FEEDING ECOLOGY, NUTRITION, AND ENERGETICS OF LIVESTOCK IN A NOMADIC PASTORAL ECOSYSTEM (TURKANA, KENYA, CAMELS, CATTLE, SHEEP/GOATS).

摘要

Field studies were conducted during 1981-82 to determine the effects of pronounced seasonality on various aspects of the feeding ecology, activity, nutrition, and productivity for camels, cattle, goats, sheep, and donkeys used by nomads to exploit a drought-pulsed savanna in Ngisonyoka Turkana, Kenya. Work also included a preliminary vegetation survey.; Cattle and camels were grazing and browsing specialists, respectively, while the other species were feeding generalists. Shifts in diet compositions and habitat use occurred with season. In aggregate, these animals provided an opportunistic harvesting capacity that exhibited an equitable use of all forage classes from a complementary array of feeding sites.; Dietary percentages of crude protein (CP), cell solubles (CS), and in vitro digestible dry matter (IVDDM) were highest for livestock during brief wet seasons (April-May) and variously declined thereafter, with associated increases in percent holocellulose and lignin. Small-bodied species (goats, sheep) and/or those that largely consumed browse (camels) typically had diets higher in % CP and % CS and lower in % fiber than those of the large grazers (cattle, donkeys). Camel diets were clearly the lowest in terms of % IVDDM.; Relative to the dry season, the wet season was a time of reduced travel, increased feeding time, and higher water intake for most species. However, feeding time for camels and water intake for camels and donkeys tended to be seasonally static. Potential constraints on feeding time were most likely for cattle in the late-dry period (November-March).; Analyses of seasonal allocation patterns and requirements for nitrogen and energy indicated that the late-dry period was also the time of markedly reduced lactation, lowered feed intake, weight loss, and negative nitrogen and energy balance for all species. Camels were typically the most productive species overall in absolute terms (especially for milk), but in relative terms (W(,kg)('0.75)) camels were the least productive species for all intervals except the late dry, when camels appeared least affected by nutritional constraints. Attempts to simulate observed weight dynamics by modeling suggested that cattle, but especially camels, lowered their basal demand for energy in the dry season.