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Abstract: The Florida manatee (Trichechus manatus latirostris) is a threatened herbivorous marine mammal with a long intestinal tract and prolonged intestinal transit time that should allow symbiotic microbes in their large intestine to thoroughly digest otherwise indigestible fiber in their diet. Nevertheless, the apparent digestibility (AD) of fiber has not been well documented in Florida manatees. This study measured the AD of dry matter (DM), crude protein, neutral detergent fiber (NDF), and acid detergent fiber (ADF) in three adult and two sub-adult manatees offered diets that are typically fed to rehabilitating manatees recovering from illness or injury. These diets were composed principally of romaine lettuce with or without added vegetables and fruit. Acid detergent lignin (ADL) was used as a marker; hemicellulose was calculated as NDF-ADF, and cellulose as ADF-ADL. Acid insoluble ash (AIA) proved unsuitable as a marker because concentrations were lower in feces than in food. The AD of all the nutrients measured was high (> 61%) and was very high for cellulose (> 86%). The AD of all nutrients except hemicellulose decreased as ADL in the food increased (r ≤ -0.74, p ≤ 0.02). Intake of DM increased both as ADL in food increased and AD of DM decreased (r2 ≥ 0.77, p ≤ 0.002). Our results demonstrate that evaluations of nutrient and energy requirements of manatees during rehabilitation must take account of the high AD of fiber in typical diets. Furthermore, measuring ADL in the diet may help to more accurately estimate energy availability from the diet of manatees.
Key Words: Florida manatee, Trichechus manatus latirostris, apparent digestibility, fiber, protein, lignin
Page Numbers: 513-524