1A.L. Fidgett1,2*, E.J. Harper2, D.C. Houston1, R.G. Nager1 and P.F. Surai3

1Institute of Biomedical and Life Sciences, Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom; 2Waltham Centre for Pet Nutrition, Waltham-on-the-Wolds, Leicestershire, LE14 4RT, United Kingdom; 3Department of Biochemistry and Nutrition, Scottish Agricultural College, Ayr, KA6 5HW, United Kingdom.

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 in both her own and her offspring's fitness. There is good evidence in lesser black-backed gulls (Larus fuscus) of a trade-off between the number and the quality of eggs. By removing eggs as they were laid, the number of eggs produced by lesser black-backed gulls was experimentally increased beyond the normal clutch size of three, at the expense of chick viability. Neither hatching nor fledging success of the eggs was related to their fresh mass, but to their position in the laying sequence, suggesting that changes in egg composition had 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. Analysis of egg composition was performed for three eggs (first, third and last egg laid), from 12 extended clutches (all greater than three eggs). Analyses were performed at the Central Nutritional Laboratory (Pedigree Masterfoods) and composition factors measured were water, lipid, crude protein, ash, selected essential amino and fatty acids. Levels of total carotenoids and fat-soluble vitamins A and E were measured at the Scottish Agricultural College. On average birds were able to produce three times the normal clutch size. Egg mass declined significantly over the laying sequence, but weight of the last laid egg did not fall below the weight of the last egg in a normal three-egg clutch. Eggs laid at the end of a sequence contain relatively less protein and lipid and relatively more water than earlier-laid eggs. On a finer scale, 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. This was not the case for vitamin E and total carotenoids. There was a highly significant decline in the levels of these compounds from first to third eggs and the decline appeared to plateau after the third egg, since there was no further significant decline between third and last 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. 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. While extended clutches are not a common natural occurrence, they demonstrate the extremes of egg production and how seriously an embryo may be compromised by very small changes in egg composition. However, it is possible to override this effect by means of supplementary feeding. Avian captive breeding programmes have utilised the practice of pulling eggs from a female to maximise reproductive effort in any one breeding season. Without due attention to the nutrition of the laying female, this practise may in fact negate the benefits of increased egg yield by producing eggs of poorer quality which either fail to hatch, result in weakened offspring or have a biased sex ratio. 1 Presented at the Third Comparative Nutrition Symposium, August 2000, Asilomar, California, USA


P. Wolf

Institute of Animal Nutrition, Hanover School of Veterinary Medicine, Bischofsholer Damm 15, D-30173

In recent years handrearing of pet birds has become a standard procedure of breeding valuable pet birds (e.g. African greys). In this case nestlings are fed with a special powdered complete diet, mixed with water (a.e. 1st to 4th day of life: 1 part diet diluted with 6 parts water; 5th to 8th day of life: 1 part diet diluted with 4 parts of water; from the 9th day of life: 1 part of water : 2 parts of diet). This prepared solution is administered directly by a syringe into the crop during the first few days of life or afterwards into the beak by a teaspoon. The labelled ingredients of commercial handrearing diets comprise only a few nutrient contents (i.g. crude protein or crude fat), whereas data on amino acids or minerals are frequently absent. Therefore this investigation should give among other things a quantitative idea of the energy and nutrient contents in commercial handrearing diets (n=11) in order to assess the suitability for rearing young pet birds.
nutrient contents1) of handrearing diets2) necessary nutrient contents3) for
nutrients x ± s min. max. budgerigars lovebirds
crude protein 14.4 ± 1.82 12.4 17.8 9.54 8.90
lysine 0.735 ± 0.110 0.491 0.880 0.329 0.316
met + cys4) 0.462 ± 0.184 0.234 0.695 0.469 0.368
arginine 0.729 ± 0.143 0.591 1.140 0.484 0.430
calcium 0.616 ± 0.243 0.349 1.145 0.276 0.271
phosphorus 0.312 ± 0.121 0.175 0.518 0.156 0.160
magnesium 0.086 ± 0.024 0.053 0.128 0.011 0.012
sodium 0.133 ± 0.095 0.049 0.356 0.028 0.036
potassium 0.346 ± 0.119 0.236 0.552 0.069 0.072
1)g/MJ ME 2) MJ ME/kg dry matter: Æ 15.2 ± 1.16 (min.: 13.0; max. 16.8); crude fat: 7.38 ± 1.10 g/MJ ME; starch: 29.5 ± 3.16 g/MJ ME; sugar: 2.48 ± 2.47 g/MJ ME; 3) derived from growth rates of youngs as well as the body composition (Kamphues et al. 1996); 4) methionine + cystine A comparison of the analysed nutrient contents and the factorially derived necessary nutrient contents in handrearing diets for budgerigars and lovebirds shows sufficient crude protein, lysine and arginine contents. On the other hand some of the products showed a lack of the sulphureous containing amino acids methionine and cystine (feather growth ¯). All minerals met the requirements of the youngs, but some mineral concentrations were higher than needed (i.g. high calcium contents ® possible interactions with copper or zinc; high sodium contents among a limited water intake). Furthermore some of the handrearing diets contain an excessive high content of vitamin A (up to 47,000 IE/kg diet). In general the results verify, that on the one hand the requirements of sulphureous amino acids for feather growth in nestlings are frequently underestimated and hat on the other hand the calcium requirements (mineralisation of skeleton) is often overestimated. Probably the primarily problem of handrearing in pet birds is not caused by insufficient energy and nutrient contents of the diets, but to the consistency of the suspended diets within the gastrointestinal tract (i.g. stasis of the crop content).
Reference: Kamphues, J., N. Rabehl and P. Wolf (1996): Derivation of necessary nutrient concentrations related to energy content in diets for growing pet birds (canaries, budgerigars, lovebirds). Proc. of the European Society of
Veterinary and Comparative Nutrition, Veldhoven, 12.9.1996, 29-30.


D.L. McDonald1, L. Baeten2, J. Dein2, E. Norkus3 and E.S. Dierenfeld1*

1Department of Wildlife Nutrition, Wildlife Conservation Society, Bronx Zoo, New York 10460, USA; 2USGS-National Wildlife Health Center, Madison, Wisconsin 53711-6223, USA; 3Our Lady of Mercy Medical Center, Bronx, New York 10460, USA.

In order to identify any differences in sera chemistry that may be linked to reproductive success, blood samples were evaluated from the Puerto Rican Parrot (Amazona vittata; N=26) and the Hispaniolan Parrot (Amazona ventralis; N=11) maintained in captivity at two sites on the island of Puerto Rico. Circulating carotenoids and minerals were assessed and compared among various breeding categories. Significant differences were detected for Ca:P ratios for the Puerto Rican Parrot and the Hispaniolan Parrot when compared to published values for other psittacines, with phosphorus values all exceeding 8.7 mmol/L in the former two species. Calcium values were lowest in the infertile Puerto Rican Parrots (x,- = 1.25mmol/L) but due to the small sample size, these results are not conclusive. Iron levels in infertile Puerto Rican Parrots (x,- = 60.89 mmol/L) were all higher than those for poultry (28.66-53.73 mmol/L) while values for other breeding categories (x,- = 35.6 mmol/L) were within the lower range for poultry. Sodium values were higher in most Puerto Rican (x,- = 166.06 mmol/L) and Hispaniolan Parrots (x,- = 172.29) when compared to both poultry (122-162 mmol/L) and other captive psittacines (134-158 mmol/L), with highest values detected in infertile Puerto Rican Parrots (x,- = 180.96 mmol/L). Zinc values were low for both Puerto Rican (x,- = 27.64) and Hispaniolan Parrots (x,- = 17.37), mainly falling below the minimum normal value for poultry of 28 mmol/L. Total carotenoid values for the Puerto Rican Parrot (x,- = 679.12 mg/dL) were nearly double those of the Hispaniolan Parrot (353.43 mg/dL). No b-carotene was detected in any of the samples and, due to the large intraspecific variation, no statistically significant differences were detected in values for either retinol (x,- = 91mg/dL) or vitamin A palmitate (x,- = 31 mg/dL). Values for a-tocopherol were significantly lower in infertile Puerto Rican Parrots (0.65mg/dL) when compared to fertile or infertile Hispaniolan Parrots (2.21mg/dL) and, even though differences were detected among other breeding categories, these were not statistically significant. Little variation was observed with a-tocopherol either among groups or between species. The higher iron and lower a-tocopherol values may have dietary implications for the higher infertility in the Puerto Rican Parrot and the higher sodium values for both the Puerto Rican Parrot and the Hispaniolan Parrot may require further investigation.


J.D. Blount

Institute of Biomedical and Life Sciences, Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom

Carotenoids are a diverse group of more than 600 lipid-soluble hydrocarbons that animals obtain in the diet. Since carotenoids are widely responsible for the pigmentation of integument in birds and fish, it is common practice to supplement the diets of certain species in zoos with carotenoids to achieve a visual appearance that seems species-typical. But studies of wild animals indicate that carotenoids have profound effects on reproductive success both directly and indirectly. For example, females prefer to mate with the most brightly pigmented males, and parents preferentially feed chicks with brighter gapes. It has been suggested that such signals have evolved as honest indicators of foraging efficiency, or health (because debilitation with gut parasitism can impair the assimilation of dietary carotenoids, and immune system or antioxidant activity can diminish the pool of body carotenoids). Carotenoids are also the reason why egg yolk is yellow. In a series of supplemental feeding experiments in wild lesser black-backed gulls (Larus fuscus), I have found that dietary carotenoids are subject to mechanisms of physiological discrimination, yolk is not maximally enriched with carotenoids under natural feeding conditions, and females with the dullest integument pigmentation are least able to sustain the level at which carotenoids are deposited through the clutch. Carotenoid-rich eggs have higher antioxidant activity and give rise to chicks with enhanced immune function. In light of these findings, dietary supplementation with carotenoids would seem a promising tactic to attempt to enhance reproductive success in zoo animals. But to that end more research is needed to identify phylogenetic and ecogenetic patterns in species requirements for individual carotenoids.


G.M. Dorrestein* and M.A.F. Carati

Dept. Vet Pathology, Section Exotic Animals and Wildlife, Utrecht University, Yalelaan 1, 3584 Cl Utrecht, The Netherlands

Iron is an essential element in fish nutrition, but it can also act as a potent toxin. Iron accumulates when uptake exceeds utilisation and excretion. Iron overload can be primary, for example genetic disorders or adaptation, and secondary as a result of a high dietary iron content. In a dietary iron overload, iron is initially visible in the hepatocytes, later in the macrophages. The purpose of this study is to find out if fish show iron storage, what the iron contents is of commercial fish food, and at what iron level in the diet Koi carps (Cyprinus carpio) start loading iron in the liver.

Material and Methods
In a retrospective study, liver tissue of 130 fishes, presented the last 5 years for necropsy at the Diagnostic Service of the Dept Veterinary Pathology, Utrecht University, were analysed. The paraffin embedded liver tissues were re-cut in 5 :m slides, and were stained with Haematoxylin and Eosin (HE) and with Prussian Blue (PB) for iron. These livers were microscopically evaluated and the amount of iron in the liver was scored semi-quantitative from zero to four, according to the staining intensity and the number of cells affected. Hepatocytes and macrophages were scored separately. Eight commercially available fish foods, especially for carps, were analysed by the Weende-analysis and Flame Atomic Absorption Spectrometry (FAAS) was used for iron determination. A feeding study was done using Koi carps. All the Koi were about 15 cm and 45 gram. Four groups of 9 Koi’s were housed in separate tanks at a water-temperature 18oC. After acclimatisation for 3 weeks on a food with 50 mg/kg iron, each group of Koi’s were fed for 6 weeks ad-lib with diets containing different amounts of iron (0, 150, 300 and 600 mg/kg iron). After six weeks, the livers will be evaluated as well by histology as by FAAS. Weekly water-samples will also be analysed.

The first part of this study showed that 44 out of 130 (=33.8%) livers were positive for iron. The iron was present in the hepatocytes only (14.6%), in hepatocytes and macrophages (13.8%) and only in macrophages (5.4%). The average iron level in the eight commercial foods was 243 mg/kg Fe, (range 155 to 324 mg/kg Fe). The iron requirement recommended by the National Research Council (NRC 1993) in carp nutrition is 150 mg/kg. Fresh livers of 23 carps were collected at the beginning of the food study and analysed with FAAS for the iron contents. The average level was 259 :g/g liver (SD +/- 88, range 151 – 438 :g/g liver). The results of the feeding study will be presente