Effects of stocking density on performance, egg quality, reproductive hormones, and antioxidant capacity in egg-laying ducks

Figures & data

Table 1. Ingredients and nutrient composition of experimental diet (as-fed basis).

Items	Experimental diet
Ingredients (%)
Corn	35.97
Corn starch	16.80
Wheat bran	10.00
Soybean meal	10.00
Peanut meal	16.00
Limestone	8.48
Calcium hydrogen phosphate	1.20
Sodium chloride	0.30
Premix^a	1.00
L-Lys•HCl (98.5%)	0.22
DL-Met (99%)	0.03
Total	100.00
Calculated nutritional value
Metabolic energy (MJ/kg)	10.46
Crude protein (%)	17.17
Ca (%)	3.60
Total P (%)	0.56
Available P (%)	0.35
Lys (%)	0.85
Met (%)	0.51
Met + Cys (%)	0.86

^aThe premix provided per kilogram diet: vitamin A, 3.96 mg; vitamin D₃, 0.066 mg; vitamin E, 20 mg; vitamin K₃, 2.75 mg; vitamin B₁, 4.4 mg; vitamin B₂, 9.0 mg; vitamin B₆, 4.4 mg; vitamin B₁₂, 0.02 mg; choline, 500 mg; nicotinic acid, 30 mg; pantothenic acid, 22 mg; folic acid, 1.1 mg; biotin, 0.22 mg; Fe, 60 mg; Cu, 8.0 mg; Mn, 100 mg; Zn, 90 mg; iodine, 0.5 mg; Se, 0.2 mg; Co, 0.26 mg.

Table 2. Effects of stocking density on egg production performance (20–40 weeks) of laying ducks.

Item	Stocking density (birds/m^2)					SEM^2	P-value
	4	5	6	7	8		SD^3	Linear	Quadratic
Egg production (%)	88.07^a	85.18^a,b	80.61^b,c	76.04^c	67.14^d	1.246	<0.001	<0.001	0.015
Egg weight (g)	65.46	64.61	64.64	65.60	65.46	0.736	0.784	0.673	0.405
Egg mass (g/d)	57.67^a	55.03^a,b	52.13^b,c	49.86^c	43.96^d	1.030	<0.001	<0.001	0.135
Feed intake (g/d)	163.35^a,b	170.75^a	157.39^b	162.15^a,b	148.00^c	2.235	<0.001	<0.001	0.005
FCR^1	2.84^c	3.11^a,b,c	3.03^b,c	3.25^a,b	3.38^a	0.067	<0.001	<0.001	0.988

¹FCR, feed/egg conversion ratio.

²SEM, standard error of means, n = 8.

³SD, stocking density.

^a–dMean values within the same row with different superscripts differ significantly (P < 0.05).

Table 3. Effects of stocking density on egg components and quality of laying ducks during the laying period from 20 to 40 weeks of age.

Item	Stocking density (birds/m^2)					SEM^1	P-value
	4	5	6	7	8		SD^2	Linear	Quadratic
Egg weight (g)	64.35	64.71	64.68	65.05	64.82	0.541	0.927	0.460	0.706
Yolk weight (g)	19.38	19.24	19.82	19.51	19.67	0.224	0.393	0.241	0.729
Albumen weight (g)	36.97	37.69	36.99	37.77	37.42	0.507	0.704	0.551	0.727
Eggshell weight (g)	8.00	7.78	7.87	7.77	7.73	0.107	0.434	0.119	0.659
Yolk (%)	30.13	29.73	30.68	30.00	30.35	0.375	0.468	0.558	0.930
Albumen (%)	57.43	58.25	57.16	58.05	57.72	0.412	0.344	0.778	0.843
Eggshell (%)	12.44	12.02	12.16	11.95	11.93	0.171	0.239	0.056	0.511
Egg shape index	1.38	1.36	1.37	1.43	1.36	0.023	0.189	0.681	0.603
Eggshell strength (N)	53.41^a	52.22^a,b	54.14^a	51.45^a,b	48.77^b	0.975	0.005	0.003	0.045
Eggshell thickness (mm)	39.66^a,b	40.30^a	40.09^a	38.54^b,c	38.18^c	0.318	<0.001	<0.001	0.008
Albumen height (mm)	6.10	5.87	6.20	5.99	5.97	0.129	0.443	0.737	0.845
Yolk colour	4.85	4.76	4.84	4.79	4.81	0.096	0.963	0.847	0.795
Haugh unit	75.36	72.49	75.61	73.51	75.55	1.087	0.169	0.685	0.266

¹SEM, standard error of means, n = 8.

²SD, stocking density.

^a–cMean values within the same row with different superscripts differ significantly (P < 0.05).

Table 4. Effects of stocking density on plasma reproductive hormones concentrations of laying ducks.

Item	Stocking density (birds/m^2)					SEM^1	P-value
	4	5	6	7	8		SD^2	Linear	Quadratic
E2 (pg/mL)	193.44	159.81	125.93	120.85	108.34	25.070	0.131	0.012	0.454
LH (mIU/mL)	2.22	1.96	2.18	2.06	1.75	0.281	0.774	0.360	0.674
FSH (mIU/mL)	4.32^a	3.67^a,b	3.63^a,b	2.56^a,b	2.08^b	0.501	0.022	0.001	0.720
Progesterone (pg/mL)	408.55	398.61	366.74	361.07	323.03	34.913	0.452	0.067	0.820

E2, estradiol-17β; LH, luteinizing hormone; FSH, follicle-stimulating hormone.

¹SEM, standard error of means, n = 8.

²SD, stocking density.

^a,bMean values within the same row with different superscripts differ significantly (P < 0.05).

Table 5. Effects of stocking density on antioxidant indices in plasma and liver.

Item	Stocking density (birds/m^2)					SEM^1	P-value
	4	5	6	7	8		SD^2	Linear	Quadratic
Plasma
SOD (U/mL)	165.09^a	154.94^a,b	153.55^a,b	145.01^a,b	132.12^b	7.062	0.029	0.002	0.636
GSH-Px (U/mL)	381.18^a	369.82^a,b	361.11^a,b	341.07^a,b	291.63^b	19.663	0.024	0.002	0.242
T-AOC (U/mL)	13.26	11.68	11.32	9.39	7.13	1.697	0.127	0.010	0.648
MDA (nmol/mL)	11.05^b	11.55^b	13.09^a,b	13.10^a,b	16.86^a	0.991	0.002	<0.001	0.188
Liver
SOD (U/mg prot)	183.34	188.60	185.68	178.77	164.17	16.447	0.848	0.361	0.482
GSH-Px (U/mg prot)	69.62	70.03	67.49	65.73	55.00	6.018	0.397	0.087	0.347
T-AOC (U/mg prot)	1.15	0.81	0.81	0.84	0.74	0.133	0.236	0.072	0.297
MDA (nmol/mg prot)	0.68^b	0.81^a,b	0.88^a,b	0.95^a,b	1.02^a	0.080	0.049	0.003	0.758

SOD, superoxide dismutase; GSH-Px, glutathione peroxidase; T-AOC, total antioxidant capacity; MDA, malondialdehyde.

¹SEM, standard error of means, n = 8.

²SD, stocking density.

^a,bMean values within the same row with different superscripts differ significantly (P < 0.05).