By Mike Rankin
For many livestock producers, the onset of winter means digging into those stored forage inventories with the realization that any forage additions can only be accomplished by the writing of a large check. Though the nation's forage inventory is as high as it's been since 2005, there are still good reasons to use this time of year for taking a census of bales, silage reserves and livestock needs. For those in the South, a winter pasture assessment is also in play.
Though measuring and counting may seem mundane, it's better to know now that you might come up a bit short than to find out next March when forage replacement costs are at their peak. Further, any farm that requires a year-end balance sheet, which most do, will also need to have an accurate account of stored forage (and its value). There's no better way to impress your farm loan officer, aside from a good check, than with a detailed, accurate account of year-end forage supplies and future needs, especially if the former is larger than the latter.
Baled hay:
Baled hay is relatively easy: Make a count and determine the weight per bale for each type (and perhaps cutting). The critical point to be made here is that bale weights must be accurate. This may involve some time taken for scaling groups of bales. If a "guess" is off by 100 or more pounds per large bale, this can result in a fairly significant error over a season's worth of harvested forage. Also be sure to take into account moisture if feed needs are being determined on a dry matter basis.
Silage:
There are two types of silage inventory estimates: inaccurate and almost accurate. Keep in mind . . . these are estimates. An inaccurate estimate is easy and can be done from the comfort of your living room. An almost accurate estimate takes some effort. Actually, silage bales and, to a lesser degree, silo bags lend themselves to relatively solid estimates. In the case of baleage, an accurate weight, number and moisture are all that is needed. For bags, which tend to have less variation front to back than other types of silos, there are several charts and spreadsheets that can be used. Note that unfilled ends need to be accounted for, as do feeding and handling losses.
Horizontal bunker or pile silos have many inherent variables when it comes to accurately estimating stored forage. Density (pounds per cubic foot); length; width; dome height and slope; and ramp length all differ between storage units. There are many spreadsheets (for example, here, here and here) that can help with this task, but it's up to you to safely obtain accurate dimensions. I've also found that the accuracy of measurements is directly related to the type of weather that prevails on the day calculations are being made. It's good to get this job done before weather conditions totally disintegrate. Further, given the size of some silage piles and bunkers, a misrepresentation of actual density can result in an inventory estimate that is significantly off the mark.
Tower silos have the advantage of a fixed diameter. Still, there is the realization that more forage exists in the bottom 10 feet of a silo than in the top 10 feet. Further, if some silage has already been fed from a tower silo, it needs to be accounted for using a silo chart such as this one.
Forage quality
Once the forage census duties are complete, the next chore is to match forage inventories with livestock needs. Inventory livestock by age and/or feed requirements. Forage quality plays a large role in feedout rates. For this reason, forages need to be tested so that reasonable ration inclusion rates can be calculated. Your nutritionist can help with this task; forages of differing quality need to be allocated to those livestock classes where they are best utilized. Finally, begin multiplying animal numbers by days and forage needs, then compare total forage needs with forage inventories. Again, keep straight whether calculations are being made on an as-fed or dry matter (preferred) basis.
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