Ingestion behavior and forage intake by grazing cows in temperate climate. Review

Abstract

The objective was to review, based on predominantly recent publications, the knowledge on the components of the ingestion behavior (IB) of cows that graze in a temperate climate, and their relationship with the characteristics of the pastures that regulate the daily forage intake (FI). The components of IB that regulate FI are bite mass (BM, g DM bite-1), bite rate (BR, bites min-1), intake rate (IR, g DM min-1) and grazing time (GT, min d-1). The mass, height and density of pasture forage affect BM and consequently, FI. Pasture height is related to IB components and is useful for assessing FI. Based on studies in temperate pastures in a vegetative state, it is highlighted that the FI of cows increases with increases in pasture height, because they harvest bites of greater BM, which allows them to obtain high IRs. But there is evidence that IR may decrease in pastures that are too tall; to process larger bites, cows reduce their BR and execute more compound and chewing jaw movements. In contrast, in short pastures, cows increase their BR and GT, to remedy the reduction in IR due to harvesting lighter weight bites, although this does not fully compensate for the decrease in IR. Therefore, to maintain high IRs, cows should not be forced to consume forage at high grazing intensities.