Beyond the Law of Supply and Demand for Forages

M.L. Eastridge and J.L. Firkins 
Department of Animal Sciences

The law of supply and demand apply to forages  large supply, low demand, low prices; low supply, high demand, high prices. On the other hand, marketability is another issue, especially with respect to silages, with proximity to market being a key point. But because of the requirement for fiber in the diet, forages can not be totally replaced in the ration with nonforage feeds, even if supply is very limited and prices are quite high. Variability in weather conditions often causes havoc with forage production, and although it is a little early to tell for this year, we need to be prepared to adjust feeding programs to the supply and quality of forages available.

Current research in the Department of Animal Sciences at OSU has shed some light on the amount of forage needed in rations for lactating dairy cows. But, before we discuss the lactating cows, lets take a snapshot at the dry cow program. Far-off dry cows should be fed primarily forage and a small amount of grain, with the grain serving principally as a carrier of minerals and vitamins. At 21 days prepartum, cows should be switched to a ration designed to transition cows for the ration that will be fed postpartum. The transition ration should contain about 14 to 15% CP, consist of 8 to 10 lb of grain, and the forages be those that will be fed postpartum. Always preserve the highest quality forage on the farm for the close-up dry cows and the lactating cows.

Given that forages are needed to provide fiber, what is the amount of forage needed in the diet to supply the minimum amount of effective fiber? Oops, lets first define effective fiber. It is the fiber in the diet that will stimulate rumination (cud chewing)  more chewing, more saliva flow to buffer the rumen. Effectiveness of the fiber is determined by the source of the fiber and the particle size of the fiber source.