Detailed Explanation of Energy and Protein Nutritional Requirements for Laying Hens (Lecture 5.1)

1. Basic ConceptsEnergy can be defined as the ability to do work. All activities of animals, such as respiration, heartbeat, blood circulation, muscle activity, nerve activity, growth, production of products, and draft work, require energy. The energy required by animals mainly comes from the chemical energy in the three major nutrients of feed. In the body, chemical energy can be converted into heat energy (oxidation of fat, glucose, or amino acids) or mechanical energy (muscle activity), and can also be stored in the body.Feed energy mainly comes from carbohydrates, fats, and proteins. The chemical energy needed by animals is stored in the chemical bonds of these three major nutrients. After animals consume feed, the three major nutrients enter the body through digestion and absorption, release energy during glycolysis, the tricarboxylic acid cycle, or oxidative phosphorylation, and ultimately meet the body's needs in the form of ATP. In the animal body, energy conversion and material metabolism are inseparable. Animals can only obtain energy by degrading the three major nutrients, and only by utilizing this energy can they achieve all life activities, including material synthesis.The energy substances in feed (mainly carbohydrates, fats, and proteins) become digestible energy after digestion and absorption (i.e., gross energy - fecal energy = digestible energy). After digestible energy undergoes body metabolism, some substances that cannot be utilized by the body are excreted through the kidneys. The utilizable portion is metabolizable energy (gross energy - fecal energy - urinary energy = metabolizable energy). Metabolizable energy generates heat loss during metabolism in the body (i.e., heat increment), and the remaining portion is net energy (gross energy - fecal energy - urinary energy - heat increment = net energy). Net energy is further divided into net energy for maintenance and net energy for production, which is utilized by the body to maintain life activities and growth and development, or converted into products.Carbohydrates is the general term for polyhydroxy aldehydes, ketones, or their simple derivatives, as well as compounds that can be hydrolyzed to produce the above products. In routine nutritional analysis, these nutrients include nitrogen-free extract and crude fiber. They are an important class of nutrients, accounting for more than half of animal feed. Because of their abundant sources and low cost, they have become the main energy source in animal production.In addition to directly oxidizing to provide energy, carbohydrates can also be converted into glycogen and fat for storage.Lipids are a class of substances that exist in animal and plant tissues, are insoluble in water, but soluble in organic solvents such as ether, benzene, and chloroform. They have high energy value and are an important class of nutrients in animal nutrition, with many types and varying chemical compositions. In routine feed analysis, these substances are collectively referred to as crude fat. Lipids are the most energy-rich nutrients, and under physiological conditions, the energy content of lipids is about 2.25 times that of proteins and carbohydrates. Essential fatty acids (EFA) are polyunsaturated fatty acids. Linoleic acid, alpha-linolenic acid, and arachidonic acid are generally considered EFAs. EFAs are the main components of lipids in biological membranes such as cell membranes, mitochondrial membranes, and plasma membranes. They play a key role in the characteristics of most membranes and also participate in phospholipid synthesis.Protein is an important component of cells and plays a crucial role in life processes.The main constituent elements of proteins are carbon, hydrogen, oxygen, and nitrogen. Most proteins also contain sulfur, and a few contain elements such as phosphorus, iron, copper, and iodine. Although the nitrogen content of various proteins is not completely equal, the differences are not great, and it is generally calculated at 16%.Proteins are polymers of amino acids. Various proteins are formed due to differences in the number, type, and arrangement order of the amino acids that make up proteins. Therefore, it can be said that protein nutrition is actually amino acid nutrition. At present, more than 180 kinds of amino acids have been discovered in various organisms, but only 20 kinds of amino acids commonly constitute the proteins of animals and plants.Amino acids absorbed through the intestine can be used in the body for protein synthesis (including body protein and product protein), decomposition for energy, or conversion into other substances. In amino acid metabolism, the main reactions are transamination, deamination, and decarboxylation.Protein synthesis is a very complex series of processes. The basic raw materials for synthesis are amino acids, and the energy required for synthesis reactions is provided by ATP and GTP.Body protein is a dynamic equilibrium system. Protein deposition is the result of its synthesis and degradation. Growing pigs deposit on average1 gramof protein requires synthesis of 5-6 grams.[fly]The storage of proteins and amino acids in the body is very limited, and mainly occurs in the liver. Liver protein content increases with feeding, and within a short time can store 50% of the total ingested protein. Ex[/fly]cess protein can only be converted into carbohydrates and fats, or decomposed to produce heat.Essential amino acids refer to amino acids that animals cannot synthesize themselves or whose synthesized amount cannot meet the animal's needs, and must be provided by feed. The types of essential amino acids required by various animals are roughly the same, but there are also certain differences due to their different genetic characteristics.Non-essential amino acids refer to amino acids that can be synthesized in the animal body and fully meet the needs without being provided by feed (this does not mean that animals do not need these amino acids during growth and maintenance of life). In practice, conventional feed (except for purified amino acid diets) provides a large amount of non-essential amino acids while providing essential amino acids. Only the insufficient portion is synthesized in the body, but generally the needs can be met.Limiting amino acids refer to amino acids whose ratio of the amount contained in a given feed to the amount of essential amino acids required by animals is relatively low. Due to the deficiency of these amino acids, the animal's utilization of other essential and non-essential amino acids is limited. The one with the lowest ratio is called the first limiting amino acid, followed by the second, third, fourth... limiting amino acids.In production practice, the order of limiting amino acids in feed can guide the balance of feed amino acids and the addition of synthetic amino acids. In commonly used cereal grains and other plant-based feeds, for pigs, lysine is often the first limiting amino acid; for poultry, methionine is generally the first limiting amino acid.Digestible amino acids refer to amino acids that are absorbed after the ingested feed protein is digested.Available amino acids refer to amino acids in ingested protein that can be digested and absorbed by animals and used for protein synthesis. In the evaluation of feed protein and amino acid quality, it mainly refers to the digestible amino acids of poultry. Since in the determination of amino acid digestibility in poultry, because feces and urine are difficult to separate, urinary amino acids are deducted during calculation. To make the name consistent with the determination method, it is called available amino acids. However, under normal conditions, the amount of amino acids contained in urine is very small, and its nitrogen content is less than 2% of the total urinary nitrogen, so it can be ignored. Therefore, in essence, it is still the determination of feed amino acid digestibility.The so-called ideal protein refers to a protein whose amino acid composition and proportions are consistent with the amino acid composition and proportions of the protein required by animals, including the composition and proportions among essential amino acids and between essential and non-essential amino acids. The utilization rate of such protein by animals should be 100%. In recent years, a large amount of research has been conducted on ideal protein amino acid patterns for pigs and poultry, and some patterns have been proposed.The issue of protein quality is essentially a question of whether the quantity and proportions of essential amino acids are appropriate. In actual production, the protein and essential amino acid content and proportions of commonly used feeds are mostly not ideal compared with animal requirements, and some are far from adequate. Therefore, how to balance feed amino acids is an important issue, directly involving the quality and utilization rate of feed protein. To facilitate the balancing of feed amino acids, synthetic amino acids such as synthetic lysine and methionine are often added in production. By adding synthetic amino acids, the crude protein level of feed can be reduced, the quality of feed protein can be improved, and its utilization rate can be increased, thereby reducing nitrogen excretion.2. Requirements of Laying Hens for Dietary Metabolizable Energy, Protein, and Major Amino Acids (Kcal/kg, %)Data SourceStageMetabolizable EnergyCrude ProteinLysineMethionine + CystineUS NRC1994 Standards(Brown-egg strains)0-6 weeks280017.00.800.596-12 weeks280015.00.560.4912-18 weeks285014.00.420.3918 weeks - laying285016.00.490.44Laying period2900mg/day165007606453. Personal Recommendations:Chick development generally lags behind, and body weight at 6 weeks of age is generally difficult to reach the standard. Protein and amino acid levels are the main factors affecting chick growth and development. It is recommended to avoid miscellaneous meals as much as possible and appropriately increase protein and amino acid levels. However, they should not be too high, otherwise it will cause gout. For the 6-12 week stage, the standards can be followed. For the 12-18 week stage, it is recommended to reduce metabolizable energy and protein amino acid levels (metabolizable energy 2700 Kcal/kg, crude protein 12%, lysine 0.45%, methionine + cystine 0.37%), replace soybean meal with miscellaneous meals, and add more wheat bran, DDG, and other roughage to increase the crude fiber level. This not only reduces costs but also helps stimulate intestinal development, laying a good foundation for ensuring feed intake and digestion absorption during the laying period. For the laying period, the metabolizable energy of the feed should be made as high as possible. If it is a corn-soybean meal type feed, the metabolizable energy can be designed at above 2750 Kcal/kg, crude protein 14.5-15.0%, lysine 0.75%, methionine + cystine 0.6%. If a relatively large amount of miscellaneous meals is added, the metabolizable energy can generally only reach 2700 Kcal/kg, and the crude protein level should be controlled at 15.5-16%.
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Finally something new again, support.
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Hehe, learned something, very in-depth presentation
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Learned something, thank you
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Well explained, practical.
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The level of detail for this topic is hard to gauge. In the end, I thought it better to keep it more accessible, hoping that ordinary farmers can generally have a basic understanding of feed energy and protein amino acid nutrition, try to avoid them going to extremes when mixing their own feed, and try to maintain the balance of feed energy and protein.
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Question: Why is it that feed using miscellaneous meals has lower metabolizable energy but requires higher crude protein? Is it because of considering the digestibility and utilization of amino acids?
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Good question. Yes, that is the case. At the same time, the effective content of some other essential amino acids (such as threonine and tryptophan) is also lower than that of soybean meal.
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When we design formulas, if the soybean meal usage in laying hen feed is below 15%, the crude protein generally needs to be designed at above 15.5% for other essential amino acids to meet the requirements (lysine and methionine are additionally added for balance).
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Finally looking forward to it!
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Thanks for your hard work, Teacher! It would be even better if there were some case analyses.
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Your suggestion is very good. In posts related to formula design, I will do some practical case analyses.