Influence of time of calcium intake on bone and dietary calcium utilization

The effect of feeding time on shell quality and oviposition time in broiler breeders

Three experiments were performed to determine the effect of feeding time on shell quality and oviposition time in broiler breeders. Mean eggshell thickness was increased significantly by 3.5 microm (approximately 1%) per h delay in feeding time when hens were housed in individual cages. However, eggshell thickness was not significantly affected by feeding time when birds were housed on litter floors. Mean oviposition time was delayed relative to lights on by 5 min per h delay in feeding time. Egg weight was not significantly affected by feeding time, suggesting that differences in shell thickness and oviposition times were not due to increased oviducal transit times. Producers who wish to implement delayed feeding may have to turn lights on earlier than usual to compensate for delayed oviposition times.

Biological and Economic Optimum Level of Calcium in White Leghorn Laying Hens

Calcium is important in eggshell formation; inadequate levels in the diet of laying hens may affect shell quality and egg production. An experiment with 250 Leghorn Hy-Line W-98 hens was conducted to evaluate 5 dietary Ca levels (2.96, 3.22, 3.83, 4.31, and 4.82%) in 3 laying periods. The evaluated variables were egg production (EP), egg mass (EM), average daily feed intake (ADFI), feed conversion (FC), and specific gravity (SG). The biological optimum level (BOL) of Ca for maximum egg production and specific gravity, and the economic optimum level (EOL) to maximize profits were calculated. There was no interaction between Ca level and laying period. The results show that the Ca level of the diet (P < 0.05) affected the intake of this nutrient (3.34, 3.68, 4.26, 4.89, and 5.39 g bird/day), ADFI (113, 114, 111, 113, and 111 g bird/day), and SG (1.080, 1.081, 1.082, 1.083, and 1.083). As the hens aged, EP and SG diminished (P < 0.05). BOL for maximum EP and SG were 4.34 and 4.62%, and EOL was 4.38%.

Influence of dietary calcium level and particle size of calcium source on in vivo calcium solubilization by commercial Leghorns

Six experiments were conducted in which hens with oviposition times between 0730 h and 0930 h were intubated with limestone at different levels or particle sizes at time of oviposition. Feed was withdrawn from all hens approximately 15.5 to 17.5 h prior to intubation, and the same feed but without supplemental Ca was immediately returned after limestone intubation. Excrement of each hen was collected from intubation (oviposition) until the next oviposition (24 to 27 h duration) in all experiments except Experiment 4. In Experiment 4, excreta were collected for 25 h after first oviposition. Five hens prior to intubation of Ca source and all hens at termination of an experiment were killed, and the contents of the digestive system were collected. Excreta and digestive system contents were analyzed for total Ca and quantity of insolubilized limestone. Approximately 50% of the Ca found in the excreta from hens with 3.75 g Ca intake was recovered in the same form as ingested (limestone). Percentage of Ca solubilized in the digestive system decreased (P less than .05) as Ca intake increased. Although in vitro solubility of larger limestone particles (2 to 5 mm) was much less than smaller particles (.5 to .8 mm), percentage of Ca solubilized in the digestive system during the 25 h following intubation increased (P less than .05) as particle size increased, suggesting a greater retention time of the larger limestone particles in the gizzard.