Animal nutrition – the need to feed 1)Homeostatic mechanisms manage an animal´s energy budget 2)An animal´s diet must supply carbon skeletons and essential nutrients 3)The main stages of food processing are ingestion, digestion, absorption and elimination 4)Each organ of the mammalian digestive system has specialized food-processing functions 5)Evolutionary adaptations of vertebrate digestive systems are often associated with diet
All animals eat other organisms Animals obtain food by different methods: suspension feeders → Herbivores Carnivores Omnivores All consume prokaryotes
Animals obtain food by different methods: bulk feeders ↓
Homeostatic mechanisms manage an animal´s energy budget Glucose regulation is an excellent example of homeostasis Inside cell: ATP generation – based on oxidation of energy-rich molecules Cells store energy in form of glycogen, fat Ghrelin – triggers feeling of hunger x insulin, leptin (from fat tissue) suppress appetite
Obesity can be useful, to overcome „hungry“ periods Human’s energy needs = 0.3 kg of fat/day Undernourshment - own protein used Overnourishment → obesity Important fat depots →
An animal´s diet must supply carbon skeletons and essential nutrients Besides energy the food has to contain: Carbon skeletons Amino acids Fatty acids Vitamins (C in primates) Minerals Missing one or more essential nutrients = malnourishment
Penguins can use their muscle protein as a source of AA for new feathers after molting Animals require 20 AA Most species can synthesize about half of these 8 AA are essential in adults, + histidine in infants
Essential fatty acids Are only certain unsaturated fatty acids (with double bonds) Deficiencies are rare Vitamins Required only small amount – 0.01 to 100 mg per day 13 vitamins essential to humans Water-soluble vitamins generally function as coenzymes Fat-soluble – part in visual pigments (A), calcium absorption (D) etc. Minerals Simple inorganic nutrients for bones, hemoglobin, cofactors, hormones, acid-base balance etc. - required mg/day Excess could be harmful
The main stages of food processing are ingestion, digestion, absorption and elimination Polysaccharides => monosaccharides Proteins => amino acids Fats => glycerol and fatty acids Nucleic acids => nucleotides Macro- molecules too large for cell membrane and species specific
Complete digestive tract
Each organ of the mammalian digestive system has specialized food-processing functions
The stomach Gastric juice pH 2-3 (HCl) → unfolds = denatures proteins Pepsin → hydrolysis of proteins Cleaving into smaller polypeptides
The small intestine - enzymatic actions: Most of enzymatic hydrolysis and absorption of nutrients occur there
How hormones help coordinate the secretion of digestive juices: positive and negative feedback
Absorption of nutrients In human – folds, villi and microvilli enhance absorption surface up to 300 m 2
Absorption of nutrients Hepatic portal vein – direct connection to liver Vertebrates have an associated network of vessels: the lymphatic system – with clear fluid lymph Fatty acids and monoglycerids enter epithelial cells → chylomicrons
Evolutionary adaptations of vertebrate digestive systems are often associated with diet Dental adaptations Incisors, canines, premolars, molars A mammal´s dentition is generally correlated with its diet In particular, mammals have specialized dentition that best enables them to ingest their usual diet Poisonous snakes (rattlesnakes) – have fangs for injection of venom into prey
Evolutionary adaptations of vertebrate digestive systems are often associated with diet Stomach and intestinal adaptations Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation In the hoatzin – large muscular crop with symbiotic microorganisms
Evolutionary adaptations of vertebrate digestive systems are often associated with diet - symbiotic adaptations Many herbivorous animals have fermentation chambers (rumen, cecum) where symbiotic microorganisms digest cellulose Rabbits, rodents eat green feces