ARS | Publication request: Digestive utilization of ozone-exposed forage by rabbits (Oryctolagus cuniculus)

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 7, 2012
Publication Date: January 31, 2012
Repository URL: http://handle.nal.usda.gov/10113/54039
Citation: Gilliland, N.J., Chappelka, A., Muntifering, R.B., Booker, F.L., Ditchkoff, S. 2012. Digestive utilization of ozone-exposed forage by rabbits (Oryctolagus cuniculus). Environmental Pollution. 163:281-286.

Interpretive Summary: Air pollutants such as ozone reduce growth and yield of many crops and forages in the United States and elsewhere in world. Ozone can also affect the chemistry of many plants, which might have indirect effects on grazing animals. In this study, the effect of elevated ozone (2x ambient) on forage quality and subsequent nutrient utilization by rabbits, a mammalian herbivore, was evaluated. A mixture of common Southern Piedmont grassland species was exposed to ambient (non-filtered, NF) or twice-ambient (2x) ozone in open-top chambers for six weeks, harvested and analyzed for fiber, lignin, crude protein and phenolics. Samples of the forages were fed to white rabbits for 10 days in controlled feeding trials. Forage digestibility by rabbits was significantly lower for 2X than NF diets. The decreased digestibility was associated with increased concentrations of saponifiable phenolics. Elevated ozone concentrations would be expected to have a negative impact on forage quality resulting in decreased nutrient (dry matter) utilization by both ruminant and non-ruminant mammalian herbivores in Southern Piedmont grasslands under projected future climate scenarios.

Technical Abstract: A mixture of common Southern Piedmont (USA) grassland species (Lolium arundinacea, Paspalum dilatatum, Cynodon dactylon and Trifolium repens) was exposed to ozone [ambient (non-filtered; NF) and twice-ambient (2X) concentrations] and fed to individually caged New Zealand white rabbits (Oryctolagus cuniculus) in a digestibility experiment. Forages and feed refusals were analyzed for concentrations of total cell wall constituents, lignin, crude protein, and soluble and hydrolyzable phenolic fractions. Neutral detergent fiber and acid detergent fiber digestibility by rabbits were significantly lower for 2X than NF forage. Decreased digestibility could not be attributed to lignin concentrations, but was associated with increased concentrations of acid-hydrolyzable and saponifiable phenolics. Exposure of forage to elevated ozone resulted in decreased digestible dry matter intake by rabbits. Elevated ozone concentrations could be expected to have a negative impact on forage quality, resulting in decreased nutrient utilization by mammalian herbivores in Southern Piedmont grasslands under projected future climate scenarios.