title: Phosphorus utilization in finishing broiler chickens: effects of dietary calcium and microbial phytase.
abstract: A decrease in dietary P, especially in finishing broilers (21 to 38 d old), is a crucial issue in poultry production from an environmental and economic point of view. Nevertheless, P must be considered together with other dietary components such as Ca and microbial phytase. Different corn and soybean meal-based diets varying in Ca [low (LCa) 0.37, medium (MCa) 0.57, and high (HCa) 0.77%], and nonphytate P [nPP; low (LnPP) 0.18 and high (HnPP) 0.32%] content were tested with and without microbial phytase [0 or 500 phytase units (FTU)/kg]. Feed intake, BW gain, bone mineralization, and mineral retention were examined in 144 Ross PM3 broilers (22 to 38 d old) reared in individual cages. Growth performance was not significantly affected by the treatments. Nevertheless, a numerical decrease of ADG and ADFI was observed in HCa-LnPP and LCa-HnPP associated with an increase of feed conversion ratio. Decreased dietary Ca reduced tibia ash content (Ca, linear: P < 0.001; quadratic: P = 0.034) and tibia ash weight for the highest level of nPP (Ca × nPP; P = 0.035). In parallel, increasing dietary Ca reduced the flow of retained P (P = 0.022) but also tibia ash weight in LnPP diets (Ca × nPP; P = 0.035). The responses of the animals in terms of tibia ash content and P retention were improved by the addition of microbial phytase especially for the lowest P diets (nPP × phytase, P = 0.021 and P = 0.009; respectively). Phytase increased dry tibia weight, bone breaking strength, and tibia diameter in broilers fed the highest Ca diets (Ca × phytase; P < 0.05). We conclude that is possible to decrease P levels in finishing broilers, if the Ca content is appropriate. Nevertheless, decreasing the dietary P and Ca cannot allow a maximization of bone mineralization, but the optimal threshold remains to be determined.
authors.affiliation: INRA, UR83, F-37380 Nouzilly, France. xaviere.rousseau@gmail.com
authors.forename: X
authors.initials: X
authors.lastname: Rousseau
authors.forename: M P
authors.initials: MP
authors.lastname: Létourneau-Montminy
authors.forename: N
authors.initials: N
authors.lastname: Même
authors.forename: M
authors.initials: M
authors.lastname: Magnin
authors.forename: Y
authors.initials: Y
authors.lastname: Nys
authors.forename: A
authors.initials: A
authors.lastname: Narcy
mesh_terms: D010832:6-Phytase / Q000145:classification / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D015519:Bone Density; D001846:Bone Development; D002118:Calcium / Q000378:metabolism; D002136:Calcium, Dietary / Q000494:pharmacology*; D002645:Chickens / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D008297:Male; D010758:Phosphorus / Q000378:metabolism*
chemical_list: D002136:Calcium, Dietary; D010758:Phosphorus; D010832:6-Phytase; D002118:Calcium