& ECKEL

fed continuously at a rate of 50 to 200 mg/ head/day in a minimum of 1 pound of medicated feed/head/day and is not to be self-fed.

A team of researchers led by Dr. David Lalman from Oklahoma State University compiled the results of 26 experiments from 21 publications evaluating the effects of monensin supplementation on performance and reproduction of mature beef cows. This was published in the journal Translational Animal Science last summer and is freely available at https://doi.org/10.1093/tas/ txac086.

Key findings for mature cows were:

Ї Bodyweight and body condition score changes were not affected by feeding monensin.

Ї Monensin significantly decreased forage intake by 7.8 percent.

Ї Milk production was increased by 5.4 percent in a small data set of experiments.

Ї Monensin also decreased the days to estrus post-calving by 18 days and increased the number of cows showing estrus before breeding by 19 percent.

Ї Calculated energetics from feed intake and performance data show feeding monensin increases dietary energy by 4.7 percent.

This supports using monensin to help push thin cattle to start cycling before breeding that would otherwise be late breeders or open.

In current conditions, with limiting forage resources and high feed costs the 8 percent reduction in feed intake by mature cows is a major consideration in using monensin while supplementing cows this winter.

The combination of reduced feed intake, increased milk production, and earlier estrus activity has the potential to have long-term positive impacts on cowherd efficiency.

We will look at the results from the analysis of including monensin in diets for developing replacement heifers in a future article.