Energy expenditure related to the act of eating in Granadina goats given diets of different physical form

Abstract

The energy cost of eating was measured in four goats averaging 38 kg and fitted with rumen cannulas. Heat production (HP) was estimated in each goat over restricted periods of approximately 15 min while standing and eating continuously in a confinement respiration chamber. The animals were given feeds of different nature and physical form ranging from shrubs to concentrates. The energy cost of eating was calculated from the increment in HP above the average HP during the prefeeding period. The energy cost was related to the type and amount of feed consumed and also to the time spent eating. In a parallel experiment, similar amounts of the feeds eaten normally (oral feeding) were introduced into the rumen through a fistula. The increases in HP during and after fistula-feeding were negligible, which indicates that all of the increase in HP during eating is to be attributed to the energy cost of eating per se, mainly to theact of food prehension, mastication and propulsion in the alimentary tract. The rate of ingestion (g DM/min) ranged from 6·3 for fresh cut lucerne (Medicago sativa) to 46-99 for concentrates. The energy cost of eating (J/kg body weight (BW) per g DM) averaged 7·08 for fresh cut lucerne, 9·02 for roughages and 1·55 for concentrates and was 2·24 and 4·75 for pelleted and chopped lucerne hay respectively. When theenergy cost was expressed as a function of time spent eating, it ranged from 45 to 144 J/kg BW per min, depending on the physical form of the feed.