EFFECT OF DIETARY RESTRICTION OF CALCIUM AND PHOSPHORUS ON BROILER PERFORMANCE AND BONE CHARACTERISTICS

Abstract

Six weeks feeding trial using 180 one-day old unsexed Hubbard chicks was carried out to study the effects of early restriction of calcium and phosphorus on growth performance, bone characteristics and economic efficiency in broilers. Three starter diets were used from 1 to 21 days; T100 (100% of Ca & non-phytate Phosphorus NPP requirements) 1.00% Ca and 0.50% NPP; T80 (80% of Ca & NPP requirements) 0.80% Ca and 0.40% NPP and T60 (60% of Ca & NPP requirements) 0.60% Ca and 0.30% NPP. Three grower diets were used from 22 to 42 days; T100 (100% of Ca & NPP requirements) 0.90% Ca and 0.45% NPP; T80 (80% of Ca & NPP requirements) 0.72% Ca and 0.36% NPP and T60 (60% of Ca & NPP requirements) 0.54% Ca and 0.27% NPP. Six dietary treatments were distributed according to diets fed consecutively during starter and grower phases as; (100/100) fed starter T100 then grower T100; (100/80) fed starter T100 then grower T80; (100/60) fed starter T100 then grower T60; (80/80) fed starter T80 then grower T80; (80/60) fed starter T80 then grower T60 and (60/60) fed starter T60 then grower T60. Each treatment comprised of 30 chicks in 5 replicates of 6 chicks each. Results showed that live body weight and daily weight gain were not significantly affected by restricted Ca and NPP diets, where daily feed consumption and feed conversion ratio were significantly affected. Plasma Ca and P concentrations were significantly affected however alkaline phosphatase (ALP) activity was not significantly affected by reduction of dietary Ca and NPP. Percentages of tibia weight, ash and Ca were significantly affected by dietary treatments. In the same manner, tibia length and width were significantly affected by treatments. Histological observation from tibia diaphysis sections shows some dissimilarities between treatments. Birds of (80/80), (80/60) or (60/60) treatments recorded significantly (P≤0.05) better economic values when compared with those of (100/100) treatment. In conclusion, it could be recommended that early restriction of Ca and NPP could keep better utilization of both Ca and NPP to maintain performance and bone structures as well as minimize feed cost.