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the feed is in the mouth, the senses of touch and then taste stimulate more saliva plus gastric and pancreatic (cephalic stage) secretions. The action of the saliva moistens and begins the breakdown of


the feed, also - with the help of the chewing action - releases sapid and odoriferous substances that stimulate the taste buds and olfactory nerves (retronasal).


GASTRIC DIGESTION


Gastric secretion is governed by three successive types of stimuli: 1. Cephalic stimuli: these take place before any feed reaches the stomach. Its mechanism is nervous, transmitted by the pneumogastric nerve (vagus). This involves innate and conditioned reflexes (sight, smell, feeding habits etc.). Its importance is heavily influenced by the taste of the feed: the more appetizing, the more intense the stimulation. 2. Gastric stimulation: these stimuli are principally chemical. 3. Intestinal stimuli: these are primarily inhibitors, transmitted via the GIP (Gastric Inhibitory Peptide) hormone secreted by the arrival of chyme in the duodenum.


DUODENAL DIGESTION Bile and pancreatic secretions are triggered as the acid chyme reaches the duodenum; this is the point of departure and arrival of fundamental secretory reflexes. During the cephalic phase of gastric secretion, the vagi transmit impulses to the pancreas which results in the production of a certain amount of enzymes in the acini.


FEED INTAKE The feed has to be formulated for the requirements (energy, vitamins, minerals, etc) that the animal needs for each stage of its life. The actual intake will depend on several factors but the following two merit highlighting:


1. PALATABILITY This is the quality of a feed that is perceived by the oral senses; these manifestations are physical (depending on the technology of preparation) and chemical (gustation and retro-nasal stimulation).


2. APPETENCE This is the consequent attraction of sensory action before taking the feed (smell) and during intake (taste). Appetence exerts a positive effect on feed intake until the satiation threshold is reached.


FACTORS INVOLVED The feeding behaviour of animals is the sum of factors from the moment the feed is sensed, through the action of eating and until feeding ceases. These factors can be interrupted and altered by other issues (see Table 2 above right): As a result of everything explained so far, the use of an


appropriate aroma for animal feeds can improve consumption and hence production parameters. The example in Table 3 is of a trial in piglets weaned at 21 days


and comparing two types of feed: a standard feed with no aroma and the same feed with a coconut-milk aroma added. Results clearly


THE MEDIUM


IN RELATION TO: THE ANIMAL


FACTORS


- Species, age, weight… - Digestive tolerance - often associated with feed digestibility.


- Health status of the animal - The threshold of satiety (this would be the result of the volume of feed, the metabolic threshold).


- Hygiene of site/trough. - Temperature - Moisture present - Ventilation


THE FEED


- Digestibility - Appetency - Palatability


demonstrated that animals receiving the feed plus aroma consumed more feed (9%), had a better average daily weight gain (+14%) and had a better feed conversion ratio (4.5%). Therefore, we can conclude that the aroma improved palatability


making the animals eat more and - after the positive response in the cephalic phase - also obtained a better assimilation of the nutrients by the animals’ digestive system.


Trial using feed flavoured with Fluidarom coconut-milk aroma Table 3


Initial weight (21 days) Final weight (49 days)


Average daily weight gain (kg) Average daily feed intake Feed Conversion Ratio


Control 6.637 14.16 0.269 0.501 1.867


Fluidarom % 6.72


15.31 0.307 0.546 1.783


8


14 9


4.5


FLAVOURING FEED Flavours are made with natural essential oils and aromatic substances identical to nature (all listed or in the process of reauthorization under the EU Regulation 1831/2003). Each composition must be orientated not only to give a particular


taste or smell but to be able to stimulate the senses of well-being in the cephalic phase. Animals, like humans, compare the sight and smell of a meal with certain experiences: if the food was good the memory is good but the opposite can also occur when disagreeable odours and tastes are encountered. Thus the influence of the cephalic phase within feeding behaviour


and digestion is of paramount importance when choosing one feed or another and the answer depends on many external and internal factors the most important of which are smell and taste. Palatability and appetite influence the level of consumption and


so need to be improved through adequate flavouring, especially in cases where satiety levels are not met. The justification of the use of flavours is not merely a commercial


one or of marketing and image, it is of solutions to problems; flavours make the feed more attractive to the animal and thus it is consumed more avidly and in greater quantity.


FEED COMPOUNDER MARCH 2011 PAGE 29


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