Differences in the eggshell quality and tibia strength in Lohmann White and Czech Hen housed in cages and on litter

© Slovak University of Agriculture in Nitra Faculty of Agriobiology and Food Resources, 2014 http://www.fapz.uniag.sk/ DOI: 10.15414/afz.2014.17.03.75–78


Introduction
Eggshell quality is one of the most important problems facing poultry industry; it economically influences egg production and hatchability. The eggshell quality is often expressed through its weight, percentage, thickness and strength. Composition of the eggshell and its characteristics are affected by many factors from which housing system and genotype are very important. Several studies were done in order to evaluate the effect of housing systems on eggshell quality including cages and litter systems, and to indicate which housing system is more effective for better eggshell quality. Pištěková et al. (2006), Zemková et al. (2007) and Singh et al. (2009) detected heavier eggs on litter, whereas Moorthy et al. (2000), Leyendecker et al. (2001a); Lichovníková and Zeman (2008) and Tůmová et al. (2011) found heavier eggs in cages. Hidalgo et al. (2008) showed the effect of housing on the eggshell thickness and the strength, they stated that the shell thickness was the lowest in eggs produced in cages, while barn eggs presented the highest values. On the other hand, Pištěková et al. (2006) suggested that difference in the shell strength in eggs from deep litter system and in eggs from cage system was not found statistically significant. Pores density was higher in cage system than on litter (Tůmová et al., 2011).
Eggshell parameters can be related to serum calcium concentration, because it is the major structural element in the eggshell and large amounts of Ca are required to synthesize the shell. Řezáč et al. (2000) reported that the highest serum Ca levels in laying hens producing eggs with damaged shells, similar results were found by Pavlík et al. (2009) who reported that increased serum Ca level was associated with decreasing the eggshell strength and the thickness. Tibia breaking strength is an important welfare problem for laying hens. Leyendecker et al. (2001a) suggested that the eggshell stability and the thickness seem to be negatively correlated with the bone strength. Several studies have shown a higher incidence of bone fragility in caged laying hens compared to hens kept in alternative housing system. Leyendecker et al. (2005) reported that, the weakness of the bones of hens kept in conventional cages is estimated to be mainly due to the limited opportunity to exercise. Not only housing system affects eggshell quality but also genotype has a great effect on eggshell characteristics (Tůmová et al., 2007;Zita et al., 2009;Ledvinka et al., 2011). Tůmová et al., (2007) confirmed the effect of genotype on the eggshell weight which were higher in eggs of Plymouth Rock strain than Blue strain.

Mohamed Ketta*, Eva Tůmová
Czech University of Life Sciences Prague, Czech Republic Ledvinka et al. (2011) observed the significant effect of genotype on the eggshell thickness and the eggshell strength. On the other hand, Leyendecker et al. (2001b) found a thinner eggshell in brown eggs compared to the white ones. Basmacioglu and Ergul (2005) did not report a significant effect of the genotype on the shell strength and the thickness. Moreover, non-significant differences in the shell strength were determined by Tůmová et al. (2007) in variable brown strains.
Eggshell quality is also influenced by interaction between housing and genotype. Leyendecker et al. (2001b) reported genotype and housing system interactions on eggshell parameters. Vits et al. (2005) pointed out that eggshell quality characteristics were lower in enriched cages than in conventional cages, and that Lohmann Brown hens showed better results compared to Lohmann LSL. Singh et al. (2009) suggested that strain should be considered when using alternative housing systems.
The present study was conducted to investigate the differences in the eggshell parameters and the tibia strength in Lohmann White and Czech Hen housed in cages and on litter.

Material and methods
In the experiment with 123 laying hens of Lohmann White and pure breed Czech Hen, birds were housed in conventional cages Eurovent (72 hens, 550 cm 2 hen, 3 hens in a cage, 12 cages for genotype) and in six littered pens (60 hens, 7 hens per m 2 , 10 hens per pen and 3 pens for each genotype). The experiment was carried out in the second half of the laying cycle. Laying hens in both housing systems were fed commercial type of feed mixtures. The daily photoperiod consisted of 15 h light and 9 h darkness. Eggs for the egg shell quality assessment were collected in two weeks interval, two days in row, all eggs laid from each cage or litter pen and there were analyzed 300 eggs of Lohmann and 150 eggs of Czech Hen. Eggs were weighed, and the shell strength was determined by the shell-breaking method using a QC-SPA device (TSS York, UK). Egg shell weight was determined after drying. Egg shell thickness was evaluated by QCT shell thickness micrometer (TSS York, UK). Egg shell proportion was calculated from egg shell weight, which was determined after drying, and egg weight. Tibia characteristics were determined in 48 hens, 12 birds per a group, at 50 weeks of age. After slaughtering, both tibias were completely removed from the carcass. Weight, strength were measured in the right tibia. Tibia strength was measured by QC-SPA device (TSS York, UK) and thickness by micrometer QCT (TSS York, UK). Tibia Ca content was analysed in the left tibia after ashing at 550 °C overnight using a method AOAC 965.17 based on vanad-molybden reagent and spectrophotometry analysis on Solaar M6 apparatus (TJA Solutions, Cambridge, UK).
Egg shell quality data and tibia measurements were evaluated by two-way (housing, genotype) analysis of variance using the GLM procedure of SAS (SAS Institute Inc., Cary, Nc, 2003).

Results and discussion
In our study, significant interaction between housing system and genotype were detected. The significant interaction of housing system and genotype revealed that egg weight (Table 1)   Hen. The eggshell thickness was higher on litter system than in cages; however, Hidalgo et al. (2008) showed that shell thickness was the lowest in eggs produced in cages, while free-range and barn eggs presented the highest values. Non-significant interactions were detected for the eggshell strength. On the other hand, Tůmová et al. (2011) found significant interactions of housing and genotype in brown-egg hybrid kept in conventional cages and on litter.
The eggshell quality can be also characterized by pore density. There were no significant interactions between genotype and housing system on eggshell pore density (Table 2). On the other hand, we found numerically higher pore density in cages than on litter, especially in the shell sharp end. Similar results were reported by Tůmová et al. (2011), who detected a higher pore density on the sharp end and in the equatorial area in eggs from hens from litter. The significant interactions (P ≤0.004) in the tibia strength were observed between housing system and genotype (Table 3) which is in agreement with results of Vits et al. (2005). Tibia strength in Czech Hens was stronger in both housing systems than those of Lohmann White.
Moreover the effect of housing system on the tibia breaking strength was found. The tibia strength was higher on litter system than in conventional cages which is in agreement with Newman and Leeson (1998), Leyendecker et al. (2001c), on the other hand Vits et al. (2005) did not detect difference in tibia strength among the housing systems. Leyendecker et al. (2005) reported that, the weakness of the bones of hens kept in conventional cages is estimated to be mainly due to the limited opportunity to exercise. Serum Ca concentration also did not significantly affected by interaction between housing system and genotype; however, numerically higher concentration was in Lohmann White.

Conclusions
The results of the present investigation showed significant interactions between genotype and housing systems on the egg weight, the eggshell thickness and the tibia strength. The results indicated that genotypes can have a different reaction in the eggshell quality depending on housing system, and these interactions can be more important than individual factors.