Lecture 4, Measures of Protein Quality in Ruminants and Non-Ruminants PDF

MEASURES OF PROTEIN QUALITY IN RUMINANTS AND NON RUMINANTS Dr. Muhammad Mahboob Ali Hamid Assistant Professor Institute of Animal & Dairy Sciences University of Agriculture, Faisalabad [email protected] ...

MEASURES OF PROTEIN QUALITY IN RUMINANTS AND NON RUMINANTS Dr. Muhammad Mahboob Ali Hamid Assistant Professor Institute of Animal & Dairy Sciences University of Agriculture, Faisalabad [email protected] EXPRESSIONS OF PROTEIN Digestible crude protein (DCP ) True protein (TP) Protein efficiency ratio (PER) Net protein retention (NPR) Gross protein value (GPV) Protein replacement value (PRV) Biological value (BV) Net protein utilisation (NPU) Net protein value (NPV) Biological assays Protein equivalent (PE) Degradibi1ity PROTEIN EFFICIENCY RATIO (PER) It can be calculated as; PER = Weight gain (gm)/Protein intake (gm) Limitations i) It is only applicable for monogastric animals. ii) If only protein is given, no energy source then some pert of protein will burnt to produce energy. For sustaining of life but regardless of loss of weight. iii) Dietary caloric value should be optimum. iv) Protein intake should be optimum, not excessive. In case of excessive protein intake, body have to pay in the form of energy loss. Energy is lost for burning purposes. v) A.A. profile of protein in PER must be adequate in quantity and proportion. BIOLOGICAL VALUE (BV) (Thomas-Mitchell ) EXAMPLE (NUMERICAL) Data Feed Consumed Daily (gm) = 6.0 N2 in feed (%) = 1.043 Daily N2 intake (mg) = 62.6 Total urine N2 excreted daily (mg) = 32.8 Endogenous Urinary N2 daily (mg) = 22.0 Total N2 excreted in feces daily (mg) = 20.9 Metabolic Fecal N2 excreted (mg) = 10.7 FORMULA BIOLOGICAL VALUE (BV) It is the %age of absorbed N2 retained within the body for maintenance and growth, production, reproduction etc. A N2 balance trial is conducted in which N2 intake and urinary and fecal excretions are measured, and from these observations BV is determined. BIOLOGICAL VALUE (BV) Higher the adequate and proportionate of essential amino acid in the diet ---- Higher will be the BV and vice verse. Increased BV ---- Better protein source Decreased BV ---- Poor protein source BV value depends upon the quality, quantity and proportion of essential amino acids. For example, in maize, methionine is less and lysine is more while in Soyabean, Animal protein always have higher BV than that of vegetable protein.  DISADVANTAGES/LIMITATIONS Not applicable for ruminants because of presence of microbes in the rumen which synthesize amino acids from a variety of N2 compounds. BV may judge protein quality to combine functions such as growth, maintenance and production etc. but not for a single one. There is a difficulty in measuring the endogenous nitrogen fractions. Especially in the poultry, it is more difficult where they excrete urine and feces together. The BV determinate at a specific level of protein (N) intake may not apply on a feed having different levels of protein (N). Adequate non-nitrogenous sources to provide energy and also of minerals and vitamins should be present in all test diets. NET PROTEIN UTILIZATION (NPU) It is the %age of dietary protein which is converted into body protein. Formula: Nitrogen retention may be estimated by carcass analysis such as; NPU = BV x digestibility It is limited to those animals that can only use for carcass analysis. Although it is not laborious NITROGEN BALANCE INDEX (NBI) It accounts the same data on intake and out go of N2, as used in determination of BV. It can be calculated by the following equation; Whereas: B = Nitrogen balance B0 = Nitrogen balance when N2 intake is zero. A = Absorbed N2 NET PROTEIN RATIO (NPR) Net protein Ratio indicates the weight gain of a group of animals fed on test diet (containing protein) plus the weight loss of a similar group fed on a protein free diet, the total divided by the weight of protein consumed by the first group. Weight loss occurs due to feeding of protein free diet. It is applied, specifically on the non-ruminants. It can be calculated as; NPR = weight gain + weight loss weight of protein intake ESSENTIAL AMINO ACID INDEX It is also known as EAAI (Essential amino acid index) There are two types of dietary amino acids; i) Dietary essential a.a. ii) Non-dietary essential a.a. In Soyabean, a.a. profile required by bird is very good but overall, vegetable source are quite poor protein source due to imbalance a.a. profile. ESSENTIAL AMINO ACID INDEX It Is Geometric Mean of Egg Ratios Of Essential Amino Acids As Compared With Standard Protein In Egg Protein PROTEIN EQUIVALENT Or NPN has half biological value as true protein for animal University of Agriculture, Faisalabad, Pakistan Institute of Animal and Dairy Sciences