Digestive system morphology and physiology
The nutritional requirements of animals are greatly influenced by the nature of their gastrointestinal tracts (Cheeke and Dierenfeld, 2010). Both the animals food selection and dietary strategy and the ability of the animal to derive nutritional benefit from particular types of feedstuffs is closely linked to the animals digestive physiology (Cheeke and Dierenfeld, 2010). Animals have evolved to occupy vitrually all ecological niches and in many cases have developed specialised feeding strategies to do so. Lions are obligate carnivores with a simple digestive tract (Mazak, 1981; Seymour, 1989; Feldhamer et al, 2004). The gastrointestinal tract (GI) of a lion is short and simple (Stevens and Hume, 1995). The oesophagus of the lion is approximately 70-80cm long (AZA,2012). Lions have a stomach, a short non-compartmentalized colon and a short small intestine with limited area for absorption (Stevens and Hume, 1995). The Stomach of a lion cam hold a substantial volume approximately 20% of their ow bodywight (AZA,2012). The small intestine comprises 74% of the total gasrtointestinal tract length at 6-7m (AZa, 2012). They possess a small cecum, approximately 10com or 1% of the length of their tract, which is present at the intersection between the small and large intestine (AZA,2012). The large intestine is is just over 1m or 13% the total length of their gastrointestinal tract (AZA, 2012). The lions digestive tract allows for storage of large meals in the stomach and efficient digestion of vertebrate prey (AZA,2012). This type of GI tract is adapted to utilise a meat, and therefore lions have high energy, protein and ether extract digestibility (Stevens and Hume, 1995).
Lions are autoenzymatic digesters meaning their digestive processes are carried out by enzymes that the animals secretes into the digestive tract(Cheeke and Dierenfeld, 2010). Food is consumed, chewed and swallowed, moving down the oesophagus into the stomach (Cheeke and Dierenfeld, 2012). Functions of the stomach include digestion and absorption, food storage and mixing, and secretion (Cheeke and Dierenfeld, 2010).
The stomach of most autoenzymatic digesters consists of four functionally distinct zones (Cheeke and Dierenfeld, 2010). The oesophageal region is basically an extension of the oesophagus, where there is some limited bacterial growth but no glandular secretions (Cheeke and Dierenfeld, 2010). The cardiac region, adjacent to the oesophageal region, contains glands which exude mucus (Cheeke and Dierenfeld, 2010). This mucus consists of glycoproteins, has an alkaline reaction and serves to protect the stomach lining from being digested by the proteolytic enzymes and strong acid secreted into the stomach (Cheeke and Dierenfeld, 2010). The fundus gland and pyloric regions are the sites of other gastric secretions, including mucus, HCl and pepsin, a proteolytic enzyme (Cheeke and Diernfield, 2010). The HCl secretion is responsible for the low pH of the stomach (Cheeke and Dierenfeld, 2010). The high acidity serves to sterilise the stomach contents, and kill virtually all bacteria consumed by way of the diet (Cheeke and Dierenfeld, 2010). The low pH of the stomach also serves to cause some hydrolysis of proteins and polysaccharides, and denaturation of proteins, exposing the bonds of the amino acid polymer to further enzymatic digestion in the stomach and small intestine (Cheeke and Dierenfeld, 2010). It also activates the gastric glands to secrete the proenzyme pepsinogen, forming the active proteolytic enzyme pepsin (Cheeke and Dierenfeld, 2010). Ingesta exits the stomach from the pyloric region and enters the duodenum of the small intestine (Cheeke and Dierenfeld, 2010). The release of food from the stomach is controlled by the pyloric sphincter which is regulated horomonally so as not to overload the digestive capacity of the small intestine (Cheeke and Dierenfeld, 2010).
The major site of digestion and absorption in autoenzymatic digesters is the small intestine, which is has three distinct regions, the duodenum, the jejunum and the ileum (Cheeke and Dierenfeld, 2010). Both the digestive and absorptive functions of the intestine is facilitated by the large surface area (Cheeke and Dierenfeld, 2010). Digestion is the preparation of ingested nutrients for absorption (Cheeke and Dierenfeld, 2010). Normally only small molecules are absorbed, thus proteins are hydrolysed into smaller units (peptides and amino acids), complex carbohydrates into simple sugars (monosaccharides) and fats into monoacylglycerides and fatty acids (Cheeke and Dierenfeld, 2010). Minerals and vitamins generally do not undergo digestion, and are absorbed as such (Cheeke and Dierenfeld, 2010).
Lions are autoenzymatic digesters meaning their digestive processes are carried out by enzymes that the animals secretes into the digestive tract(Cheeke and Dierenfeld, 2010). Food is consumed, chewed and swallowed, moving down the oesophagus into the stomach (Cheeke and Dierenfeld, 2012). Functions of the stomach include digestion and absorption, food storage and mixing, and secretion (Cheeke and Dierenfeld, 2010).
The stomach of most autoenzymatic digesters consists of four functionally distinct zones (Cheeke and Dierenfeld, 2010). The oesophageal region is basically an extension of the oesophagus, where there is some limited bacterial growth but no glandular secretions (Cheeke and Dierenfeld, 2010). The cardiac region, adjacent to the oesophageal region, contains glands which exude mucus (Cheeke and Dierenfeld, 2010). This mucus consists of glycoproteins, has an alkaline reaction and serves to protect the stomach lining from being digested by the proteolytic enzymes and strong acid secreted into the stomach (Cheeke and Dierenfeld, 2010). The fundus gland and pyloric regions are the sites of other gastric secretions, including mucus, HCl and pepsin, a proteolytic enzyme (Cheeke and Diernfield, 2010). The HCl secretion is responsible for the low pH of the stomach (Cheeke and Dierenfeld, 2010). The high acidity serves to sterilise the stomach contents, and kill virtually all bacteria consumed by way of the diet (Cheeke and Dierenfeld, 2010). The low pH of the stomach also serves to cause some hydrolysis of proteins and polysaccharides, and denaturation of proteins, exposing the bonds of the amino acid polymer to further enzymatic digestion in the stomach and small intestine (Cheeke and Dierenfeld, 2010). It also activates the gastric glands to secrete the proenzyme pepsinogen, forming the active proteolytic enzyme pepsin (Cheeke and Dierenfeld, 2010). Ingesta exits the stomach from the pyloric region and enters the duodenum of the small intestine (Cheeke and Dierenfeld, 2010). The release of food from the stomach is controlled by the pyloric sphincter which is regulated horomonally so as not to overload the digestive capacity of the small intestine (Cheeke and Dierenfeld, 2010).
The major site of digestion and absorption in autoenzymatic digesters is the small intestine, which is has three distinct regions, the duodenum, the jejunum and the ileum (Cheeke and Dierenfeld, 2010). Both the digestive and absorptive functions of the intestine is facilitated by the large surface area (Cheeke and Dierenfeld, 2010). Digestion is the preparation of ingested nutrients for absorption (Cheeke and Dierenfeld, 2010). Normally only small molecules are absorbed, thus proteins are hydrolysed into smaller units (peptides and amino acids), complex carbohydrates into simple sugars (monosaccharides) and fats into monoacylglycerides and fatty acids (Cheeke and Dierenfeld, 2010). Minerals and vitamins generally do not undergo digestion, and are absorbed as such (Cheeke and Dierenfeld, 2010).