Introduction

The relationship between the nutrient content of the material diet and egg production and hatchability has been studied for many nutrients in the domestic fowl (Gallus gallus) (Beer, 1969; Naber, 1979; Anon, 1979). The confounding influence of various strains, interacting nutrients, antibiotics, husbandry, and a host of other variables on this relationship continues to be the focus of research papers. There are thousands of birds and egg-laying reptiles, however, for which there is virtually no such information and on which there is little chance of doing the appropriate dietary studies. Some of these species are endangered, and our only hope for their continued survival may be through captive breeding programs where successful reproduction may depend upon manufactured and supplemented diets. To what extent can nutritional knowledge of a few domestic species be applied to the variety of species that exist? As yet, this question cannot be answered. However, this review will argue that a knowledge of the evolutionarily conserved processes that link maternal diet with egg quality, can provide a basis for evaluating the diverse nutritional needs of other species even when few individuals are available for study. In particular, there are a number of proteins whose function is to transport specific nutrients to the oocyte; these protein-nutrient complexes become yolk constituents for later use by the embryo. The amounts, and relative saturation, of these proteins may indicate the specific nutrient needs of the embryo and the nutrient status of the mother respectively.