How to supplement calcium for laying hens? These key points of calcium supplementation need to be mastered

To achieve high production and reduce the egg breakage rate in hens, the calcium supply should be checked during the laying period. Feed is the main factor determining eggshell quality and eggshell strength. Trials have shown that calcium deposition in the hen's bones increases during the half month before the start of laying. Therefore, from 4 months of age until a 5% laying rate is reached, hens should be fed a compound feed with a higher calcium content. It is now generally agreed that a calcium level of 3.2%-3.5% in the diet of laying hens is the optimal level, while under high temperatures or a high laying rate (75%-80%), the calcium level can be raised to 3.6%-3.8%; adding it to 4% for a short period can thicken the eggshell, but further increases are unfavorable to laying and cannot improve eggshell quality. Insufficient calcium in the feed promotes feed intake, resulting in excessive feed consumption, increased body weight of hens, and more fat deposition in the liver; when the calcium content in the feed is supersaturated, it reduces the appetite of the chickens. When raised on the floor, several feed troughs specially filled with coarse sand grains and crushed shells can be placed in the chicken house, allowing the chickens to eat freely.

Under normal circumstances, the hen's bones have enough calcium reserves to form several eggs; when sufficient calcium cannot be obtained from the feed, the eggshell will become poor, soft eggs or shell-less eggs will be laid, and even paralysis may occur. The longer the calcium in the bones is mobilized to form the eggshell, the worse the eggshell strength becomes.

Hens feel calcium-deficient during eggshell formation at night. Calcium ingested by the chicken during the first half of the light period passes through the digestive tract, is absorbed in the small intestine into the blood, and is deposited in the bones, then mobilized when necessary to form the eggshell. Only the calcium ingested in the latter half of the day is used directly for eggshell formation. Therefore, it is best to supplement calcium for hens from 12:00 to 20:00; when hens can eat calcium freely, they can regulate the amount themselves. For example, during eggshell formation, calcium intake is normally 92%, while during non-formation periods calcium intake is only 68%. Hens with lower body weight and low feed intake should be fed a little more calcium.

Shells and stone powder are commonly used as calcium sources; when the ratio of shells to stone powder in the diet is 2:1, eggshell strength is the best. Chickens absorb animal-derived calcium sources best, plant-derived calcium sources are absorbed relatively poorly, and heat-sterilized eggshells are the best calcium source.

In trials with crossbred chickens, when the broken-shell rate of 61-week-old chickens reached 3.5%, adding granular shell powder at 2% of the total feed amount in the afternoon significantly reduced broken eggs and made the eggshells smooth; by 72 weeks of age the average broken-egg rate was only 1.59%, achieving good results.

The proportions of calcium, phosphorus and vitamin D3 affect eggshell strength. Calcium 3%-3.5% and phosphorus 0.45% are optimal, and vitamin D3 at 10-12 times the standard for vitamin A is best. Calcium determines the brittleness of the eggshell, and phosphorus determines the elasticity of the eggshell. A deficiency of vitamin D3 disrupts the calcium balance in the body, resulting in defective eggshells. Generally, the eggshell quality of eggs laid from 14:00 to 17:00 in the afternoon is very good, mainly related to the prolonged interval between laying and the chicken obtaining sufficient calcium supplementation.