Browsing Journal of Range Management, Volume 38, Number 3 (May 1985) by Authors
Effects of Hunger Satiation on Diet Quality by Grazing SheepJung, H. G.; Koong, L. J. (Society for Range Management, 1985-07-01)The effect of hunger satiation on selectivity for diet quality by sheep grazing a smooth bromegrass (Bromus inermis) pasture was studied with esophageal fistulated sheep. Fifteen wethers (45.8 +/- .7 kg) were allotted to 5 treatments: nonfasted, fasted for 16 h and then fed 0, 135, 271, or 407 g of pelleted feed. Nonfasted animals were confined at 0800 h and sheep receiving pellets were fed at 0700 h. One animal from each treatment was included in groups released for grazing at 0900, 0930, and 1000 h. Sheep grazed the smooth bromegrass pasture for 30 min. The experiment was conducted on 4 consecutive days. Nonfasted sheep had a lower rate of intake than fasted animals (0 g pelleted feed) (47 vs. 124 mg/min/kg BW^0.75, P<.05), but the quality of the diet selected did not differ (P>.05). All treatment groups selected diets of higher quality than the green fraction of the pasture collected by handclipping. Consumption of increasing quantities of pelleted feed by fasted animals resulted in linear (P<.05) increases in in vitro dry matter disappearance and crude protein content of diet samples. Rate of forage intake and cell wall content of the ingested forage declined linearly (P<.05) with increasing consumption of pelleted feed by previously fasted sheep. Composition of forage cell wall material in the diet samples also changed with pellet feeding, cellulose content increased while lignin content decreased. Overnight fasting of esophageal fistulated sheep did not influence selectivity for forage quality relative to nonfasted animals, but satiation of hunger, as a result of ingestion of a highly digestible feed after a fast, resulted in increased diet quality selected by the animals.