2.3. Laying Performance and Egg Quality

Body weight (BW) was recorded per cage on arrival (16 weeks of age), at the start of the administration of experimental feeds (22 weeks of age) and at weeks 25 and 31 of age of the experimental period. Feed consumption was recorded at each weighing control to calculate average daily feed intake (DFI). Health status of the animals was checked daily and necropsies were performed from all dead animals. The number of eggs laid and their weight were daily monitored. Average laying index (egg/hen and day), egg weight (g) and egg mass (laying index x egg weight; g/day) were determined weekly. Average daily feed intake (DFI; g/day) and feed conversion ratio (FCR; g feed/g egg) were also calculated globally. Furthermore, the number of eggs with shell quality problems (soft shelled eggs, shell-less eggs) was registered daily. On days 52, 53 and 59 of the experimental period, all the eggs laid in the last 24 h (approximately 150 eggs/treatment) were collected for egg quality measurements. The sampled eggs were individually weighed and broken on a flat surface. Subsequently, the height of the inner thick albumen (Haugh units) was measured with an electronic albumen height gauge. The Haugh units were calculated 100 × log₁₀ (H + 7.57 − 1.7W^0.37), where H is the height of the albumen and W is the weight of the egg, according to Haugh [15]. The shells were broken in three parts and shell thickness was a mean value of measurements at these three locations taken by using a dial pipe gauge (3001 digital Baxlo, Instrumentos de Medida y Precisión S.L., Barcelona, Spain). Additionally, yolk color was determined by the Roche yolk color fan (Hoffmann-La Roche Ltd., Basel, Switzerland; color scale from 15, dark orange, to 1, light pale).