Ruth Tanner’s comments (Letters, 9 April) cannot be left unchallenged. She says “the fast-growing, low-welfare breeds we use rely solely on the import of soy for feed – the only grain they can be fed”. Initially, this gives the impression that soy is the sole component of a poultry diet, which is untrue. Diets are a combination of several raw materials balanced to supply all the energy and nutrients required.

Furthermore, poultry may cope easily with more than one grain; in fact, the major component of UK poultry diets is wheat (usually home-grown, not imported). True, soy is the best balanced plant protein source, but there has been a substantial research effort into investigating alternatives, either home-grown or from other northern European countries (for example peas, canola, lupins, sunflower, potato protein concentrate and corn gluten) that do need supplementing with pure amino acids (as does soy). Finally, soy is imported from North and South America in boats that go nowhere near the strait of Hormuz, so trade is not influenced by the current situation in Iran.
Prof Julian Wiseman
Emeritus professor of animal production, University of Nottingham