The Influence of Diet Composition upon Growth and Development of Sandhill Cranes

Abstract

-Experiments were conducted to evaluate the effect of protein, metabolizable energy, and sulfur amino acid content of five diets upon growth and development of captive Florida Sandhill Crane (Grus canadensis pratensis) and Greater Sandhill Crane (G. c. tabida) chicks raised under controlled conditions. A high protein (32%) diet resulted in faster growth than that obtained when a lower protein (24%) ration was supplied. Florida Sandhill Crane chicks fed a diet containing 2,160 kcal/kg grew significantly slower than chicks fed a ration containing 2,830 kcal/kg. Reducing the sulfur amino acid content of a ration containing 24% protein from 0.88% to 0.73% significantly slowed the growth of young cranes. A 17% incidence of leg disorders and a 25% incidence of wing abnormalities occurred between 7 and 28 days of age among Greater Sandhill Cranes fed a high protein diet. Florida Sandhill Cranes grew slower than Greater Sandhill Cranes irrespective of the type of ration they were provided and did not develop leg or wing abnormalities. Abnormalities invariably developed only in the most rapidly growing Greater Sandhill Cranes. Diets that promoted slower growth reduced the incidence of abnormalities. A ration formulated to contain a low (0.73%) sulfur amino acid level appeared to be the most suitable for slowing growth rates of captive-reared Sandhill Cranes and reducing the risk of abnormaiwing or leg development. The Endangered Wildlife Research Program at the Patuxent Wildlife Research Center is engaged in comprehensive research on Whooping Crane (Grus americana) and Sandhill Crane (G. canadensis) biology, captive production, and reintroduction techniques (Erickson 1968, 1976). Crane chicks reared from eggs taken from parents are susceptible to leg and wing abnormalities at this facility and other institutions (Carpenter et al. 1976, Kepler 1978, Archibald and Viess 1978). The abnormalities generally appear between 10 and 28 days of age. Wing abnormalities consist of unilateral or bilateral twisting of the wing feathers similar to a condition called “angel wing” in waterfowl (Francis et al. 1967). Most often the carpal bones twist or droop, resulting in the displacement of young primary feathers from the normal position. A slight rotation or bending of one leg, frequently occurring as early as 7-10 days of age, is usually the first indication of abnormal leg development. Shortly afterward, leg bones become twisted, sometimes slipping from the intertarsal joints. Since leg rotation and displacement of tibiotarsus or femur bones from joints can occur within 48 h in apparently normal individuals that are 18 to 28 days of age, leg disorders can develop rapidly. The condition, which in some respects resembles chondrodystrophy (perosis) in poultry, usually worsens to the extent that standing is no longer possible and death frequently follows. Little is known about skeletal deformities among crane chicks in the wild, however, chicks raised by their parents in captivity appear to be less susceptible to wing and leg disorders than those raised from eggs collected from nests. No such deformities have occurred among 18 chicks recently parent-reared at the Patuxent facility. Preliminary tests of possible causes of leg disorders focused upon environmental factors such as floor surfaces, bedding materials, and pen design. The latter was considered since crane chicks are unusually aggressive (Littlefield and Ryder 1968, Drewien 1973) and active, and it was hypothesized that some leg disorders might result from injuries sustained striking enclosure surfaces. Altering environmental conditions reduced the incidence of leg disorders, particularly among Florida Sandhill Cranes (G. c. prutensis) when chicks were raised in pens containing 1 O-l 5 cm of sugarcane bedding. Leg disorders continued to occur, however, particularly among Greater Sandhill Cranes (G. c. tabida) and young Whooping Cranes raised under similar conditions. Specific nutrient requirements of cranes are unknown; however, diets fed to cranes that developed disorders were specially formulated to contain ample amounts of nutrients (choline, nicotinic acid, biotin, folic acid, manganese, and zinc) whose deficiency is known to raise the incidence of perosis and other leg disorders in poultry. These nutrients were pro-