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item Burns, Joseph

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2002
Publication Date: 7/16/2002
Citation: Burns, J.C., Sollenberger, L.E. 2002. Grazing behavior of ruminants and daily performance from warm-season grasses.. Crop Science.

Interpretive Summary: The daily dry matter intake of grazing animals is the major determinant of subsequent animal daily performance. This aspect is difficult to measure in grazing trials. Efforts have been made to understand animal ingestive behavior and to relate short-term animal response to long-term animal daily responses. This paper presents the approaches used to measure animal daily dry matter intake from short-term ingestive behavior measurements and clarifies the pasture canopy-ingestive animal behavior interactions that occur in a grazing setting. The importance of ingestive mastication in particle reduction and the relationship between particle size of the ingested forage and season-long animal daily gain is presented. The concept of particle size as the currency that relates the pasture canopy and animal performance is proposed.

Technical Abstract: An estimate of the animal-production potential of pastures can be assessed by knowing the daily dry matter (DM) intake of the grazing animal and the digestibility of the DM consumed. The objective of this paper is to examine the relationships between pasture canopy characteristics, ingestive behavior and daily animal response from warm-season pastures. Of daily DM intake and digestibility of the DM consumed, the former is the most variable and the most difficult to determine. One approach to estimating daily DM intake has been to use the components of ingestive behavior to determine a short-term intake rate (g min-1) which can be scaled using grazing time (min-d) to give a 24-h dry matter intake (kg d-1). This approach has been used experimentally with some success, but has not found application in production settings. While aspects of ingestive behavior, including ingestive mastication, are common to all grazing ruminants, literature indicates that differences occur among ruminant species and that animals ingest different pasture species differently. This results in plant-animal interactions. Frequently these dynamics are not clearly addressed for cool-season and warm-season pastures in literature reviews which adds undue confusion to the general area. Ingestive behavior is discussed relative to animal- and pasture-generated bounds which operate within paddocks and can greatly alter ingestive behavior estimates. Also presented are relationships between diet particle size, associated with ingestive mastication, and steer daily gains.