A complex Enrichment Diet improves growth and health in the endangered Wyoming toad (Bufo baxteri)

Evaluating the Efficiency of Black Soldier Fly (Hermetia illucens) Larvae in Converting Mackerel Head Waste into Valuable Resources

The seafood processing industry generates significant waste, including mackerel heads (MH), constituting 20-32% of total waste. This study explored the potential of utilizing MH as a feed source for black soldier fly larvae (BSF larvae). BSF larvae are known for their ability to efficiently convert organic materials into nutrient-rich biomass. Five concentrations of MH (0, 10, 20, 30, 40, and 50% in chicken feed) were fed to BSF larvae for eight days. After harvesting, their growth, MH conversion efficiency, nutritional content, and heavy metals reduction potential were measured. BSF larvae showed optimal growth when fed with a feed containing 20% MH, resulting in a 14.36-fold increase in weight compared to the control group, as determined by the Fisher's Least Significant Difference Test. BSF larvae maintained a survival rate of 99.33%. With the lowest feed conversion ratio (FCR) of 2.09 at 20% MH, feed efficiency was improved by up to 65.15%, and feed reduction up to 73.53%. MH enhanced lipid and protein content in BSF larvae. Furthermore, BSF larvae in this study showed higher polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as other amino acids which are required for breeding animals. The current study highlights the potential of MH as a feed source for BSF larvae, improving nutritional biomass. It also suggests BSF larvae as an eco-friendly option for handling seafood processing waste and as an alternative feed source for animals.

An Update on Companion Inland Bearded Dragon (Pogona vitticeps) Nutrition

Evidence-based recommendations for the amount, type, and frequency of food items and supplements are lacking for bearded dragons. General recommendations based on ecological data, a few studies, and experts in the field are to: provide at least 50% high-fiber plant matter dusted in pure calcium and less than 50% adult and lower fat larval insects gut loaded with an 8% calcium diet and dusted with pure calcium, provide ultraviolet B lighting for vitamin D3 synthesis, provide multivitamins on a weekly basis, or monthly at minimum, provide a water dish large enough to soak and drink.

Lack of vitamin B12 impairs innate and adaptive immunity of Cuban tree frog (Osteopilus septentrionalis) tadpoles

Vitamin B12 is a micronutrient required by a variety of organisms for healthy cellular functioning. Despite the systemic effects observed in cases of B12 deficiency, relatively little is known about how vitamin B12 affects immune health, especially in amphibians, which are declining at unprecedented rates. In this study, we tested how supplementing an algae diet with B12 affects the innate and adaptive immunity of Cuban tree frog (Osteopilus septentrionalis) tadpoles. We found that innate immunity, as measured by a bacterial killing assay, was significantly more robust in B12-supplemented tadpoles than control tadpoles, but no significant differences were found in natural antibody production or hematocrit between groups. Adaptive immunity, as measured by Aeromonas hydrophila-specific IgY antibodies, was significantly greater in tadpoles challenged with A. hydrophila and supplemented with B12 than in control tadpoles, those only challenged with A. hydrophila, and those only given B12. Our results suggest that vitamin B12 is an important factor in maintaining a functional immune system in tadpoles, which may also be true for all vertebrates.

Vitamin A, Vitamin E, and Carotenoid Concentrations in Livers of Marine Toads (Rhinella marina)

Global amphibian population decline is a major concern. Therefore, conservation centers have become increasingly needed for population sustainability breeding programs. This need makes proper nutrition programs while in human care imperative. The specific nutritional focus of this current research was to analyze vitamin A, vitamin E, and carotenoid (apocarotenoid, β-carotene, β-carotene ester, β-cryptoxanthin, lutein, lutein ester, zeaxanthin, and zeaxanthin ester) concentrations in the liver of 66 free-range marine toads (Rhinella marina) over a two-month period after entering human management. Toads were fed supplemented crickets randomly assigned to one of two diets: Diet 1 consisted of brown house crickets (Acheta domestica) gut loaded with Mazuri® Cricket Diet 5M38 and small amounts of sweet potato and carrots; Diet 2 consisted of an identical diet with the gut loaded crickets additionally dusted with Repashy® Superfoods Vitamin A Plus. Ten toads were euthanized prior to human management on Day 0 to assess baseline liver nutrients. Seven toads consuming each of the two diets (14 toads total) were euthanized on Days 9, 15, 32, and 62. Regardless of diet treatment, there were decreases (p < 0.05) in all the analyzed nutrient concentrations over the 62-day human management period. The results from this study indicate that higher dietary vitamin A, vitamin E, and carotenoid content may be needed and/or the cricket gut loading and dusting techniques used to feed the amphibians food source insects may be inadequate.

Does dietary β-carotene influence ontogenetic colour change in the southern corroboree frog?

Ontogenetic colour change occurs in a diversity of vertebrate taxa and may be closely linked to dietary changes throughout development. In various species, red, orange and yellow colouration can be enhanced by the consumption of carotenoids. However, a paucity of long-term dietary manipulation studies means that little is known of the role of individual carotenoid compounds in ontogenetic colour change. We know even less about the influence of individual compounds at different doses (dose effects). The present study aimed to use a large dietary manipulation experiment to investigate the effect of dietary β-carotene supplementation on colouration in southern corroboree frogs (Pseudophryne corroboree) during early post-metamorphic development. Frogs were reared on four dietary treatments with four β-carotene concentrations (0, 1, 2 and 3 mg g-1), with frog colour measured every 8 weeks for 32 weeks. β-Carotene was not found to influence colouration at any dose. However, colouration was found to become more conspicuous over time, including in the control treatment. Moreover, all frogs expressed colour maximally at a similar point in development. These results imply that, for our study species, (1) β-carotene may contribute little or nothing to colouration, (2) frogs can manufacture their own colour, (3) colour development is a continual process and (4) there may have been selection for synchronised development of colour expression. We discuss the potential adaptive benefit of ontogenetic colour change in P. corroboree. More broadly, we draw attention to the potential for adaptive developmental synchrony in the expression of colouration in aposematic species.

Evaluation of vitamin A gut loading in black soldier fly larvae (Hermetia illucens)

Black soldier fly (BSF) larvae are potentially an excellent source of calcium for insectivores; however, previous studies have identified that they lack appreciable amounts of fat-soluble vitamins (A, D₃ , and E). To make BSF larvae a more complete food item, fat-soluble vitamins should either be provided via gut loading or with a multivitamin dusting supplement. The purpose of this study is to identify factors associated with gut loading vitamin A into BSF larvae and to develop feeding recommendations for a more consistent gut-loading process. Factors that were addressed include the vitamin A concentration added to the diet, length of time given to gut load, moisture content of the diet, and density of larvae during feeding. Diets and larvae were analyzed for vitamin A concentration using high-performance liquid chromatography. Larval vitamin A concentrations increased in a nonlinear fashion with increasing dietary vitamin A. Length of time (F = 150.818, p < .001), moisture content of the diet (F = 41.436, p < .001), and larval density (F = 78.407, p < .001) were all found to be significant factors contributing to the larvae's gut-loading capacity. On the basis of our results and vitamin A recommendations from the National Resource Council for rats and poultry, gut-loading recommendations for BSF larvae when fed to insectivorous reptiles and amphibians are as follows: vitamin A concentration of diet between 16,000 and 20,000 mcg retinol equivalents/kg, gut-loading time period of 24 h, moisture content of the diet approximately 60%, and larval density between 0.1 and 1 larvae per each gram of moist substrate.

Effect of carotenoid class and dose on the larval growth and development of the critically endangered southern corroboree frog

Dietary carotenoids are expected to improve vertebrate growth and development, though evidence for beneficial effects remains limited. One reason for this might be that few studies have directly compared the effects of carotenoids from different classes (carotenes versus xanthophylls) at more than one dose. Here, we tested the effect of two doses of dietary β-carotene and lutein (representing two different carotenoid classes) on the growth and development of larval southern corroboree frogs (Pseudophryne corroboree). Individuals were supplemented with either β-carotene or lutein at one of two doses (0.1 mg g^-1, 1 mg g^-1), or given a diet without carotenoids (control). Each dietary treatment included 36 replicate individuals, and individuals remained on the same diet until metamorphosis (25-39 weeks). We measured larval survival, larval growth (body length), time to metamorphosis, metamorphic body size (mass and SVL), and body condition. Lutein had no detectable effect on larval growth and development. However, larvae receiving a high dose (1 mg g^-1) of β-carotene metamorphosed significantly faster than all other dietary treatments, despite no significant differences in growth rate. This result indicates that β-carotene supplementation in P. corroboree has positive effects on development independent of growth effects. Our study provides new evidence for differential effects of carotenoid class and dose on vertebrate development. From a conservation perspective, our findings are expected to assist with the recovery of P. corroboree by expediting the generation of frogs required for the maintenance of captive insurance colonies, or the provision of frogs for release. More broadly, our study highlights the potential for dietary manipulation to assist with the ex situ management of threatened amphibian species worldwide.

Comparison of the nutritional content of the captive and wild diets of the critically endangered mountain chicken frog (Leptodactylus fallax) to improve its captive husbandry

It is vital to provide appropriate nutrition to maintain healthy populations in conservation breeding programs. Knowledge of the wild diet of a species can be used to inform captive diet formulation. The nutritional content of the wild diet of the critically endangered mountain chicken frog (Leptodactylus fallax) is unknown, like that of most amphibians. In this study, we analyzed the nutritional content of food items that comprise 91% of the wild diet of L. fallax, by dry weight of food items, and all food items offered to captive L. fallax at ZSL London Zoo and Jersey Zoo. We subsequently compared the nutritional content of the wild diet and captive diet at ZSL London Zoo consumed by L. fallax. To the authors' knowledge, this is the first study to directly compare the nutritional content of the wild and captive diets of an anuran amphibian. The captive diet at ZSL London Zoo, without dusting of nutritional supplements, was higher in gross energy and crude fat and lower in ash, calcium and calcium:phosphorus ratio than the wild diet. Most of the food items in the captive diets had a high omega-6:omega-3 fatty acid ratio and in the wild diet had a low omega-6:omega-3 fatty acid ratio. We recommend a combination of modifications to the captive diets to better reflect the nutritional content of the wild diet. Nutritional analysis of captive and wild diets is recommended for other species in conservation breeding programs to improve captive husbandry and ultimately fitness.

Reproductive Medicine in Amphibians

Reproduction of amphibians includes ovulation, spermiation, fertilization, oviposition, larval stage and development, and metamorphosis. A problem at any stage could lead to reproductive failure. To stimulate reproduction, environmental conditions must be arranged to simulate changes in natural habits. Reproductive life history is well documented in amphibians; a thorough knowledge of this subject will aid the practitioner in diagnosis and treatment. Technologies for artificial reproduction are developing rapidly, and some protocols may be transferable to privately kept or endangered species. Reproductive tract disorders are rarely described; no bacterial or viral diseases are known that specifically target the amphibian reproductive system.

The influence of carotenoid supplementation at different life-stages on the foraging performance of the Southern Corroboree frog (Pseudophryne corroboree): A test of the Silver Spoon and Environmental Matching Hypotheses

Organismal performance can be significantly affected by the nutritional conditions experienced during different life-stages. The Silver Spoon Hypothesis predicts that individuals will always perform better as adults when they experience advantageous conditions during development. In contrast, the Environmental Matching Hypothesis predicts that individuals will perform better if they experience similar conditions during development and adulthood. Past tests of these hypotheses have focussed on the effect of food quantity on growth and development, with little attempt to investigate the effect of individual nutrients on behavioural traits. This study aimed to test the predictions of the Environmental Matching and Silver Spoon Hypotheses by investigating the influence of carotenoid supplementation at different life-stages on the foraging performance of Pseudophryne corroboree. To assess foraging performance, adults were presented with prey in either a cryptic or conspicuous foraging matrix. There was no effect of diet treatment on time to first movement towards prey, number of stalking events, time spent actively foraging, proportion of successful strikes, proportion of prey consumed or number of pedal luring events. These findings indicate that carotenoid supplementation at different life-stages does not influence the foraging performance of P. corroboree, providing no support for either the Silver Spoon or Environmental Matching Hypotheses.

Vitamin A values of wild-caught Cuban tree frogs (Osteopilus septentrionalis) and marine toads (Rhinella marina) in whole body, liver, and serum

Recent issues surrounding captive amphibians are often nutritionally related problems, such as hypovitaminosis A. Although supplementation of frogs with vitamin A is a topic of investigation, the underlying issue is understanding vitamin A metabolism in amphibian species. To develop a range of "normal" vitamin A concentrations for captive amphibians, baseline vitamin A concentrations must be established in wild amphibian species. In this study, two species, Cuban tree frogs (Osteopilus septentrionalis; n = 59) and marine toads (Rhinella marina; n = 20) were collected from the wild as part of an invasive species control program at Zoo Miami, Miami, Florida. Serum, liver, and whole body samples were analyzed for vitamin A content. The Cuban tree frogs showed higher concentrations on average of vitamin A in serum (82.8 ppb), liver (248.3 IU/g), and whole body (5474.7 IU/kg) samples compared with marine toads (60.1 ppb; 105.3 IU/g; 940.7 IU/kg, respectively), but differences were not significant (P = 0.22). What can be considered "normal" values of vitamin A concentrations across different amphibian species requires further investigation. Although all amphibians collected in this study appeared healthy, a larger sample size of animals, with known health histories and diets, may provide stronger evidence of normal expectations.

Efficacy of fenbendazole and levamisole treatments in captive Houston toads (Bufo [Anaxyrus] houstonensis)

Effective disease monitoring and prevention is critical to the success of captive amphibian care. Nematodes, including the genera Rhabdias and Strongyloides, are known to contribute to mortality in captive amphibians and have been identified in the Houston Zoo's endangered Houston toad (Bufo [Anaxyrus] houstonensis) captive assurance colony. Five years of fecal data for the toad colony were compiled and analyzed in order to investigate the efficacy of two anthelminthic medications, fenbendazole (FBZ) and levamisole (LMS), which were used to control nematode infections. Both FBZ (dusted onto food items) and topical LMS (6.5 to 13.5 mg/kg) significantly reduced the number of nematode eggs, larvae, and adults observed by fecal parasitologic examination. There were no significant differences between treatments, and egg reappearance periods were difficult to compare as a result of low sample size. No adverse effects from either anthelminthic treatment were observed. Both topical LMS and oral FBZ appear to be safe and efficacious treatments for the reduction of the internal nematode burden in captive Houston toads.

Nutrition and health in amphibian husbandry

Amphibian biology is intricate, and there are many inter-related factors that need to be understood before establishing successful Conservation Breeding Programs (CBPs). Nutritional needs of amphibians are highly integrated with disease and their husbandry needs, and the diversity of developmental stages, natural habitats, and feeding strategies result in many different recommendations for proper care and feeding. This review identifies several areas where there is substantial room for improvement in maintaining healthy ex situ amphibian populations specifically in the areas of obtaining and utilizing natural history data for both amphibians and their dietary items, achieving more appropriate environmental parameters, understanding stress and hormone production, and promoting better physical and population health. Using a scientific or research framework to answer questions about disease, nutrition, husbandry, genetics, and endocrinology of ex situ amphibians will improve specialists' understanding of the needs of these species. In general, there is a lack of baseline data and comparative information for most basic aspects of amphibian biology as well as standardized laboratory approaches. Instituting a formalized research approach in multiple scientific disciplines will be beneficial not only to the management of current ex situ populations, but also in moving forward with future conservation and reintroduction projects. This overview of gaps in knowledge concerning ex situ amphibian care should serve as a foundation for much needed future research in these areas.

Causes of mortality in anuran amphibians from an ex situ survival assurance colony in Panama

The success of ex situ survival assurance populations as tools for amphibian conservation depends on the health and reproductive success of founder populations. Necropsy examination and histopathology of animals that die in assurance populations are useful for the identification of population-limiting disease problems and can help to direct applied research efforts in areas such as amphibian husbandry and nutrition. This study reviewed postmortem findings in 167 frogs from 13 species that died in a large Panamanian rescue and survival assurance population between 2006 and 2011. Common problems identified in long-term captive animals, especially in Atelopus species, were epithelial squamous metaplasia suggestive of vitamin A deficiency and a polycystic nephropathy resembling lesions seen in laboratory animals with electrolyte imbalances. Metabolic bone disease was a significant contributor to morbidity in captive-bred juvenile frogs of Gastrotheca cornuta, Hemiphractus fasciatus, and Hylomantis lemur. Findings common to multiple species included poor overall nutritional condition that was sometimes attributable to maladaptation to captive husbandry and epidermal hyperplasia and hyperkeratosis possibly reflecting environmental skin irritation. Infectious diseases and endoparasitism were most common in recently captured animals and included chytridiomycosis and Rhabdias sp. lungworms. Applied research efforts to improve sustainability of survival assurance populations should focus on elucidating optimal husbandry practices for diverse species, improving methods for nutritional supplementation of cultured insects and examination of the role of water composition in disease development.

Updates on amphibian nutrition and nutritive value of common feeder insects

The study of amphibian nutrition requires a detailed review of species-specific natural prey analysis. Invertebrate nutrient composition has been formally studied for more than 60 years and presents the following conclusions: (1) in general, insects are poor in overall calcium content; (2) larval insects have high fat and protein components; and (3) altering the gut contents of some insects can improve their overall nutritive quality. The fat-soluble vitamin profile for most inverts is lacking. There are new guidelines for calcium and vitamin A supplementation that can help augment invertebrate nutrient profiles to match the minimum NRC requirements established for rats.

Vitamin A (retinoid) metabolism and actions: What we know and what we need to know about amphibians

Vitamin A status is an important consideration in the health of both wild and captive amphibians. Data concerning whole body vitamin A homeostasis in amphibians are scarce, although these animals have been used as experimental models to study the actions of vitamin A in vision, limb regeneration and embryogenesis. The available data suggest that many aspects of vitamin A biology in amphibians are similar to the canonical characteristics of vitamin A metabolism and actions established in mammals. This is consistent with the evolutionary conservation of these important biological processes. Amphibians must obtain vitamin A in their diet, with captive animals being prone to vitamin A deficiency. There is still much to be learned about vitamin A biology in amphibians that can only be achieved through rigorous scientific research. Improved understanding of amphibian vitamin A biology will aid the conservation of endangered amphibians in the wild, as well as the successful maintenance of ex situ populations.

Effect of a Punica granatum enriched diet on immunocompetence in Rhinella marina

Direct ingestion of plant materials has been shown to have immunomodulatory effects on a variety of herbivores. Studies have also shown that compounds ingested indirectly by predators through prey items can affect the general physiology of the ingesting organism. Relatively little data exists, however, concerning the modulation of a predator's immune system via compounds obtained indirectly through prey. In this study, we sought to determine if the immune-stimulating properties of Punica granatum (pomegranate) could be conveyed from a prey organism, Acheta domestica, to a predator, Rhinella marina, through diet specialization. Experimental crickets were fed a diet of agar supplemented with 10 mg/mL of lyophilized, powdered, whole pomegranate while control crickets were fed unadulterated agar. Experimental toads consumed a diet consisting of crickets fed the pomegranate-enriched diet, while control toads consumed a diet consisting of crickets fed the standard agar diet. Blood samples were taken weekly and leukocyte profiles and neutrophil phagocytic activity were determined for all toads over an 8-week period. Complement activity was measured at 6 weeks. Toads fed the pomegranate-enriched diet showed altered leukocyte profiles as evidenced by an increase in circulating eosinophil number and a decrease in the number of circulating lymphocytes, monocytes, and basophils as compared to controls, indicating an immunomodulatory effect of the pomegranate-enhanced diet. These results suggest that pomegranate-derived immunomodulatory compounds can be transferred from prey to predator, and suggests that the flora in the environment where insectivores forage could have a significant effect on the physiology of the animal.

Carotenoid supplementation enhances reproductive success in captive strawberry poison frogs (Oophaga pumilio)

Amphibians are currently experiencing the most severe declines in biodiversity of any vertebrate, and their requirements for successful reproduction are poorly understood. Here, we show that supplementing the diet of prey items (fruit flies) with carotenoids has strong positive effects on the reproduction of captive strawberry poison frogs (Oophaga pumilio), substantially increasing the number of metamorphs produced by pairs. This improved reproduction most likely arose via increases in the quality of both the fertilized eggs from which tadpoles develop and trophic eggs that are fed to tadpoles by mothers. Frogs in this colony had previously been diagnosed with a Vitamin A deficiency, and this supplementation may have resolved this issue. These results support growing evidence of the importance of carotenoids in vertebrate reproduction and highlight the nuanced ways in which nutrition constrains captive populations.

Differences in carotenoid accumulation among three feeder-cricket species: implications for carotenoid delivery to captive insectivores

There are a limited number of feeder-invertebrates available to feed captive insectivores, and many are deficient in certain nutrients. Gut-loading is used to increase the diversity of nutrients present in the captive insectivore diet; however, little is known about delivery of carotenoids via gut-loading. Carotenoids may influence health and reproduction due to their roles in immune and antioxidant systems. We assessed interspecific variation in carotenoid accumulation and retention in three feeder-cricket species (Gryllus bimaculatus, Gryllodes sigillatus and Acheta domesticus) fed one of three diets (wheat-bran, fish-food based formulated diet, and fresh fruit and vegetables). Out of the three species of feeder-cricket in the fish-food-based dietary treatment group, G. bimaculatus had the greatest total carotenoid concentration. All cricket species fed the wheat-bran diet had very low carotenoid concentrations. Species on the fish-food-based diet had intermediate carotenoid concentrations, and those on the fruit and vegetable diet had the highest concentrations. Carotenoid retention was poor across all species. Overall, this study shows that, by providing captive insectivores with G. bimaculatus crickets recently fed a carotenoid-rich diet, the quantity of carotenoids in the diet can be increased.