Responses of two Negev Desert phasianids, the chukar (Alectoris chukar) and the sand partridge (Ammoperdix heyi), to diets of different water content

Abstract

Dry matter intake, water influx and body mass changes were measured in eight chukars (Alectoris chukar; mean body mass 428 g, SD 55) and eight sand partridges (Ammoperdix heyi; mean body mass 186 g, SD 13) offered three ad libitum diets differing in water content. The diets, offered for 28 days, were as follows: ‘control’, chow (10% water) + water; ‘alfalfa’, chow + alfalfa (78% water); and ‘duckweed’, chow + duckweed (92% water). The initial responses of the chukars and sand partridges to both experimental diets were decreases in dry matter intake, water influx and body mass. Responses were greater to the alfalfa diet than to the duckweed diet and in chukars than in sand partridges. Chukars offered alfalfa lost 33·7% body mass over the first 21 days and then gained 3·8% over the last 7 days. Sand partridges offered alfalfa lost 15·0% over the first 14 days, maintained body mass over days 15–21 and gained 8·8% over days 22–28. The maintenance of body mass was accomplished without an increase in alfalfa intake, but with an increase in chow intake. Water influx during days 15–21 was only 60% of control for the sand partridges, but their dry matter intake was 93% of control. Chukars and sand partridges offered duckweed increased their duckweed intake 1·5 and 1·7 fold, respectively, during days 8–28. Their dry matter intakes and water influxes were similar to the respective controls during this period, and both steadily increased their body masses. It may be concluded that the initial decreases in dry matter intake and body mass in both species were a result of insufficient water intake. The smaller initial body mass loss in both species while feeding on duckweed than on alfalfa, was due to the higher water content of the duckweed. The smaller body mass loss for sand partridges than for chukars was due to the former's lower water:dry matter intake requirement.