Abstract
An experiment was conducted to determine the digestible calcium (Ca) and digestible phosphorous (P) requirements of 10-day-old broiler chickens. Fifteen corn-soybean meal-based diets containing 3.3, 3.9, 4.4, 5.0, and 5.5 g/kg standardized ileal digestible (SID) Ca and 4.0, 5.0, and 6.0 g/kg SID P was fed to broilers from d 1 to 10. Each experimental diet was randomly allocated to 6 replicate cages (12 birds per cage). Body weight and feed intake were recorded at the start and end of the experiment and the feed conversion ratio was calculated. On d 10, birds were euthanized to collect ileal digesta, toes and tibia for the determination of digestible Ca and P, toe ash concentration and the concentrations of ash, Ca, and P in tibia. Titanium dioxide (5 g/kg) was included in all diets as an indigestible indicator for apparent ileal digestibility measurements. Total excreta were collected from d 1 to 10 for the measurement of total tract retention of Ca and P. Fixed effects of the experiment were dietary concentrations of SID Ca and SID P and their interaction. If the interaction or main effects were significant (P < 0.05), the parameter estimates for second-order response surface model were determined using General Linear Model procedure of SAS software. The growth performance, bone mineralization and mineral utilization of broiler starters were found to be optimized at 5 g/kg SID P concentration. Required SID Ca for maximum weight gain and bone mineralization was determined to be 3.32 and 4.36 to 4.78 g/kg, respectively, at 5 g/kg SID P concentration, which correspond to SID Ca to SID P ratios of 0.66 and 0.87 to 0.96, respectively. The estimated SID Ca requirement for weight gain is lower than the current Ca recommendation (9.6 g/kg total Ca or 4.4 g/kg SID Ca) for broiler starters. However, bone mineralization is maximized around the current total Ca recommendation at 8.9 to 9.8 g/kg (4.36–4.78 g/kg SID Ca) and indicates that bone mineralization requires more Ca than growth performance.
Highlights
Calcium is important to build up skeletal health and a wide range of functions in the body such as blood clotting, muscle contraction, nerve impulse transmission, egg production, enzyme activation, metabolic reactions, protein synthesis, maintenance of osmotic and acid-base balances, and components in membranes (Crenshaw, 2001)
Recommendations for the requirement of digestible Ca and digestible P for growth performance, bone ash and Ca retention have been established (Gonzalez-Vega et al, 2016a,b; Merriman et al, 2017; Lagos et al, 2019a, 2019b). These requirements are based on standardized total tract digestible (STTD) Ca and STTD P values and it was found that the requirement of STTD Ca was greater when bone ash was used as a response criterion compared to growth performance
Analyzed concentrations (Table 11) of proximate components, phytate, Ca, and P of ingredients were within the range reported in the literature (National Research Council 1994, National Research Council, 2012; Browning and Cowieson, 2014; Mutucumarana et al, 2014b, 2014c, 2015)
Summary
Calcium is important to build up skeletal health and a wide range of functions in the body such as blood clotting, muscle contraction, nerve impulse transmission, egg production, enzyme activation, metabolic reactions, protein synthesis, maintenance of osmotic and acid-base balances, and components in membranes (Crenshaw, 2001). Recommendations for the requirement of digestible Ca and digestible P for growth performance, bone ash and Ca retention have been established (Gonzalez-Vega et al, 2016a,b; Merriman et al, 2017; Lagos et al, 2019a, 2019b). These requirements are based on standardized total tract digestible (STTD) Ca and STTD P values and it was found that the requirement of STTD Ca was greater when bone ash was used as a response criterion compared to growth performance.
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