Nutritional Aspects of Breeding in Birds

This study set out to investigate the relationships between dietary nutrition, female quality and egg production. Representing a considerable investment of her resources, a female bird deposits all the chemical nutrients required for the growth of an avian embryo within a sealed unit over a short period of time. Variation in both the total amount of resources allocated to a clutch of eggs and the distribution of those resources within a clutch can have a profound influence on both her offspring's and her own fitness. Cockatiels (Nymphicus hollandicus) were used as a model for a parrot species, to examine the interaction between the body condition of females before breeding and the quality of diet they obtain during egg formation on subsequent clutch production. Feeding a supplement of high quality nutrients had a positive influence on breeding performance. Clutch mass was 32% larger in birds that received the supplement all through the breeding cycle, versus the birds who only received a maintenance diet over the same time period. Clutch size rather than egg size was increased. High quality nutrition offered during the period of egg production did not produce significantly larger clutches. Instead there was a significant increase in clutch mass when a feeding supplement was offered during the pre-laying period, suggesting an important contribution from endogenous reserves to egg production. Feeding a supplement of high quality nutrients did not appear to affect egg mass, an attribute often used as a measure of egg quality. Chicks hatching from eggs laid by birds fed a supplement of high quality nutrients tended to gain weight and grow skeletally faster than those hatching from eggs laid by birds with no exposure to the high quality diet. To examine interspecific variation in egg composition, eggs of 18 bird species, representing 10 avian orders, a range of dietary habits and many of the eight classes of developmental maturity of chicks at hatching, were collected and analysed. The gross composition (lipid, protein and water contents), amino acid and essential fatty acid profiles of their eggs are presented. Differences in egg composition are discussed in terms of developmental maturity of chick at hatching, and maternal diet. Variation in egg composition and therefore quality, also occurs within a species and this was examined in detail by manipulating the egg production of lesser black-backed gulls Lams fuscus. Birds were experimentally induced to lay extended clutches, presumably representing their physiological and nutritional extremes of egg production, and a number of egg composition variables was measured. It is known from previous work that changes in egg composition have a substantial effect on offspring survival. The objective of this study was to examine the chemical composition of experimentally induced extended clutches in more detail, in order to elucidate which aspects of the eggs are involved in this trade-off. The gross composition (lipid, protein and water contents), amino acid and essential fatty acid profiles of their eggs are presented. An enzyme-linked immunosorbent assay was developed to measure variation in yolk immunoglobulins, the avian equivalent of maternally-derived passive immunity, across extended laying sequences. The weight of amino and fatty acids declined in absolute terms within an extended sequence, but relative to egg mass remained at the same concentration. Earlier laid eggs contained significantly greater quantities of vitamin E and carotenoids, a phenomenon also observed in normal three-egg clutches. Both compounds are powerful antioxidants that protect both against peroxidative damage during development and the oxidative stress associated with hatching. Caroteniods are also believed to enhance the immune system and last-laid eggs have been demonstrated to contain significantly less immunoglobulin G (IgG) than earlier laid eggs. Smaller eggs contained most major nutrients in the same proportions as larger eggs, suggesting a blueprint for egg composition exists within the female, with limited scope for variation. That the last egg laid in extended clutches was not smaller than third eggs in normal clutches indicates the probability of a minimum size threshold below which an egg is unlikely to hatch and survive. Thus differential mortality of chicks hatching from eggs laid later in a sequence may result from them having suffered more oxidative stress during development or having an increased susceptibility to pathogens. Both the crystallographic and chemical structure of lysozyme have been documented for many bird species other than domesticated birds, yet there has been comparatively little work done on levels of lysozyme activity in wild bird eggs and their ecological importance. Investigating lysozyme activity in eggs of experimentally extended clutches laid by L. fusais, within a clutch, later-laid eggs exhibited demonstrably less lysozyme activity and therefore had a lower lysozyme concentration. Since egg mass also declined significantly with lading position, these later-laid eggs were also more likely to contain less lysozyme in absolute terms. On its own, the decreasing lysozyme concentration observed in experimentally extended gull egg clutches, may not be biologically significant but combined with declines in other components of the egg already described it may contribute cumulatively to the decreased hatchability and fledging success observed in previous research. These investigations of chemical composition of eggs, both within and between species, demonstrate the complexity of the avian female's reproductive system. Female body condition is an integral part of that system and it would appear to influence egg production long before oviposition

Metabolome-Informed Microbiome Analysis Refines Metadata Classifications and Reveals Unexpected Medication Transfer in Captive Cheetahs.

Even high-quality collection and reporting of study metadata in microbiome studies can lead to various forms of inadvertently missing or mischaracterized information that can alter the interpretation or outcome of the studies, especially with nonmodel organisms. Metabolomic profiling of fecal microbiome samples can provide empirical insight into unanticipated confounding factors that are not possible to obtain even from detailed care records. We illustrate this point using data from cheetahs from the San Diego Zoo Safari Park. The metabolomic characterization indicated that one cheetah had to be moved from the non-antibiotic-exposed group to the antibiotic-exposed group. The detection of the antibiotic in this second cheetah was likely due to grooming interactions with the cheetah that was administered antibiotics. Similarly, because transit time for stool is variable, fecal samples within the first few days of antibiotic prescription do not all contain detected antibiotics, and the microbiome is not yet affected. These insights significantly altered the way the samples were grouped for analysis (antibiotic versus no antibiotic) and the subsequent understanding of the effect of the antibiotics on the cheetah microbiome. Metabolomics also revealed information about numerous other medications and provided unexpected dietary insights that in turn improved our understanding of the molecular patterns on the impact on the community microbial structure. These results suggest that untargeted metabolomic data provide empirical evidence to correct records and aid in the monitoring of the health of nonmodel organisms in captivity, although we also expect that these methods may be appropriate for other social animals, such as cats.IMPORTANCE Metabolome-informed analyses can enhance omics studies by enabling the correct partitioning of samples by identifying hidden confounders inadvertently misrepresented or omitted from carefully curated metadata. We demonstrate here the utility of metabolomics in a study characterizing the microbiome associated with liver disease in cheetahs. Metabolome-informed reinterpretation of metagenome and metabolome profiles factored in an unexpected transfer of antibiotics, preventing misinterpretation of the data. Our work suggests that untargeted metabolomics can be used to verify, augment, and correct sample metadata to support improved grouping of sample data for microbiome analyses, here for nonmodel organisms in captivity. However, the techniques also suggest a path forward for correcting clinical information in microbiome studies more broadly to enable higher-precision analyses

Animal Welfare in Conservation Breeding: Applications and Challenges

Animal welfare and conservation breeding have overlapping and compatible goals that are occasionally divergent. Efforts to improve enclosures, provide enriching experiences, and address behavioral and physical needs further the causes of animal welfare in all zoo settings. However, by mitigating stress, increasing behavioral competence, and enhancing reproduction, health, and survival, conservation breeding programs must also focus on preparing animals for release into the wild. Therefore, conservation breeding facilities must strike a balance of promoting high welfare, while minimizing the effects of captivity to increase population sustainability. As part of the Hawaii Endangered Bird Conservation Program, San Diego Zoo Global operates two captive breeding facilities that house a number of endangered Hawaiian bird species. At our facilities we aim to increase captive animal welfare through husbandry, nutrition, behavior-based enrichment, and integrated veterinary practices. These efforts help foster a captive environment that promotes the development of species-typical behaviors. By using the “Opportunities to Thrive” guiding principles, we outline an outcome-based welfare strategy, and detail some of the related management inputs, such as transitioning to parental rearing, and conducting veterinary exams remotely. Throughout we highlight our evidence-based approach for evaluating our practices, by monitoring welfare and the effectiveness of our inputs. Additionally we focus on some of the unique challenges associated with improving welfare in conservation breeding facilitates and outline concrete future steps for improving and evaluating welfare outcomes that also meet conservation goals

Ex situ diet influences the bacterial community associated with the skin of red-eyed tree frogs (Agalychnis callidryas)

Amphibians support symbiotic bacterial communities on their skin that protect against a range of infectious pathogens, including the amphibian chytrid fungus. The conditions under which amphibians are maintained in captivity (e.g. diet, substrate, enrichment) in ex situ conservation programmes may affect the composition of the bacterial community. In addition, ex situ amphibian populations may support different bacterial communities in comparison to in situ populations of the same species. This could have implications for the suitability of populations intended for reintroduction, as well as the success of probiotic bacterial inoculations intended to provide amphibians with a bacterial community that resists invasion by the chytrid fungus. We aimed to investigate the effect of a carotenoid-enriched diet on the culturable bacterial community associated with captive red-eyed tree frogs (Agalychnis callidryas) and make comparisons to bacteria isolated from a wild population from the Chiquibul Rainforest in Belize. We successfully showed carotenoid availability influences the overall community composition, species richness and abundance of the bacterial community associated with the skin of captive frogs, with A. callidryas fed a carotenoid-enriched diet supporting a greater species richness and abundance of bacteria than those fed a carotenoid-free diet. Our results suggest that availability of carotenoids in the diet of captive frogs is likely to be beneficial for the bacterial community associated with the skin. We also found wild A. callidryas hosted more than double the number of different bacterial species than captive frogs with very little commonality between species. This suggests frogs in captivity may support a reduced and diverged bacterial community in comparison to wild populations of the same species, which could have particular relevance for ex situ conservation projects

Evaluating Environmental Enrichment Methods in Three Zoo-Housed Varanidae Lizard Species

Environmental enrichment has been shown to enhance the behavioural repertoire and reduce the occurrence of abnormal behaviours, particularly in zoo-housed mammals. However, evidence of its effectiveness in reptiles is lacking. Previously, it was believed that reptiles lacked the cognitive sophistication to benefit from enrichment provision, but studies have demonstrated instances of improved longevity, physical condition and problem-solving behaviour as a result of enhancing husbandry routines. In this study, we evaluate the effectiveness of food- and scent-based enrichment for three varanid species (Komodo dragon, emerald tree monitor lizard and crocodile monitor). Scent piles, scent trails and hanging feeders resulted in a significant increase in exploratory behaviour, with engagement diminishing ≤330 min post provision. The provision of food- versus scent-based enrichment did not result in differences in enrichment engagement across the three species, suggesting that scent is just as effective in increasing natural behaviours. Enhancing the environment in which zoo animals reside is important for their health and wellbeing and also provides visitors with the opportunity to observe naturalistic behaviours. For little known and understudied species such as varanids, evidence of successful (and even unsuccessful) husbandry and management practice is vital for advancing best practice in the zoo industry.</jats:p

Data from: Ex situ diet influences the bacterial community associated with the skin of red-eyed tree frogs (Agalychnis callidryas)

Amphibians support symbiotic bacterial communities on their skin that protect against a range of infectious pathogens, including the amphibian chytrid fungus. The conditions under which amphibians are maintained in captivity (e.g. diet, substrate, enrichment) in ex situ conservation programmes may affect the composition of the bacterial community. In addition, ex situ amphibian populations may support different bacterial communities in comparison to in situ populations of the same species. This could have implications for the suitability of populations intended for reintroduction, as well as the success of probiotic bacterial inoculations intended to provide amphibians with a bacterial community that resists invasion by the chytrid fungus. We aimed to investigate the effect of a carotenoid-enriched diet on the culturable bacterial community associated with captive red-eyed tree frogs (Agalychnis callidryas) and make comparisons to bacteria isolated from a wild population from the Chiquibul Rainforest in Belize. We successfully showed carotenoid availability influences the overall community composition, species richness and abundance of the bacterial community associated with the skin of captive frogs, with A. callidryas fed a carotenoid-enriched diet supporting a greater species richness and abundance of bacteria than those fed a carotenoid-free diet. Our results suggest that availability of carotenoids in the diet of captive frogs is likely to be beneficial for the bacterial community associated with the skin. We also found wild A. callidryas hosted more than double the number of different bacterial species than captive frogs with very little commonality between species. This suggests frogs in captivity may support a reduced and diverged bacterial community in comparison to wild populations of the same species, which could have particular relevance for ex situ conservation projects

Bacterial communities on Agalychnis callidryas

Bacterial counts from swab cultures of captive Agalychnis callidryas grown on R2A media. Frogs were fed on carotenoid enriched or normal diets. Data are divided by gender

Bacteria isolated from wild <i>Agalychnis callidryas</i>, and captive <i>A. callidryas</i> fed on a carotenoid-enriched and a carotenoid-free diet.

<p>Bacteria isolated from wild <i>Agalychnis callidryas</i>, and captive <i>A. callidryas</i> fed on a carotenoid-enriched and a carotenoid-free diet.</p

Species richness (number of different bacterial morphotypes isolated from each individual) of the culturable bacterial community associated with the skin of <i>Agalychnis callidryas</i> fed a carotenoid-enriched and carotenoid-free diet.

<p>Error bars show ±1 S.E.M. An *indicates a significant difference.</p