1. The effects of maize particle size and
steam pelleting on growth and nutrient utilisation were studied with broiler chicks. 2. The presence or absence of 10 microg/kg of
1,25 dihydroxycholecalciferol in diets adequate or deficient in
phosphorus was also investigated. Food efficiency was superior with the fine maize diets but
calcium retention and
phytate phosphorus retention were greatest with the coarse maize diets. Pelleting improved food efficiency and growth in both experiments while
phytate phosphorus utilisation was decreased. 3. Addition of
1,25-dihydroxycholecalciferol to the diet increased 16-d
body weight,
bone ash, plasma dialysable
phosphorus and retentions of total
phosphorus and
phytate phosphorus while decreasing
phosphorus deficiency
rickets and tibial
dyschondroplasia. 4. There were significant interactions between maize particle size and food form. The improvement in
calcium retention observed with the coarse maize diets was reduced when the diets were pelleted. When fed as a mash, coarse maize diets resulted in increased plasma dialysable
phosphorus levels but when the diet was pelleted this response was eliminated. 5. There was also a significant interaction between particle size and
phosphorus concentration in that chicks given diets deficient in
phosphorus had improved
bone ash when fed coarse maize as compared to fine maize. However, this response was eliminated when the diets were adequate in
phosphorus. 6. In one experiment, fine maize diets had higher metabolisable energy values and there was a significant interaction between maize particle size and food form as pelleting improved the metabolisable energy value of coarse maize diets but not fine maize diets. In another experiment only pelleting of the factors studied improved the metabolisable energy value of the diets.