Effect of separate calcium feeding and a limited feeding program on the metabolizable energy of the diet and on nitrogen, calcium and phosphorus retention in laying hens.

We first carried out an 8-day balance study with 8 laying hens fed ad libitum a low Ca diet (0.30 p. 100 Ca) and a maximum of 14 g/day/hen of seashells in order to study whether totally separate Ca feeding (SCF) would increase the corrected metabolizable energy (cME) value of the diet and the retention of nitrogen, calcium and phosphorus. These experimental birds (group 2) were compared to 7 control birds (group 1) fed ad libitum a normal Ca diet (3.7 p. 100 Ca). During egg-forming (L0) days, the SCF treatment induced significant increases (table 2) in feed intake (121 vs 110 g/d) and in corrected metabolized energy (377 vs 342 Kcal/d). Neither the cME value nor N, P or Ca retention was significantly modified. During the non-egg-forming (L) days, the SCF treatment (table 4) considerably decreased Ca source intake (3.8 vs 11.8 g/d), resulting in a negative Ca balance and an increase in the cME value of the ingested feed mixture (2988 vs 2685 Kcal/kgl. However, the difference was not significant (3087 vs 2984) when Ca intake was corrected. When all the types of days were pooled (L + 0 + LO), the recorded effects of SCF were about the