Nutritional Regulation and Management of Heat Stress in Laying Hens in Summer

The most ideal environment temperature for chicken is 15~20 ℃. In this temperature range, the chicken grows fastest and the feed utilization rate is also the highest. Excessive ambient temperature will have a very adverse effect on chickens. When the temperature reaches above 32 ℃, it will cause a series of adverse reactions in physiology and spirit of chickens. In the midsummer season, due to the high temperature of the external environment and the heat production of the chicken itself, laying hens are prone to heat stress, resulting in a decrease in egg production, lighter egg weight, thinner eggshells, more deaths, and even a large number of deaths. Serious economic losses. Therefore, it is extremely important to do a good job of heatstroke prevention and cooling of laying hens in summer. While doing a good job of preventing heatstroke and cooling in the chicken coop, the diet formula of laying hens should be adjusted appropriately.

1. The harm of heat stress to laying hens

Heat stress is a physiological reaction of chickens to reduce the deep temperature in the body. The main characteristics are the decrease of feed intake, the decrease of production performance, the increase of gasping, the increase of drinking water and the drooping of wings. Heat stress of laying hens mostly occurs in chicken houses with poor ventilation and poor sanitary conditions when the temperature exceeds 32 ℃. The severity of heat stress increases with the increase of the temperature, when the temperature exceeds 39 ℃, it can quickly lead to heat stress in laying hens and cause a large number of deaths of chickens. Heat stress can cause some chickens to die, and some chickens are not dead, but they have adverse effects on their growth and production performance. The intake of chickens decreased, and the intake of nutrients such as energy, vitamins and minerals decreased, resulting in slower growth of chickens, reduced feed conversion rate, decreased disease resistance, and increased pecking. egg productionEggs(3871, -93.00, -2.35%)Weight reduction, egg laying rate and eggshell quality decreased, egg fertilization rate, hatching rate decreased.

2. Some management measures

In summer, the day hot humidity, intestinal disease, parasitic diseases. Turn on the light in the middle of the night and drink some water. The chicken breathes faster and evaporates water in the respiratory system to dissipate heat. Approximately 50-60% of heat dissipation. Drinking cold water and pulling out hot water are also the main ways to dissipate heat, accounting for 30-40%. The radiation heat dissipation of the skin accounts for only 10%. When the temperature at 10cm on the back of the chicken reaches more than 40 degrees, this radiation heat dissipation basically stops. As mentioned above, it is basically known that the heat dissipation of chickens needs water to ensure. Extreme experiments show that when the temperature and poison in the chicken house are at 46 degrees, as long as the newly pumped well water (about 15 degrees) can be supplied for the chickens to drink, there is basically no big problem for the chickens. In other words, large groups of chickens will not die of heat, and some sick chickens will die if they are weak. So, in general, with enough water, the flock will be fine. But on long summer nights, the chicken still has to open its mouth and gasp for air, consuming a lot of water without being replenished. The chicken will die of heat stroke. Chickens in dark conditions, difficult to find water. It is recommended to turn on the light for half an hour at the middle point before turning off the light and turning on the light the next day to let the chicken drink water. It's a simple, yet very effective management tool. If the light is automatically controlled, it can be set. If there is no automatic control, you have to turn on the light yourself. The half hour of turning on the light should be recorded in the comprehensive lighting time. This should be the case when the temperature is above 28 degrees. ---- Heat stress is the main cause of the drop in egg production. The temperature varies from place to place, but the parameter indicators remain unchanged.

Change the work and rest time, when it gets dark, don't turn on the lights, let the chickens rest, turn on the lights for half an hour in the middle of the night, then turn off the lights, turn on the lights in the early morning to feed, while the weather is cool, the chickens can eat more, the chickens are full, and the eggs are almost laid. Avoiding the heat, the chickens are still feeding and laying eggs. Inadequate feeding. Here, many old chicken breeders, considering that people are sleeping, are difficult to operate! Especially for chicken farms that hire breeders, we must persuade employees. Only in this way can we effectively increase the summer feed intake of chickens. Eggs are neither light nor small, fully enclosed modern chicken coop, creating a suitable environment. Not suitable for the above practice.

3. Improve the feeding environment

Chicken house, equipment inspection and maintenance. Before summer comes (before the middle of May in North China), a comprehensive inspection of chicken coops should be carried out:

(1) Check whether the ventilation equipment is perfect and effective, I .e. check whether the fan motor is running normally in the longitudinally ventilated chicken coop (it is appropriate for the fan to meet the maximum wind speed of 3 m/s in the coop), and check whether the belt is aging and loose; Timely repair, clean and lubricate shutters to ensure normal opening and closing, check whether the airtightness of the chicken coop is good, accurately calculate the area of the air inlet, and scientifically set and adjust the air inlet position; the roof of the chicken house with natural ventilation must be equipped with skylights, and the bottom of the walls on the north and south sides must be equipped with vents to ensure smooth air flow in the house. In addition, ceiling fans should be installed in the house.

(2) Check whether the water pump, filter paper and fan work normally in the chicken house where the water curtain is installed.

(3) Check whether the function of the drinking water system is perfect, whether there is leakage and blockage (check the nipples and filters of the drinking water dispenser one by one). According to the chicken's habit of throwing water to cool down, the conditional chicken farm can be equipped with water tanks and prepare two sets of drinking water systems, which can not only meet the chicken's habit, but also meet the chicken's drinking water needs to the greatest extent.

Do a good job in greening work to improve the microclimate of the chicken coop. It is best to plant tall trees around the chicken coop, which will not affect ventilation but also play a role of shading, avoid direct sunlight on chickens, and plant lawns can absorb a large amount of heat to avoid sunlight reflection into the chicken coop. Practice has proved that reasonable greening can effectively reduce the temperature of 3-5 ℃. Supply chickens with sufficient clean drinking water: the water temperature is as low as possible, and the water temperature can be reduced by taking the normal running water at the end of the water line and recycling it after treatment. Water spray is used to spray water on the top of the chicken house and the chicken body during the hottest period from 11:00 a.m. to 16:00 p.m. every day, I .e. when the temperature exceeds 33 ℃, the chicken body spray should spray cold water 30-40cm above the head of the chicken, and the smaller the droplet, the better. while spraying water, the air flow in the chicken house should be ensured, and it is best to adopt longitudinal ventilation. Note: In the case of high temperature and high humidity (muggy) inside and outside the house, the cooling effect of water spray is poor. At this time, the amount of water spray should be strictly controlled. The roof should be cooled down. The thermal insulation performance of the roof should be confirmed when building the chicken house. The roof should be painted white in high temperature weather in summer, which can reflect the heat radiation of the sun to the maximum extent and reduce the temperature of the chicken house. The chicken farm can reduce the temperature of the chicken house by 2-3 ℃ by spraying water on the roof. To adjust the density of chickens, it is necessary to adjust the chickens in the cages in time before summer, that is, to put as few chickens as possible in each chicken cage, so as to achieve uniform distribution of chickens in the chicken coop and reduce the heat stress caused by man-made excessive density. This work is especially important when the stock of chicken coop is not satisfied.

Improve environmental sanitation, clean up manure in a timely manner, and control the breeding of mosquitoes and flies. In summer, when the temperature is high, the respiration of chickens is accelerated, the evaporation of water is large, and when the drinking water of chickens is large, the metabolism of water of chickens is large, which will inevitably lead to an increase in humidity. Therefore, timely ventilation must be carried out to keep the air in the house fresh. It is advisable for people not to feel dazzling, tears, choking nose and excessive ammonia smell in the chicken house. Moldy feed is not allowed in the trough, in order to reduce the spread of the disease; adhere to the chicken disinfection, especially the sink, the ground and other places conducive to the growth of bacteria should be the focus, adhere to once a day. Strengthening epidemic prevention and disease eradication. In summer, we should focus on the prevention of colibacillosis, mycoplasma disease and other conditional diseases, monitor the antibody level of viral diseases on time, and vaccinate timely according to the monitoring results, so as to maintain the good health level of chickens, enhance their resistance, and reduce the impact of heat stress and disease on chickens. Nutritional control measures, different seasons, laying hens feed intake has a great change. In the high temperature environment in summer, chickens need to have enough nutrition to maintain normal physiology and production. When the ambient temperature exceeds 27 ℃, the feed intake of laying hens will decrease with the increase of temperature. In order to solve this contradiction, it is necessary to adjust the feed nutrition according to the feed intake of chickens and increase the nutrient concentration to make up for the deficiency of energy, crude protein, minerals and multivitamin intake caused by heat stress. Commonly used feed additives such as vitamin C, sodium bicarbonate, and compound enzyme preparations, micro ecology, oligosaccharides and so on.

4, adjust the level of nutrition in feed

Although increasing the nutrient concentration of compound feed will increase the cost, it is an effective means to reduce heat stress. In addition to increasing protein and metabolizable energy levels, other levels such as calcium, phosphorus, vitamins, and amino acids should be increased accordingly. The increase depends on the decrease in feed intake, which is generally increased by about 5% to 10%. It is assumed that in the compound feed used before summer, energy is 11.5MJ/kg, crude protein is 16%, methionine is 0.34, and Ca is 3.5. Under the normal condition of 120g feed per layer, energy 1.38MJ/kg, crude protein 19.2g, methionine 0.4g,Ca4.2g can be obtained. If each chicken eats 105g of feed in summer, only 16.8g of crude protein, 0.36g of methionine, Ca3.67 g and 1.21MJ/kg of energy can be obtained. Obviously lower than the original nutritional level. Therefore, the nutritional level in the feed should be adjusted. For example, the adjusted value of crude protein is:(19.2/105)× 100%= 18.2, methionine is 0.39, and Ca is 4.00.

Energy concentration adjustment. Heat stress causes a decrease in feed intake and makes the energy intake insufficient. A large number of studies have shown that increasing the content of energy substances in feed can improve the production of heat-stressed poultry. At present, an ideal way to improve the energy in the feed is to replace carbohydrates with fat. Because carbohydrates generate more heat in the process of digestion and metabolism, it is easy to increase the burden of heat dissipation, so its proportion should be appropriately reduced; while fat has low heat production, which increases the retention of energy in the body. At the same time, fat can change the palatability of feed and prolong the residence time of feed in the digestive tract, so as to improve the feed intake and digestion and absorption of laying hens. During heat stress, the amount of fat in the feed should be 2% ~ 3%, but the fat is easy to oxidize and deteriorate, so antioxidants should be added at the same time.

Protein, amino acid adjustment. In the heat stress, the traditional way is often to increase the content of crude protein in the feed to make up for the lack of protein intake of laying hens, but the heat produced by protein metabolism is much higher than that of carbohydrates and fat, which increases the accumulation of metabolic heat production in the body. Therefore, the protein level should be at the lower limit as far as possible when adjusting the feed formula. In order to improve the utilization rate of protein and ensure its nutritional needs, it is necessary to add essential amino acids according to the surplus and deficiency of dietary amino acids. Methionine can be added by 10% ~ 15%, and attention should be paid to maintaining the balance of amino acids. At present, many nutritionists advocate replacing protein with amino acids. Amino acids can be directly absorbed into the body without the decomposition of protease in the intestine, which can reduce the burden of heat stress damaged intestine and quickly supplement the body's needs. However, the addition of amino acids will increase the cost of feed, and the study of amino acid addition in heat stress is still in its infancy, and there is a lack of mature adding scheme. Studies have found that methionine and lysine can relieve heat stress and are two basic amino acids that must be added. Their addition amount is generally 360mg of methionine and 720mg of lysine per day.

Adjustment of minerals and vitamins. Heat stress can affect the quality of eggshell (eggshell thinning, brittle), the reason in addition to the uterine carbonic acid enzyme and vitamin D activity decreased, the lowering of blood calcium is also an important reason. In order to ensure that chickens consume at least 3.5gCa per day, the calcium content in the feed can be increased to 4%, but the ratio of calcium and phosphorus should be kept at 4: 1, and more than 50% of the total calcium is granular calcium source. Where conditions permit, reliable quality shell powder can be used instead of stone powder, or stone powder and shell powder can be mixed, so that the ratio of shell powder to stone powder is about 1:3 to 1:4. In addition to Ca, the shell powder still contains a small amount of amino acid polysaccharide, which can promote feeding and beneficial digestion. The smell of meat and bone meal, blood and feather powder should be used with caution or not. For raw materials that do not contain protein and energy, such as zeolite powder and maifanite powder, use less and add no more than 3%.

In addition, the excretion of minerals in feces and urine increases under conditions of heat stress. Heat stress or affect the absorption of Mn, S, Se, Co, Mg plasma, or increase the demand for them, should be in accordance with the reduction of dietary intake to increase the content of the feed. There are many reports about increasing the amount of vitamins. Some studies have reported that heat stress does not affect the absolute intake of vitamin A, while vitamin E, vitamin C and B vitamins have great changes, and the amount of addition can be adjusted to 2~3 times of the normal amount. Vitamin C is the most important vitamin in heat stress, which can inhibit the rise of body temperature in poultry, and appropriately increase the content of vitamin C can promote antibody synthesis and T cell proliferation, which can improve the feed intake and egg production rate of laying hens, and also promote the recovery of damaged tissue cells. High temperature can inhibit the synthesis of vitamin C in the body of laying hens, which requires additional compensation. Can add 150~200 mg/kg in drinking water. Vitamins are physiologically resistant to stress and have a synergistic effect with riboflavin in reducing heat stress, so they should be added appropriately in the diet.

Adjust the electrolyte balance. Supplementing electrolytes, such as sodium, potassium and chlorine, is beneficial to maintain electrolyte balance or increase alkali storage, thus effectively reducing the heat stress response. Heat stress causes the release of aldosterone in laying hens to increase, aldosterone has the function of sodium and potassium excretion, so the blood potassium is reduced, and the concentration of potassium ion can be increased by adding potassium chloride. Generally, the concentration of potassium chloride is 0.15-0.30%. Shi Jing-hua (2004) added 0.5 baking soda to the feed, which plays an important role in maintaining carbon dioxide or pH value in the blood of heat-stressed chickens, and can reduce defective eggs by 1% ~ 2%, increase egg laying rate by 2% ~ 3%, increase eggshell thickness, and improve the utilization rate of protein in the diet.

It is recommended to use VC. High temperature and humidity in summer, coupled with repeated medication, can easily lead to changes in the pH value of the water, affecting the effect of VC. It is recommended to add the package VC, the use efficiency is greatly improved. A ton of material to add about 200 grams. Add mold removal products to reduce the occurrence of intestinal disease, remove mycotoxins and intestinal endotoxins, especially Aspergillus flavus, bacterial viruses, etc., reduce the occurrence of diarrhea, reduce the moisture content of feces, and supplement minerals.

It is suggested to add compound enzyme preparation in feed. In order to improve the absorption and conversion rate of feed nutrients. Eliminate anti-nutritional factors to improve feed utilization, supplement the activity of endogenous enzymes, activate the digestion and decomposition function of endogenous enzymes, and improve the activity of endogenous enzymes. Improve the intestinal microflora, improve immune function, improve the utilization of plant phosphorus, affect the neuroendocrine system and metabolic hormone levels. It is suggested to use micro-ecological products: to promote the growth and reproduction of normal intestinal microflora of laying hens, to inhibit the growth and reproduction of pathogenic bacteria, to regulate intestinal function, to rapidly build intestinal micro-ecological balance, to reduce diarrhea caused by intractable enteritis, to reduce ammonia odor emission, to reduce the occurrence of eggs, to increase the weight of eliminated chickens, and to improve the feed absorption and conversion rate.

The use of oligosaccharins is recommended. Adjust the intestinal bacterial ecology: as a nutrient for the growth and reproduction of bifidobacteria, inhibit the growth of harmful bacteria, increase the absorption of nutrients, and reduce the output of harmful toxins in the intestinal tract, delay aging, and maintain immune function. Like lactic acid bacteria and dietary fiber, it is a good helper for the whole intestine, the body is environmentally friendly and promotes normal defecation.

Summary

The heat stress caused by high temperature environment in summer has a significant effect on laying hens, such as egg laying rate, egg weight and egg quality. The high temperature and high humidity environment in summer causes the high content of harmful gases in the chicken house, which is conducive to the breeding or survival of pathogenic microorganisms. Long-term heat stress causes the decline of body immunity and induces diseases, which seriously affects the production efficiency of laying hens. A series of nutrition and management control measures can effectively alleviate the heat stress of laying hens in summer. At the same time, it is necessary to control the environmental conditions of breeding in summer and strengthen the management of breeding.