Small intestine of Animals

two other digestive organs mix with the food to continue the process of digestion. One of these organs is the pancreas. It produces a juice that contains a wide array of enzymes to breakdown down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine or even a part of that wall. The liver produces yet another digestive juice—bile. The bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder into the bile ducts to reach the intestine and mix with the fat in our food. The bile acids dissolve the fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After the fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.

He wall of the small intestine is thrown into circular folds with fingerlike projections, called villi. The epithelial cells of each villus have extensions called microvilli. A large number of villi with their microvilli increase the small intestine's surface area for nutrient absorption and give the intestinal wall a soft, velvety appearance.

Stomach of Animals

The stomach stores, dissolves, and partially digests the contents of a meal, then delivers this partially digested food to the small intestine in amounts optimal for maximal digestion and absorption. Parietal cells within gastric glands in the folds of the stomach lumen secrete hydrochloric acid (HCl), which makes gastric juice acidic, with a pH less than 2. During a meal, the rate of HCl production increases markedly—seeing, smelling, tasting, and chewing food sends information through the vagus nerves to the parietal cells, causing them to increase acid production. Stomach distention, hydrogen ion concentration, and peptides send messages through long and short neural reflexes to increase gastrin release, which increases HCl production. On average, the stomach produces 2 liters of HCl daily.

Microscopic View: Gastric Mucosa
The lining of the stomach contains deep collections of cells organized into gastric glands. These gastric glands secrete various substances into the stomach. The openings of the gastric glands into the surface of the stomach are called gastric pits. Mucous cells in the gastric pits secrete mucus. In the deeper part of the gland, parietal cells secrete hydrochloric acid. G cells, which are present predominantly only in the antrum of the stomach, secrete gastrin. ECL cells secrete histamine, and chief cells secrete pepsinogen (an inactive form of the pepsin-digesting enzyme pepsin). Intrinsic factor, needed for the absorption of vitamin B12, is also secreted by the gastric mucosa (most likely the parietal cells).

The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. One of the unsolved puzzles of the digestive system is why the acid juice of the stomach does not dissolve the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.

Gastrointestinal Tract of Animals

Pharynx

Swallowing, a reflex action which moves food into the esophagus, occurs in the pharynx, a region that opens into the ose, mouth, and larynx. During swallowing, food normally enters only the esophagus, a long, muscular tube that extends to the stomach, because the nasal and laryngeal passages are blocked. The nasopharyngeal openings are covered when the soft palate moves back. The opening to the larynx at the top of the trachea, called the glottis, is covered when the trachea moves up under a flap of tissue, called the epiglottis.

The esophagus is the organ into which the swallowed food is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike valve closing the passage between the two organs. However, as the food approaches the closed ring, the surrounding muscles relax and allow the food to pass.

The food then enters the stomach, which has three mechanical tasks to do. First, the stomach must store the swallowed food and liquid. This requires the muscle of the upper part of the stomach to relax and accept large volumes of swallowed material. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine. Several factors affect emptying of the stomach, including the nature of the food (mainly its fat and protein content) and he degree of muscle action of the emptying stomach and the next organ to receive the contents (the small intestine).

Aromas and flavours advantages for the animal

To enhance and improve the smell and taste of feedstuff:

To make the unusual and solid feed attractive to young mammals, for an easier changeover from milk to solid feed

Aim: to motivate suckling animals for an early intake of solid feed (pre-starter, starter), which prepares the digestive system (adaptation of enzyme activity and of intestinal flora) for the later stage of weaning, thus helping to reduce the general stress at this period of life
nto enhance the appetite

Aim: securing and improving the feed intake for optimal growth
nto stimulate salivary gland secretion

Aim: more saliva production for easier swallowing of feed rich in dry matter, consequently increased bile and digestive enzyme production

Advantages for the Feed Producer

To standardise the feed during changes of recipes and variation of raw material qualities

Aim: to give flexibility in feed optimisation without compromising feed intake
nto cover less palatable feed additives or feed components (e.g. acids, certain fats, rapeseed, pharmaceuticals )

Aim: to ensure feed and medicine intake
nas a marketing tool in the feed industry

Aim: differentiation against competitor products, improvement of smelling attractiveness also for the farmer

Sweeteners

Definition: Substitutes for sugar, which have the same sweetening power with a lower dosage. The high intensity communicates at low levels a long lasting sweet taste and some remove bitter/metallic after tastes (e.g. NHDC)

Sweet effects just on taste perception

Palatability agents, which intensify at low levels the gustatory and olfactory sensations

Without or less caloric energy compared to sugar, explanation: most of the sweeteners can not be split with the help of body own enzymes

Aromas and flavours

Aroma: The sum of volatile substances, which are released by inhaling through the nose as well as by chewing through warmth and mechanical processing in the mouth (faucal-nasal connection) and received via the olfactory epithelium.

Flavour: Each of the gustatory cells located in the taste buds on the tongue is specialized in one of the five tastes (sweet, sour, bitter, salty and umami). Flavours are substances, which are perceived and classified as a specific taste through the combination of their chemical stimuli. หรือ flavouring substance

Bouquet: Totality of the aromas and flavours contained in a feedstuff which interact with the physical properties of the nutrition to form an overall impression.

Note: Classification of the perception of a flavour profile (e.g. fruity, spicy, flowery etc.)

Aroma as a source of information

1. As with us humans, the sensory control of the nutrition to be ingested plays a major role for our livestock in order to identify and judge the quality.

2. The aroma of a feedstuff contains a multitude of information for its identification by the animal. This enables the animal to differentiate between e.g. edible and inedible plants, high-energy or foul feedstuffs.

3. The aroma of a feedstuff is decisive for its acceptance by the animal.

4. Each type of animal has different preferences.
   
   The sensory overall impression results from the following sensory perceptions.

Smell: The perception of even the smallest quantities of volatile chemical substances, which have passed into the gas phase, occurs among vertebrates via the olfactory epithelium of the nose due to the contact of these substances via the sensory cells. The sensory stimuli are forwarded to the olfactory region of the brain and processed to an olfactory impression.
à volatile substances, gaseous

Taste: Taste is a sensation caused by macroscopic chemical substances coming into contact with the receptor cells of the tongue, palate and fauces. Each of the gustatory cells located in the taste buds on the tongue is specialized in one of the five tastes (sweet, sour, bitter, salty and umami). The taste of a feedstuff supplies important information to mammals and birds via the composition (e.g. edible, inedible, poisonous, energy value etc.).
à non-volatile substances, soluble in water, oil or saliva

Tactile perception: The overall impression of a feedstuff is not only influenced by taste and smell, but also by its physical properties and the associated mechanical sensations.