Abstract

Nutrient composition of the manatee pellet was designed to resemble natural forage, such as water hyacinths, and artificial forages, such as romaine lettuce, that have been used successfully to maintain and grow rescued manatees. The nutrient composition of water hyacinths and romaine lettuce was determined by either standard feed analysis or from a search of the literature. A standard manatee pellet was produced based on the nutrient composition of romaine lettuce and water hyacinths, along with information gained from personnel engaged in feeding manatees. Alfalfa was used instead of romaine lettuce or water hyacinths as the forage component in the pellet because it has been successfully used before to feed rescued manatees. Pellets were considered to be a "romaine lettuce concentrate" to assist in determining daily requirements. The dried pellets had a nutrient density 20 times that of romaine lettuce. The pellets varied in size but were roughly one-inch cylinders with a diameter of approximately 0.75 inch and had a mean weight of 5.3 g (SD = 0.8). The pellets were cooked to destroy pathogens, extruded and expanded to allow them to float and take up water, thus avoiding a potential problem of dehydration and constipation in the animals. It is believed that Manatees do not drink salt water and probably not much fresh water. The animals apparently get most of their water from free-water in the food and metabolic-water that is obtained from metabolism. The standard pellets were light green in color and were dried to contain less than 10% moisture in order to inhibit the growth of microorganisms and permit long-term storage. The extruded pellets had a mean density of 0.875 g/cm³ (SD = 0.11) and would float for more than 30 minutes. The pellets absorb 3.4 g of water per gram of pellet in about 5 minutes and are estimated to contain 0.14 g of metabolic water per gram, for a total water source of 3.5 g of water per g of pellet and 25 g of water per g of protein. Each g of romaine lettuce is estimated to contain 0.95 g of free-water and 0.015 g of metabolic-water or 0.965 g of available water per g of lettuce; however, because of its high free water content, the lettuce supplies 19.3 g of water per g of nutrient contained in the lettuce and 120 g of water per g of protein. Thus, romaine lettuce supplies about 4.8 times more available water per gram of protein than pellets. The daily water requirement for manatees kept in either fresh or salt water is not currently known. Therefore, the complete supplementation of natural forage in the manatee diet by pellets may require the incorporation of more free and metabolic water into the pellet. The pellets were stored for protection and convenience of use at room temperature in sealed, labeled, plastic 5-gallon buckets (9 kg of pellets) and 3-gallon buckets (5.5 kg of pellets). The pellets have been stored for 6 months at room temperature in our laboratory. After 6 months of storage the pellets show no obvious deterioration in appearance or aroma and were readily accepted by the manatees. A 5-gallon bucket holds the equivalent of about 180 kg (400 lbs) of lettuce and a 3-gallon bucket holds the equivalent of about 110 kg (240 lbs) of lettuce. The 3-gallon buckets seem to be more convenient for testing purposes. The pellets were tested for acceptance by manatees at Sea World of Orlando, Mote Marine Laboratory and Homosassa Springs Wildlife Park. At Sea World the pellets were offered to animals that had never received any kind of concentrate feed and to animals that had received some concentrate feed (monkey chow). Monkey chow is used by some attractions as a treat but large amounts cannot be fed because of the danger of dehydration and constipation. Neither group of Sea World animals seemed to accept the pellets readily and apparently acceptance of pellets by recently rescued animals would probably require some training. However, the captive animals at Mote seemed to accept the pellets and are currently being observed to see if they continue to accept pellets. Five manatees at Homosassa Springs Wildlife were offered the pellets and immediately accepted them. The animals would seek out the pellets even in the presence of lettuce. Replacing lettuce with pellets in the captive manatee diet would represent a significant savings in feed costs since the cost of a 5-gallon bucket of pellets is estimated to be less than $25 while the nutrient equivalent of 400 lbs of lettuce costs about $400. Lettuce costs per animal at Homosassa Springs is estimated to be approximately $600 per month. Replacement of lettuce with pellets would reduce the cost to less than $50 per animal per month.

Acknowledgments

Mr. Wayne T. McClellan and Mr. Joseph P. Cardeilhac provided technical assistance. The authors wish to thank the handlers at all of the attractions for their valuable contributions to this project. This project was supported by a grant from the Florida Fish and Wildlife Conservation Commission.