Influence of dietary ingredients on calcium utilization in the laying hen

Experiments were conducted to evaluate the benefit of calcium supplementation with or without other dietary ingredients on egg shell quality. A total of 250 Hyline hens, 44 weeks of age, were randomly divided among five treatments (Experiment 1). The dietary treatments were as follows: Treatment 1, controls (C) were fed a 3.5% calcium diet ad libitum; Treatment 2, hens were fed a .08% calcium diet (LC); Treatment 3, hens were intubated with limestone following 24-hr consumption of .08% calcium diet (LCI); Treatment 4, feed removed for 24 hr (NF); Treatment 5, feed removed for 24 hr and hens then intubated with limestone (NFI). All diets were restored to the control calcium level after 48 hr. Experiment 2 was identical to Experiment 1 except Dekalb XL hens, 50 weeks of age, were used. Eggs were collected daily for 5 days for egg specific gravity, egg weight, and shell weight determinations. Forty hens were sacrificed in Experiment 2 at 48 hr into the experiment to measure calcium distribution in the gastrointestinal (GI) tract and feces. Results indicated that hens fed the LCI treatment produced eggs with significantly higher specific gravity and heavier shells than hens given limestone with an empty GI tract. The calcium analysis of the GI tract revealed that much of the calcium supplement did not move beyond the gizzard in hens fed the NFI treatment. It was concluded that hens not only needed other nutrients for maximum utilization of dietary and skeletal calcium, but other nutrients or dry matter may also be needed to facilitate the passage of calcium from the gizzard.