What should be paid attention to when using limestone as calcium source feed

① Different calcium sources should be reasonably matched: when limestone particles are used as calcium sources, the egg laying rate is better in the diet containing 3.75% calcium, but the egg weight will be reduced by .6 g for every 1% calcium in the diet. ② The calcium content should be stable: only when the phosphorus content is sufficient, the calcium content in the diet is as high as 6.5%, which has no adverse effect on the egg production, but it is easy to cause proctoptosis. When the available phosphorus content is only .2%, 6.5% calcium will reduce the production performance and increase the mortality. Feeding a low-calcium diet (1.5%-1.8%) will reduce the quality of eggshells within 24-48 hours. ③ Grasp the particle size: In the United States, the particle size of various feed-grade limestone products ranges from 5 to 5,6 microns. The storage time of limestone in glandular and muscular stomachs of laying hens mainly depends on the size of limestone particles. The big time is long, and the small time is short. The standard of limestone particles for laying hens is 335 microns, while the particles for laying hens are (14-2 microns), both of which have higher biological value than those for powdery hens. It has been found that compared with laying hens, the granular limestone of young hens is digested in hens at a faster speed. ④ Limestone with high magnesium content can't be used: the magnesium content of limestone varies from place to place. The biological effectiveness of limestone is quite good, and the biological effectiveness of limestone powder (gravel) containing 38%-4% calcium and -.3% magnesium can reach 91%-1%. Limestone containing 33%-37% calcium and .4%-.5% magnesium has a biological effectiveness of 7%-9%. The most important factor affecting its utilization is magnesium, and the availability of calcium decreases by 5% with the increase of magnesium content by 1%. The biological effectiveness of calcium in dolomite limestone containing 1%-12% magnesium is only 51%-73%. However, the magnesium content in limestone should not exceed .5%, and it can still be used when it reaches 1%, and it should never be used when it exceeds 1.5%. Editor: Chicken is auspicious.