Effect of naked oats and enzyme supplementation on performance of hens and quality traits of eggs

The experiment was conducted on 192 Hy-Line hens at the age of 25 weeks, divided into 3 groups, 64 individually caged birds per group. Three diets were prepared: the control diet contained 450 g maize per kg, in two experimental diets maize was replaced by naked oats with or without the addition of an enzymatic preparation containing β-glucanase. Performance was recorded for 14 weeks; in the 5th week 30 eggs were collected from each group and their interior quality parameters were determined. Neither naked oats nor enzyme supplementation significantly affected performance parameters. The naked oats had no significant effect on the weight of eggs (62.8 g on average), albumen quality (74 Haugh units on average) and yolk weight, but decreased the shell weight by 0.6 percentage points and yolk colour by 0.7 points on the 15-point Roche scale.


INTRODUCTION
The presence of ß-glucans that form viscous gels in the alimentary tract can limit the use of naked oats in poultry diets (Jamroz et al., 1994;Svihus and Gullord, 2002).The viscosity of intestinal contents decreases after exogenous enzyme supplementation (Aimonen and Uusi-Rauva, 1991;Boros, 1997).
The aim of the study was to evaluate the effect of complete replacement of maize by naked oats in a laying hen diet and of ß-glucanase supplementation on the laying rate and internal quality of eggs.

MATERIAL AND METHODS
Three groups of 64 individually caged 25-week-old Hy-Line hens were fed diets containing 450 g yellow maize (control) or 450 g of naked oats per kg.The diet with naked oats was unsupplemented or supplemented with the enzymatic preparation Avizyme 1200, containing β-glucanase.The diets contained neither grass-lucerne meal or any pigment additives.Details of methodology and nutritional value of diets were described by Sokół et al. (2004).The experiment was carried out for 14 weeks.Eggs were collected daily, the laying rate was calculated.In the fifth week of the experiment 30 eggs from each group were randomly collected.On the next day the eggs were weighed and broken, the colour of yolks compared with a 15-strip Roche colour fan, the height of the thick albumen was measured, yolks and shells were weighed.The Haugh unit value (HU) was calculated according to the equation: HU = 100 log (H-1.7W 0.37 + 7.6) where H is the maximum height of the thick white in mm; W is the weight of the egg in grams.
The shell index was calculated according to the equation: Shell index = shell weight (g) / shell area (cm 2 ) × 100 where shell area = 4.68 × shell weight 2/3  The results of the experiment were subjected to one-way analysis of variance (SPSS 10.0).

RESULTS AND DISCUSSION
The laying rate in the control group was high (93.2%), in the groups fed both diets with naked oats it was slightly lower (91.3 and 91.7%, respectively), while daily feed intake was similar in all groups and equalled about 135 g/bird.Also Kosieradzka (1999) reported that quails fed a diet with a high level of naked oats had a tendency towards lowering laying performance.Supplementation of the naked oat diet with β-glucanase did not improve the laying rate significantly.
The replacement of maize with naked oats in the diets for hens had no effect on egg weight, quality of thick albumen, yolk weight or the content of yolk (Table 1).Kosieradzka (1999) also did not find any differences in the value of these parameters in eggs of quails fed a diet with 50% naked oats.The colour of yolks was acceptable in all groups, but the yolks from the group fed with naked oats were paler than yolks from the control group (P<0.05)fed the maize diet.Yellow maize, used in the control diet, is a good source of xanthophylls, it seems that naked oats had less xanthophylls, however, due to supplementation of this diet with β-glucanase the yolks were slightly better coloured.The unfavourable effect of a high proportion of naked oats in hen diets on the yolk colour was also reported by Cave et al. (1992) and in quails by Kosieradzka (1999).The percentage content of the shell was lower (P<0.05)and the quality of the shell, as measured by the shell index, was significantly worse (P<0.05) in the group fed the naked oat diet supplemented with the enzymatic preparation, as compared with both remaining groups.Deterioration of shell quality due to the addition of the enzymatic preparation to diets containing oats was also reported by Aimonen and Uusi-Rauva (1991) and Kosieradzka (1999).

CONCLUSIONS
Naked oats may replace maize in diets for laying hens without adversely affecting egg interior quality.Supplementing such diets with enzyme preparations containing β-glucanase is not necessary and may decrease shell quality.

Table 1 .
Performance and quality of eggs