Measures to reduce foul odors in livestock houses -- August 2008

　　Foul odors are a mixture of foul-smelling gases released from various foul-smelling substances. These include carbon dioxide produced during livestock respiration; gases produced by livestock excrement and organic matter during production under anaerobic conditions, where carbohydrates mainly produce foul-smelling gases such as ammonia and hydrogen sulfide under anaerobic conditions. Foul-smelling gases have an irritating and toxic effect on livestock, causing respiratory diseases; high concentrations of foul-smelling gases can cause acute poisoning, central nervous system paralysis, and other diseases, as well as reducing immune function, affecting normal body metabolism, and even causing livestock death in severe cases. Therefore, the author suggests taking the following measures to reduce the concentration of foul odors in livestock houses and ensure the healthy growth of livestock.

　　Rational design of livestock houses Starting with the design of livestock houses, design manure removal devices and drainage systems inside the livestock houses. The ground and manure gutters should have a certain slope, and the bottom of the manure gutters should be circular, which is conducive to the discharge of manure. The cover plates of the manure gutters in pig houses should be designed as semi-leaky instead of fully leaky to reduce the emission of foul odors from the manure gutters.

　　Scientific management Ventilation is the most effective way to reduce foul odors in livestock houses. In the cold winter, in order to keep warm, livestock houses often reduce ventilation and seal doors and windows, leading to an increase in the concentration of foul odors. To deal with the contradiction between ventilation and heat preservation, chimneys should be installed on the roof to extract the air from the house, and necessary ventilation should be carried out at noon every day when the outside temperature is higher, thereby reducing the concentration of foul odors. Manure and sewage should be removed in time, especially in summer, when high temperatures are conducive to the survival of microorganisms and are more likely to produce odors. Change bedding frequently; bedding can absorb a certain amount of foul odor. Generally, wheat straw, rice straw, or dry grass all have good absorption capacity for foul odors. In addition, keep the livestock house dry; regularly check waterers or water troughs to avoid leakage and overflow, increasing air humidity. Because many foul-smelling gases increase the concentration of foul odors in livestock houses after dissolving in water.

　　Correct feed selection and reasonable feeding The higher the feed digestibility, the less residual protein in the excrement, and the less foul odor in the livestock house. High-quality feed, especially high-quality protein feed, has high digestibility, which can reduce the residual protein in the excrement and reduce the production of foul odors. Data show that the digestibility of lysine in extracted cottonseed cake by pigs is 65%, and the digestibility of lysine in extracted soybean cake is 87%. There are many methods for processing and preparing feed, including physical, chemical, and microbial methods, and various methods have an impact on the digestibility of feed nutrients. Studies have shown that the digestibility of crude protein in whole barley by pigs is only 60.3%, while the digestibility of crude protein in finely ground barley is 84.4%.

　　Scientific diet formulation The substances that form foul odors are mainly produced by the decomposition of protein in livestock excrement. Therefore, using the ideal protein model and available amino acids to design feed formulas and reasonably formulating the protein content in the diet to reduce the protein content in the excrement is feasible. Ideal protein is a protein with an ideal ratio of amino acids based on the amino acid needs of animal growth, pregnancy, lactation, and egg production. Data show that for every 1% decrease in the protein content of pig diets, the amount of nitrogen excreted decreases by 8.4%, and adding lysine and methionine to pig diets can reduce the crude protein in the feed by 1% to 2%, which does not affect production performance but can reduce nitrogen excretion in feces by 25%. When formulated according to the ideal protein model, the crude protein level can be reduced by 2% to 3%, and nitrogen excretion can be reduced by 20% to 25%.