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This study was conducted to evaluate the efficiency of dietary zinc forms and dosages on egg production performance, egg quality, and bone characteristics in laying hens. Forty-two-week-old, 144 Lohmann LSL-Lite laying hens were allocated to 12 experimental groups in a 4 (forms) × 3 (dosages) factorial arrangement. Four zinc forms including zinc-sulphate and zinc-oxide as inorganic forms, zinc-glycine as organic form and nano zinc-oxide powder as nano form at different dosages (50, 75 and 100 mg per kg diet) were tested. Compared to the inorganic (zinc-sulphate) form, the zinc-glycine supplementation significantly depressed the egg weight, egg mass and feed conversion ratio. The eggshell thickness was significantly decreased by supplementation with nano zinc-oxide. The shear force of tibia was significantly decreased by zinc-glycine or nano zinc-oxide supplemented in the diet when compared to inorganic forms of zinc. On the other hand, the dietary 50 mg/kg dosage of zinc was sufficient for optimum performance and the dietary 75 mg/kg dosage of zinc significantly improved shear force of tibia in laying hens. Tibia zinc content increased with the dietary 100 mg/kg dosage of zinc. The interactions between zinc forms and dosages had a significant effect on egg weight, feed intake, feed conversion ratio, eggshell thickness, shear force and shear stress of bone, and tibia calcium concentration. The highest egg weight and the lowest eggshell thickness were observed for the group fed with nano Zn-oxide at 100 mg/kg in the diet. These results showed that nano zinc form supplementation negatively affects the eggshell thickness and bone mechanical properties. The zinc in nano form may not be suggested for feeding laying hens, but other forms of zinc could be used safely in layer diets.

The aim of this study was to investigate the effect of seven different levels (0, 25, 50, 100, 200, 400, and 600 mg/kg) of a phytogenic feed additive containing a mixture of essential oils from thyme, black cumin, fennel, anise and rosemary on performance, eggshell quality, bone biomechanical properties and bone mineralization in laying hens. This study consisted of a total of 112, 21-weekold super nick laying hens, which were randomly distributed into seven experimental groups. during the 12-week experimental period, each experimental group of four replicates of four birds each was fed with seven treatment diets. egg weight and egg mass were positively linearly affected by essential oil mixture supplementation. also, eggshell thickness was increased quadratically by essential oil mixture supplementation. The biomechanical properties and tibia mineral content were adversely affected by essential oil mixture supplementation at the level of 600 and 400 mg/ kg, respectively. These results demonstrated that dietary supplementation with a low or medium concentration of essential oils improved bone parameters, while at high levels were adversely affected in laying hens.Key words: mixture essential oils, laying hens, bone, eggshell quality, performanceThe use of phytogenic feed additives such as plant extracts and essential oils in poultry nutrition has gained recent interest, through the ban of using antibiotics. Generally, the interest in essential oils as feed additive has mainly focused on the effect on performance (Çabuk et al.,

1. A total of 72 H&N Brown Nick laying hens, 76 weeks of age (moulted at 60 weeks of age), were randomly assigned into a 3 × 3 factorial arrangement with three limestone particle sizes and three dietary Ca concentrations (30, 36 and 42 g/kg Ca); with 8 replicates per treatments, and one hen (individual) per experimental unit. 2. Particle sizes of the limestone were: distributions smaller than 2 mm (Fine), between 2 to 5 mm (Medium), and larger than 5 mm (Large). The fine, medium and large limestone particles were all obtained from the same source, and sieve sizes used had screen sizes 2 mm and 5 mm. 3. The different concentrations of dietary Ca, particle size or interactions had no significant effect on egg production, egg weight, egg mass, feed intake or feed conversion ratio. 4. The concentrations of dietary Ca and particle sizes had no significant effect on egg breaking strength, eggshell as % by weight of whole egg or eggshell thickness. The interactions between Ca concentrations and particle sizes had a significant effect on eggshell breaking strength, but not on other parameters. 5. Different dietary particle sizes had no significant effect on the Ca, P and Mg mineral contents of eggshell. While the different concentrations of Ca in diets had a significant effect on the P content of eggshell, they had no significant effect on Ca and Mg contents. 6. Different dietary concentrations of Ca had a significant effect on shear stress, and Ca and Mg contents of tibiae, but not other parameters. Also, dietary particle sizes had a significant effect on shear stress and Ca contents of tibiae. The interaction between Ca concentrations and particle sizes had a significant effect on tibia shear force and Ca content. 7. According to the results of this study, moulted brown laying hens should be fed 36 g/kg Ca and a medium limestone particle size (2-5 mm) in the diet to maintain performance, eggshell and bone quality.

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This study was conducted to determine the effects of supplementation of different levels of cadmium and boron on performance, eggshell quality, and mineral concentrations of bone in layer diets. In this trial, a total of 144 layer chickens, 21 weeks old, were randomly divided into 12 experimental groups. In each experimental group, there were four replicates, and in each of the replicates, there were three hens. Experimental diets consisted of all possible combinations of four levels of added cadmium (0, 5, 15, and 45 mg/kg) and three levels of added boron (0, 60, and 120 mg/kg) to the basal diet. Added cadmium (15 or 45 mg/kg) had a significant adverse effect on performance parameters (P < 0.01). Eggshell thickness increased with the addition of 5 mg/kg level of cadmium to the diet (P < 0.01). Tibia cadmium content increased with the addition of cadmium and boron in the diet (P < 0.01). However, tibia boron content decreased with the supplementation of cadmium (P < 0.01). These results indicate that the addition of boron to the diet did not prevent adverse effect of cadmium on performance and eggshell quality, or accumulation of cadmium in bone.

O. 2010. Effects of xylanase enzyme supplementation to corn/wheat-based diets on performance and egg quality in laying hens. Can. J. Anim. Sci. 90: 207Á212. This study was conducted to determine the effects of xylanase supplementation of corn/wheat-based diets on the performance and egg quality of laying hens. At 52 wk of age, 180 White Leghorn LSL laying hens were fed 15 diets, consisting of five corn:wheat ratios and three levels of enzyme. None of the treatments affected performance or egg quality, except for egg yolk index and egg yolk color. The egg yolk color was improved by the increase in dietary corn level. It is concluded that wheat can be used instead of corn as an energy feedstuff in laying hen diets. Aucun traitement n'a affecte´le rendement ni la qualite´des oeufs, hormis la couleur et l'indice du jaune. La couleur du jaune s'ame´liore avec la proportion de maı¨s dans la ration. On en conclu qu'on pourrait remplacer le maı¨s par du ble´comme source d'e´nergie dans la ration des pondeuses. Mots clé s: Qualite´des oeufs, pondeuse, rendement, xylanaseIn the poultry industry, to formulate a balanced leastcost diet, both accurate nutrient composition of feedstuffs and requirements of the birds must be defined. It is important to have accurate energy values for feed ingredients because dietary energy is a major cost in formulating a least-cost ration. Corn and wheat have been used in many countries as major ingredients for poultry rations because of their high energy content.Wheat is an excellent replacement for corn in poultry feeds, but dietary modifications need to be made because of its anti-nutritive fraction, non-starch polysaccharide (NSP). Wheat contains a relatively high level of NSP as a structural carbohydrate (Annison 1990; Ward 1995;Jaroni et al. 1999). The majority of the carbohydrate fraction is derived from b-glucan and arabinoxylan in the grain cell wall (Annison and Choct 1991;Classen and Bedford 1991). Xylans are the main NSP of wheat, and high levels of wheat in poultry diets can increase the viscosity of the gut contents, which impedes the circulation and absorption of nutrients, causing reduced feed intake, body weight gain, and feed efficiency (Annison and Choct 1991). The anti-nutritive effects of NSP are probably mediated by a number of mechanisms, including increased digesta viscosity complexing of NSP with digestive enzymes, binding of bile salts, thus reducing lipid solubilization and absorption (Ebihara and Schneeman 1989) and increasing fermentation in the small intestine with subsequent decrease in nutrient digestion (Choct et al. 1996).The use of enzymes in commercial layer diets has become more common in recent years (Lazaro et al. 2003;Mathlouthi et al. 2003; Ç iftci et al. 2003;Rafuse et al. 2004). Enzymes may be targeted at carbohydrates, proteins or lipids (Leeson and Summers 1997). In poultry diets, enzymes are responsible for increasing the digestibility of feed ingredients and reducing the incidence of wet droppings, which may result from the presence of NSP (Cho...