Ruminants protein requirements

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. 

The starting point for the factorial calculation of the protein requirements of ruminants adopted by AFRC (1993) is basal endogenous nitrogen (BEN) excretion, which can be predicted as follows ... 

As indicated above, most of the protein systems for ruminants (see Chapter 13) used around the world base their estimates of protein requirements for maintenance on endogenous losses of nitrogen but use different factors to translate endogenous losses into dietary requirements. For example, using the UK metabolisable protein... 

In addition to a general requirement for protein, non-ruminant animals have a specific dietary requirement for the ten or so essential (or indispensable) amino acids. Over the past 30 years many experiments have been conducted to determine the quantitative requirements for essential amino acids, and protein requirements have now been supplemented (or even replaced) by requirements for some or all of these amino acids. Requirements may also be stated in terms of ideal protein (protein containing essential amino acids in exactly the proportions required by the animal) or standardised deal digestible amino acids , as explained in Chapter 13. 

The problems associated with the factorial approach to mineral requirements are the same as those associated with factorial estimates of protein requirement. Whereas the mineral composition of liveweight gain may be readily (if laboriously) determined by carcass analysis, the assessment of endogenous losses, and therefore availabihty, is more difficult. Diets for ruminants that are completely free of an element are particularly difficult to prepare. Perhaps because of these difficulties with the technique, theoretical estimates of mineral requirements do not always agree with practical estimates. 

Protein requirements for maintenance are estimated from endogenous urinary nitrogen and metabolic faecal nitrogen excretion. There are also small losses of nitrogen in hair and scurf. In ruminants the protein requirement for maintenance can generally be met by microbial protein synthesis. 

Different feeding standards adopt different approaches to estimate energy and protein requirements for growth. Protein requirements for pigs and poultry are generally more detailed than those of ruminants and horses because they include estimates of requirements for specific amino acids. 

Protein requirements for ruminant animals are stated in terms of metabolisable protein, and protein supply to rumen microbes are expressed in terms of effective rumen-degrad-able (ERDP) protein or effective rumen-degradable nitrogen (EDN). 

AFRC, 1993. Energy and Protein Requirements of Ruminants. CAB International, Wallingford, UK. 

Lactosylurea. Lactosylurea is formed under acid conditions from lactose and urea (McAllan et al 1975) conversion of 75% of the lactose was achieved. Widell (1979) described a method for its preparation from whey and urea intended for feeding to ruminants. Ruminants can utilize nonprotein nitrogen compounds for protein synthesis, but urea itself can cause difficulties through too rapid decomposition to ammonia by the rumen enzymes. Lactosylurea appears to meet the requirements for satisfactory palatability, controlled nonprotein nitrogen release, and low toxicity. 

Animal organisms generally require effective assistance of intestinal flora, as in ruminants, to assimilate inorganic nitrogen into body protein. This accounts for the human needs of a daily requirement of 70-80 grams of protein, However, over half of the protein-constituent amino adds can be derived from other amino acids by their own enzymic reactions. Thus, amino acids are classified as essential or nonessential. Amino acid requirements vary with the physiological state of the animal, age. and possibly with the nature of the intestinal flora. 

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). 

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