ANSC 303 – Exam 1 Review Fall 2013 Below are a list of concepts and information discussed in class and corresponding examples of questions that may appear on exam 1 related that information. Introduction to Animal Nutrition - The goals of animal nutrition are to efficiently convert feedstuffs into high quality products by the animal (meat, milk, etc.) and/or maximize performance and longevity - The efficiency of nutrient conversion is low, so improvements in nutrition and this efficiency can greatly impact an operation o Nutrition accounts for >50% of the total operating costs for most animal production operations o Overfeeding is wasteful and underfeeding reduces performance - Animal nutrition must meet the increasing global demands for high quality protein diets, address concerns for food safety and quality, and meet the demands of improved animal genetics - A nutrient is a chemical element in a diet that supports life processes - A diet is a mixture of feedstuffs used to supply nutrients and a ration is the daily supply of feed - The value of a feedstuff depends on its concentration of the 6 major nutrient categories. Digestive System - Animals digest feed because food is not ingested in a suitable and the physical nature of food determines: o Prehension and mastication o Digestive anatomy o For example, cattle are strict herbivores that use their tongue for prehension of forage and use extensive molars to masticate this forage. The process of rumination further enhances mastication. They use the extensive fermentative capacity of their stomach (4 compartments) to effectively utilize high fiber feedstuffs. A cat with small molars and little fermentative capacity in their large intestine could not effectively utilize the same diet. - Identify the organs of the digestive system for both monogastrics and ruminants and the accessory structures that contribute to digestion. - The purpose of the mouth is to take in food, chew it, and mix it with saliva. o Saliva composition varies with species, but it is used to lubricate, buffer, and perhaps start digestion. - The esophagus connects the mouth and stomach, and its musculature depends on use (swallowing only vs. regurgitation). o In young ruminants the reticular groove elongates the esophagus creating a direct passage from the mouth to the abomasum (by‐passes rumen). - The glandular stomach is the stomach in non‐ruminants and the abomasum in ruminants. o This organ mixes food, allows controlled release of digesta into the small intestine, and begins digestion through production of HCl, pepsinogen, and renin. o There are 4 regions of the stomach and each has different functions. - Parietal cells in the stomach (fundic region) produce HCl to begin protein digestion, activate pepsinogen, and kill bacteria. - Chief cells secrete pepsinogen with is activated by HCl to pepsin to begin protein digestion. - Pepsin clots milk in young non‐ruminant animals while renin clots milk in ruminant animals. - Rumen development in young ruminant animals results from increases in size, musculature, and microbial populations. Animals must consume solid feed to begin this process. - Size and capacity of the ruminant stomach compartments is not the same, and pseudo‐ruminants are missing the omasum. o The reticulum begins fermentation and traps foreign objects. o The rumen is responsible for the majority of fermentation and begins absorption. o The omasum reduces particle size further and assists in absorption of water and VFAs. o The abomasum acts as the true stomach. - Fermentation in the reticulum and rumen depends on bacteria and protozoa and results in production of VFA, gas, heat, microbial crude protein, B vitamins, and vitamin K. This represents a symbiotic relationship between the animals and the microbes. - The rumen microbial population is diverse and located close to their preferred substrate. For example, cellulolytic bacteria are located in the fiber mat. - Rumination is the process by which r uminant animals re‐chew coarse material resulting in a further reduction of particle size and increased input of saliva into the rumen. The process involves regurgitation, remastication, reensalivation, and reswallowing. - Eructation is the process by which ruminant animals expel the gases created by fermentation. - Identify the segments of the small intestine and their function in digestion and absorption. o The small intestine is responsible for digestion and absorption of: soluble carbohydrates, lipids, protein, vitamins, and minerals. o Secretions enter the small intestine from within and from ducts. Mucus and brush border enzymes are made within the small intestine, and pancreatic juices and bile enter from outside the intestine through ducts. -