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| Author(s): |
Ludmilla Geraldo Di Santo
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Jaboticabal. 2021-07-13. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2021-06-25 |
| Advisor: | Aulus Cavalieri Carciofi |
| Abstract | |
Tortoises are reptiles that, in captivity, commonly exhibit metabolic disorders such as hepatic lipidosis, due to unbalanced diets with high energy content. The present study had as objectives to evaluate the nutritional parameters, energy metabolism and general health with emphasis on the hepatic tissue of adult red-footed-tortoises fed with three extruded feeds with high levels of starch or fat, compared to the control diet containing high levels of fiber. Forty-four adults tortoises were used, males and females, distributed in three extruded feeds (Control, Starch and Fat), totalizing 15 repetitions (tortoises) per treatment, except for the Starch diet (14 tortoises) because one animal died during the adaptation period. The experimental period lasted 19 months, and included: blood samples collection for biochemical, fat metabolism and hematologic analysis on day 4 (baseline), 183 and 369 (final); hepatic biopsy of 18 tortoises for histopathologic evaluation at days 1 to 3 (baseline) and at days 366 to 368 (final); evaluation of feed preferences of the experimental feeds at days 5 and 19 (individual evaluation) and at days 575 and 587 (collective evaluation); evaluation of gastrointestinal transit time, digestibility assay, and volatile fatty acids, lactate, ammonia and faeces pH (days 120 to 270); resting energy expenditure determination by respirometry (days 423 to 437); determination of daily energy expenditure, body water composition and body water flux using the double labelled water – DLW (baseline: days 60 to 75; final: days 447 to 469); determination of body composition using DEXA (days 366 to 368) and levels of plasmatic lipoproteins (days 572 to 573). Data was submitted to analysis of variance and means compared by Tukey’s test (P < 0,05). Dry matter, organic matter, starch, ether extract and energy digestibility were higher in the Starch diet (P<,0001), wherein the fat was not well used and most of it was eliminated in the faeces. The microbial intestinal fermentation products were similar among the diets (P>0,05), but presented lower values than ruminants and other fermentative herbivorous reptiles such as iguanas. The intake of digestible fiber was higher in Control diet, digestible starch in Starch diet and fat in the Fat diet (P<0,05), but there were no differences regarding the digestible energy. All these factors culminated in the animal's growth and weight gain throughout the x experimental period, being similar among diets. The haematological and serum biochemistry parameters were within the reference values, overall, there was no effect of diet, but of sex and period (P>0,05). The Starch diet provided higher levels of hepatic enzymes and serum cholesterol, HDL, and LDL lipoproteins for the males. The lipoproteins maintained the pattern of cholesterol and triglyceride composition like those found in mammals and were influenced by vitellogenesis of females. Despite the low utilization of fat, the Fat diet resulted in higher levels of VLDL carrier of triglycerides and cholesterol in the females, followed by higher total concentration of triglycerides (P<0,05). Regarding the cholesterol and triglycerides LDL fraction, there was an increase linked to the consumption of the Control diet. The histopathological evaluation made possible to verify a decrease in the hepatic steatosis, but alterations, such as hemosiderosis, increase in melanomacrophages and lipofuscin deposition increased in the final period samples. There was diet effect regarding the presence of lipofuscin, having a lesser extent in the Starch diet (P=0,021). The body composition evaluated by DEXA shown lower bone mineral density and mineral content in females, in addition to presenting greater lean mass (P<0,001). In the DLW analysis, there was no effect of the diet on the assessment of body composition. The CO2 production and energy expenditure were higher at baseline (P<0,05) due to the higher environmental temperature associated with greater body weight. The body water flux was constant regardless the diet or period (P>0,05). The energy expenditure, accessed by the indirect calorimetry, was similar among diets, but it was lower compared to DLW. As the diet fat was eliminated in the faeces almost in its totality, there was no effect of this substrate on health and metabolism parameters. The maintenance of body composition, regardless of diet, provided an energy expenditure, with activity restriction and at the beginning of the digestive period, of 9,68±1,04 kJ/kg/day, and, when considering the animal under muscular and reproductive activity, of 22,86±2,30 kJ/kg/day. (AU) | |
| FAPESP's process: | 17/24585-9 - Starch ou fat intake on digestibility, energetic metabolism and health of tortoises (Chelonoidis carbonaria) |
| Grantee: | Ludmilla Geraldo di Santo |
| Support Opportunities: | Scholarships in Brazil - Doctorate |