings. Always read, understand and follow the label and use directions.

Rumensin: Mature reproducing beef cows

• For improved feed efficiency when receiving supplemental feed: Feed continuously at a rate of 50-200 mg/hd/d. Cows on pasture or in dry lot must receive a minimum of 1 lb of Type C Medicated Feed per head per day. Do not self-feed.

• For the prevention and control of coccidiosis: Feed Rumensin at a rate to provide 0.14-0.42 mg/lb of body weight per day up to 200 mg/hd/d.

Rumensin: Growing cattle on pasture or in drylot (stockers and feeders and dairy and beef replacement heifers)

• For increased rate of weight gain: Feed 50-200 mg/hd/d of Rumensin in at least 1 lb of Type C Medicated Feed. Or, after the 5th day, feed 400 mg/hd/d every other day in at least 2 lbs of Type C Medicated Feed. The Type C Medicated Feed must contain 25-400 g/ton of Rumensin.

• For the prevention and control of coccidiosis: Feed Rumensin at a rate to provide 0.14-0.42 mg/lb of body weight per day up to 200 mg/hd/d. The Type C Medicated Feed must contain 25-400 g/ton of Rumensin.

• Free-choice supplements: 50-200 mg/hd/d of Rumensin.

Rumensin: Feedlot cattle

• For improved feed efficiency — Thoroughly mix Rumensin 80 to make a complete feed that provides 5-40 g/ton (90% DM basis). Feed continuously to provide not less than 50 nor more than 480 mg/hd/d. No additional improvement in feed efficiency has been shown from feeding Rumensin at levels greater than 30 g/ton (360 mg/hd/d).

• For the prevention and control of coccidiosis due to Eimeria bovis and Eimeria zuernii — Feed continuously (10-40 g/ton) to provide 0.14-0.42 mg per pound of body weight per day, depending on severity of challenge, up to a maximum of 480 mg/hd/d.

1Kunkle, WE & RS Sand. 1991. Effect of Body Condition on Rebreeding. Florida Cooperative Extension Service Fact Sheet AS 51. University of Florida, Gainesville, Fla.

2McDougald, LR. 1980. Chemotherapy of Coccidiosis. PL Long (ed.). The Biology of the Coccidia. University Park Press, Baltimore. p. 373-427.

3Long, PL & TK Jeffers. 1982. Studies on the Stage of Action of Ionophorous Antibiotics Against Eimeria. J. Parasitology 68(3):363-371.

4Summary of Trial Nos. T1F207848, T1F307853, T1F367767, T1F427824 & T1F4896A3. Elanco Animal Health. Data on file.

5Thomas, EE. Critical Point Feeding of Rumensin in the Beef Cow Operation. Elanco Animal Health.

Greenfield, IN.

6Rumensin (monensin sodium) Freedom of Information Summary (NADA 95-735).

Rumensin® is a trademark for Elanco’s brand of monensin sodium.

© 2009 Elanco Animal Health.

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