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| Author(s): |
Pierina Jocelyn Mendoza Yengle
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Jaboticabal. 2021-05-11. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2021-04-15 |
| Advisor: | Aulus Cavalieri Carciofi |
| Abstract | |
There is very little information about egg incubation conditions, nutrient requirements, and captive management of the red-footed tortoise (Chelonoidis carbonaria) for conservation purposes. In the first study of this thesis, it was considered that reptile embryos respond to temperature changes with metabolic and physiological adjustments that influence hatchling success, phenotype, behaviour, and growth rate. Climate change and global warming can affect the reptile population by altering the frequencies of hatchling survival and phenotypes. Therefore, previous studies proposed artificial incubation as a potential strategy for mitigating these effects. Red-footed tortoise eggs were collected and incubated at constant temperatures of 27.5°C and 29.5°C to investigate the physiological effects of temperature on embryo development, hatchling morphology and early growth rate. The direct effects of temperature on the incubation period, lost egg mass, hatching index, hatchling size, and mass were evaluated at hatching and at three months of age. Hatchlings from 29.5°C presented shorter incubation times (141 says) than those from 27.5°C (201 days; P<0.05). Egg mass loss, hatchling mass, and size at hatching were not different between the incubation temperatures (P>0.05). However, the hatching index (survival rate) was lower (64.5% versus 100%) in eggs incubated at 29.5°C, but the hatchling mass and straight plastron width were higher at 3 months of age than those for eggs incubated at 27.5°C (P<0.05). These results clearly indicate that incubation temperature has an important influence on hatchling success and hatchling size and mass in the first months by influencing the early growth rate. The second objective of the thesis considered that changes in the carapace are an important problem, observed in many zoos around the world. The objective was to determine the effect of two diets, one with a high fiber content and the other with a high starch content, on energy metabolism, nutrient digestibility, and growth of the red-footed tortoise. Following a completely randomized design, with 20 hatchlings, randomly divided into two experimental diets (10 hatchlings per feed). The study lasted 18 months, during which the animals received only their respective experimental diet, and water ad libitum. The evaluations performed on the animals included: determination of the apparent digestibility coefficients of the nutrients and gastrointestinal transit time at 5 and 11 months; determination of the metabolic rate at rest and postprandial, with calculation of the heat increment in respirometry chambers by indirect calorimetry at 6 and 12 months; evaluation of the growth and characteristics of the carapace, with special attention to the formation of pyramiding; and determination of body composition by dual energy X-ray absorptiometry (DXA) when the animals reached 250 g of body mass. Values of P <0.05 were considered significant. The analyzes were conducted by R Studio Software (version 3.2.3, AT). Animals fed with the high starch diet showed higher mass-specific dry matter intake (12.75±3.11mg) compared to animals fed with the high fiber diet (10.20±3.37mg) (P<0.05). They also presented shorter transit times and gastrointestinal retention offood, of 2.95±1.01 and 8.09±2.05 days, respectively (P<0.05), compared to animals fed a high fiber diet. (4.23±1.40 and 10.05±2.41 days, respectively). Higher digestive efficiencies of the evaluated nutrients were observed in animals fed with the high starch diet, with an apparent energy digestibility coefficient of 75.73±2.68% compared to 68.10±2.35% for the high fiber diet. (P<0.05). The apparent digestibility of crude protein, however, was higher in the high fiber diet (P<0.05). Regarding the production of heat production at rest and post-prandial at the preferred temperature, these were not affected by the diet (P>0.05). Heat increments of 43.85 ± 14.92 and 41.33 ± 14.66 kJ/kg/day were observed for the high starch and high fiber diet, respectively (P>0.05). The animals fed with the high starch diet presented, at 13 months, wider plastrons and carapaces, resulting in higher growth rates of the carapace width than the hatchlings fed with the high fiber diet (P<0.05). Under the two animal diets, they developed pyramiding growth, but those fed with the high starch diet developed this doming with greater intensity (P<0.05). Additionally, hatchlings fed with the high starch diet had lower mineral content (1.88±0.15% versus 2.15±0.19%) and lower bone density (0.13±0.01g/mm2 versus 0.15±0.02g/mm2) than those fed with the high fiber diet (P<0.05). In the third study, hatchlings fed with the high fiber diet were kept at two temperatures (18 ° C and 28 ° C), to assess the effect of temperature on the consumption of gross and digestible energy, resting and post-prandial metabolic rate at 6 and 12 months old, and surface body temperature. Higher mass-specific consumption of gross energy and body mass gain were obtained in the spring and summer. The highest and lowest resting metabolic rate at 28°C were obtained in spring and winter, respectively. At 28°C, the animals showed higher daily consumption of gross and digestible energy, oxygen consumption, CO2 production, and rest and post-prandial metabolic rate, with a heat production at rest of 30.56±4.07kJ/kg/day at 28 °C and only 7.71±1.26 kJ/kg/day at 18°C (P<0.05). Specific heat increment coefficient was also affected by temperature, with digestion being less energy-intensive at 28°C than at 18°C (P<0.05). Atypical respiratory coefficients were observed at 18°C (0.30-0.50). In addition, a strong influence of body mass has been described on the resting metabolic rate with an allometric exponent of 0.62 and 0.92 at 28°C and 18°C, respectively. In addition, it was observed the priority of thermoregulating the surface temperature of the head under low temperature, and animals presented higher surface body temperatures after feeding. In conclusion, the present work indicates the importance of considering the effect of temperature and the composition of the diet on energy metabolism and growth of red-footed tortoise. Feeds with higher digestible energy, such as high starch, can induce accelerated carapace growth with less mineralization. In addition, the importance of considering the difference in energy requirements in different thermal regimes. (AU) | |
| FAPESP's process: | 19/14923-0 - Effect of starch and fiber on the energy metabolism and growth of red-footed tortoise (Chelonoidis carbonaria) |
| Grantee: | Pierina Jocelyn Mendoza Yengle |
| Support Opportunities: | Scholarships in Brazil - Master |