Perfil metabólico e desempenho zootécnico de filhotes de peixe-boi da Amazônia (Trichechus inunguis) mantidos em cativeiro, alimentados com diferentes sucedâneos do leite materno

Abstract

This study evaluates the metabolic profile, the zootechnical performance, and the correlation between subcutaneous fat thickness and body measurements of captive Amazonian manatee calves (Trichechus inunguis) fed different substitutes for maternal milk. Ten calves with average weight of 65.75 kg and mean age of 15.3 months were fed different milk diets in two phases. During the first phase, the calves were fed substitute 1 (S1), which is what was routinely used by Laboratory of Aquatic Mammals of the National Institute of Amazonian Research LMA/INPA. During the second phase they were fed substitute 2 (S2), which was formulated based on the nutritional composition of T. inunguis maternal milk. Each phase lasted 62 days, when blood samples were collected for biochemical and haematological analysis. Body measurements, milk consumption and subcutaneous fat thickness (EGS) measurements were also collected during this period. Values of total protein (PT), albumin (ALB), globulin (GLO), glucose (GLI), total lipids (LT), cholesterol (COL), triglycerides (TRI), calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), hematocrit (Ht) and hemoglobin (Hb) were evaluated to determine the metabolic profile. Gained weight (GP), linear growth gain (GCL), liquid milk consumption (CLL), dry matter intake (IMS), and feed conversion ratio (CA) were evaluated for analysis of zootechnical performance. Measurements for EGS (cm) were obtained using a portable ultrasound machine. The measurements of weight, linear length (CL), maximum circumference (CM) and tail base circumference (CBC) were performed using an analog scale (kg) and a tape measure (cm) respectively. There was a decrease of PT, ALB, GLO, Ca, P and K after feeding the animals with S2 when compared to values obtained with S1. After the period of feeding S2, the values of GLI, LT, COL, and TRI (36.70±12.90 mg/dL, 519.30±44.99 mg/dL, 180.10±35.57 mg/dL and 65.20±22.09 mg/dL respectively) were well below the values found when the animals were fed with S1 (53.50±9.28 mg/dL, 733.70±128.07 mg/dL, 307.20±84.42 mg/dL and 153.70±59.38 mg/dL respectively). Sodium levels were higher when S2 was administered (148.16±1.15 mmol/l) than when S1 was given (143.47±0.99 mmol/l). Values of Ht and Mg did not differ between treatments. The metabolic profile was within normal levels for the species, with the exception of ALB and GLO levels, which were below and above standard respectively. When analyzing zootechnical performance there was a significantly higher GP (p<0.0001) and GCL (p=0.0090) when the animals were fed S2 (12.30 ± 4.64 and 7.85 ± 2.87 respectively) than when fed S1 (6.31 ± 3.70 and 5.37 ± 3.47 respectively). CLL decreased (p=0.0038) and IMS increased (p<0.0001) when S2 was administrated. Individuals had a better CA when fed S2 (15.01 kg of milk/kg) than S1. There was no correlation (p>0.05) between EGS and weight (r=0.0084 and r=0.1650 for S1 and S2 respectively), EGS and CL (r=0.0565 for S1 and r=0.2127 for S2), EGS and CM (r=0.0105 for S1 and r=0.0906 for S2) and EGS and CBC (r=0.0559 and r=0.2449 for S1 and S2 respectively). S2 was more efficient, resulting in increased weight gain and growth of the animals. Additionally, the metabolic profile performed proved to be a viable method for the nutritional assessment of this species. EGS was found to not be a good indicator of body condition for Amazonian manatee calves, as despite variation in its levels, no effects on growth or weight were observed. S2 showed satisfactory results in the zootechnical performance of T. inunguis and may be used as a new artificial substitute in the diet of captive calves. Keywords: Amazonian manatee, nutrition, Serum biochemical, Hemogram, weight gain, subcutaneous fat thickness, body condition