Influence of the main cereal in the diet and particle size of the cereal on productive performance and digestive traits of brown-egg laying pullets

A total of 864 brown-egg laying pullets was used to study the effects of the main cereal of the diet (500 g maize or wheat/kg) and particle size of the cereal (hammer milled to pass through a 6-, 8-, and 10-mm screen) on growth performance and digestive traits from 1 to 120 d of age. Each of the six treatments was replicated six times (24 pullets per replicate). Type of cereal did not affect pullet performance at any age. From 1 to 45 d of age, body weight (BW) gain was increased (P<0.001) and feed conversion ratio was improved (P<0.05) as the particle size of the cereal was reduced, but no effects were observed after this age. At 45 d of age, pullets fed maize tended (P<0.10) to have a heavier relative weight (RW, g/kg BW) of the total digestive tract and proventriculi and a higher relative length (RL, cm/kg BW) of the small intestines (SI) than pullets fed wheat. Also at this age, the RW of the digestive tract increased (P<0.05) with increases in the particle size of the cereal. At 120 d of age, dietary treatment did not affect the RW of any of the organs studied or gizzard pH but the RL of the SI was higher (P<0.05) for pullets fed wheat than for pullets fed maize. Also, the RL of the SI was reduced (P<0.05) as the particle size of the cereal increased. We conclude that 500 g wheat/kg can be included in pullet feeds from 1 to 120 d of age, and that particle size of the cereal affects pullet performance during the first 45 d of life but not thereafter. Therefore, it is recommended to grind the cereal used in this period with a screen size of no more than 8 mm.