Influence of energy concentration and feed form of the diet on growth performance and digestive traits of brown egg-laying pullets from 1 to 120 days of age

A total of 1152 one-day-old Hy-Line Brown pullets were used to study the influence of energy content of the diet and feed form on productive performance and digestive tract traits. From 1 to 45 days (d) of age, there were six diets arranged factorially with three Apparent Metabolizable Energy (AMEn) concentrations (low, medium and high) and two feed forms (mash and pellets). From 45 to 120 d all diets were fed in mash form and therefore, the only difference was the energy content. Each of the 6 treatments was replicated 8 times and the experimental unit was formed by 24 pullets housed in 2 adjacent cages. For the entire experiment, body weight (BW) gain and feed to gain ratio improved as the AMEn of the diet increased (P<0.001). Pullets fed pellets from 1 to 45 d of age had higher feed intake and BW gain (P<0.001) in this period and higher BW gain (P<0.01) cumulatively, than pullets fed mash. At 45 d of age, the relative weight (RW; g/kg BW) of all the segments of the gastrointestinal tract (GIT) was lower for pullets fed with the high- than for pullets fed the medium- or low-energy diets. At 120 d of age the RW of the gizzard was higher (P<0.01) for pullets fed the low energy diets than for pullets fed the other diets. The relative length (RL; cm/kg BW) of the GIT was not affected by the energy content of the diet. Feeding pellets reduced the RW of the proventriculus (P<0.05), the gizzard (P<0.001) and the digestive tract (P<0.001), and the RL of the small intestine (P<0.05) and the ceca (P<0.001) at 45 d of age. The effects of feeding pellets on RW of gizzard and proventriculus were still evident at 120 d of age. We concluded that feeding pellets from 1 to 45 d of age improved feed intake and BW of pullets at 120 d of age, and that an increase in the energy content of the diet increased pullet performance at all ages but reduced the RW of the proventriculus and gizzard.