Ruminants energy requirements

Acetate is simultaneously produced and used (oxidized) by the gut, possibly accounting for up to 50% of the gut s energy requirement in ruminants. Propionate and butyrate produced in the rumen and/or hind gut fermentations (nonruminant herbivores) are extensively metabolized by the visceral tissues, so that only insignificant amounts reach the portal circulation. Plasma fatty acids, rather than acetate, are the major energy source for skeletal muscle energy in ruminants and other mammals (53). 

The primary fate of dietary fibers is digestion and catabolism by the gut microflora to short-chain fatty acids and carbon dioxide. The major products of this microbiai mctaboiism — acetic, propionic, and butyTic acid — are important sources of energy for ruminants (sheeps cows). Dietary fiber is retained in a chamber of their gastrointeslinai tracts, calied the rumen, where it is converted to short-chain fatty acids by the gut micro flora. The fatty acids produced may supply 3 75 y<> of the energy requirement of the ruminant. 

Table 11.5 also shows that, as one would expect, dietary fat is used for maintenance with high energetic efficiency. However, when protein is used to provide energy for maintenance, there is an appreciable heat increment of about 0.2, which is in part attributable to the energy required for urea synthesis (see Chapter 9). In ruminants, energy for maintenance is absorbed largely in the form of volatile fatty acids. Experiments in which the pure acids have been infused singly into the rumen of fasting sheep have shown that there are differences between them in the efficiency with which their energy is utilised (Table 11.5). But when the acids are combined into mixtures representing the extremes likely to be found in the rumen, the efficiency of utilisation is uniform and high. Nevertheless the efficiency is still less than that for...

In the UK metabolisable energy system for ruminants, animal requirements are expressed in terms of net energy (NE) and food energy values are expressed as metabolisable energy (ME). Animal ME requirements are calculated using efficiency factors (k) for different productive processes (e.g. maintenance, lactation or growth), which depend on the ME concentration of the diet (M/D). 

One of the most comprehensive approaches used to predict the energy requirements for maintenance of ruminants is provided by CSIRO (2007), which has adopted two generalised equations for the prediction of MEm as follows ... 

The energy requirements of ruminant animals and the energy values of foods are currently expressed in the UK in terms of metabolisable energy (see Chapters 11 and 12). 

Susenbeth, A., T. Dickel, K.H. Sudekum, W. Drochner and H. Steingass, 2004. Energy requirements of cattle for standing and for ingestion, estimated by a ruminal emptying technique. J. Anim. Sci. 82, 129-136. 

This subject is discussed in depth in Chapter 4, Feed evaluation and diet formulation in the Agriculture and Food Research Council (AFRC) advisory manual Energy and Protein Requirements of Ruminants (Alderman and Cottrill, 1993), and more recently by Coleman et al. (1999). 

Alderman, G. and Cottrill, B.R. (Compilers) (1993) Energy and Protein Requirements of Ruminants. CAB International, Wallingford, UK, 159 pp. 

Like all other animals, poultry require five components in their diet as a source of nutrients energy, protein, minerals, vitamins and water. A nutrient shortage or imbalance in relation to other nutrients will affect performance adversely. Poultry need a well-balanced and easily digested diet for optimal production of eggs and meat and are very sensitive to dietary quality because they grow quickly and make relatively little use of fibrous, bulky feeds such as lucerne hay or pasture, since they are non-ruminants (have a simple stomach compartment). 

Because humans and most other mammals lack the enzymes needed for digestion of cellulose, they require starch as their dietary source of carbohydrates. Grazing animals such as cows, however, have in their first stomach microorganisms that are able to digest cellulose. The energy stored in cellulose is thus moved up the biological food chain when these ruminant animals eat grass and are then used for food. 

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