Low Blood Calcium (Hypocalcemia)

Hens that are actively laying eggs require adequate calcium in their diet to produce strong, normal eggshells. When calcium intake is insufficient, eggshell quality declines, resulting in thin or fragile shells. These weak-shelled eggs are more likely to break during the laying process, increasing the risk of secondary reproductive conditions such as salpingitis, internal laying, and egg peritonitis.

Approximately 2.2 grams of calcium are needed to produce a single eggshell. Shell formation primarily occurs overnight while the hen is resting. The calcium used comes from two sources: dietary intake (especially what is consumed in the evening) and calcium reserves stored in the medullary bone. These bone reserves are replenished by calcium consumed throughout the day, which is why hens often eat slightly more feed on days they lay eggs.

For calcium to be utilized effectively, it must be absorbed through the small intestine. Several factors can interfere with this process:

• Calcium-to-phosphorus ratio: An imbalance—either too much or too little phosphorus relative to calcium—can impair absorption. Maintaining the proper ratio is essential.
• Heat stress: Panting reduces blood carbon dioxide (CO₂) levels, which can lower circulating ionized calcium.
• Intestinal parasites: Damage caused by organisms such as Eimeria (coccidia) and large roundworms can impair nutrient absorption, including calcium.
• Phytate-rich foods: Phytic acid, found in grains, legumes, nuts, seeds, and soybeans, can bind calcium in the digestive tract and reduce its availability.
• Gastrointestinal health: Disruptions to the gut microbiome or intestinal lining can decrease calcium absorption.
• Calcium particle size: Fine calcium particles are absorbed quickly, while larger particles (such as coarse limestone) remain in the gizzard longer, providing a slow release of calcium overnight.
• Oxalate-rich foods or plants: Foods high in oxalates (e.g., spinach, chard) bind calcium in the intestine, forming compounds that cannot be absorbed.