80 80 LOHMANN › MANAGEMENT GUIDE › NUTRITION › PRODUCTION PERIOD FEED STRUCTURE AND PRESENTATION Structure can be defined ”as the size and internal binding strength of feed particles.” In nature, hens are used to selecting and recognising a wide variety of raw materials to obtain the necessary nutrient levels to meet their physiological and nutritional needs. However, in addition to preference based on composition, these preferences are determined by the structure of the feed (macro- and microstructure), smell, the bird's previous experiences (social factor), and the distribution of the feed in the feeders. All these factors are encompassed in what we call palatability and are closely related to feed intake. Pullets and layers prefer particles that fit the size of their beak and are easy to pick up. This is why they prefer larger particles. In this section, we will focus on the microstructure and macrostructure of the feed and its importance for birds. Feed Presentation From a practical point of view and as an approximation, the following reference equations are proposed for determining the metabolisable energy requirements of hens in production. FOR WHITE HENS (Sakomura et al., 2005) AMEn (kcal/d) = [(165.74-2.37*T) x (BW0,75)] + (6.68 x ADWG) + (2.4 x EM) FOR WHITE AND BROWN HENS (Fedna, 2018) AMEn (kcal/d) = [(143.7-1.612* T) x (125 x BW0,75) ]+ (5 x ADWG) + (2.53 x EM) AMEn = Apparent Metabolizable Energy with zero nitrogen retention in kcal / hen / day T = Temperature in °C BW = live weight in kilograms / hen ADWG = Average Daily Weight Gain in grams / hen / day EM = daily Egg Mass (% laying x egg weight) in grams / hen / day Based on the obtained value and knowing the energy of the diet, the approximate feed intake of the hen can be estimated using a simple calculation: Feed intake (g/hen/day) = energy requirements kcal / hen / day / feed AMEn kcal / kg x 103 g / kg Hence, the importance of correctly determining the energy of the feed, as the daily nutrient intake is referenced to the estimated consumption level. FEED ENERGY
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