Novel insights into heat tolerance: the impact of dwarf and frizzled feather traits on crossbreed chicken performance under thermal stress

Figures & data

Table 1. Diet composition and its nutritional values given to experimental birds.

Ingredients, %	Feed composition and nutritional values
	1–35 days	36–91 days
Corn	61.20	66.80
Soybean meal	28.39	22.96
Peanut cake	6.00	6.00
CaCO3	1.05	0.85
NaCl	0.35	0.36
Premix	1.25	1.25
Total	100.00	100.00
Nutritional values
Metabolic energy, MJ/kg	11.60	11.98
Crude protein, %	20.00	16.50
Crude fibre, %	6.00	6.00
Calcium, %	1.00	0.90
Total phosphorus, %	0.4–0.6	0.4–0.6
Crude ash, %	7.00	9.00
Methionine, %	0.45–0.7	0.45–0.7

Moisture content was not more than 13%. Premix provided the following per kilogram of diet: iron (Fe) 95 mg; zinc (Zn) 75 mg; manganese (Mn) 75 mg; copper (Cu) 10 mg; iodide 0.6 mg; selenium 0.3 mg; vitamin A 6000 IU; vitamin D 1250 IU; vitamin E 15 mg; vitamin K 2.2 mg; vitamin B1 1.5 mg; vitamin B2 8.0 mg; vitamin B6 2.5 mg; vitamin B12 0.011 mg; niacin 44 mg; d-pantothenic acid 11 mg; folic acid 0.9 mg; biotin 0.11 mg; choline 1100 mg.

Table 2. Gene primer sequences for quantitative RT-PCR.

Genes	Primer sequence (5′ to 3′)	Annealing temperature (°C)	Product length (bp)
HSP90	F: TGACCTTGTCAACAATCTTGGTACTAT R: CCTGCAGTGCTTCCATGAAA	56	68
HSP70	F: GCGCCAGGCCACCAAAGATG R: GCCCCCTCCCAAGTCAAAGATG	58	154
GHR	F: CAAGGTGGGAAGAGCACAGT R: TCCATACTTGGGGTTTCTGC	56	122
IGF-1	F: ACCTTGGCCTGTGTTTGCTTAC R: AGCCTCTGTCTCCACATACGAAC	58	111
IGF-1R	F: CAGGAACGATGGAGGAGAAG R: ACGCAAGCAGTGTTGTTGTC	58	154
GAPDH	F: GAGGGTAGTGAAGGCTGCTG R: CATCAAAGGTGGAGGAATGG	57	113
IL-4	F: GCTCTCAGTGCCGCTGATG R: GGAAACCTCTCCCTGGATGTC	58	68
IL-6	F: AGGACGAGATGTGCAAGAAGTTC R: TTGGGCAGGTTGAGGTTGTT	57	221
IL-10	F: CAGACCAGCACCAGTCATCA R: TCCCGTTCTCATCCATCTTCTC	57	163
IL-1β	F: GGAGGTTTTTGAGCCCGTC R: TCGAAGATGTCGAAGGACTG	55	204
SOD	F: AGGGGGTCATCCACTTCC R: CCCATTTGTGTTGTCTCCAA	54	122
CAT	F: GGGGAGCTGTTTACTGCAAG R: CTTCCATTGGCTATGGCATT	55	131

HSP70: heat shock protein 70; HSP90: heat shock protein 90; FASN: fatty acid synthase; ACC: acetyl-CoA carboxylase; GHR: growth hormone receptor; IGF-1: insulin growth factor-1; IGF-1R: insulin growth factor-1 receptor; IL-4: interleukin-4; IL-6: interleukine-6; IL-10: interleukin-10; IL-1 β: interleukine-1 β, SOD: superoxide dismutase; CAT: catalase; GAPDH: glyceraldehyde 3-phosphate dehydrogenase (Kim et al. 2020).

Table 3. Feed consumption and growth performance of crossbreed after seven-day heat stress (HS).

Parameters	Treatments		SEM	p Value
	CN	HS
Performance parameters
Weight gain ratio, %	7.39	4.54	0.47	.01
Feed intake, g/chicken/d	40.16	35.113	7.40	.15
Live weight, initial, g	560.26	556.41	9.87	.54
Live weight, final, g	601.66	581.67	13.09	.63
Protein efficiency ratio	1.11	0.90	0.04	.01
Total protein intake/day, g/d	6.95	5.69	11.36	.00
Body organ index
Liver, %	2.21	2.30	0.06	.57
Spleen, %	0.28	0.30	0.02	.23
Pectoral, %	10.50	10.14	0.14	.21
Thigh, %	11.85	12.07	0.21	.64

Different meat quality parameters were investigated under heat stress (HS) and control group (CN). Student’s t-test was performed to analyse the effect of heat stress on each chicken strain separately. p < .05 was considered as significant difference. All data were presented as mean values (n = 6). All the values used to calculate the weight gain ratio and protein efficiency ratio were measured in grams (g). Following formulas were used to calculate feed intake, weight gain ratio and protein efficiency ratio: feed intake (g/chicken/d) = feed consumed (g)/total number of birds/total days of experiment. Protein efficiency ratio = chicken weight gain (g)/total protein intake (g). Weight gain ratio (%) = (final body weight (g) – initial body weight (g))/initial body weight (g) × 100%. Weight index of different organs was measured after seven days of heat stress. All the measurements for different body organs were taken in grams (g). Following formula was used to calculate body organ index: body organ index (%) = organ weight (g)/total carcass weight (g) × 100%.

Figure 1. Histological effect induced by heat stress (HS) on the liver and spleen of crossbreed. Magnification was 20×, and scale denotes 50 μm. Control groups illustrate WP (white pulp), RP (red pulp) and CA (central artery) in spleen (a1) and the central vein (CV), sinusoidal cells (S) and hepatocytes in liver (b1). Panels a2–a4 and b2–b4 are HS groups of spleen and liver tissues, respectively. For histological comparison, different shapes were used to depict the pathological changes. Spleen (a2–a4): (

) indicates the consumption of mild inflammatory cells, (

) represents mild vacuole degeneration, (

) shows red blood cell hyperplasia, (

) shows degeneration of red and white pulp. Liver (b2–b4): b2 depicts tissue inflammation with mononuclear cell infiltration (

) and vacuolar degeneration (

); b3 shows dilated CV with mild hyperplasia (

), tissue haemorrhages with necrosis (

) and mild inflammatory cells infiltration (

); b4 shows dilation in portal area with red blood cells hyperplasia (

), mononuclear cell infiltration (

) and vacuolar degeneration (

).

Figure 2. Relative mRNA expression levels of somatotropic genes related to muscle growth and heat shock proteins in liver and pectoralis major muscle tissues isolated after seven days of heat stress (HS). X-axis represents the treatments (HS or CN) and respective genes, while Y-axis shows the relative mRNA expression level. Relative mRNA expression of growth hormone receptor (GHR), insulin growth factor-1 (IGF-1) and its receptor (IGF-1R) in liver (a) and pectoral muscles (b). Relative mRNA expression of HSP70 and HSP90 in liver (c), pectoral muscle (d) and hypothalamus (e). Significant difference at (p < .01) is shown with **, while * depicts significant difference of p < .05. CN and HS represent control group and heat stress group, respectively.

Figure 3. Effect of heat stress (HS) on antioxidant and immune status of crossbreed chicken. Relative mRNA expression levels of superoxide dismutase (SOD) and catalase (CAT) in liver (a) and in pectoral muscle (b). Relative mRNA expression levels of IL-4, IL-6 (c), IL-10 and IL-1β (d) in hepatic tissues. *Significant difference at p < .05. CN and HS represent control group and heat stress group, respectively.

Table 4. Effect of heat stress on meat colour parameters after seven days of heat stress.

Parameters	Treatments		SEM	p Value
	CN	HS
Pectoral muscle
L*-value	41.54	42.53	1.06	.41
a*-value	0.32	0.43	0.15	.70
b*-value	4.83	5.77	0.58	.10
Thigh muscle
L*-value	45.62	46.51	0.73	.28
a*-value	2.84	1.98	0.35	.04
b*-value	3.89	4.88	0.86	.27

Different meat colour parameters were investigated under heat stress (HS) and control group (CN). Student’s t-test was performed to analyse the effect of heat stress on each chicken strain separately. p < .05 was considered as significant difference. All data were presented as mean values (n = 6).

Table 5. Effect of heat stress on drip loss, cook loss, water holding capacity, and shear force of pectoral and thigh muscle after seven days of heat stress.

Parameters	Treatments		SEM	p Value
	CN	HS
Pectoral muscle
Drip loss, %	2.09	2.50	0.66	.47
Cook loss, %	17.37	19.42	4.56	.58
Water loss, %	11.04	10.95	1.60	.94
Shear force, %	24.37	37.28	5.67	.04
Thigh muscle
Drip loss, %	1.54	1.96	0.35	.33
Cook loss, %	15.82	17.73	2.61	.14
Water loss, %	10.17	9.27	2.77	.64
Shear force, %	23.75	29.52	3.20	.05

Different meat quality parameters were investigated under heat stress (HS) and control group (CN). Student’s t-test was performed to analyse the effect of heat stress on each chicken strain separately. p < .05 was considered as significant difference. All data were presented as mean values (n = 6).

Kim WS, Ghassemi Nejad J, Peng DQ, Jung US, Kim MJ, Jo YH, Jo JH, Lee JS, Lee HG. 2020. Identification of heat shock protein gene expression in hair follicles as a novel indicator of heat stress in beef calves. Animal. 14(7):1502–1509. doi: 10.1017/S1751731120000075.

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Data availability statement

No new data were created in this study.