1. Heritability: Heritability is relatively high (35-50%), and gilts are not selected for those mothers who have had a late puberty; 2. Ammonia levels: Studies have shown that high concentrations of ammonia (20-35ppm) will postpone estrus, so should reduce the concentration of ammonia in the homes; 3. Temperature: 29 °C or more will affect the performance of estrus and reduce ovulation rate; 4. Turning and synchronizing: Turning or merging gilts can help estrus; 5. Sunshine time: The length of sunshine hours has a positive or negative effect on heat; Contact with boars: The most effective method of stimulating estrus in sows is to make nose-nose contact with a boar that is sexually active. Amino Acids are biologically important organic compounds composed of amine and carboxylic acid functional groups, along with a side-chain specific to each amino acid. With biological significance, amino acids are important in nutrition and are commonly used in Nutritional Supplements, fertilizers, and food technology. Industrial uses include the production of drugs, biodegradable plastics, and chiral catalysts. Amino Acids Natural Amino Acids,Amino Acids Powder,Amino Acids Particles,Amino Acids Tablets SINOCHEM PHARMACEUTICAL CO., LTD , http://www.sinochemnutrition.com