Toxicology Subject

Toxicology is an applied discipline that studies the harmful effects of exogenous factors (chemical, physical, and biological factors) on biological systems. It is a science that studies the toxicity, severity, frequency, and mechanism of toxic effects of chemical substances on organisms, as well as qualitative and quantitative evaluation of toxic effects. It is a discipline that predicts its harm to the human body and the ecological environment, and provides a scientific basis for determining the safety limit and taking preventive measures.​​

 

What is theoretical basis of toxicology?

Mainly apply the theory and technology of basic disciplines such as physiology, pharmacology, biology, biochemistry and pathology; study the absorption, distribution, metabolism and excretion, and toxic effects of foreign substances through animal experiments, clinical observations and epidemiological investigation methods. 

Its mechanism and poisoning treatment are not only to protect human beings and other organisms from the harmful effects of chemical substances and protect people's health, but also to directly develop poisons with good selective effects. 

More selective drugs and pesticides, etc., and conduct safety evaluation or risk evaluation of chemical substances, formulate health standards, and provide scientific basis. 

Toxicology is closely related to pharmacology, and has now developed into an independent discipline with certain basic theories and experimental methods, and has gradually formed some new branches of toxicology.​​

 

What is the effect of toxicology?

The currently accepted definition of toxicology is the science that studies the harm of exogenous chemicals to living organisms. 

Since the purpose of toxicology research is to provide a scientific basis for the protection of the health or safety of organisms, toxicology belongs to preventive medicine in terms of the nature of the discipline, and runs through the idea of ​​prevention first. 

Since the research objects of toxicology are wide, including chemical factors, physical factors, and biological factors, and organisms include humans, animals, and plants, toxicology is related to pharmacology, physiology, pathology, chemistry, biochemistry, and biology.

It is connected to industry, agriculture, the economy.

It is connected to forensic science, clinical medicine, ecology and environmental protection.

It is connected, so to speak, to the entire future of life on earth. Therefore, toxicology is widely used in clinical medicine, pharmacy, environmental protection, zoology, prenatal and postnatal care, occupational labor protection and food hygiene. Therefore, the classification of toxicology is very complicated, and it can be classified from different angles, and it is not completely consistent.​​

 

Toxicological Classification

From the research content, it can be divided into three parts: descriptive toxicology, mechanism toxicology and management toxicology (also known as regulatory toxicology). It can be divided into: forensic toxicology, clinical toxicology, management toxicology or regulatory toxicology, research toxicology, etc. 

From applied toxicology viewpoint, it can be divided into: food toxicology, industrial toxicology, pesticide toxicology, military toxicology, radiotoxicology, environmental toxicology, ecotoxicology and other branches. 

The research objects can be divided into: insect toxicology, veterinary toxicology, human toxicology and plant toxicology. 

From the research fields, it can be divided into: drug toxicology, environmental toxicology, food toxicology, industrial toxicology, clinical toxicology, forensic toxicology, analytical toxicology, military toxicology, management toxicology, etc. 

From the target organs or systems studied, it can be divided into: organ toxicology, liver toxicology, renal toxicology, ocular toxicology, ear toxicology, neurotoxicology, reproductive toxicology, immune toxicology.

 

Toxicology Overview on Toxicology and Us

Toxicology sounds like a very deep and emerging discipline, far from us. In fact, it has a profound history and is closely related to our lives. Toxicology is the study of the adverse effects (side effects or harmful effects) of chemical substances and physical factors on an organism. 

The adverse effects can be very obvious, such as death, cancer, pain, dermatitis, etc., or they can be subtle effects, such as the developing children's brains are extremely sensitive to trace lead exposure, which will lead to the decline of learning and memory, and harm life. Realizing this is far more important than knowing what doses of lead can kill children.

 

Chemical substances in the definition of toxicology can be naturally occurring products or artificially synthesized substances. These things may be necessary, or they may be deadly poisons. And different dosages will make these chemicals have different effects on humans. For example, botulinum toxin is the most deadly poison, and at the same time it is used reasonably in a very small amount, and it is also a powerful tool for medical beauty to remove wrinkles. 

Physical factors are often associated with occupational health problems. temperature and noise. Lack of sleep, the adverse effects of jet lag, etc., can all cause irritating inefficiencies. These factors also have a huge impact on the environment, including changes in temperature that can affect the survival and reproduction of fish.

Toxicology and Environmental Health

Toxicology can also be considered in the context of environmental health. The environments we generally consider are the home, school, workplace, outdoors, indoors, ocean, air, etc. And we define environmental health as "ensure that all organisms have the best chance of maintaining or exploiting the full range of genetics". The value of this definition is best seen in children. This is also why ethical assessments of efficacy tests for relevant children and pregnant women are difficult to pass. For example, the lead exposure mentioned earlier, even in very low doses, can lead to learning disabilities in children. These harmful environmental changes can affect children throughout their lives, affecting their best chances of maintaining and realizing their full genetic potential. In other words, the life and death of an adult who has given birth to a baby is relatively less important.

 

What is the History of Toxicology?

The history of toxicology can be traced back to 2696 BC, the father of Chinese herbal medicine, Shennong, famous for tasting 365 kinds of Chinese herbal medicines, is said to have died of poisoning caused by excessive drug doses. The Black Death (1347-1351) bubonic and pneumonic plague swept across Europe during the Middle Ages, causing one of the worst plagues in human history. 

Bioaccumulation of experimental poisons in animals by Leonardo da Vinci (1452-1519) during the Renaissance. Paracelsus (1493-1541) physician, alchemist, father of toxicology. Attempts have been made to combine medicine and alchemy to form a new medical chemistry. 

Who is known as the Father of Modern Toxicology?

Matthew Swiss scientist Paul Offila (1787-1853), known as the "father of modern toxicology", published "Toxicology" in 1813, in which the symptoms of poisoning were described in detail. 

Who discovered DDT?

Hermann Muller discovered the insecticidal properties of DDT in 1939 and won the Nobel Prize in Physiology and Medicine in 1948, while DDT was banned in 1972. 

Until recently, Fukushima, Japan, in 2011, the nuclear power plant accident caused massive human and property damage. 

Visible toxicology related events throughout almost the entire history of our human development. 

 

Public safety incident pertaining to toxicology

Understanding the toxicological properties of some legal or illegal drugs is important for developing sound public policy. The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) were established in the United States to protect the health and welfare of people and the environment. 

In 1962, a new anti-pregnancy drug called thalidomide (thalidomide) was found to have the side effect of causing birth defects in babies, now known as dolphin babies. This new drug has been widely promoted in Europe before, leading to the tragedy of tens of thousands of families in Europe, but it failed to enter the US market under the strong blocking of US FDA experts, so that Americans escaped this nightmare. 

Later legislation mandated that all new drugs must be fully tested in animals and humans before they can be approved for use by the FDA.

 

Rachel Carson published her landmark book Silent Spring in 1962, which focused on the environmental impact of chemicals and expressed concerns about the adverse effects of pesticides on human health. Among them, DDT, as an efficient insecticide, does not directly cause animal death, but it will thin the eggshells of birds, resulting in the reduction of especially carnivorous birds. Moreover, such pesticides accumulate in the fat of animals and eventually enter the human body through the food chain. 

DDT also passes into the baby's body with breast milk during breastfeeding. Eventually DDT was banned in 1972.

 

There are many other similar public safety incidents. For example, we are familiar with the poisoned milk powder incident, the poisoned rice incident, the aggravation of environmental pollution in recent years, and the public's attention to the risky ingredients in daily cosmetics.

 

What is the Role of Toxicology?

Toxicology cannot solve all environmental health problems, but it can help us better critically analyze the surrounding environment and events that affect local and even global, better judge the impact of chemical substances and physical factors on our lives and work. This leads to forward-looking questions that in turn lead to reducing the risk of exposure to hazards, both across industries and within, and promoting humans to “maintain or realize their full genetic potential.”

 

Knowing more about toxicology can help us make some day-to-day decisions. When promoting human health and improving environmental quality, it can also act according to the basic principles of toxicology (dose-response relationship, individual susceptibility). 

Actions were taken to reduce the exposure of infants and young children, for example, once it was realized that infants and children were underweight, have particularly sensitive developing nervous systems, and were more susceptible to chemicals than adults. 

Knowledge of toxicology will help us better judge the impact of chemical substances and physical factors on our lives, provide forward-looking insights, and ultimately influence decision-making.

 

Key Points of Whole Body Weight control of Broiler Breeders

In the breeding process of broiler breeders, in order to give full play to its excellent genetic potential and obtain the best economic benefits, it is necessary to provide a good house environment, with special attention to the whole-process weight control and uniformity management of breeders. Below, the author talks about some of his own views based on breeding experience for reference by peers.

 

1. Weight control during the brooding period (0-28 days old)

According to the physiological characteristics of chicks, do a good job in the control of the environmental conditions of the early chicken house and the management of the chicken flock to ensure that the bones, immune system, cardiovascular function, and feather growth are well developed in the early stage. Because one of the key factors in weight control is to give chicks a good start, especially the first 72 hours of a chicken's life is important, not only to determine the ability to resist disease attack, but this initial stage determines the development of the chicken skeleton. 

7-14 days of age should meet or exceed the weight standard. In the brooding period, high-energy (12.1 MJ/kg) and high-protein (19%-19.5%) full-price compound feed should be provided. 

The accumulated feed of hens should reach 850-900 grams per chicken at the end of 4 weeks, and the accumulated energy should be 10.5 MJ.

 

Matters needing attention

At any stage of early growth, if the body weight is not up to the standard or the appetite is lost, corresponding measures should be taken immediately. Taking measures as soon as possible can avoid the adverse consequences caused by poor uniformity and hindered development of important physiological organs in the later stage of brooding. 

The 4-week-old body weight of the hens is between 380-450 grams. If the body weight is too large at the end of the 4th week, the body shape of the adult chicken is too large, and higher feed amount and nutrition are required.

If the body weight is too small, the body shape of the adult chicken is too small, which affects the qualified rate of hatching eggs. 

The roosters should be fed ad libitum for the first 4 weeks, and the body weight should be monitored every day from the 4th week. Once it reaches 690 grams, it will be restricted immediately. It is not advisable to raise the frame by pulling, because the change of feed amount is too large and the stress on the rooster is too great, which directly leads to the rapid decline of the fertilization rate in the later stage of laying eggs. For hens, when the feeding time is less than 4 hours, switch to the 4/3 method.

 

2. Weight control during the breeding period (29-154 days old)

 

2.1 Early stage of breeding (29--70 days old)

This stage is the stage in which the growth rate of broiler breeders is relatively fast. It is best to use the method of restricting feeding intensity to control the rapid weight growth, so it is also called the stage of reducing maintenance needs. 

The average weekly feeding is 2--3 grams. This stage is only for the purpose of bone growth, maintenance needs, feather growth and weight gain. The feeding range is small to ensure an average weight gain of about 95 grams. 

If the uniformity of the flock is unsatisfactory at the end of the 4th week, the breeders should be raised in three pens according to their body weight, and different amounts of feed should be given to different pens. 

OBJECTIVE: To control the uniformity by staging, so as to achieve the same weight standard in 10-12 weeks. The feeding program can only be used as a reference when determining the feeding amount. 

The feeding amount should be calculated according to the difference between the actual body weight and the body weight standard, as well as the current feeding amount.

 

29-70 days of age is a critical period for the development of rooster muscles, tendons and ligaments. At this stage, the rooster's legs develop rapidly. Any deviation from the growth curve standard can have a negative impact on the rooster's survival rate and production performance after adulthood. At the age of 8 weeks, 85% of the skeleton development is basically completed, so this stage must reach or even exceed the early weight standard. Otherwise, the mature size of the rooster will be smaller than the optimal size.

 

2.2 Mid-term breeding (78-98 days old)

At this stage, chickens are very sensitive to changes in light time and intensity, and are prone to leg disease and coccidiosis, requiring complete shading and rearing, and timely correction of any accidental light leakage. 

The growth and development at this stage does not change significantly with the change of the feeding amount. The breeder should be grown according to the body weight standard to ensure that the weekly weight gain of the breeder meets the standard. Increase the amount of feed by 3-5 grams per week to ensure a weekly weight gain of 95 grams.

 

2.3 Late growth period (105-154 days old)

This stage is the energy reserve stage of broiler breeders, and the total body weight is increased by more than 1500 grams to meet the development of reproductive organs. 

At this stage, because the reproductive system is in a vigorous period, to prepare for light stimulation, the feeding range also needs to be increased, with an average of 6-8 grams per week. 

If the amount of feeding is too small, it will inhibit the development of the reproductive system and directly lead to hypoplasia of the ovaries and fallopian tubes. For roosters, it affects testicular development and ultimately sperm production in the later stages of laying eggs.

 

In order to ensure the weekly weight gain of breeders at this stage, it is recommended to increase the feed amount by 10%-15% from the age of 105 days. Regardless of the size of the body weight, the feed should be increased proportionally.

The increase in body weight of breeders stimulates physiological changes and reaches sexual maturity. 

The gradual increase in weight gain will ensure a smooth physiological transition to sexual maturity and full sexual maturity at around 210 days of age. 

Insufficient body weight gain and poor ovarian development can have the following effects: 

• delayed onset of lay 
• low egg weight in the early laying period
• increased proportion of defective and deformed eggs
• decreased fertilization rate
• increased brooding tendency
• poor uniformity

 

If the actual body weight at this stage exceeds the standard, resulting in poor sexual maturity and body weight uniformity, it will cause the ovaries and fallopian tubes to pack too much fat and affect the fertilization rate, premature birth, and the proportion of unqualified eggs will increase. The amount of feed and the fertilization rate decreased.

 

The breeding of roosters is equally important to the feeding of hens of the same breed, and the requirements for hens are basically applicable to roosters. 

If the 105-day-old is underweight or overweight, the weight standard should be re-established to ensure that the weekly weight gain of the flock before sexual maturity and the same increase in body weight as the standard curve.

 

2.4 Before and after the mixed group of male and female

Problems that are easy to occur before and after mixing: due to stress such as changing feeding equipment, mixing, adding light, etc., the rooster is prone to unsatisfactory weekly weight gain, which seriously affects the performance of the breeding rooster.

 Measures to be taken: Consciously add 3-5 grams of stress feed before and after mixing the group, take a random weight measurement at least twice a week, and closely monitor the weight change. Strengthen the management of rooster buckets to prevent male and female from stealing feed from each other. 

The mixing time is generally 21-23 weeks, and the mixing time is late, which can control the weight more effectively. 

After mixing the group, pay attention to observe the feeding behavior to ensure the correct and effective implementation of male and female feeding.

 

2.5 Control of feeding amount

During the brooding period, when formulating the weekly feed amount, the principle of forward-looking and backward-looking and step-by-step should be followed, and the comprehensive decision should be made according to the quality of the feed, the environmental conditions of the chicken house, and the increase in the weight of the chickens. 

In the early stage, the weekly increase in feed amount should be small, and in the later stage, with the rapid growth and development of the breeder, the feed amount will be gradually increased. 

Regularly measuring the body weight every week, and frequently touching and evaluating the chickens, can enable managers to adjust the feed amount in time, and have a more comprehensive grasp of the basic development status of the chicken flock. It is also the main basis for checking whether the feeding amount is accurate.

 

3. Weight control during the laying period (155-462 days old)

 

3.1 The expected production period is light stimulation to 5% egg production rate (155-182 days old)

This stage is the stage of rapid growth of sexual maturation and non-reproductive organs. The increase in light time is generally based on the growth and development of chickens at 22 weeks. 

The following factors need to be considered in the determination of the light program for the expected date of delivery: 

• whether the body weight at 22 weeks reaches the standard body weight, 
• whether the nutrient storage meets the standard, more than 80% of the chickens with a V-shaped chest muscle cross section
• the number of chickens with 1 to 2 main wing feathers remaining

 

After 23 weeks, do not add too hastily, but add a small amount and several times. Overfeeding at this stage will directly lead to abnormal uterine structure, excess body weight, poor egg quality, and low hatchability of breeding hens. Before the egg production rate reaches 5%, feed 2-3 times a week, no more than 3 grams each time. After the egg production rate reaches 5%, feed every day until the egg production peak is reached.

 

3.2 The early stage of egg laying is 5% egg laying - peak egg laying (183-210 days old)

This stage is the stage of rising egg production, and both body weight and egg weight are increasing. Therefore, chickens with 10% egg production rate should be regarded as 20%-25% chicken feeding, otherwise the hens use their own body fat reserves to supplement the feed. Insufficient nutrients, chickens show a slow rise in egg production.

 Breeders should gain continuous weight gain from the start of production to the peak of egg production, and maintain a certain weight gain (about 15-20 grams per week) throughout the egg-laying period after the peak of egg production. 

Feeding principle: hens need to increase feed first, that is, the increase in feed must precede the increase in egg production rate. 

The main reason for this need is that the egg production rate of many individual hens is higher than the average egg production rate of the flock.

 

The chickens in the rising stage of egg production should implement dynamic management, draw the egg weight curve according to the daily egg weight and add a trend line to understand the growth trend of egg weight and guide feeding.

 

3.3 Peak egg production period (211-280 days old)

This stage is the peak egg production period, and it is necessary to maintain the balance of physical energy and energy intake. 

To ensure that chickens can take in sufficient nutrients every day, high yields have a material basis. Factors that affect the maintenance of physical fitness include body weight, egg production, egg weight, and ambient temperature.

 

3.4 Late peak period (281-462 days old)

In order to maintain the persistence of high-yield breeding hens and maximize the yield of qualified eggs, it is necessary to reduce feed after the peak. 

If a breeder eats more than it needs, it can continue to gain weight through fat deposition. Fat deposition rate is a key factor affecting the decline of egg production rate and fertilization rate after the peak period. Therefore, the feeding amount should be adjusted according to changes in body weight and egg production rate to adjust the rate of fat deposition. 

The exact timing of breeder feed reduction should depend on the growth history of the flock and the condition of the flock. For flocks with high egg production rate, the first feed reduction should not be earlier than 34 weeks, and the feed reduction should be carried out gradually.

 

After the peak of egg production, the feeding amount is reduced in a planned way, so that the weekly weight gain of the flock is kept at 15-20 grams, which can maintain a good egg production rate, fertilization rate, hatching rate and egg weight. 

The amount of feed should be determined weekly on the basis of analyzing data such as body weight, egg weight, feed consumption time, number of eggs produced per day and the condition of the flock, and should be adjusted in time according to changes in the ambient temperature of the chicken house. 

The total amount of material reduction is about 8% - 12% of the peak material amount. The principle of material reduction: first fast and then slow, reduce the material by 0.5-1 grams per week.

 

4. Weight control of roosters during laying period

Breeding male breeding management and weight control should be adjusted according to the growth and development of male reproductive organs-testis, which can be divided into the following periods: 

• 0-12 weeks testis basically do not grow (initial phase)
• 12-27 weeks testis growth and rapid development period (growth period)
• 27-35 weeks testicular development peak maintenance period
• 35-50 weeks testicular atrophy, testicular atrophy period after 50 weeks

The good or bad management of the male rooster determines the rate of testicular atrophy.

 

The most critical factor in the laying period is to continue to control the body weight of the males to ensure that the males have good physiological conditions for mating. Feed the rooster while the hen is cutting. 

General principles of feeding

The feeding range is determined according to the actual weekly weight gain. After the peak, it is appropriate to control the weekly weight gain at 15-20 grams, control the number and weight of the males, maintain a high fertilization rate, and make the actual weight of the males consistent with the weight standard. 

Use well-maintained equipment to implement strict male and female feeding. Weigh males at least once a week for average male body weight and weekly gain. 

In addition, males should be culled based on male physical characteristics, feather condition, and male alertness and activity in order to maintain an optimal male-female ratio and prevent males from over-mating. After the peak, if the male and female feeding is well implemented, generally 1 gram of feed is added every 4 weeks.

 

Conclusion

In a word, in the whole production cycle of broiler breeders, as grass-roots managers, we should always evaluate and observe the behavior of chickens, analyze and summarize more, take corresponding measures in time for the abnormal situation of the chickens, and try our best to achieve the best quality of breeders. 

Optimum production performance is obtained when the actual body weight curve matches the standard curve.

See also:

Feed of Commercial Broiler Chicken

Economic Benefits of Chicken Farming

 

 

Effects of feed shape on performance of commercial broiler chickens

Commercial broilers can achieve good growth rates if they can meet their daily nutritional needs. To some extent, the bird's daily nutrient requirements depend on the nutrient content of the diet; however, it is the feed or nutrient intake that the bird actually responds to. In order to obtain a good growth rate and effective nutrient utilization in commercial broiler chickens, the key is that the chickens have a good feed intake. Feed shape has a crucial impact on feed intake. Poor feed shape can inhibit feed intake and negatively impact bird growth rates. Both feed nutrient concentration and feed shape are optimal to maximize feed intake and maximize the performance of commercial broiler chickens.

 

The effect of feed shape on the performance of commercial broiler chickens

In general, the feed fed to modern commercial broilers is pelletized. Pelletized poultry feed can increase bird weight gain compared to untreated meal. 

In part, this improvement in performance is due to increased feed intake. 

Feeding pellets to the flock also reduces energy consumption during feeding. Thus, the energy used for growth and development increases accordingly.

 

A high-quality pellet feed will enhance this benign effect. High-quality pelleted feed should have strong pellet persistence and low powder content. Persistence refers to the ability to keep feed pellets intact during feed handling and transport. 

The poor persistence of feed pellets will cause the pellets in the feed to be damaged and the feed powder fine particles to gradually increase. 

Gradually increasing the fine particle size of the feed will affect the growth rate of the flock and increase the feed to meat ratio.

 

In order to give full play to the production performance of commercial broiler chickens, the accumulation of fine powder particles in the feed should be minimized.

 

Improve feed conditions

Feed conditions, especially the accumulation of fine powdery particles in the feed, result in poor pellet quality, which can negatively impact the performance of commercial broilers. The results of field investigation showed that some chicken flocks were fed with only 28-37% complete pellets, and poor quality pellets was a very important factor hindering the ideal production performance of commercial broiler chickens.

 

How to improve the quality of pellets?

 

Factors affecting the quality of pellets:

 

• The raw material of the ration
• Dietary fat content 
• The particle size of the diet

 

Raw material

Wheat and its by-products have good viscous properties to obtain better particle quality. The lack of stickiness in corn results in poor kernel quality. The particle breakage of corn-based formula feed is much more serious than that of wheat-based formula feed. The addition of wheat is beneficial for improving pellet quality, but may compromise the flexibility of minimum cost diet formulations.

 

Dietary fat

Adding more than 2% fat to the feed mixer, especially for corn-based formula diets, will reduce the quality of pellets. In any case, a certain amount of fat is allowed to be added to the diet before pelleting, but it cannot affect the pellet quality of the feed.

 

The size of granule

The general assumption is that grinding raw materials into finer powder particles will improve the quality of pelleted feed; however, the scientific basis for this is not very clear. 

The potential benefits of grinding raw materials to a finer powder to improve pellet quality must be balanced against the increased energy costs associated with doing so by the feed mill. 

In the case of poor pellet quality and a high likelihood of pellet breakage, grinding the raw material into a finer powder will result in an increase in the powdered pellets in the feed and negatively impact the performance of commercial broilers.

 

Compared with the feed with coarser pellets, the feed pellets that are too fine will increase the waste of feed and increase the energy consumption during feeding, and the intake of nutritionally unbalanced diets due to picky eaters.

 

Flocks prefer coarser to finer pelleted feed, and this preference is often associated with increased feed intake and improved flock performance.

 

When the quality of feed pellets is poor and the pellets are damaged, the use of feed with coarser pellets may be beneficial to the performance of the flock. Rather than feeding pellets that are more easily broken into fine powders, it is better to feed better quality coarse pellets. The uniformity of feed pellets is also important for flock performance.

 Flocks fed diets with uniform particle size also had better production performance, increased feed intake, and grew faster. Flocks are more likely to eat uniformly sized feed and are less picky eaters. 

The uniformity of the pellets is also good for the quality of the pelleted feed. If the feed pellets in the pellets are all the same size, the chance of pellet breakage is relatively small.

 

Feed particle size has a great impact on the performance of commercial broilers; feed particles that are too fine will reduce feed intake and growth rate. However, feed pellets that are too coarse can also have a negative impact on the performance of commercial broilers. 

What kind of pellet feed can maximize the performance of the chicken flock? 

In fact, the existing data is still not enough to answer this question. The data provided by NiretAl. (1994) suggested that the optimum particle size of the brooding material should be 0.7-0.9mm in the case of powder. 

If pellet feed is used, Aviagen recommends that 0-10-day-old flocks should be fed sieved crushed pellets, 11-28-day-old feed pellets with a particle diameter of 2-3mm, and 29-day-old flocks To the market feeding pellets with a diameter of 3mm. 

There is currently no data on the optimal particle size of the raw materials for making pellets. This depends on factors such as different raw materials and feed mill equipment and feed processing. 

The general principle is that the raw pellets used to make pellets should be fine enough to ensure pellet quality without affecting flock performance. To achieve this balance, the quality of pellets should be regularly monitored in conjunction with flock performance.

 

Conclusion

The ideal feed intake is the basis for efficient use of feed and optimal growth rate in the flock. Pellets quality/feed shape has a very important impact on feed intake and growth rate. 

Poor pellet quality can result in reduced feed intake by birds. It is important to understand the error between the nutrient content of the feed (as determined by the nutritionist) and the actual intake by the birds, and to minimize the gap between the two. Improving the quality of pelleted feed plays a very important role in the performance of chicken flocks.

See also:

Economic Benefits of Chicken Farming

Broiler Body Weight

 

 

 

Introduction of reasonable fertilization method for fish ponds

You may use fertilizers directly and let them dissolve slowly. Water currents help to disperse the dissolved chemicals through the entire pond area. In small ponds one may use at least one fertilizing point per 1000 m2 of water area. In case of larger ponds , use 2-3 points per hectare, tentatively.

 

1. Retain the fertile water

When the pond is cleared in winter, the pond where the fish are grown should try to retain the fertile water of the original pond, so that once the fish species are put into the fish pond, there will be richer feed for consumption.

 

2. Avoid using raw fertilizers

The fertilizers used in fish ponds must be fermented, and raw fertilizers must not be applied.

 

3. Fertilize according to the weather and water quality

The amount of fertilization depends on the weather and water quality. In spring and autumn, the weather is cool, the water temperature is low, the decomposition of organic matter is slow, the oxygen consumption is low, the fish's food intake is small, the activity ability is poor, and the dissolved oxygen in the water is also large. Vigorous, the amount of fertilization should be small and many times. The specific method should be considered according to the conditions of the fish pond itself and the activity of the fish observed in the early morning in the pond, as well as the weather.

When the water quality is fertile, the weather is sultry, and the air pressure is low, most of the fish float their heads. At this time, the application should be stopped or less applied; if the water quality is thin, the weather is cool, and the fish are active in the water, more fertilizer should be applied.

If human and animal manure is used as fertilizer, it must be fermented to prevent the rapid fermentation of immature fertilizer at high temperature and a large amount of oxygen consumption, causing pond fish to float and die due to lack of oxygen.

 

4. Sprinkling the whole pond

Fertilizer should avoid the food court, adopt the method of sprinkling the whole pond, and avoid pouring the whole bucket of fertilizer into the pond.

 

5. Sewage should be tested first

If domestic sewage is used, it must be tested first, and then used after it is determined to be non-toxic.

 

6. Fertilization of fingerling ponds

The fertilization of fingerling ponds is slightly different from that of adult fish. After clearing the pond, irrigate the pond with water, and then apply a certain amount of fertilizer, in order to cultivate the food that the small fry can eat. 

The timing of fertilization must be mastered, either sooner or later. If it is applied early, the individual plankton will grow too large and the fry cannot be swallowed; if applied late, the fry will not be able to eat, which will affect the growth.

 

 

I.  The basic elements of the HMM model (Hidden Markov Model)

1. Five basic elements of HMM

In HMM, there are 5 basic elements: {I, O, A, B, π}. Let us have an introduction to these 5 basic elements in combination with the sequence marking task:

 

(1) I: state sequence. Here, it refers to the label behind each word.

(2) O: Observation sequence. Here, it refers to each word itself.

(3) A: State transition probability matrix. Here, it refers to the probability that a certain annotation will transfer to the next annotation.

(4) B: Observation probability matrix, that is, emission probability matrix. Here, it refers to the probability of generating a certain word under a certain label.

(5) π: Initial probability matrix. Here, refers to the initialization probability of each annotation.

in:

I = ( i 1 , i 2 , i 3 . . . i N ) I = ({i_1,i_2,i_3...i_N})I=(i

1

​

 ,i

2

​

 ,i

3

​

 ...i

N

​

 ) state sequence

O = ( o 1 , o 2 , o 3 . . . o N ) O = ({o_1,o_2,o_3...o_N})O=(o

1

​

 ,o

2

​

 ,o

3

​

 ...o

N

​

 ) observation sequence

A = [ a i j ] N ∗ N A = [a_{ij}]_{N*N}A=[a

ij

​

 ]

N∗N

​

  State transition probability matrix

B = [ b j ( k ) ] N ∗ N B = [b_j(k)]_{N*N}B=[b

j

​

 (k)]

N∗N

​

  Observation probability matrix

π initial state probability vector

 

2. HMM model

 

Model: λ = (A,B,π)

A, B, π are the three elements of the Hidden Markov Model

These three elements are obtained through statistics, these three values ​​are the parameters of the model, and the process of obtaining these three values ​​is the process of model training, so the HMM algorithm is a relatively simple algorithm. 

The model has been known, and it can be considered that the fully connected path of each state has been known. Given an observation sequence, the optimal path among all paths is solved by the veterbi algorithm.

 

3. Two assumptions of the HMM model

(1) Homogeneous Markov assumption (also called first-order Markov assumption)

The state of the hidden Markov chain at any time t only depends on the state at the previous time, and has nothing to do with the state at other times and the observed state.

P ( i t ∣ i t − 1 , o t − 1 , . . . , i 1 ) = P ( i t ∣ i t − 1 ) P(i_t|i_{t-1},o_{t-1},..., i_1) = P(i_t|i_{t-1})P(i

t

​

 ∣i

t−1

​

 ,o

t−1

​

 ,...,i

1

​

 )=P(i

t

​

 ∣i

t−1

​

 )

(2) Observational Independence Hypothesis

The observed state at any time only depends on the state of the Markov chain at that time, and has nothing to do with the observed states at other times.

The above elements can be counted from the training corpus. Finally, based on these statistics, we apply the Viterbi algorithm to calculate the label sequence behind the word sequence.

 

2. There are three application scenarios for the Hidden Markov Model

We only use one of them for named entity recognition - to find the most likely label sequence behind the observation sequence.

Finally, let's talk about the three problems that HMM solves:

 

1. Evaluation (probability calculation problem)

Knowing the model parameters λ= (A, B, π), calculate the probability of a certain observation sequence, that is, find P(O|λ)

 

2. Learning (learning problems)

Given a sequence of observations O = ( o 1 , o 2 , . . . , o n ) O=(o_1,o_2,...,o_n)O=(o

1

​

 ,o

2

​

 ,...,o

n

​

 ), how to adjust the model parameters λ=(π, A, B) to maximize P(O|λ)? , this is the algorithm to find the model

 

3. Decoding (prediction problem or decoding problem) is the most commonly used

Given an observation sequence O and a model λ, find the most probable state sequence S(s1,s2,…st+1).

For example: through entity labeling and training, we can get the model λ, now given an observation sequence = I work in Phoenix Finance, to find the most likely named entities, and want to find the corresponding state sequence S = (I, in , Phoenix Finance, Work).

 

3. Find the model λ: solve the second problem

HMM is a generative model, so the joint probability is sought

 

Note: When we usually say, finding the model refers to finding the objective function. For example, in linear regression, our objective function is $h(λ)=λ_1X+λ_2$, and finding the objective function only requires the parameter λ, so usually We say that seeking model is seeking parameters.

1

P ( X , Y ) P(X,Y)P(X,Y)

 

Fourth, Viterbi algorithm (Viterbi): solve the third problem

The Viterbi algorithm mainly uses dynamic programming to solve the prediction problem of HMM: always model and observation sequence, find the most probable state sequence

 

Suppose the sequence of states is: x 1 , x 2 , x 3 . . . x N x_1,x_2,x_3 ... x_Nx

1

​

 ,x

2

​

 ,x

3

​

 ...x

N

​

 

The corresponding observation sequence is: y 1 , y 3 , y 3 . . . y N y_1,y_3,y_3 ... y_Ny

1

​

 ,y

3

​

 ,y

3

​

 ...y

N

​

 

Then our problem is transformed into: the known input sequence y 1 , y 3 , y 3 . . . y N y_1,y_3,y_3 ... y_Ny

1

​

 ,y

3

​

 ,y

3

​

 ...y

N

​

 , corresponding to the most probable Chinese characters x 1 , x 2 , x 3 . . . x N x_1,x_2,x_3 ... x_Nx

1

​

 ,x

2

​

 ,x

3

​

 ...x

N

​

 . What is the most likely sequence of Chinese characters?

formula:

x 1 , x 2 , x 3 . . . x N = A r g M a x P ( x 1 , x 2 , x 3 . . . x N ∣ y 1 , y 3 , y 3 . . . y N ) = A r g M a x ∏ i = 1 N P ( y i ∣ x i ) ∗ P ( x i ∣ x i − 1 ) x_1,x_2,x_3 ... x_N = ArgMaxP(x_1,x_2,x_3 ... x_N|y_1,y_3,y_3 . .. y_N) = ArgMax \prod_{i=1}^N P(y_i|x_i)*P(x_i|x_{i-1})x

1

​

 ,x

2

​

 ,x

3

​

 ...x

N

​

 =ArgMaxP(x

1

​

 ,x

2

​

 ,x

3

​

 ...x

N

​

 ∣y

1

​

 ,y

3

​

 ,y

3

​

 ...y

N

​

 )=ArgMax∏

i=1

N

​

 P(y

i

​

 ∣x

i

​

 )∗P(x

i

​

 ∣x

i−1

​

 )

 

where the formula A r g M a x ∏ i = 1 N P ( y i ∣ x i ) ∗ P ( x i ∣ x i − 1 ) ArgMax \prod_{i=1}^N P(y_i|x_i)*P(x_i|x_{i-1 })ArgMax∏

i=1

N

​

 P(y

i

​

 ∣x

i

​

 )∗P(x

i

​

 ∣x

i−1

​

 ) is mainly transformed by the Bayesian formula

 

We know that the Bayesian formula is: P ( A ∣ B ) = P ( B ∣ A ) ∗ P ( A ) P ( B ) P(A|B) = \frac {P(B|A)*P(A )}{P(B)}P(A∣B)=

P(B)

P(B∣A)∗P(A)

​

 

Then P ( x ∣ y ) = P ( y ∣ x ) ∗ P ( x ) P ( y ) P(x|y) = \frac {P(y|x)*P(x)}{P(y) }P(x∣y)=

P(y)

P(y∣x)∗P(x)

​

 , where P(y) is a known constant, where P(x) is actually P ( x t ∣ x t − 1 ) P(x_t|x_{t-1})P(x

t

​

 ∣x

t−1

​

 ), according to the Markov hypothesis, the current moment hypothesis is related to the previous moment.

 

For example, enter the observation sequence:

I love China

O O O B

O B O I

O O B I

B O I B

That is, the third line sought is the optimal path:

 

Fourth, the Viterbi algorithm (Viterbi)

Note: During the calculation of the viberbi algorithm, the shortest path between two points is calculated, not the shortest path between the two layers.

1

1. Nature

If the path p with the highest probability (or the shortest path) passes through a certain point, such as a on the way, then the sub-path Q from the starting point S to a on this path must be the shortest path between S and X22.

Otherwise, replacing Q with the shortest path R from S to a constitutes a shorter path than P, which is obviously contradictory. It is proved that the optimality principle is satisfied.

 

2. Algorithms

If you find the shortest path between S and E, what better way than to traverse all the paths?

 

In fact there must be a shortest path among all paths:

 

 

Let's start solving step by step from scratch:

(1) First, the starting point is S, and there are three possible paths from S to A column: S-A1, S-A2, S-A3, as shown in the following figure:

 

 

We cannot arbitrarily say which segment of S-A1, S-A2, and S-A3 must be part of the global shortest path. So far, any segment may be an alternative to the global shortest path.

(2). Then start the second layer

<1> We start with the first node of the second layer:

 

As shown above, there are only 3 paths through B1:

 

S-A1-B1

 

S-A2-B1

 

S-A3-B1

If the final second layer node passes through B1, the shortest path must be selected from these three paths, then the other two can be deleted.

<2> Then we start the second node of the second layer:

 

 

Similarly, as shown in the figure above, there are 3 paths through B2:

 

S-A1-B2

 

S-A2-B2

 

S-A3-B2

If the final second layer node passes through B2, the shortest path must be selected from these three paths, and the other two can be deleted.

 

<3> Then we start the third node of the second layer:

 

Similarly, as shown in the figure above, there are also 3 paths through B3:

 

S-A1-B3

 

S-A2-B3

 

S-A3-B3

If the final second layer node passes through B3, one of the shortest paths must be selected from these three paths, and the other two can be deleted.

<4> After all the stages of the second layer are traversed, there are three paths left.

 

We don't yet have enough information to tell which one must be a subpath of the global shortest path.

(3) Then we continue the algorithm at the third layer:

 

We don't yet have enough information to tell which one must be a subpath of the global shortest path.

(4) Then we continue the algorithm at the last layer:

 

Point E is already the end point. We can know which one is the shortest path by comparing the total length of the three paths.