Influence of Substituting Dietary Soybean for Air-Classified Sunflower (Helianthus annuus L.) Meal on Egg Production and Steroid Hormones in Early-Phase Laying Hens V Laudadio 1 , E Ceci 2 , SN Nahashon 3 , M Introna 1 , NMB Lastella 1 and V Tufarelli 1 1 Department of DETO, Section of Veterinary Science and Animal Production, University of Bari ‘Aldo Moro’,Valenzano, BA, Italy; 2 Department of Veterinary Medicine, University of Bari ‘Aldo Moro’, Valenzano, BA, Italy; 3 Department of Agricultural Sciences, Tennessee State University, Nashville, TN, USA Contents Soybean meal (SBM) is the most widely and expensive protein source used in the formulation of poultry diets; however, when the price of SBM increases, poultry nutritionists seek alternative sources that are more economical in formulating least-cost rations. This research aimed to evaluate the effects of dietary air-classified sunflower meal (SFM) on some productive parameters and plasma steroid hormones in laying hens. In this trial, 20-week-old laying hens (ISA Brown strain) in the early phase of production were randomly assigned to two groups and fed wheat middlings-based diets containing soybean (135 g/kg; 48% CP) or air-classified SFM (160 g/kg; 41% CP) as the main protein source. Laying performance, egg size and feed conversion ratio were evaluated for 10 week. Plasma steroid hormones (progesterone and oestradiol) in the hens were quantified weekly. Substituting SBM with air- classified SFM did not change (p > 0.05) the hens’ growth performance, whereas feed consumption and efficiency were positively influenced (p < 0.05) by SFM treatment. Egg production rate was improved in hens fed the SFM diet (p < 0.05), as well as the percentage of medium-size eggs that was higher for SFM treatment (p < 0.05). Steroid hormones levels were affected by dietary treatment (p < 0.01). From our findings, it could be effective to include air-classified SFM in early-phase laying hen diets as an alternative protein source substituting SBM, without negative influence on productive performance and egg traits, reducing also the production costs. Introduction Sunflower (Helianthus annus L.) is high oil-yielding seed crop cultivated worldwide, which adapts very well to a wide range of climatic and soil conditions. Sunflower meal (SFM), a by-product of sunflower oil extraction, is mainly used as animal feed (Villamide and Sanjuan 1998). The energy content of SFM compares favourably with that of other oilseed meals that increases when the residual oil content increases and as the fibre content decreases. Sunflower meal also compares favourably with other oilseed meals as a source of Ca and P and excellent source of water-soluble B-complex vitamins (Garcia-Moreno et al. 2012). Moreover, in contrast to soybean meal (SBM) or rapeseed meal, SFM contains low antinutritional compounds (Canibe et al. 1999) and true amino acid digestibility that tends to increase significantly with CP content (Villamide and Sanjuan 1998). However, the use of SFM is often limited by its availability. Sunflower meal can be fed to many classes of livestock species and most SFM is fed to ruminants (Tufarelli et al. 2009), but it has been reported that SFM could be successfully used also in poultry (Brenes et al. 2008). However, its use in poultry feeding could be difficult as young birds are sensitive to a high-fibre content in their diets. The crude fibre content of SFM may be up to threefold higher than that of SBM, with the portion of fibre originating from the husk being highly lignified and resistant to bacterial degradation in the digestive tract (Bedford and Classen 1992). This problem may be overcome by reducing the fibre content of SFM. Some promising results have been reported when meals are heat-treated (Laudadio and Tufarelli 2011), pin-milled (Wu and Nichols 2005) or air-classified (Wu and Abbott 2003; Gunawardena et al. 2010). Air classification is used to produce protein concen- trates in cereals and legumes (Tabil et al. 1995). Meal particles produced by pin milling are different in their shape, size and density. Air classification differentiates the protein (fine fraction, FF) and fibre (coarse fraction, CF) particles (Owusu-Ansah and McCurdy 1991). The fine and light particles contain protein, whereas the coarse and heavier particles mostly contain fibrous granules (Gunawardena et al. 2010). Because some protein bodies still adhere to the starch granules at the end of pin milling, it is necessary to reprocess the CF by pin milling and air classification, resulting in increased protein yield (Tabil et al. 1995). The FF enriched in protein may be useful for general food or feed applica- tions, while the coarse fraction was rich in fibre and appropriate as a dietary fibre source (Ferrari et al. 2009; Laudadio et al. 2013). Thus, the SFM low-fibre fraction may have better feeding value for monogastrics, while the high-fibre fraction could be intended for feeding ruminants. Recently, the application of micronization in feed research has shown that the reduction in size of various seeds alters the structure, surface area and functional properties of particles (Laudadio and Tufarelli 2011). Micronization, coupled to air classifi- cation, has been considered a useful tool for improving some technology performances and nutritional proper- ties as well as to enrich the meal fractions of healthy compounds (Laudadio and Tufarelli 2011; Rizzello et al. 2012). To our knowledge, data on the effects of feeding air-classified SFM fraction to laying hens have not been published. Therefore, the aim of this study was to evaluate the utilization of air-classified SFM as alternative protein source to SBM in laying hens diet by assessing its effects on productive performance and steroid hormones. © 2013 Blackwell Verlag GmbH Reprod Dom Anim 49, 158–163 (2014); doi: 10.1111/rda.12245 ISSN 0936–6768