Controlling variation in feed intake through bunk management

ABSTRACT The desire to control variation in daily feed intake by feedlot cattle stems from the obvious concern that a significant aberration in grain intake can lead to clinical acidosis or death. Although less dramatic, aberrations also occur when cattle have unrestricted access to feed. A cyclic pattern of higher and lower daily DMI can cause gain efficiency to be less than that predicted from the mean DMI because responses in ADG to changes in DMI are not linear. If bunk management is a means of ameliorating either of these events, it is presumed that management ascribed to the pen is affecting variability in daily DMI by individuals within the pen. Two likely mechanisms by which bunk management may affect intake patterns are limiting availability of feed to prevent overconsumption events or affecting animal behavior so that daily intake is more consistent. Bunk management approaches that have been evaluated for their effect on production rates, and in some instances on day-to-day variability in DMI, include: 1) limiting the quantity of feed available or the amount of time feed is available each day; 2) the timing and frequency of feed deliveries; 3) linear bunk space allocation; and 4) mixed diet or segregated ingredient feeding. When bunk management approaches alter responses, it may be that the approach has a direct biological and/or behavioral effect on the animal or that the approach itself involves less variation, which is consequently favorable to the animal (or the data). The causes of variable results in bunk management research can be ambiguous. Management and feeding systems are difficult to standardize, which can cause the definitions of controls, the characterizations of treatments, and the context of responses to be inconsistent. A rudimentary limitation is that in systems where individual daily DMI is known, competition for access to feed is usually not comparable to typical pen feeding. There is evidence of favorable responses to some bunk management approaches that could be used commercially. Effects on production efficiency in these studies are of significant biological and economic importance, and underlying mechanisms must be more fully characterized to allow broad application.

Implications

Feed delivery management research is fraught with ambiguities. Feed delivery management can affect production efficiency of cattle fed high-grain diets. Although variability in feed delivery, as we assess it in feeding programs, may not be documenting variability in intake by individuals within a pen, systems that achieve more consistent feed deliveries seem beneficial. Bunk management programs that prevent cyclic intake patterns and/or overconsumption for pens of steers may be most beneficial. Both the reference point from which the magnitude of feed delivery deviations is measured and the types of deviations that occur are relevant when assessing variability. To minimize variation, management must anticipate physiological and behavioral responses by cattle to their environment. More research is needed to develop management programs that minimize digestive disorders and are adaptable to different diets, cattle, climates, and feeding situations.

Key Words: Cattle, Feed Intake, Feedlots, Management

© 2003, by the American Society of Animal Science. All rights reserved.

J. Anim. Sci. 2003. 81(E. Suppl. 2):E133-E138