ABSTRACT
The role of pasture in the diet of ruminant livestock Michael R. F. Lee, University of Bristol and Rothamsted Research, UK; M. Jordana Rivero, Rothamsted Research, UK; and John W. Cone, Wageningen University, The Netherlands
1 Introduction
2 Energy
3 Proteins
4 Minerals and vitamins
5 Other nutritional factors
6 Anti-nutritional factors
7 Future trends and conclusion
8 Acknowledgement
9 Where to look for further information
10 References
The feeding requirements of livestock for macro-(water, energy and protein) and micronutrients (minerals and vitamins) are the bedrock of any sustainable farming enterprise. For monogastric livestock such as chickens (broilers and layers) and pigs, their requirements are defined precisely and delivered in well-balanced rations, whereas for ruminants although requirements are known (Table 1), rationing to match requirements is often not as precise due to several factors as follows: i) intake and quality of pasture at grazing are often not known; ii) variability of the forage component of the diet (mainly silage or hay) at housing can be large across cuts and even within cuts, for example, across a silage clamp face; iii) genetic variability of ruminant livestock (within and across breeds) is wide compared with monogastric livestock making rationing less precise; iv) environment variability (housing and at grazing) is wide compared with much more controlled conditions traditionally when feeding monogastric livestock; and v) the foregut microbial fermentation and the symbiotic role rumen microorganisms play in metabolism and nutrient composition post-rumen. The complexities around these factors lead many ruminant livestock enterprises to optimise rations in order to meet production targets (milk yields and live weight gain), through supplementation of the diet with human-edible
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