SELF-SELECTION OF DIETARY-PROTEIN AND ENERGY BY BROILERS GROWN UNDER A TROPICAL CLIMATE - EFFECT OF FEED PARTICLE-SIZE ON THE FEED CHOICE

Broilers, 2 wk of age, that had been previously adapted to energy:prot ein choice feeding, were offered corn (either ground, cracked, or pres ented as whole grains) and a protein concentrate (43.7% CP) in mash or pellet form. When corn was fed as whole grains, protein concentrate i n the selected diet was significantly higher (35.1%) than with cracked corn (29.3%) or ground corn (29.1%). Presenting the concentrate as pe llets resulted in a significantly higher concentration in the diet (32 .7%) than when mash concentrate was fed (29.6%). Live BW at 4 and 6 wk of age were not significantly affected by feed texture. However, offe ring corn as whole grains or concentrate as pellets induced a signific ant improvement in feed efficiency. Total time to eat larger size part icles (whole grains, pelleted concentrate) was significantly less than total time to eat ground corn or mash concentrate. Furthermore, the m ean duration of the feeding bouts was two times shorter for whole grai ns (48 s) than for ground corn (98 s) and for pelleted concentrate (56 s) than for mash concentrate (114 s). Chickens ate whole grains or pe llets at a significantly slower rate (number of pecks per second feedi ng time) than when eating ground corn or mash concentrate. There was a rejection during the first 24 h when the form of the concentrate (mas h to pellets) was changed. Full adaptation to the new size of the conc entrate required about 3 d.