By Travis Meteer, University of Illinois Extension
First-calf cows are dealing with a large demand for nutrition. Nutrients are needed to support maintenance (normal bodily processes), lactation (milk for her calf), growth, and reproduction. Mature cows do not have the demand of growth… they are done growing. Virgin heifers do not have the nutrient demand for lactation… they do not have a calf. Thus, first-calf cows experience the most demand for nutrients and are the most difficult to get re-bred.
The flow of nutrients results in reproduction being one of the last served. This should make some sense. Cows not able to support themselves and their newborn calf are not good candidates for re-breeding. They likely will not offer longevity and productivity in the given environment. However, if the farmer is delivering the feed in a drylot, it is his fault for not supplying the correct amount to the cow.
Proper heifer development and setting the stage before she calves is the most important. I suggest having bred heifers in a BCS of 6 or even 7 knowing they will lose some weight during their first lactation. I think it is crucial that you select for moderate milk genetics that allow cows to maintain themselves on forages and does not require continuous supplement.
If you find yourself looking at thin 3 year-olds right now, you will need to start feeding an energy dense supplement to get them gaining weight. Research has shown thin cows gaining weight will cycle and breed much faster than thin cows just maintaining or especially losing weight.
Young cows are an investment yet to pay off. In general, it takes roughly 6 calves for a cow to pay herself off. Knowing this, mismanagement of 3 year olds can be a costly mistake to a beef farm. If you are trying to build your cow-herd it will start with getting those currently in it to re-breed.