Supplementation of two sources and three levels of iodine in the diet of laying hens: effects on performance, egg quality, serum and egg yolk lipids, antioxidant status, and iodine accumulation in eggs

Figures & data

Table 1. Ingredients and chemical composition of the basal diet.

Item	Amount
Ingredients (%)
Corn	54.46
Soybean meal (44.0% crude protein)	18.62
Full fat soybean (35.9% crude protein)	5.00
Corn gluten meal (55.7% crude protein)	3.00
Wheat bran	5.72
Soybean oil	1.05
DL-methionine 98.5%	0.18
L-lysine-HCl 98.0%	0.09
Limestone coarse	5.45
Limestone fine	4.00
Dicalcium phosphate	1.54
Common salt	0.33
Sodium bicarbonate	0.06
Vitamin-mineral premix*	0.50
Calculated composition (% as-fed basis unless indicated)
Metabolizable energy (MJ/kg)	11.30
Crude protein	17.40
Methionine + cysteine	0.75
Lysine	0.90
Calcium	3.90
Available phosphorus	0.36
Analysed composition (% as-fed basis)
Dry matter	90.00
Crude ash	11.20
Crude protein	17.43
Ether extract	4.17
Crude fibre	3.29
Calcium	3.96
Total phosphorus	0.63

*Provided per kilogram of diet: vitamin A (as retinyl acetate), 9000 IU; cholecalciferol, 4000 IU; vitamin E (as dl-α-tocopheryl acetate), 63 mg; vitamin K₃, 2.3 mg, thiamine, 2.6 mg; riboflavin, 6.5 mg; niacin, 48 mg; D-calcium pantothenic acid, 15 mg; vitamin B₆, 3.0 mg; biotin, 0.2 mg; choline chloride, 770 mg; vitamin B₁₂, 0.02 mg; folic acid, 1.7 mg; manganese (as MnSO₄•H₂O), 105 mg; iron (as FeSO₄•7H₂O), 38 mg; zinc (as ZnO), 126 mg; copper (as CuSO₄), 16 mg; selenium (as Na₂SeO₃), 0.28 mg.

Table 2. Feed iodine source, level and analysis for the different diets*.

Iodine source	Theoretical iodine supplementation (mg/kg of feed)	Analysed iodine level (mg/kg of feed)
Control	0	0.87
CIOD^†	2.0	2.85
	4.0	4.85
	8.0	8.84
EDDI^‡	2.0	2.89
	4.0	4.81
	8.0	8.81

*Values are based on triplicate determinations and presented as means (as-fed basis).

^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide.

Figure 1. Weekly performance as affected by dietary iodine source and level in laying hens (29–42 wk of age). CIOD: calcium iodate; EDDI: ethylenediamine dihydroiodide.

Table 3. Effects of dietary treatments on performance variables in laying hens (30–42 weeks of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine Source		Iodine level (mg/kg)			Pooled
Item	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD	EDDI	2.0	4.0	8.0	SEM^#
Egg production (%)
1–6 wk	96.69	96.70^a	96.52^a	96.01^a,^1	96.59^a	96.70^a	92.60^b,^1^,*	96.41^a	95.30^b	96.64^a	96.61^a	94.30^b	0.306
7–12 wk	96.40	96.24^a	96.25^a	92.12^b,^2^,*	96.18^a	96.21^a	86.62^c,^2^,*	94.87^a	93.00^b	96.21^a	96.23^a	89.37^b
Egg weight (g)
1–6 wk	60.22^2	60.07^2	60.02^2	60.06^2	60.22^2	60.17^2	59.77^2	60.05	60.06	60.15	60.10	59.92	0.105
7–12 wk	61.20^1	61.22^1	61.12^1	61.06^1	61.22^1	61.22^1	60.89^1	61.13	61.11	61.22	61.17	60.97
Egg mass (g/hen/d)
1–6 wk	58.22	58.09^a	57.94^a	57.66^a	58.17^a	58.18^a	55.36^b,^1^,*	57.90	57.24	58.13^a	58.06^a	56.51^b	0.210
7–12 wk	59.00	58.91^a	58.83^a	56.24^b,*	58.88^a	58.90^a	52.75^c,^2^,*	57.99^a	56.84^b	58.90^a	58.87^a	54.50^b
Feed intake (g/hen/d)
1–6 wk	104.92^2	104.89^2	104.62^a,^2	104.87^a	104.79^a,^2	104.80^a,^2	102.58^b,^1^,*	104.79^a	104.06^b	104.84^a	104.71^a	103.73^b	0.226
7–12 wk	106.65^1	105.98^1	106.07^a,^1	104.20^b,*	106.02^a,^1	105.85^a,^1	98.98^c,^2^,*	105.42^a	103.62^b	106.00^a	105.96^a	101.59^b
Feed to egg ratio (g/g)
1–6 wk	1.80	1.81	1.81^b	1.82^b,^2	1.80^b	1.80^b	1.85^a,^2^,*	1.81	1.82	1.80^b	1.80^b	1.84^a	0.004
7–12 wk	1.81	1.80^c	1.80^c	1.85^b,^1^,*	1.80^c	1.80^c	1.88^a,^1^,*	1.82	1.83	1.80^b	1.80^b	1.87^a
Body weight change (g)
1–6 wk	42.50^1	45.17^1	40.67^1	41.17^1	43.17^1	42.83^1	42.33^1	42.33	42.78	44.17	41.75	41.75	1.698
7–12 wk	22.50^2	22.50^2	23.15^2	21.67^2	22.67^2	22.50^2	24.33^2	22.44	22.83	22.08	22.82	23.00
Abnormal eggs^$ (%)
1–6 wk	0.25^2	0.19^2	0.14^2	0.22^2	0.28^2	0.16^2	0.30^2	0.18	0.25	0.24	0.15	0.26	0.024
7–12 wk	0.47^1	0.36^b,^1	0.34^b,^1	0.40^b,^1	0.47^b,^1	0.32^b,^1	0.94^a,^1^,*	0.37^b	0.58^a	0.41^b	0.33^b	0.67^a

^a–cIn each row within each time period LSmeans with different superscripts are significantly different (p < 0.05); ^1,2In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < 0.05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < 0.05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; ^#SEM: standard error of LSmeans; ^$Abnormal eggs: the percentage of all cracked, broken soft-shelled, and shellness eggs of total laid eggs; wk: week.

Table 4. Effects of dietary treatments on external egg quality characteristics in laying hens (29–42 wk of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine Source		Iodine level (mg/kg)
Item^¶	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD	EDDI	2.0	4.0	8.0	Pooled SEM^#
Eggshell weight (%)
0 wk	9.36^1	9.43^1	9.37^1	9.34^1	9.38^1	9.34^1	9.44^1	9.38	9.38	9.40	9.36	9.39	0.018
3 wk	9.32^12	9.25^12	9.30^12	9.32^12	9.20^12	9.26^12	9.29^12	9.29	9.25	9.22	9.28	9.31
6 wk	9.16^23	9.11^23	9.23^23	9.26^23	9.18^23	9.13^23	9.15^23	9.20	9.16	9.14	9.18	9.21
9 wk	9.09^3	9.05^3	9.16^3	9.11^3	9.16^3	9.07^3	9.11^3	9.11	9.11	9.11	9.12	9.11
12 wk	9.06^3	8.99^3	9.09^3	9.08^3	9.10^3	8.98^3	9.04^3	9.05	9.04	9.04	9.03	9.06
Eggshell thickness (mm)
0 wk	0.394^1	0.402^1	0.397^1	0.393^1	0.396^1	0.391^1	0.396^1	0.397	0.394	0.399	0.394	0.394	0.0008
3 wk	0.387^12	0.395^12	0.394^12	0.388^12	0.393^12	0.389^12	0.388^12	0.392	0.390	0.394	0.391	0.388
6 wk	0.384^23	0.387^23	0.391^23	0.384^23	0.386^23	0.387^23	0.384^23	0.388	0.385	0.386	0.389	0.384
9 wk	0.381^23	0.386^23	0.388^23	0.382^23	0.384^23	0.385^23	0.381^23	0.385	0.383	0.385	0.387	0.381
12 wk	0.379^3	0.381^3	0.385^3	0.378^3	0.380^3	0.383^3	0.379^3	0.381	0.381	0.381	0.384	0.379
Eggshell strength (N/cm^2)
0 wk	46.52	46.28	46.23	46.38	46.56	46.34	46.69^1	46.29	46.53	46.42	46.2833	46.53	0.125
3 wk	46.73	46.53	46.58	46.67	46.83	46.79	46.39^12	46.59	46.67	46.68	46.68	46.53
6 wk	45.09	46.73	46.49	46.03	46.03	46.11	44.88^23	46.42	45.67	46.38	46.30	45.45
9 wk	46.28	46.51^a	46.44^a	45.08^ab	46.23^a	46.10^a	42.89^b,^3^,*	46.01	45.08	46.37^a	46.27^a	43.99^b
12 wk	46.61	46.72^a	46.41^a	45.72^ab	46.62^a	46.58^a	42.63^b,^3^,*	46.28	45.28	46.67^a	46.49^a	44.18^b
Eggshell calcium (%)
0 wk	38.06	38.12	37.93	37.50	37.18	37.85	37.00	37.85	37.34	37.65	37.89	37.25	0.121
3 wk	38.20	38.71	38.85	38.31	38.60	38.76	38.49	38.62	38.61	38.65	38.80	38.40
6 wk	38.45	38.23	38.65	38.23	38.07	38.79	38.96	38.37	38.61	38.15	38.72	38.60
9 wk	38.60	38.37	38.04	38.34	38.27	38.26	38.37	38.25	38.30	38.32	38.15	38.36
12 wk	38.51	38.74	38.83	38.37	38.74	38.52	38.77	38.65	38.68	38.74	38.68	38.57
Eggshell phosphorus (%)
0 wk	0.102	0.104	0.101	0.105	0.105	0.106	0.103	0.103	0.105	0.105	0.104	0.104	0.0021
3 wk	0.108	0.106	0.107	0.105	0.107	0.105	0.107	0.106	0.106	0.106	0.106	0.106
6 wk	0.105	0.107	0.105	0.106	0.106	0.105	0.104	0.106	0.105	0.106	0.105	0.105
9 wk	0.107	0.107	0.109	0.108	0.108	0.108	0.107	0.108	0.107	0.108	0.108	0.108
12 wk	0.108	0.107	0.109	0.109	0.109	0.108	0.107	0.108	0.108	0.108	0.108	0.108

^a,bIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–3In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; ^¶Eggs laid in the last 3 d of each period were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week; d: day.

Table 5. Effects of dietary treatments on internal egg quality characteristics in laying hens (29–42 wk of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled
Item	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD	EDDI	2.0	4.0	8.0	SEM^#
Yolk weight (%)
0 wk	26.23^3	26.12^3	26.22^3	26.55^3	26.31^3	26.13^3	26.08^3	26.30	26.17	26.21	26.17	26.32	0.070
3 wk	26.31^23	26.38^23	26.70^23	26.72^23	26.58^23	26.21^23	26.38^23	26.60	26.39	26.48	26.46	26.55
6 wk	26.66^123	26.64^123	26.86^123	26.99^123	26.72^123	26.51^123	26.63^123	26.83	26.62	26.68	26.68	26.81
9 wk	26.96^12	26.77^12	27.02^12	27.29^12	27.01^12	27.01^12	27.12^12	27.26	27.05	26.89	27.01	27.56
12 wk	27.19^1	27.58^1	27.22^1	27.41^1	27.38^1	27.20^1	27.49^1	27.40	27.29	27.48	27.11	27.45
Albumen weight (%)
0 wk	64.41^1	64.45^1	64.41^1	64.11^1	64.31^1	64.53^1	64.48^1	64.32	64.44	64.38	64.47	64.30	0.069
3 wk	64.37^12	64.37^12	64.00^12	63.96^12	64.22^12	64.53^12	64.33^12	64.11	64.36	64.30	64.27	64.14
6 wk	64.18^12	64.25^12	63.91^12	63.75^12	64.10^12	64.36^12	64.22^12	63.97	64.23	64.18	64.13	63.99
9 wk	63.95^12	64.18^12	63.82^12	63.60^12	63.83^12	63.92^12	63.77^12	63.63	63.84	64.00	63.87	63.34
12 wk	63.75^2	63.43^2	63.69^2	63.51^2	63.52^2	63.82^2	63.47^2	63.54	63.67	63.48	63.86	63.49
Yolk index (%)
0 wk	42.33	42.00	40.35	42.50	42.18	41.85	42.00	41.62	42.01	42.09	41.10	42.25	0.123
3 wk	42.50	42.83	42.50	43.42	42.83	43.27	42.83	42.92	42.98	42.83	42.88	43.13
6 wk	42.33	42.92	41.33	42.50	40.42	41.83	42.33	42.25	41.53	41.67	41.58	42.42
9 wk	42.00	41.42	42.83	41.35	41.85	43.18	41.77	41.87	42.27	41.63	43.01	41.56
12 wk	40.35	42.77	42.68	40.00	43.35	41.92	43.18	41.82	42.82	43.06	42.30	41.59
Yolk colour (Roche)
0 wk	10.25	10.58	10.42	10.33	10.33	10.25	10.35	10.44	10.31	10.46	10.34	10.34	0.155
3 wk	9.75	10.17	10.00	9.92	9.83	10.00	10.00	10.03	9.94	10.00	10.00	9.96
6 wk	9.42	10.00	10.00	10.06	10.01	10.08	10.05	10.02	10.04	10.00	10.04	10.05
9 wk	9.92	10.17	10.04	10.25	10.15	10.08	10.11	10.15	10.12	10.16	10.06	10.18
12 wk	10.00	9.92	10.23	10.25	10.32	10.17	10.18	10.13	10.22	10.12	10.20	10.22
Haugh unit
0 wk	90.28	90.54	90.37	90.69	90.49	90.26	90.46^1	90.53	90.40	90.51	90.31	90.58	0.212
3 wk	89.95	89.82	90.82	90.55	89.99	90.47	88.96^1	90.39	89.81	89.90	90.64	89.75
6 wk	89.45	89.69	90.09	90.45	89.45	89.63	87.71^12	90.08	88.93	89.57	89.86	89.08
9 wk	88.39	88.66^ab	89.53^a	88.66^ab	88.61^ab	89.11^a	85.06^b,^23	88.95	87.59	88.64^ab	89.32^a	86.86^b
12 wk	88.13	88.25^a	89.08^a	88.34^a	88.30^a	89.52^a	83.31^b,^3^,*	88.56	87.04	88.28^ab	89.30^a	85.82^b

^a,bIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–4In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD, calcium iodate; ^‡EDDI, ethylenediamine dihydroiodide; ^¶Eggs laid in the last 3 d of each period were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week; d: day.

Table 6. Effects of dietary treatments on serum triglyceride and cholesterol levels (29–42 wk of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled SEM^#
Item	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD^†	EDDI^‡	2.0	4.0	8.0
Triglycerides (mg/dL)
0 wk	1328.79^2	1348.82^2	1330.00^2	1342.08^2	1320.00^2	1339.91^2	1349.60^3	1340.30	1336.50	1334.41	1334.95	1345.84	5.142
3 wk	1375.59^12	1386.25^12	1380.00^12	1390.00^12	1365.00^12	1379.00^12	1396.55^3	1385.42	1380.18	1375.63	1379.50	1393.28
6 wk	1408.12^12	1434.85^12	1404.40^12	1423.60^12	1406.67^12	1425.00^12	1450.56^23	1420.95	1427.41	1420.76	1414.70	1437.08
9 wk	1441.46^1	1450.16^1	1455.00^1	1445.67^1	1455.00^1	1440.00^1	1520.57^2	1450.28	1471.85	1452.58	1447.50	1483.12
12 wk	1471.01^1	1474.51^b,^1	1480.33^b,^1	1471.97^b,^1	1468.18^b,^1	1474.57^b,^1	1628.87^a,^1^,*	1475.60^b	1523.87^a	1471.34^b	1477.45^b	1550.42^a
Total cholesterol (mg/dL)
0 wk	108.56^3	116.49^2	114.35^2	113.22^2	106.97^3	109.95^3	115.89^3	114.69	110.94	111.73	112.15	114.56	2.385
3 wk	119.51^23	124.72^2	122.33^2	120.17^2	117.38^23	119.57^23	121.32^3	122.41	119.42	121.05	120.95	120.75
6 wk	132.71^12	135.24^12	130.15^12	131.23^12	127.48^12	128.52^12	134.38^23	132.21	130.13	131.36	129.33	132.81
9 wk	141.30^1	146.59^1	143.38^1	143.97^1	141.52^1	138.78^12	151.28^2	144.65	143.86	144.06	141.08	147.63
12 wk	146.53^1	150.13^b,^1	147.39^b,^1	148.42^b,^1	147.92^b,^1	145.23^b,^1	175.14^a,^1^,*	148.65^b	156.10^a	149.03^b	146.31^b	161.78^a
LDL cholesterol (mg/dL)
0 wk	40.35^3	45.17^3	42.45^3	44.00^3	39.34^3	42.35^3	44.23^4	43.87	41.97	42.26	42.40	44.12	1.158
3 wk	43.61^3	47.58^3	45.64^3	48.30^23	42.59^23	45.95^3	47.85^34	47.17	45.46	45.08	45.80	48.08
6 wk	47.90^2	52.55^2	51.95^2	50.04^2	48.32^2	51.30^2	51.56^3	51.51	50.39	50.44	51.63	50.80
9 wk	52.96^1	54.20^12	56.91^12	53.98^12	50.46^12	52.67^12	60.47^2	55.03	54.53	52.33	54.79	57.23
12 wk	55.32^1	58.01^b,^1	59.84^b,^1	58.06^b,^1	54.02^b,^1	57.15^b,^1	67.12^a,^1^,*	58.64	59.43	56.02^b	58.50^ab	62.59^a
HDL cholesterol (mg/dL)
0 wk	29.34^4	28.40^3	27.69^3	26.60^3	28.99^4	26.20^4	26.94^3	27.56	27.38	28.70	26.95	26.77	0.765
3 wk	32.66^34	30.60^3	30.31^3	30.26^23	31.63^34	32.29^3	31.86^2	30.39	31.93	31.12	31.30	31.06
6 wk	34.59^23	32.94^23	32.15^23	32.05^2	34.79^23	35.30^23	34.07^12	32.38	34.72	33.86	33.72	33.06
9 wk	38.70^12	37.66^12	36.10^12	36.95^1	37.81^12	38.37^2	35.82^12	36.90	37.33	37.74	37.24	36.39
12 wk	42.18^1	41.29^a,^1	40.95^a,^1	41.57^a,^1	42.50^a,^1	43.47^a,^1	37.08^b,^1^,*	41.27	41.02	41.89^a	42.21^a	39.33^b

^a,bIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–4In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; Serum obtained from 18 birds per treatment (3 per replicate) were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week; d: day.

Table 7. Effects of dietary treatments on egg yolk triglyceride and cholesterol levels (29–42 wk of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled SEM^#
Item	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD^†	EDDI^‡	2.0	4.0	8.0
Triglycerides (mg/g)
0 wk	166.63^4	172.11^4	164.60^4	170.91^4	172.57^4	163.02^4	168.24^4	169.21	167.94	172.34	163.81	169.58	1.831
3 wk	173.81^3	178.33^3	171.04^3	175.09^3	178.31^3	169.34^3	171.51^3	174.82	173.05	178.32	170.19	173.30
6 wk	180.84^2	185.95^2	177.90^2	181.12^2	185.72^2	176.21^2	188.01^2	181.66	183.31	185.84	177.06	184.57
9 wk	187.52^12	186.23^12	181.37^12	187.11^12	186.61^12	183.55^12	194.09^12	184.90	188.08	186.42	182.46	190.60
12 wk	188.40^1	187.97^b,^1	187.35^b,^1	188.89^b,^1	187.91^b,^1	187.93^b,^1	203.31^a,^1^,*	188.07	193.05	187.94^b	187.64^b	196.10^a
Total cholesterol (mg/g)
0 wk	14.83^4	15.27^4	15.06^4	15.47^4	15.09^4	15.30^4	15.23^4	15.27	15.21	15.18	15.18	15.35	0.191
3 wk	16.02^3	16.33^3	16.10^3	16.24^3	15.98^3	16.13^3	16.25^3	16.22	16.12	16.16	16.11	16.24
6 wk	16.38^23	16.66^23	16.44^23	16.38^23	16.37^23	16.65^23	16.47^3	16.49	16.50	16.52	16.55	16.42
9 wk	16.56^12	16.77^12	16.64^12	16.53^12	16.68^12	16.89^12	17.73^2	16.65	17.10	16.73	16.76	17.13
12 wk	16.80^1	17.04^b,^1	16.99^b,^1	16.73^b,^1	16.82^b,^1	17.10^b,^1	19.50^a,^1^,*	16.92^b	17.81^a	16.93^b	17.05^b	18.12^a
LDL cholesterol (mg/g)
0 wk	7.52^4	7.98^4	7.36^4	7.60^4	7.41^4	7.85^4	7.87^4	7.65	7.71	7.70	7.61	7.73	0.119
3 wk	8.01^34	8.12^34	7.73^34	7.90^34	7.91^34	8.38^34	8.08^34	7.92	8.12	8.02	8.05	7.99
6 wk	8.41^23	8.59^23	8.25^23	8.37^23	8.22^23	8.54^23	8.55^3	8.40	8.44	8.41	8.40	8.46
9 wk	8.78^12	8.93^12	8.62^12	8.73^12	8.52^12	8.80^12	9.27^2	8.76	8.86	8.73	8.71	9.00
12 wk	9.16^1	9.28^b,^1	8.98^b,^1	9.11^b,^1	9.28^b,^1	9.14^b,^1	10.77^a,^1^,*	9.12^b	9.73^a	9.28^b	9.06^b	9.94^a
HDL cholesterol (mg/g)
0 wk	3.30^4	3.01^4	3.26^4	3.15^4	3.44^4	3.12^4	3.30^3	3.14	3.29	3.23	3.19	3.22	0.050
3 wk	3.98^34	3.51^34	3.82^34	3.70^34	3.97^34	3.62^34	3.69^23	3.68	3.76	3.74	3.72	3.69
6 wk	4.38^23	4.21^23	4.22^23	4.15^23	4.35^23	4.32^2	4.00^123	4.19	4.22	4.28	4.27	4.08
9 wk	5.28^12	4.94^12	4.92^12	5.15^12	4.93^12	5.37^12	4.51^12	5.00	4.94	4.93	5.15	4.83
12 wk	5.68^1	5.48^a,^1	5.41^a,^1	5.56^a,^1	5.55^a,^1	5.51^a,^1	4.74^b,^1^,*	5.48	5.27	5.51^a	5.46	5.15

^a,bIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–4In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; ^¶Eggs laid in the last 3 d of each period were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week; d: day.

Table 8. Effects of dietary treatments on serum triiodothyronine (T3) and thyroxine (T4) concentrations (29–42 wk of age).

Item	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled SEM^#
	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD^†	EDDI^‡	2.0	4.0	8.0
T3 (ng/mL)
0 wk	1.45	1.44	1.42	1.44^3	1.46	1.43	1.41^3	1.43	1.43	1.45	1.43	1.42	0.019
3 wk	1.46	1.45	1.43	1.44^3	1.49	1.42	1.46^3	1.44	1.46	1.47	1.42	1.45
6 wk	1.36	1.32	1.37	1.35^3	1.31	1.37	1.35^3	1.35	1.35	1.32	1.37	1.35
9 wk	1.46	1.47^bc	1.44^bc	1.63^b,^2^,	1.42^bc	1.41^c	1.78^a,^2^,*	1.51	1.53	1.44^b	1.42^b	1.71^a
12 wk	1.48	1.45^c	1.48^c	2.49^b,^1^,*	1.45^c	1.44^c	3.01^a,^1^,*	1.81^b	1.97^a	1.45^b	1.46^b	2.75^a
T4 (ng/mL)
0 wk	5.85^1	5.62^1	5.73^1	5.80^1	5.80^1	5.65^1	5.78^1	5.72	5.74	5.71	5.69	5.79	0.179
3 wk	7.34^2	7.33^2	7.36^2	7.44^2	7.15^2	7.36^2	7.49^2	7.37	7.33	7.24	7.36	7.46
6 wk	10.16^3	10.31^c,^3	11.33^bc,^3	11.90^b,^3^,*	11.30^bc,^3	11.44^bc,^3	13.33^a,^3^,*	11.18^b	12.02^a	10.81^b	11.38^b	12.61^a
9 wk	12.13^4	12.33^c,^4	12.50^c,^4	14.18^b,^4^,*	12.34^c,^4	12.82^c,^4	15.60^a,^4^,*	13.00^b	13.59^a	12.33^b	12.66^b	14.89^a
12 wk	14.53^5	14.60^c,^5	14.75^bc,^5	17.06^b,^5^,*	14.70^c,^5	14.86^bc,^5	18.51^a,^5^,*	15.47^b	16.02^a	14.65^b	14.81^b	17.78^a

^a–eIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–5In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; ^¶Serum obtained from 18 birds per treatment (3 per replicate) were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week.

Table 9. Effects of dietary treatments on antioxidant measurements in serum and egg contents (29–42 wk of age).

	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled
Item^¶	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD^†	EDDI^‡	2.0	4.0	8.0	SEM^#
Serum SOD^▼ (U/mL)
0 wk	139.61	142.21	141.99	140.61^3	143.46	143.68	141.01^3	141.60	142.72	142.84	142.84	140.81	0.623
3 wk	141.90	141.61	142.10	143.70^3	141.94	143.00	143.29^3	142.47	142.74	141.78	142.55	143.50
6 wk	142.00	142.35	141.37	143.44^3	142.97	142.62	145.17^3	142.38	143.59	142.66	142.00	144.30
9 wk	140.42	146.60	144.22	154.00^2,*	145.21	147.04	167.39^2,*	148.27	153.21	145.91^b	145.63^b	160.70^a
12 wk	143.00	145.88^c	146.87^c	185.21^b,^1^,*	149.00^c	144.99^c	194.96^a,^1^,*	159.32	162.99	147.44^b	145.93^b	190.08^a
Serum MDA^¶ (µg/mL)
0 wk	0.337	0.351	0.342	0.350	0.356	0.338	0.343^3	0.348	0.346	0.354	0.340	0.347	0.0020
3 wk	0.358	0.353	0.347	0.360	0.335	0.342	0.331^3	0.354	0.336	0.344	0.345	0.346
6 wk	0.364	0.370	0.345	0.349	0.355	0.360	0.365^23	0.355	0.360	0.363	0.353	0.357
9 wk	0.363	0.369	0.365	0.366	0.370	0.354	0.373^12	0.367	0.366	0.370	0.360	0.369
12 wk	0.346	0.338^b	0.371^b	0.364^b	0.362^b	0.366^b	0.425^a,^1^,*	0.358	0.384	0.350^b	0.368^ab	0.394^a
Serum PC^§ (µg/mL)
0 wk	0.007	0.008	0.009	0.012	0.009	0.013	0.011^2	0.001	0.011	0.009	0.011	0.012	0.0002
3 wk	0.011	0.010	0.014	0.012	0.011	0.014	0.013^2	0.012	0.013	0.011	0.014	0.013
6 wk	0.012	0.011	0.013	0.014	0.012	0.013	0.014^2	0.013	0.013	0.011	0.013	0.014
9 wk	0.012	0.012	0.012	0.014	0.012	0.012	0.016^12	0.013	0.013	0.012	0.012	0.015
12 wk	0.011	0.010^b	0.012^b	0.013^b	0.010^b	0.013^b	0.021^a,^1^,*	0.012	0.015	0.010^b	0.013^b	0.017^a
Egg SOD^▼ (U/mg)
0 wk	46.27	47.98	45.30	46.37^3	47.91	44.74	45.67^3	46.55	46.11	47.95	45.02	46.02	0.365
3 wk	45.80	45.66	47.45	47.96^3	46.64	47.61	46.77^3	47.02	47.01	46.15	47.53	47.37
6 wk	45.87	46.58	45.75	46.12^3	45.54	47.78	46.85^23	46.15	46.72	46.06	46.77	46.48
9 wk	44.96	47.68	47.87	61.62^2,*	48.68	46.83	66.66^2,*	52.39	54.06	48.18^b	47.35^b	64.14^a
12 wk	46.07	44.42^c	48.87^c	71.77^b,^1^,*	47.65^c	45.04^c	80.12^a,^1^,*	55.02	57.60	46.03^b	46.95^b	75.94^a
Egg MDA^¶ (µg/g)
0 wk	0.151	0.159	0.155	0.148	0.159	0.150	0.153^2	0.154	0.154	0.159	0.153	0.150	0.0026
3 wk	0.158	0.154	0.157	0.152	0.153	0.157	0.152^2	0.154	0.154	0.154	0.157	0.152
6 wk	0.153	0.158	0.157	0.155	0.150	0.153	0.155^2	0.157	0.153	0.154	0.155	0.155
9 wk	0.153	0.152	0.156	0.159	0.155	0.154	0.161^1	0.155	0.157	0.153	0.155	0.160
12 wk	0.158	0.157^b	0.156^b	0.157^b	0.155^b	0.154^b	0.175^a,^1^,*	0.157	0.161	0.156^b	0.155^b	0.166^a
Egg PC^§ (µg/g)
0 wk	0.138	0.137	0.140	0.129	0.129	0.128	0.141^2	0.135	0.132	0.133	0.134	0.135	0.0020
3 wk	0.140	0.139	0.137	0.135	0.134	0.134	0.143^2	0.137	0.137	0.137	0.135	0.139
6 wk	0.142	0.142	0.144	0.144	0.138	0.137	0.140^2	0.143	0.138	0.140	0.140	0.142
9 wk	0.138	0.142	0.143	0.144	0.143	0.142	0.148^12	0.143	0.145	0.142	0.143	0.146
12 wk	0.143	0.144^b	0.142^b	0.143^b	0.144^b	0.143^b	0.159^a,^1^,*	0.143	0.148	0.144	0.143	0.151

^a–eIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–3In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD: calcium iodate; ^‡EDDI: ethylenediamine dihydroiodide; ^¶Serum obtained from 18 birds per treatment (3 per replicate) and all eggs laid in the last 3 d of each period were used for individual analysis; ^#SEM: standard error of LSmeans; ^▼SOD: superoxide dismutase; ^¶MDA: malondialdehyde; ^§PC: protein carbonyl; wk: week; d: day.

Table 10. Effects of dietary treatments on iodine contents in egg compartments (29–42 wk of age).

Item^¶	Dietary treatments							Main effects
		Iodine as CIOD^† (mg/kg)			Iodine as EDDI^‡ (mg/kg)			Iodine source		Iodine level (mg/kg)			Pooled SEM^#
	Control	2.0	4.0	8.0	2.0	4.0	8.0	CIOD^†	EDDI^‡	2.0	4.0	8.0
Yolk iodine (µg/g)
0 wk	0.507	0.499^3	0.500^5	0.506^5	0.510^4	0.532^5	0.521^5	0.502	0.521	0.505	0.516	0.513	0.0162
3 wk	0.493	0.524^e,^3	0.606^d,^4^,*	0.804^b,^4^,*	0.596^d,^3^,*	0.688^c,^4^,*	0.965^a,^4^,*	0.645^b	0.750^a	0.560^c	0.647^b	0.884^a
6 wk	0.472	0.640^e,^2^,*	0.751^d,^3^,*	0.940^b,^3^,*	0.704^d,^2^,*	0.850^c,^3^,*	1.174^a,^3^,*	0.777^b	0.909^a	0.672^c	0.800^b	1.057^a
9 wk	0.449	0.689^e,^12^,*	0.819^d,^2^,*	1.311^b,^2^,*	0.765^d,^2^,*	1.078^c,^2^,*	1.477^a,^2^,*	0.940^b	1.107^a	0.727^c	0.949^b	1.394^a
12 wk	0.404	0.733^e,^1^,*	0.968^d,^1^,*	1.559^b,^1^,*	0.903^d,^1^,*	1.163^c,^1^,*	1.676^a,^1^,*	1.087^b	1.248^a	0.818^c	1.065^b	1.618^a
Albumen iodine (µg/g)
0 wk	0.104	0.100^4	0.101^3	0.103^5	0.102^3	0.104^5	0.099^5	0.101	0.102	0.101	0.103	0.101	0.0024
3 wk	0.103	0.105^d,^34^,*	0.109 ^cd,^3^,*	0.128^b,^4^,*	0.108^d,^3^,*	0.114^c,^4^,*	0.143^a,^4^,*	0.114^b	0.122^a	0.107^c	0.112^b	0.136^a
6 wk	0.101	0.112^e,^23^,*	0.124^d,^2^,*	0.170^b,^3^,*	0.121^d,^2^,*	0.138^c,^3^,*	0.210^a,^3^,*	0.135^b	0.156^a	0.117^c	0.131^b	0.190^a
9 wk	0.100	0.121^e,^12^,*	0.135^d,^2^,*	0.227^b,^2^,*	0.131^d,^2^,*	0.152^c,^2^,*	0.256^a,^2^,*	0.161^b	0.180^a	0.127^c	0.144^b	0.241^a
12 wk	0.098	0.128^e,^1^,*	0.155^d,^1^,*	0.255^b,^1^,*	0.147^d,^1^,*	0.173^c,^1^,*	0.297^a,^1^,*	0.179^b	0.206^a	0.137^c	0.164^b	0.276^a
Shell iodine (µg/g)
0 wk	16.468	16.487^3	16.500^4	16.451^5	16.251^4	16.035^5	16.602^5	16.479	16.296	16.369	16.268	16.527	0.4514
3 wk	16.289	18.479^e,^3^,*	21.750^d,^3^,*	30.612^b,^4^,*	20.489^d,^3^,*	24.530^c,^4^,*	33.592^a,^4^,*	23.614^b	26.204^a	19.484^c	23.140^b	32.102^a
6 wk	16.093	21.551^e,^2^,*	25.503^d,^2^,*	35.474^b,^3^,*	24.704^d,^2^,*	28.180^c,^3^,*	38.899^a,^3^,*	27.509^b	30.594^a	23.128^c	26.842^b	37.187^a
9 wk	15.953	23.530^e,^12^,*	27.658^d,^2^,*	39.545^b,^2^,*	26.259^d,^2^,*	31.107^c,^2^,*	42.427^a,^2^,*	30.244^b	33.264^a	24.895^c	29.383^b	40.986^a
12 wk	15.714	25.512^e,^1^,*	30.644^d,^1^,*	43.849^b,^1^,*	29.900^d,^1^,*	34.067^c,^1^,*	48.034^a,^1^,*	33.335^b	37.434^a	27.706^c	32.506^b	45.941^a

^a–eIn each row within each time period LSmeans with different superscripts are significantly different (p < .05); ^1–5In each column within each dietary treatment LSmeans with different superscripts are significantly different (p < .05); *In each row within each time period LSmeans with an asterisk indicates a significant difference from control (p < .05); ^†CIOD, calcium iodate; ^‡EDDI, ethylenediamine dihydroiodide; ^¶Eggs laid in the last 3 d of each period were used for individual analysis; ^#SEM: standard error of LSmeans; wk: week; d: day.

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