Abstract

BAYLEY, C.E. et al. Broiler response to variable rates of inclusion of calcium and non-phytate phosphorus in feed. S. Afr. j. anim. sci. [online]. 2024, vol.54, n.5, pp.631-640. ISSN 2221-4062.  https://doi.org/10.4314/sajas.v54i5.09.

A trial was conducted to investigate the response of broilers to changing levels of calcium and non-phytate phosphorus. A total of 1344 chicks were allocated to 96 cages in a controlled-environment house. Limestone and phosphoric acid were added to a maize-soya basal diet so that six levels of calcium were fed, with four levels of non-phytate phosphorus (nPP) at each. Birds were weighed on days 0, 7, 14, and 21. Each week, two birds per pen were killed and tibial ash and breaking strength were determined. Feed intake and bird weight for each pen were measured weekly. Calcium and non-phytate phosphorus had a marked effect on body-weight gain, feed intake, and gain/feed. The poorest performance was recorded for the highest Ca:P and the best at 1.36 g Ca/g nPP (7.5 g Ca and 5.5 g nPP/kg feed). Multiple regression analysis of the weekly measurements showed linear effects on body weight gain of calcium and nPP, a quadratic effect of calcium, and an interaction between calcium and nPP. The same variables influenced tibial breaking strength and ash at 14 and 21 d. Feed intake was influenced by nPP. The negative effects of high calcium on the availability of phosphorus affected bird growth. A digestible phosphorus model that takes account of calcium and nPP in the complete feed is a better predictor of performance than nPP alone. This approach is recommended if calcium and phosphorus in broilers is to be modelled and birds are to be fed more precisely.

Keywords : body weight gain; feed intake; minerals; tibial ash; tibial breaking strength.

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