Influence of feed form and energy concentration of the rearing phase diets on productivity, digestive tract development and body measurements of brown-egg laying hens fed diets varying in energy concentration from 17 to 46 wk of age

The influence of feed form and energy content of the rearing phase diets on hen productivity,gastrointestinal tract (GIT) traits and body measurements was studied in brown-egg layinghens fed diets differing in energy concentration from 17 to 46 wk of age. The experimentwas completely randomized with 12 treatments arranged as a (2 × 3) × 2 factorial with twofeed forms (mash vs. crumbles) and three AMEnconcentrations of the rearing phase diets(low, medium and high) and two AMEnconcentrations (11.10 vs. 11.52 MJ/kg) of the layingphase diets. The AMEnof the rearing phase diets differed in 0.42 MJ/kg in all three periods(1?5 wk, 5?10 wk and 10?17 wk of age). Hen productivity was determined from 17 to 46wk and GIT and body traits were measured at 46 wk of age. The characteristics of the rearingphase diets did not affect any of the production, GIT traits or body measurements studiedduring the laying phase, except body weight gain (BWG) from 17 to 46 wk of age that washigher (P < 0.01) in hens that were fed mash during the rearing phase than in hens thatwere fed crumbles. An increase in the energy content of the laying phase diet from 11.10to 11.52 MJ AMEn/kg reduced feed intake (P < 0.001) and improved feed conversion ratio(P < 0.001) from 17 to 46 wk and reduced gizzard contents (P < 0.01) at 46 wk of age butdid not affect any of the other production trait studied. The characteristics of the rearingand laying hen diets did not affect any of the GIT traits or body measurements at 46 wk ofage. Body weight of the hens was positively (P < 0.001) related with body length, body massindex, tarsus length and tarsus diameter at this age. The data indicate that neither feed formnor energy concentration of the rearing phase diets affected subsequent hen performance.An increase in the AMEncontent of the layer diet from 11.10 to 11.52 MJ/kg decreased feedintake and improved feed conversion ratio but did not affect hen production or egg quality.