Evaluation of Feeds IV Protein 1 16 23 Evaluation of Feeds IV Protein In evaluating the attributes of a feed that define protein quality it is important to make a distinction between protein quality for nonruminant and ruminant animals Fish Meal Corn Gluten Meal Feather Meal Nonruminant vs Ruminant Animals v Nonruminants To meet the protein requirements of nonruminants all essential amino acids must be supplied in the diet in the correct amounts as well as in the correct proportions v Ruminants The evaluation of protein quality of feeds is much more complex for ruminants v The diet for ruminant animals must provide nitrogen for microbial synthesis in the rumen as well as sufficient quantities of essential amino acids for absorption and metabolism in the small intestine Assessing Protein Quality Protein digestion and utilization Ruminant animals Non ruminants Hind gut fermentors Rumen Degradable Protein RDP production of microbial protein Rumen Undegradable Protein RUP protein escapes to SI Limited protein digestion in stomach Metabolizable protein MP enzymatically digested in SI Protein enzymatically digested in SI Protein quality depends on Protein quality depends on How much RDP How much RUP Profile of EAA in RUP Profile of EAA Bioavailability of EAA 1 2 3 1 Evaluation of Feeds IV Protein 1 16 23 Methods to assess protein quality in nonruminants I Protein Efficiency Ratio II Biological Value III Ideal Protein Concept Soybeans Sunflower seed Rapeseed Cottonseed Flaxseed Peanuts 4 5 6 Methods of measuring protein quality in nonruminants Protein efficiency ratio Protein Efficiency Ratio PER v Based on growth rate of an animal per unit of intake protein as a measure of protein quality v PER relates weight gain to protein consumed as follows PER weight gain g protein consumed g v Higher PER equates to improved protein quality blend of essential amino acids Protein source Casein milk protein Egg protein Soybean meal Corn grain cereal grain Casein corn grain 2 50 3 18 2 21 0 49 2 68 Methods of measuring protein quality in nonruminants Biological value BV I Biological value is a direct measure of the proportion of feed protein that can be used by the animal for synthesizing body tissues II Biological value is an indirect measure of the blend of essential amino acids in a feed III Biological value is measured as the proportion of absorbed nitrogen that is retained by the animal IV BV Nitrogen retained in body tissues digestible Nitrogen V BV N intake fecal N urine N N intake fecal N Protein Source Milk protein Fish meal Soybean meal Cottonseed meal Linseed meal Corn grain Barley grain Biological Value 0 95 to 0 97 0 75 to 0 90 0 65 to 0 75 0 60 to 0 70 0 60 to 0 70 0 50 to 0 60 0 50 to 0 60 2 Evaluation of Feeds IV Protein 1 16 23 Biological value of fish meal 100 g of fish meal protein consumed 60 g of protein as AAs absorbed 10 g of protein as urinary nitrogen excreted 40 g of fecal protein excreted 50 g of protein retained as AAs Biological value of fish meal 100 40 10 100 40 50 60 0 83 Biological value of cottonseed meal CSM 100 g of CSM protein consumed 60 g of protein as AAs absorbed 20 g of protein as urinary nitrogen excreted 40 g of fecal protein excreted 40 g of protein retained as AAs Biological value of CSM 100 40 20 100 40 40 60 0 67 Methods of measuring protein quality in nonruminants Ideal Protein Concept I The essential amino acid profile of an ideal protein is patterned after the composition of protein in lean muscle tissue II An ideal protein is one that provides the essential amino acids in the correct proportion so that muscle tissue growth can be maximized III An ideal protein is species specific Ideal protein profile for pigs of Protein Essential amino acid Arginine Histidine Isoleucine Leucine Lysine Methionine Cystine Phenylalanine Tyrosine Threonine Tryptophan Valine 3 0 1 8 3 8 5 0 7 0 3 4 5 5 4 0 1 0 4 0 7 8 9 3 Evaluation of Feeds IV Protein 1 16 23 Identifying rate limiting essential amino acids EAA Ideal EAA profile of Protein Peanut meal of protein Soybean meal of protein EAA Arginine Histidine Isoleucine Leucine Lysine Methionine Cystine Phenylalanine Tyrosine Threonine Tryptophan Valine 3 0 1 8 3 8 5 0 7 0 3 4 5 5 4 0 1 0 4 0 9 0 3 0 3 8 6 7 3 0 2 4 4 3 2 8 1 0 4 4 7 3 2 5 4 5 7 7 6 6 2 7 8 2 3 9 1 5 4 6 Rate limiting essential amino acids I The rate limiting essential amino acid EAA is the EAA that is most deficient in matching the ideal protein profile for a given animal II Lysine is typically the rate limiting EAA III Other rate limiting EAA include methionine threonine and tryptophan A R G I N I N E H I S T I D I N E L Y S I N E L E U C I N E I S O L E U C I N E T H R E O N I N E T R M Y a P n T ga O P n H e A se N M E T H I O N I N E Protein digestion and metabolism in ruminants I Rumen microbes provide a large proportion of the host animal s energy requirements by transforming dietary CHO to VFAs 70 to 75 II To accomplish this the microbes need to be supplied with nutrients to grow and multiply which involves large scale microbial synthesis III Rumen microbes bacteria protozoa fungi contain 30 to 50 CP DM basis 10 11 12 4 Evaluation of Feeds IV Protein 1 16 23 Protein digestion Ruminant animals 13 14 15 Protein digestion and metabolism in ruminants V Microbial protein is rich in Essential AA VI The BV of microbial protein is 0 6 to 0 8 similar to soybean meal VII Efficiency of microbial growth is dependent upon availability of N and the timing of availability of carbon skeletons VIII The fraction of feed protein that is hydrolyzed in the rumen to yield ammonia and carbon skeletons is called Rumen Degradable Protein RDP IX The fraction of feed protein that escapes rumen degradation and goes to the small intestine is called Rumen Undegradable Protein RUP or bypass protein In ruminants there are 2 sources of protein for enzymatic digestion microbial protein and RUP X Human edible returns 1 Per unit of feed DM 2 Per unit of human edible feed DM and 3 Per unit of human edible protein feed consumed by livestock species Lb of feed per lb of product live basis Lb of human edible feed per lb of product live basis Net protein contribution Values 1 mean more high quality protein contributed than used Average US grain finished beef Pork Broiler chicken 13 8 2 5 1 6 1 6 2 0 1 4 2 …