Effects of boron supplementation on tibia mineral, ash and weight parameters and peripherial blood leucocyte percentages of layers.

In this study the effects of 0, 50, 100, 150, 200 and 250 ppm boron (B) supplementation into laying hen diets on tibia B, calcium (Ca) and phosphorus (P) concentrations, tibia weight and ash content (in % and g DM), peripherial blood leucocyte (PBL) percentage were investigated. Boron supplementation caused significant increases in tibia B concentrations but decreased tibia Ca levels. Supplementation of B did not have any effect on tibia ash content and tibia weight. Whole blood haematocrit (HCT) and haemoglobin (Hb) levels were not significantly increased by the B addition. In general, the findings of the present study supported the hypothesis that B has an important biological role that influences mineral metabolism of the layers. Introduction Boron has been examined as a possible nutritional factor in Ca metabolism and utilisation, and thus as a factor in the development and maintenance of normal bone (Nielsen, 1992). Bone-breaking strength and bone ash content are often used as criteria for assessing the values of various dietary supplements, cage designs and animal densities for preventing bone breakage. Several studies (Kurtoğlu et al., 2001, 2002, 2005; Wilson and Ruszler, 1997, 1998) have also indicated that B is an important mineral for body weight, feed consumption, reduced mortality rate, normal cartilage and bone formation in poultry. In laying hens, a method to improve mineral balance in order to increase the bone strength of laying hens could benefit for the poultry industry (Kurtoğlu et al., 2002). It seems that B also could affect blood cell counts and composition because blood cell formation and maturation are influenced by changes in cell membrane or kidney function or in calcium metabolism (Nielsen et al., 1991). But there were only limited data on blood cell variables affecting by B supplementation in chicks or other animal species. Materials and Methods A total of 480, 40-week-old Hysex-Brown layer hybrids, which were obtained from University of Selçuk, Faculty of Veterinary Medicine, Animal Husbandry and Research Unit were used in this study. The animals were randomly divided into six groups. To limit the position differences, these groups were divided into eight subgroups consisting of 10 layers in each (8 replicates of 10 layers making a subgroup). Experimental period was 120 days. Composition and analyses of the diet was formulated as in Table 1. As the B source, orthoboric acid was used. Crude nutrient in food were analysed by the methods of AOAC (1984). At 120 day, 10 layers from each group were killed by cervical dislocation. The left tibias were removed and prepared for ash and B, Ca and P analyses (Rossi et al., 1993). Tibia mineral analyses were made by using an Inductive Coupled Plasma Atomic Emission Spectrometer (ICP AES Varion Vista Model, Australia) according to Rossi et al. (1993). Cardiac blood samples were taken into heparinized tubes. The smears were fixed in glutaraldehyde-acetone solution. Two of them were stained with May Grünwald-Giemsa and PBL percentages of the samples were determined by counting 200 leucocytes on each specimen. Data belonging to the biochemical and the other parameters were measured individually and analysed by using Duncan’s multiple range test (SPSS, 1998).