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16 K. Damaziak et al.

The statistical analysis of results was carried out using the statistical pack-agc SPSS 21.0 (SPSS 2010). Normality of parameters distribution was verified with the Kolmogorow-Smimow test (of all parameters examincd only egg lay-ing had normal distribution). The effect of cage type, hens age and the effect of cagc change on laying performance was cxamined with one-way analysis of vari-ance. Differences in egg laying betwcen groups in particular weeks were deter-mined with the T-test. The impact of cage type on egg wcight was estimated with the Mann-Whitney test, and the impact of cage change - with the Kruskal--Wallis test. The contribution of eggs in particular egg weight classes was com-pared with the Chi-square test. The differences were considcrcd significant at P < 0.01 and P < 0.05. The variability of the investigated traits was expressed by the standard error of the mean (±SE).

RESULTS AND DISCUSSION

Laying performance

The laying performance of ISA Brown hens kept in both types of cages before the change of the housing system (36-44 week of life) was at a similar level of ca. 89% (Table 2) and slightly lowerthan the standard values of 91-94% (www.hen-drix-genetics.com 2008). A significantly higher (P <0.01) laying perfonnance in group C was determined only in week 2, 5 and 6 of obscrvations (Fig. 3), which was however insignificant to the total re-sult from this period. The higher laying performance of hens kept in conventional cages compared to fumished cages was confirmed by Glatz and Bamett (1996). whereas Appleby et al. (2002) as well as Guesdon and Faure (2004) achieved a similar laying percentage in both ty'pes of cages. Egg laying was found to depend to the greatest extent on the rapid transfer to a different type of cage. In both groups analyses demonstrated a dccrease in laying performance betwccn week 44 and 46 of hens life: by 8.0% in hens moved from group C to group CF, and by 1.0%

TABLE 2. Least sąuarcs mcans (LSM) and SE of the ISA Brown laying hens production (%) depending on cage type

Hens age (weeks)	Laying production (%)				Effect or cagc type
36—ł4	Comenlional cage (C)		Fumished cagc (F)		NS
	LSM	±SE	LSM	±SE
	89.5	0.4	88.9	0.3
46-54	Furnished cage (CF)		Conventional cagc (FC)		*•
	LSM	±SE	LSM	±SE
	85.7	0.4	90.4	0.5
Effect of cage type comersion	••		**

**difference significant al P < 0.01.