Blood Plasma Mineral Profile and Qualitative Indicators of the Eggshell in Laying Hens in Different Housing Systems

The aim of this study was to compare the blood plasma mineral profile (Ca, P, K, Mg, Zn, Cu and Se) and egg-shell quality (eggshell weight, eggshell breaking strength and thickness) of laying hens housed in three different housing systems (traditional cage system, enriched cage system and deep litter system). In each housing system, 12 ISA Brown laying hens were observed during the laying period from week 22 to 75 of age. The effect (p < 0.05 and p < 0.01) of age and/or phase of the laying cycle on all mineral concentrations was determined. Eggshell breaking strength decreased (p < 0.001) with the age of birds. The results of this study indicate that the housing systems compared had no significant effect on the blood plasma mineral profile of laying hens under study and the values were within the physiological range. However, a significant effect of housing system on eggshell breaking strength and eggshell weight was found. Improved eggshell quality was obtained in most periods of the laying cycle in the enriched cage systems. Blood minerals, egg-shell quality, standard cage, enriched cage, deep litter floor Passage of the Council Directive 1999/74/EC has resulted in the replacement of traditional cages with enriched cages, litter technologies or aviaries to improve the welfare of laying hens. The shell quality remains one of the most important issues for the technology of further egg handling (Ledvinka et al. 2000). However, some authors pointed out that there are differences in eggshell quality and proportion of cracked eggs between different housing systems (Abrahamsson et al. 1995; Abrahamsson and Tauson 1997; Wall and Tauson 2002). Shell quality can be influenced by many factors including mineral nutrition. Calcium, magnesium and phosphorus are major inorganic constituents of avian eggshells (Cusack et al. 2003). Simons (1976) found small amounts of potassium, copper and zinc in the palisade layer of the eggshell. The presence of sodium, potassium, magnesium, zinc, and copper was confirmed also in the shell membranes (Wedral et al. 1974). The importance of minerals is reflected in changes of arrangement pattern of shell membrane fibres in relation to the structural composition of the eggshell, for example when using copperand magnesium-deficient diets (Leach and Gross 1983). Traces of magnesium, potassium, copper and zinc were also found in the egg cuticle. Plasma mineral concentrations during the laying period can be influenced by many factors; such as laying rate and energy requirements (Suchý et al. 2001), partial quantitative feed restriction (Sahin and Kucuk 2001), mineral supplements (Eren et al. 2004), ambient temperature (Siegel 1995; Donoghue et al. 1990; Ching 1992; Belay and Teeter 1993; Večerek et al. 2002), production type (Suchý et al. 2004), age of hens (Cerolini et al. 1990; Gyenis et al. 2006), stress (Beisel 1982; Combs and Combs 1984; Tufft and Nockles 1991; Klasing 1998), exposure to heavy metals (Zralý et al. 2008), etc. With regard to differences in eggshell quality between different housing systems we presumed also differences in the blood plasma mineral profile of hens. The objective of ACTA VET. BRNO 2009, 78: 419-429; doi:10.2754/avb200978030419 Address for correspondence: Ing. Aleš Pavlík, Ph.D. Department of Morphology, Physiology and Genetics Mendel University of Agriculture and Forestry Zemědělská 1 613 00 Brno, Czech Republic, Phone: + 420 545 133 148 Fax. +420 545 133 176 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm this study was to investigate the effects of different housing systems on plasma mineral profile in relation to eggshell quality. To our knowledge, studies comparing blood plasma mineral profile indicators among hens kept in these three systems have not yet been performed. Materials and Methods The experiments were performed in ISA BROWN pullets, kept in a hall with deep litter technology. The available area, complete diet, light-dark (L : D) cycle, temperature of housing, relative humidity of air changed according to technological instructions for ISA BROWN pullets. During the rearing period standard vaccinations were performed. At the age of 15 weeks, the animals were randomly divided into 3 of the following breeding systems: Traditional cage housing system (S) – four-floor, total (available) area 550 cm2/bird (2 birds kept on 1 120 cm2 – 32 × 35 × 45 cm), 2 nipple drinkers, belt feeder 15 cm/bird, device for claw shortening. Enriched cage housing system (EE) according to Council Directive 99/74/EC – three-floor, total area 945 cm2/ bird (8 birds kept on an area of 7 560 cm2 – 180 × 42 × 45 cm), available area 643 cm2/bird, 6 nipple drinkers, belt feeder 20 cm/bird, nest (30 × 35 × 45 cm), perching area 15 cm/bird, devices for dustbathing and scratching, device for claw shortening, Deep litter housing system (DL) – available area 2 000 cm2/bird (20 birds kept on an area of 40 000 cm2 – 200 × 200 ×180 cm), tube feeder 5 cm/bird, round drinker 2cm/bird, deep litter made of wood shavings. All of the housing technologies were situated in the same building with central system of ventilation and temperature regulation. For each technology, experimental group consisting of 12 birds were established with the mean body weight of 1,300  50 g. Throughout the study, the hens were fed a complete diet for laying hens containing 875 g·kg-1 of dry matter, energy content MEN 11.1 MJ·kg -1, content of nitrogen substances 170.7 g·kg-1, Ca 35.9 g·kg-1 and P 6.3 g·kg-1. A constant light-dark (L : D) cycle (15 : 9, switching on at 4.00 h, switching off at 19.00 h) was maintained in all three technologies as recommended in technological instructions for ISA BROWN hens. The temperature of housing was in the range from 18 to 22 °C; relative humidity ranged from 65 to 70%. No red mite and other parasite or viral infection was found during experimental period. Local Ethics Committee approved the experimental protocol. Collection of blood samples Blood samples (5 ml) of all hens in experimental groups were collected from the brachial vein of hens at the age of 22, 47 and 75 weeks, always between 07:00 and 08:30 h. Heparin was used as anticoagulant. Two ml of blood of all samples were centrifuged and the separated plasma was stored at -20 °C until analyzed. Three ml of whole blood were used for Se analysis. Blood sampling was performed randomly in hens kept in standard, enriched and deep litter technology. Biochemical indicators In blood plasma the following elements were measured: calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K), zinc (Zn), and copper (Cu); selenium concentration (Se) was measured in whole blood. The minerals were analyzed with commercially available kits Bio-La-Tests made by Pliva-Lachema, Inc., Czech Republic, with COBAS MIRA S (Roche, CH). Selenium concentration was analysed by atomic absorption spectrometry (AAS). Samples of whole heparinised blood were mineralized in a closed system using a microwave (MLS-1200, Milestone, Italy) digestion technique with HNO3 and H2O2. Samples were evaporated and the mineral residue was dissolved in water to which 20% HCl was added. Selenium was then determined with Solar 939 AA Spectrometer (Unicam, UK) using a hydride AAS technique. Determination of the eggshell quality Eggs of average size were selected on days of blood collection for the respective technologies (eggs that were too big or too small and eggs with damaged or absent eggshell were not included in the analysis). The eggs were marked with a pencil; group designation and serial number were written on each egg to avoid confusion. The eggs were analyzed immediately after the collection. Eggshells were weighed with an accuracy of 0.1 g with laboratory scales after washing with warm water and drying at room temperature for one week (egg membranes were not removed). The eggshell strength (N/cm2) was determined using the Egg Crusher EGC (VEIT Electronic, CZ). Eggshell thickness (mm) is expressed as an average value measured by Digimatic Outside Micrometer (Mitutoyo, JPN) at both poles and in the equator of the egg. Statistical evaluation The data are expressed as means ± SEM. Changes in minerals were analyzed by repeated measures ANOVA for factors housing technology as independent variable and age of hens as dependent variable. Egg quality was analyzed by two-way ANOVA for factors housing technology as independent variable and age of hens as dependent variable. ANOVA was followed by post-hoc Fisher’s LSD test for pairwise comparisons, where appropriate. All statistical analyses were performed by the Statistica 7.0 statistical software (StatSoft Inc., Tulsa, USA). The overall level of significance was defined as p < 0.05. 420