2.2. Experimental Diets

During the rearing period, all animals were fed a common commercial breeding feed based on corn, wheat and barley (weeks 16 and 17 of age) and laying feed based on wheat and corn (weeks 18 and 21 of age) until they reached a daily production of 1.07 eggs per hen. At 22 weeks of age, hens were assigned to one of the four dietary treatments: PC, positive control with no added phytase: Ca at 4.07% and P at 0.61%; NC, negative control with no added phytase: Ca at 2.97% and P at 0.37%; and two other diets in which NC diet was supplemented with ePhyt 1000^® 3-phytase (Globalfeed) at 500 (P500) and 1000 (P1000) FTU/kg feed, respectively (see enzyme details at Cambra-López et al. [13]). All the diets were formulated following the recommendations given for laying hens by FEDNA [14], except for Ca and P in the negative control, being isonutritive for the rest of the nutrients (Table 1). Feed and water were provided ad libitum throughout the experiment and diets were fed in mash form.

Ingredients and chemical composition of the experimental diets (g/kg).

¹ Provides per kilogram of feed: calcium: 200.61 g, E5 manganese (manganese oxide): 13,000 mg, E6 zinc (zinc oxide): 7400 mg, E4 copper (copper sulphate pentahydrate): 800 mg, E2 iodine (potassium iodide): 380 mg, E8 selenium (sodium selenite): 20 mg, E1 iron (carbonate ferrous): 3600 mg, E672 vitamin A: 1,500,000 UI, E671 vitamin D3: 300,000 UI, vitamin K: 300 mg, vitamin B2: 600 mg, vitamin B12: 2000 mg, niacin: 3000 mg, calcium pantothenate: 1400 mg, pantothenic acid: 1288 mg, betaine: 10,830 mg, choline chloride: 25,500 mg, E320 butylhydroxyanisol (BHA): 4 mg, E321 butylhidroxytoluene (BHT): 44 mg, E324 ethoxyquin: 6.40 mg, dry matter: 956.54 g. ^2. Calculated as the difference between total phosphorus and phytate phosphorus.