title: Biological and economic optimum level of calcium in White Leghorn laying hens.
abstract: Calcium is important in eggshell formation; inadequate levels in the diet of laying hens may affect shell quality and egg production. An experiment with 250 Leghorn Hy-Line W-98 hens was conducted to evaluate 5 dietary Ca levels (2.96, 3.22, 3.83, 4.31, and 4.82%) in 3 laying periods. The evaluated variables were egg production (EP), egg mass (EM), average daily feed intake (ADFI), feed conversion (FC), and specific gravity (SG). The biological optimum level (BOL) of Ca for maximum egg production and specific gravity, and the economic optimum level (EOL) to maximize profits were calculated. There was no interaction between Ca level and laying period. The results show that the Ca level of the diet (P < 0.05) affected the intake of this nutrient (3.34, 3.68, 4.26, 4.89, and 5.39 g bird/day), ADFI (113, 114, 111, 113, and 111 g bird/day), and SG (1.080, 1.081, 1.082, 1.083, and 1.083). As the hens aged, EP and SG diminished (P < 0.05). BOL for maximum EP and SG were 4.34 and 4.62%, and EOL was 4.38%.
authors.affiliation: Colegio de Posgraduados, Ganaderia, Montecillo, Texcoco, Mexico.
authors.forename: C
authors.initials: C
authors.lastname: Castillo
authors.forename: M
authors.initials: M
authors.lastname: Cuca
authors.forename: A
authors.initials: A
authors.lastname: Pro
authors.forename: M
authors.initials: M
authors.lastname: González
authors.forename: E
authors.initials: E
authors.lastname: Morales
mesh_terms: D000375:Aging; D000383:Agriculture / Q000191:economics; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002645:Chickens / Q000502:physiology*; D003365:Costs and Cost Analysis; D004435:Eating; D004531:Eggs; D005260:Female; D010058:Oviposition; D012044:Regression Analysis
chemical_list: D002136:Calcium, Dietary