Egg quality of brown layers fed with different levels of threonine and chelate zinc

Abstract Text: The objective of this study was to evaluate effects from Thr levels combined with chelated Zn concentrations for brown laying hens. Nine hundred sixty brown laying hens (6 replicates/treatment, 8 birds/replicate) from 22 to 26 weeks of age were allotted in a randomized bloc design under factorial scheme 5 x 4 (Met+Cys x Chelated Copper). The diets were formulated according had similar composition (2,800 kcal/kg ME, 15.5% CP) and were formulated according with the lineage of the birds, except for Thr and Zn levels. At the final day of period, two eggs per plot were evaluated for weight, specific gravity, Haugh unit, yolk index, and for percentages of yolk, albumen and shell. Statistical analysis was performed using ANOVA and contrast between mean for (P<0.05) by Tukey's test. There was no interaction effect of Thr and Zn. Egg weight (56.36 ± …g), specific gravity (1.099 ±), Haugh units (126.00±) yolk index (27.72±) and shell thickness (39.61±) shell percentage (10.05±) had no significant effect under Thr and chelate Zn levels. Effects (P <0.05) were observed for Thr on percentages of yolk and albumen (Table 1). The lower percentages of egg yolk occurred under 1.1 and 0.80% Thr and albumen under 0.65% Thr levels.

Table 1. Percentages of yolk and albumen of eggs from brown layers fed Thr

	Thr (%)
	1.1	0.95	0.80	0.65	0.50	Mean	CV (%)
Yolk %	21.92b	22.40ab	21.79b	23.08a	22.36ab	22.32	9.23
Albumen %	68.03a	67.62ab	68.14a	66.77b	67.66ab	67.64	3.24

Means bearing different superscript letters within a row differ by Tukey (P < 0.05).

In conclusion, Thr levels may affect the internal egg quality. Zn concentrations did not affect the external and internal qualities of egg.

Keywords: Albumen, yolk, chelate minerals