The effect of fasting on short‐term cattle grazing behaviour

Abstract

Abstract The effects of fasting on feeding behaviour, intake rates, and diet quality were studied with steers grazing vegetative Lolium multiflorum swards. Fasting interrupted the normal alternation of grazing and rumination and led to longer grazing times (0·65 vs. 0·45 of observed time), shorter rumination times (0·15 vs. 0·30 of observed time), and higher total dry matter (DM) intakes (6200 g DM vs. 3750 g DM d −1 )‐Fasting did not affect prehended bite size which averaged 047 g DM bite −1 . Declining bite size within a day was explicable by changes in herbage mass. Biting rate (38.9 bites min −1 ) and instantaneous intake rate (2675 g DM min −1 ) of fasted animals were considerably higher than non‐fasting animals in the mornings, but neutral detergent fibre (NDF) concentration of the diet (0 742 of organic matter) was generally not depressed by fasting. Consequently, non‐fasted animals appeared to be feeding suboptimally since their nutrient intake rates were considerably lower than that which they are capable of exhibiting. Mastication rates per unit NDF intake were considerably lower in the morning for fasted animals (0·78 chews g −1 NDF intake) which suggested that their intake rates may have led to larger ingested particle size. Therefore, on Lolium multifiorum swards, the steers attained a higher intake rate by masticating the forage less while maintaining diet quality.