Effect of dietary calcium intake on its retention by caged broiler breeder hens

Calcium is an important mineral in bone development and egg shell formation of broiler breeder hens. A study was undertaken to further examine the effect of dietary calcium intake on calcium retention of broiler breeder hens and to investigate the relationship between calcium retention and egg characteristics. Ninety broiler breeder hens were obtained from a previous study and allocated to three dietary treatments, 1.5, 2.5 and 3.5% calcium level. Feeds were isocaloric and isonitrogenous but differed only in calcium and phosphorus contents. Birds were fed and caged individually with metal trays placed below cages for excreta collection. Excreta samples (30 birds per treatment) were collected for calcium and phosphorus determinations during a 7-day period at 3-weekly intervals, i.e., 27, 33, 36 and 42 weeks of age. Other parameters measured included calcium intake of hens, hen day production, egg mass, egg weight, shell weight, shell percentage, shell thickness, egg surface area, shell weight per unit surface area, total calcium retention, shell calcium excretion, shell calcium as a percentage of calcium intake and faecal calcium as percentage of calcium intake. These results showed that dietary calcium level had significant (P<.0001) effect on calcium intake and retention. Dietary calcium level had significant effect on all parameters except egg weight and shell calcium excretion as a percentage of calcium intake. Calcium retention of hens was correlated with age, calcium intake and eggshell characteristics. Age was significantly correlated with all traits except daily calcium intake, calcium retention and shell percentage. The net effect of calcium intake and total calcium excretion was that the 2.5% calcium level (3.8 g calcium /hen/day) exhibit a significant (P<.05) higher calcium retention compared to 1.5% calcium level. This suggests that the calcium level of 2.5% and intake of 3.8 g/hen/day is adequate to support egg production, good shell quality and sufficient bone formation in broiler breeder hens.