Feed Bunk Evaluation for the High Producing Herd

Posted: January 7, 2005

Evaluating the feed bunk of high producing dairy cattle is important to help determine if they are being fed in a manner that meets their nutrient needs. Your feeding system along with your feeding strategy, or the way you manage the system, is crucial to providing the majority of your cows with balanced diets in adequate amounts.

One basic component of a balanced diet is to supply reasonably constant amounts of forage relative to concentrates throughout the day. The forage to concentrate ratio affects the relative rate of volatile fatty acid production in the rumen and this ultimately affects rumen pH. Rumen pH affects the population and species of bacteria that proliferate in the rumen, and they ultimately in turn affect how effectively feeds are digested in the rumen. Therefore much of the function of a normal dairy cow's rumen relies on a constant and adequate amount of forage entering the rumen relative to the grain, or concentrates.

When cows are allowed to sort their diet in a manner that results in large fluctuations in forage to concentrate at different periods of time throughout the day, the end result can be one or more of the following: decreased overall digestibility, increased acidosis, cows having erratic feed intake throughout the day or between days, lower milk fat tests, and an increased occurrence of metabolic disease within the herd.

Some of the typical reasons cows sort their TMR diets are as follows: contain a general long particle size, are very dry (>60 % dry matter), have great variation in density of ingredients, or contain a large amount of dry hay. In each of these cases, the cow can sort the diet because the physical attributes of the TMR allow it to be easily separated by the cow. Other feed system attributes that cause increased sorting are related to feed bunk space per cow, amount of time that feed is available, and bunk management, which is related to the number of times that a TMR is fed per day along with the number of times feed is pushed up to the cows.

Cows that sort typically eat large particles last, sort against large particles especially if the longer forage particles are feedstuffs that have stems. Typically, dry alfalfa hay is easy for dairy cows to sort; however coarse grass hay and coarsely chopped corn silage also can also be sorted. Research has shown that high producing cows have the greatest ability to sort feed over other groups of cows in the herd.

Feed sorting should be avoided if at all possible. The consequences are never good, as production and herd health suffers when cows sort. Therefore it is advisable to evaluate your feeding system in relation to any sorting problems and to use good feed management practices that avoid sorting. Some ways to reduce sorting include: feed more frequently and push -up feeds often; use high quality hay and process it properly before putting it in the TMR; process corn silage if it is dry; and be sure that the forage chopper is functioning properly and knives are sharp to avoid long pieces of corn silage stalks, leaves, and cobs; use fibrous byproduct feeds so that the finer portion of the TMR is higher in fiber; be sure that no forage component is longer than 4 inches, feed or push-up feed often and never avoid feeding to an empty bunk. Also keep in mind that anything that creates more competition in the feed bunk increases the possibility for sorting and consumption of large concentrate meals possible. Neither of these is conducive to maintaining a constant and proper rumen pH.

Jud Heinrichs
Dairy and Animal Science Extension