Effects of cyclic heat stress on the phenotypic response, meat quality and muscle glycolysis of breasts and thighs of yellow-feather broilers

Figures & data

Figure 1. Illustration of thermal application in the cyclic heat stress treatment.

Table 1. Composition and nutrient levels of experimental diets (air-dry basis, %).

Items	Content	Items	Content
Ingredients		Composition^c
Corn	63.00	ME, MJ/kg	13.04
Soybean meal	26.20	CP	18.23
Corn gluten meal	3.70	Calcium	0.82
Soybean oil	3.30	Available phosphorus	0.35
Limestone	1.57	Lysine	1.18
CaHPO4	1.11	Methionine	0.43
DL-Met	0.15	Threonine	0.69
70% Lys	0.26	Arginine	1.10
NaCl	0.30
50% Choline chloride	0.10
Phytase	0.04
Trace element^a	0.20
Vitamin^b	0.03
Thr	0.04
Total	100.00

^a Trace element for broiler provided per kg of diet: manganese sulphate, 110 mg; zinc oxide, 65 mg; iron sulphate, 82 mg; copper sulphate, 7.6 mg; iodine, 1.1 mg and selenium, 0.3 mg.

^b Vitamin for broilers provided per kilogram of diet: vitamin A, 24 mg; vitamin D3, 6 mg; vitamin E, 11 mg, vitamin K3, 1.3 mg; thiamine, 2.21 mg; riboflavin, 7.8 mg; niacin, 40 mg; pantothenic acid, 16.5 mg; biotin, 0.11 mg; folic acid, 1.2 mg; vitamin B12, 0.015 mg.

^c The nutrient levels in this table are calculated values.

Figure 2. The effects of 7 days of constant thermoneutral conditions (TN) or heat stress conditions (CHS) on (A) rectal temperature and (B) respiration rates. (A) *p < .001, n = 6/treatment; (B) *p < .001, n = 6/treatment.

Table 2. Effects of cyclic heat stress on growth performance of broilers.

Variable	Environment^a
	TN	CHS	p value
Body weight, g	859.22 ± 7.43	797.89 ± 10.80	.001
Average daily gain, g	34.61 ± 0.62	23.33 ± 1.09	<.001
Average daily feed intake, g	80.18 ± 0.69	63.64 ± 1.23	<.001
Feed conversion ratio	2.32 ± 0.05	2.75 ± 0.09	.002

^a TN: thermal neutral (23 °C and 55–60% RH); CHS: heat stress conditions (cyclic temperature of 35 °C from 10:00 to 18:00, 32 °C from 18:00 to 20:00, 28 °C from 20:00 to 08:00, and 32 °C from 08:00 to 10:00 at 40–45% RH).

Table 3. Effects of cyclic heat stress on weight, chemical composition of broiler breast and thigh meat (n = 6).

Variable	Environment^a		p value
	TN	CHS
Breast
Weight^b, g	45.50 ± 1.33	39.59 ± 1.28	.009
Moisture, %	74.51 ± 0.15	75.00 ± 0.13	.047
Protein, %	24.17 ± 0.10	24.01 ± 0.14	.378
Fat, %	0.36 ± 0.05	0.42 ± 0.06	.475
Thigh
Weight^2, g	66.86 ± 0.98	55.57 ± 2.08	.001
Moisture, %	76.03 ± 0.43	75.85 ± 0.34	.755
Protein, %	22.14 ± 0.12	21.99 ± 0.27	.628
Fat, %	1.26 ± 0.07	1.16 ± 0.10	.476

^a TN: thermal neutral (23 °C and 55–60% RH); CHS: heat stress conditions (cyclic temperature of 35 °C from 10:00 to 18:00, 32 °C from 18:00 to 20:00, 28 °C from 20:00 to 08:00, and 32 °C from 08:00 to 10:00 at 40–45% RH).

^b Breast weight or thigh weight from one side of broilers.

Table 4. Effects of cyclic heat stress on physico*chemical characteristics of broiler breast and thigh meat (n = 6).

Variable	Environment^a		p value
	TN	CHS
Breast
pH	5.85 ± 0.14	5.71 ± 0.10	.433
L* value^b	53.29 ± 0.66	55.54 ± 0.51	.022
a* value^b	2.30 ± 0.24	1.29 ± 0.43	.094
b* value^b	12.93 ± 0.63	11.60 ± 0.86	.240
Water-holding capacity, %	72.70 ± 1.33	67.65 ± 2.39	.095
Shear force (N)	12.54 ± 2.16	12.62 ± 1.11	.975
Thigh
pH	5.87 ± 0.10	5.85 ± 0.07	.853
L* value^b	49.22 ± 0.78	52.83 ± 0.80	.009
a* value^b	13.53 ± 0.46	12.28 ± 0.74	.182
b* value^b	12.11 ± 0.25	12.33 ± 0.29	.575
Water-holding capacity, %	78.04 ± 1.51	79.37 ± 0.81	.457
Shear force (N)	22.16 ± 0.89	23.94 ± 0.70	.444

^a TN: thermal neutral (23 °C and 55–60% RH); CHS: heat stress conditions (cyclic temperature of 35 °C from 10:00 to 18:00, 32 °C from 18:00 to 20:00, 28 °C from 20:00 to 08:00, 32 °C from 08:00 to 10:00 at 40–45% RH).

^b L*: lightness; a*: redness; b*: yellowness.

Table 5. Effects of cyclic heat stress on activity of three key enzymes in glycolysis (LDH: lactic dehydrogenase; PK: pyruvate kinase; HK: hexokinase) and lactic acid (LD) content of broiler breast and thigh meat (n = 6).

Variable	Environment^a		p value
	TN	CHS
Breast
LDH, U/g protein	11,401.36 ± 1176.44	11,711.22 ± 1255.23	.861
PK, U/g protein	231.71 ± 24.10	242.68 ± 37.69	.811
HK, U/g protein	3.03 ± 0.86	2.20 ± 0.50	.426
LD, mmol/g protein	0.18 ± 0.01	0.18 ± 0.02	.911
Thigh
LDH, U/g protein	24,278.11 ± 2454.52	25,498.59 ± 2716.74	.746
PK, U/g protein	602.37 ± 54.17	678.51 ± 65.12	.390
HK, U/g protein	1.61 ± 0.37	3.40 ± 0.48	.014
LD, mmol/g protein	0.33 ± 0.04	0.37 ± 0.05	.595

^a TN: thermal neutral (23 °C and 55–60% RH); CHS: heat stress conditions (cyclic temperature of 35 °C from 10:00 to 18:00, 32 °C from 18:00 to 20:00, 28 °C from 20:00 to 08:00, and 32 °C from 08:00 to 10:00 at 40–45% RH).

Alberle ED, Forrest JC, Gerrard DE, Mills EW. 2001. Principles of Meat Science. 4th ed. Dubuque, IA: Kendall/Hunt Publ. Co.

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