Calcium, magnesium and phosphorus retention in chickens with different growth rate fattened to higher age

Utilisation of calcium, magnesium and phosphorus was examined in broilers a nd laying type cockerels from Day 23 to Day 100. In meat type chickens coef ficients of apparent Ca and P retention decreased highly significantly (P < 0.01) during the whole experiment while that of Mg decreased till the age of 93 days. In egg type chickens the dependence of Ca retention on age was expressed by the parabola of the 2nd degree with a minimum on Day 70. Utili sation of Mg and P decreased linearly and highly significantly. Content of Ca and Mg in body gains of broilers increased (P < 0.01) with age. Concentr ation of P culminated on Day 45. In laying type chickens the level of Mg in creased highly significantly and that of P decreased (P < 0.01). The Ca con tent in body gains decreased tin Day 43; thereafter, an increase was record ed. Differences in average coefficients of Ca and P retention and retention per unit of body gain in slow growing hybrid and broiler chickens were not significant (P > 0.05) while retention of Mg was highly significantly high er in laying type chickens.