Geneticists have been highly successful in improving potential growth of broilers over the past
50 years, and it is likely that more genetic progress is possible. However, in order to maximise
this potential it will be necessary for nutritionists to review the way in which these fastgrowing
strains are fed. Unless changes are made to the composition of broiler feeds in the
future, constraints are likely to occur immediately after hatching, when gut capacity will not
allow the consumption of sufficient of a conventional starter feed to enable the chick to grow at
its potential, and towards the end of the growing period, when heat production is so high that it
may be impossible for a broiler to lose sufficient heat to the environment to enable it to grow at
its potential.
Issues discussed are those concerning the constraining effect of the egg onembryonic development,
early feeding of the embryo and chick, problems associated with meeting the amino acid
requirements immediately post-hatch, and various nutritional interventions that have been
suggested as methods of reducing the heat load on broilers. It is suggested that with some
manipulation of feed nutrient contents nutritionistswill be able to keep upwith the genetic changes
taking place into the near future, but that the constraining effect on growth of global warming is a
challenge that will need to be addressed by biologists and engineers in poultry research.