Lecture 5.1: energy and protein nutrition and requirements of laying hens

1. The basic concept energy can be defined as the ability to do work. All animal activities, such as breathing, heartbeat, blood circulation, muscle activity, neural activity, growth, production and exertion, require energy. The energy needed by animals mainly comes from the chemical energy of the three major nutrients in feed. In the body, chemical energy can be converted into heat energy (oxidation of fat, glucose or amino acids) or mechanical energy (muscle activity), or it can be accumulated in the body. Feed energy mainly comes from carbohydrates, fat and protein. The chemical energy needed by animals is stored in the chemical bonds of the three major nutrients. After feeding, the three nutrients are digested and absorbed into the body, and energy is released in the process of glycolysis, tricarboxylic acid cycle or oxidative phosphorylation, and finally meet the needs of the body in the form of ATP. In animals, energy conversion and material metabolism are inseparable. Animals can obtain energy only through the degradation of three major nutrients, and only by using these energies can all life activities including material synthesis be realized. After digestion and absorption, the energy substances in feed (mainly carbohydrates, fat and protein) become digestible energy (that is, feed total energy-fecal energy = digestible energy). Some substances that can not be used by the body are excreted through the kidney, and the available part is metabolic energy (total energy-fecal energy-urinary energy = metabolic energy). Metabolic energy produces heat loss in the process of metabolism in the body (that is, body heating). The rest is net energy (total energy-fecal energy-urine energy-body heating = net energy). Net energy is divided into maintenance net energy and production net energy, which is used by the body to maintain life activities and growth and development or into products. Carbohydrate (Carbohydrates) is a general term for polyhydroxyl aldehydes, ketones or their simple derivatives and compounds that can be hydrolyzed to produce the above-mentioned products. These nutrients include nitrogen-free extract and crude fiber in routine nutritional analysis, which are important nutrients and account for more than half of animal feed. Because of its abundant sources and low cost, it has become the main energy in animal production. In addition to direct oxidation and energy supply, carbohydrates can also be converted into glycogen and fat storage. Lipids are a kind of substances that exist in animal and plant tissues and are insoluble in water, but soluble in organic solvents such as ether, benzene, chloroform and so on. It has high energy value and is an important kind of nutrients in animal nutrition. It has many kinds and different chemical composition. In conventional feed analysis, these substances are collectively referred to as crude fat. Lipids are the nutrients with the highest energy content. 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, α-linoleic acid and arachidonic acid are generally considered as EFA. EFA is the main component of biofilm lipids such as cell membrane, mitochondrial membrane and plasma membrane, which plays a key role in the characteristics of most membranes and participates in the synthesis of phospholipids. Protein is an important component of cells and plays an important role in the process of life. 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 exactly the same, but the difference is not significant, generally calculated as 16%. Proteins are polymers of amino acids. A variety of proteins are formed due to the difference in the number, type and order of amino acids that make up proteins. So it can be said that the nutrition of protein is actually the nutrition of amino acids. At present, more than 180 kinds of amino acids have been found in various organisms, but there are only 20 kinds of amino acids that make up the proteins of animals and plants. Amino acids absorbed through the intestines can be used for protein synthesis (including body proteins and product proteins), decomposition and energy supply or conversion into other substances in the body. There are mainly transamination, deamination and decarboxylation reactions in the metabolism of amino acids. The synthesis of protein is a series of very complex processes. The basic raw material of protein synthesis is amino acid, and the energy needed for the synthesis reaction is provided by ATP and GTP. Body protein is a dynamic equilibrium system, and protein deposition is the result of its synthesis and degradation. On average, 5-6 grams of protein need to be synthesized in growing pigs. [fly] the storage of proteins and amino acids in the body is very limited, and mainly in the liver. The content of protein in the liver increases with eating, which can store 50% of the total protein in a short period of time. Over [/ fly] protein can only be converted into carbohydrates and fats, or decomposed to produce heat. Essential amino acids refer to the amino acids that cannot be synthesized or synthesized by animals themselves, which can not meet the needs of animals and must be provided by feed. The kinds of essential amino acids required by all kinds of animals are roughly the same, but there are also some differences due to their different genetic characteristics. Non-essential amino acids refer to the amino acids that can be synthesized and can fully meet the needs of animals without being provided by feed (it does not mean that animals do not need these amino acids in the process of growing and maintaining life). In fact, conventional feed (except pure amino acid diet) not only provides essential amino acids, but also provides a large number of non-essential amino acids, the insufficient part is synthesized by the body, but generally can meet the needs. Restricted amino acids are those whose ratio of essential amino acids in a certain feed is lower than that needed by animals. The deficiency of these amino acids limits the utilization of other essential and non-essential amino acids in animals. Among them, the lowest ratio is called the first restricted amino acid, followed by the second, the third and the fourth. Restricted amino acids. In production practice, the order of feed restricted amino acids can guide the balance of feed amino acids and the addition of synthetic amino acids. Commonly used cereals and other plant feeds, lysine is often the first limiting amino acid for pigs, and methionine is generally the first limiting amino acid for poultry. Digestible amino acid refers to the amino acid that is absorbed by the feed protein after digestion. Available amino acids refer to the amino acids that can be digested and absorbed by animals and can be used for protein synthesis. In the evaluation of feed protein and amino acid quality, it mainly refers to the digestible amino acids of poultry. Because it is difficult to separate feces from urine in the determination of amino acid digestibility of poultry, the amino acids in urine are deducted in the calculation, which is called available amino acids in order to make the name consistent with the determination method. However, under normal circumstances, the amount of amino acids in urine is very small, and its nitrogen content is less than 2% of the whole urine nitrogen, so it can be ignored. Therefore, in essence, it is to determine the digestibility of feed amino acids. The so-called ideal protein means that the composition and proportion of the amino acids of this protein are consistent with those of the proteins needed by animals, including the composition and proportion between essential amino acids and between essential and non-essential amino acids. The utilization rate of this kind of protein by animals should be 100%. In recent years, a lot of studies have been carried out on the ideal protein amino acid patterns of pigs and birds, and some models have been proposed. The quality of protein is essentially a question of whether the quantity and proportion of essential amino acids are appropriate. In the actual production, the content and proportion of protein and essential amino acids in common feed are not ideal compared with the needs of animals, and some of them are far from ideal. Therefore, how to balance feed amino acids is an important problem, which is directly related to the quality and utilization of feed protein. In order to balance feed amino acids, synthetic amino acids, such as synthetic lysine and methionine, are often added in production. By adding synthetic amino acids, the level of feed crude protein can be reduced, the quality of feed protein can be improved, its utilization rate can be increased, and the excretion of nitrogen can be reduced. 2. Dietary metabolic energy, protein and major amino acid requirements of laying hens (Kcal/kg,%) data source stage metabolic energy crude protein lysine egg + cystine American NRC 1994 standard (brown shell egg strain) 0-6 weeks 280017.00.800.596-12 weeks 280015.00.560.4912-18 weeks 285014.00.420.3918 weeks-laying 285016.00.490.44 2900mg/ day 165007606453, personal suggestion: the general development of chicks can not keep up with the laying period. 6-week-old body weight is generally not easy to reach the standard, the level of protein amino acid is the main factor affecting the growth and development of chicks, it is suggested not to use miscellaneous meal as far as possible, and the level of protein amino acid should be raised appropriately, but it should not be too high, otherwise it will cause gout. The stage of 6-12 weeks old can be carried out with reference to the standard. At the age of 12-18 weeks, it is recommended to reduce the levels of metabolic energy and protein amino acids (metabolic energy 2700Kcal/kg, crude protein 12%, lysine 0.45%, egg + cystine 0.37%), replace soybean meal with mixed meal, and add more coarse fodder such as wheat bran and DDG, so as to increase the level of crude fiber, which not only reduces the cost but also stimulates intestinal development, and lays a good foundation for ensuring feed intake, digestion and absorption in the egg laying stage. The metabolic energy of the feed during the laying period is as high as possible. If it is a corn-soybean meal feed, the metabolic energy can be designed at 2750 Kcal/kg, crude protein 14.5-15.0%, lysine 0.75%, egg + cystine 0.6%; if more miscellaneous meal is added, the metabolic energy can only reach 2700 Kcal/kg, and the crude protein level can be controlled at 15.5-16%. Finally, there is something new, support. -- Oh, I've learned. It was very in-depth-- I learned it, thank you-- well done. Practical.-- it is difficult to grasp the appropriateness of the subject. Finally, I think it is better to be popular. I hope that ordinary farmers can generally have a basic understanding of the energy and protein and amino acid nutrition of feed, so as to avoid them from going to extremes when preparing their own feed. try to maintain the balance of feed energy and protein. -- ask: why use mixed meal feed, metabolic energy is low, but crude protein is high, is to consider the digestion and utilization of amino acids?-- good question, yes, at the same time The effective contents of other essential amino acids (such as threonine and tryptophan) are also lower than those of soybean meal. When designing the formula, if the amount of soybean meal in the layer feed is less than 15%, the crude protein generally has to be designed to more than 15.5% other essential amino acids to meet the needs (lysine and methionine additional balance). -- finally looking forward to coming! Thank you for your hard work! It would be better if there were some case studies-your suggestion is good, and I will do some example analysis in my posts about recipe design.