Nitrogen and phosphorus excretions from cattle potentially present significant sources of pollution. With increasing legislation to control pollution in many countries, it is vital that environmental impact is considered in all aspects of the design and operation of cattle production systems. Although environmental impact can be reduced by appropriate manure storage, handling and application protocols, there is no doubt that reducing the total quantities of nitrogen and phosphorus excreted by cattle should be beneficial. Reducing excretions requires a sound knowledge of nitrogen and phosphorus nutrition, as provided by this book.

The general theme of the book is to increase efficiency of nitrogen and phosphorus utilization, thereby reducing the quantities required to be fed and, more importantly, reducing the quantities excreted. There are nine chapters, which provide detailed reviews of specific aspects of the subject. Separate chapters consider nitrogen and phosphorus requirements, metabolism and efficiency in the rumen and the whole animal. In addition, three general chapters cover history and concepts, reproduction, and whole-farm nutrient budgets. The standard of writing and editing is high and chapters are easy to read despite being densely written. This is aided by the clear tables and illustrations that are provided throughout the book. There is some overlap of material between chapters, but this allows each chapter to stand alone. Most chapters are written by authors from both the EU and the USA, thus providing a truly international dimension. The main message from the book is that by studying the basic biology of nitrogen and phosphorus nutrition we can specify animal requirements more precisely. This leads logically to the recommendation that if cattle are fed at their requirements, then we can reduce wastage of excess nutrients. Historically, feeding above requirements has been a strategy employed to provide a wide safety margin against deficiencies and to maximize production per animal.

One slight criticism is that nitrogen and phosphorus nutrition are considered mainly on the basis of requirements per animal. In some cases, however, a response approach might be more effective, as discussed briefly in the chapter on whole-animal nitrogen balance. A more dynamic approach might lead to scenarios where animals fed above their requirements grow faster or produce more milk, thus reducing excretions per unit of product even though excretions per animal might not be minimal. The final chapter on whole-farm efficiency explores this concept and emphasizes the need to consider interactions at all levels of integration within a farming system. An example quoted is that an increase in milk production per cow will improve efficiency of nutrient utilization for milk production, but if higher milk yields result in a higher replacement rate, then the greater number of non-productive offspring will reduce the overall efficiency gains at the farm level.

The back cover states that this book is aimed at researchers in animal nutrition, animal science and environmental (pollution) science. For these people, it provides an excellent collection of reviews. It is probably too scholarly for most producers and advisors, but would be appropriate background reading for advanced students on specialist nutrition or animal science degree courses.