Poultry digestion

T. van Kempen, J. Ch. Bodin. Near infrared reflectance spectroscopy (NIRS) appears to be superior to nitrogen-based regression as a rapid tool in predicting the poultry digestibility amino acid content of commonly used feedstulFs. Anim Feed Sci Tech 76 139-147,1998. 

The digestive system of poultry is also basically a tube, beginning at the mouth and ending at the vent (Fig. 13.1). Food is taken in via the mouth and mixed with saliva to lubricate it. The bolus moves down the oesophagus by gravity and a wave-like contraction of the muscles (peristalsis). Then it enters the crop where it is stored if the stomach is full. A certain amount of softening and fermentation may occur here. The crop is situated just outside the entrance of the chest cavity (thoracic inlet) and is an expansion of the oesophagus. 

On the other hand there is sometimes the risk that odour reduction increases the volatilization of ammonia. This can be the case with under cage diying of poultry manure or with anaerobic digestion of liquid manure. 

Except in case of the anaerobic digestion of poultry waste, methane production decreases as retention time is reduced. This is a result of the substrate being exposed for less time to the action of anaerobic bacteria. With the poultry waste, it was noted that methane production increased as the retention time was reduced. Also the methane production in the three retention times studies was much higher than that reached in the mixed wastes study when the retention time was greater than 30 days. 

Fig. 12.17 Breakthrough curves for a conservative tracer (Ck) and lime-stabilized biosolid (LSB), aerobically digested biosolid (ADB), and poultry-manure biosolid (PMB) colloids eluted from intact (a) Maurry, (b) Woolper, and (c) Bruno soil monoliths (C, effluent concentration, C, influent concentration, (after Karathanasis et al. 2005)...

Figure 2. A 16fl00 poultry layer operation in a converted dairy barn with an anaerobic-digestion biogas plant in the attached shed in the foreground (W. Gibbons farm at Ripon, Wisconsin)...

Digestion of Farm Waste (dairy bull, swine and poultry). Pp. 7 - 11, 13. 

Graham, H. (1991) The physical and chemical constitution of foods effects on carbohydrate digestion. In Euller, M.E. (ed.) In vitro Digestion for Pigs and Poultry. CAB International, Wallingford, UK, pp. 35-44. 

Commercial compound feeds for livestock are formulated to provide starch, protein and lipid components which are digested with high efficiency. In poultry diets, the... 

The second largest use of sodium bicarbonate, accounting for approximately 25% of total production, is as an agricultural feed supplement. In cattle it helps maintain rumen pH and aids fiber digestibility for poultry it helps maintain electrolyte balance by providing sodium in the diet, helps fowl tolerate heat, and improves eggshell quality. 

Z. Yi, E. T. Kornegay, and D. M. Denbow, Effect of microbial phytase on nitrogen and amino acid digestibility and nitrogen retention of turkey poults fed corn-soybean meal diets, Poultry Sc. 1996d, 75, 979-990. 

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). 

Digestion is the preparation of feed for absorption, i.e. reduction of feed particles in size and solubility by mechanical and chemical means. A summary outline of digestion and absorption in poultry follows. This provides a basic understanding of how the feed is digested and the nutrients absorbed. Readers interested in a more detailed explanation of this topic should consult a recent text on poultry nutrition or physiology. 

The entire process of digestion takes from about 2.5 to 25h in most species of poultry, depending on whether the digestive tract is full, partially full or empty when feed is ingested. 

Chitin is the main component of the hard exoskeleton of insects. Domesticated poultry have some ability to digest this component but studies suggest that the insect skeleton is not an important source of nutrients for poultry (Hossain and Blair, 2007). 

A high proportion of the phosphorus present in feedstuff s may be in the form of phytate, which is poorly digested by birds because they lack the requisite enzyme in the gut. Consequently, the content of non-phytate phosphorus in feed ingredients is used in formulating poultry diets to ensure the required level of phosphorus, rather than the total phosphorus content. It is now becoming a common practice for a microbial phytase to be added to conventional poultry diets. This achieves a greater release of the bound phosphorus in the gut and a reduced amount to be excreted in the manure and into the environment. Use of microbial phytase may also improve digestion of other nutrients in the diet, associated with breakdown of the phytate complex. 

In most poultry diets, a portion of each AA that is present is not biologically available to the animal. This is because most proteins are not fully digested and the AAs are not fully absorbed. The AAs in some proteins such as egg or milk are almost fully bioavailable, whereas those in other proteins such as certain plant seeds are less bioavailable. It is therefore more accurate to express AA requirements in terms of bioavailable (or digestible) AAs. 

Gerendai, D. and Gippert, T. (1994) The effect of saponin content of alfalfa meal on the digestibility of nutrients and on the production traitsofTetra-SLlayers.Procmfr wgs of the 9th European Poultry Conference, Glasgow, UK, 2, pp. 503-504. 

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