Breeding Birds as a Commodity

Understanding of the physiology, molecular genetics and developmental biology of avian reproduction is essential for advances in the efficient breeding of birds for commercial gain. 2. Reproduction is controlled at the central nervous level by gonadotrophin releasing hormone-I (GnRH-I) and prolactin. 3. The activity of GnRH-I neurones can be manipulated photoperiodically, through understanding of the physiology of photorefractoriness, to prevent premature onset, or to enhance persistency of reproductive function. 4. Active immunisation against prolactin releasing hormone, vasoactive intestinal peptide, delays the development of photorefractoriness and enhances persistency of reproductive function. 5. The creation of molecular maps of the chicken genome makes it possible to identify quantitative trait loci for repro- ductive traits, which will be used to identify DNA sequences for marker assisted selection. Polymorphisms in alleles of physiological candidate genes for reproductive efficiency might also be useful for marker assisted selection. 6. New understanding of the developmental biology of the chicken opens up the prospect of developing methods to control sex ratios, and to make transgenic birds. Transgenic technology will be used to introduce genes for disease resis- tance, and to make proteins for biomedical applications. 7. Nuclear transfer technology might be applied to save endangered species from extinction.