Dietary glutamine improves meat quality, skeletal muscle antioxidant capacity and glutamine metabolism in broilers under acute heat stress

Figures & data

Table 1. Ingredients and composition of diets (g/kg, as-fed basis).

Ingredients	g/kg	Chemical composition
Ground yellow maize	567.6	AME^b (MJ/kg)	12.46
Maize starch	10.0	Lysine	11.6
Soybean meal	360.0	Methionine	4.4
Soybean oil	35.0	Methionine + cystine	7.7
Dicalcium phosphate	11.0	Available phosphorus	3.8
Ground limestone	10.5	Crude protein	203.7
Iodized salt	3.0	Calcium	8.8
DL-Methionine	1.0
Micronutrients^a	1.9
Total	1000

^aProvided per kilogram of diet: Vitamin A (as all-trans retinol acetate), 10,000 IU; Vitamin B₆, 3.0 mg; Vitamin K (as menadione sodium bisulphate), 2.0 mg; Vitamin E (as all-rac-α-tocopherol acetate), 20 IU; cholecalciferol, 2600 IU; Vitamin B₁₂, 0.014 mg; riboflavin, 6.0 mg; thiamine (as thiamin mononitrate), 1.6 mg; calcium pantothenate, 20 mg; iron (from iron sulphate), 80 mg; selenium (from sodium selenite), 0.15 mg; niacin, 30 mg; copper (from copper sulphate), 8 mg; folic acid, 0.8 mg; zinc (from zinc sulphate), 40 mg; iodine (from potassium iodide), 0.35 mg; choline (as choline chloride), 500 mg; biotin, 0.12 mg.

^bAME = apparent metabolizable energy

Table 2. Effects of dietary Gln on breast and thigh meat quality in broilers under acute heat stress¹.

Item	Normal temperature	Acute heat stress
	Control	0 g/kg Gln^2	5 g/kg Gln^2	15 g/kg Gln^2	20 g/kg Gln^2	SEM^3
	Breast
pH24h	5.93c	5.69a	5.70ab	5.75ab	5.85bc	0.057
CL^4 (%)	40.6b	44.6a	43.1ab	42.6ab	40.7b	1.28
DL^4 (%)	3.83	5.36	4.90	4.56	4.27	0.800
WHC^C (%)	76.6a	71.9b	74.8ab	76.4a	76.2a	1.24
L*(lightness)	52.17b	57.80a	54.29ab	53.51b	53.09b	1.429
a*(redness)	6.01	5.48	5.50	5.68	5.98	0.523
b*(yellowness)	10.71a	9.02b	10.15ab	10.29ab	10.60a	0.532
	Thigh
pH24h	6.30b	5.94a	6.03ab	6.11ab	6.29b	0.107
CL^4 (%)	44.5b	49.4a	47.7ab	45.6b	44.2b	1.28
DL^4 (%)	3.63	4.51	4.48	4.31	4.04	0.712
WHC^4 (%)	76.7a	71.8b	73.4ab	76.1a	76.9a	1.44
L*(lightness)	58.41b	62.07a	60.67ab	59.13ab	58.91ab	1.206
a*(redness)	5.02	4.11	4.30	4.60	4.87	0.658
b*(yellowness)	6.32	5.62	5.74	6.08	6.23	1.08

a, b, c – The ‘a,b,c’ footnote implies that rows of means with no letters following them are all significantly (p < 0.05) different as they have ‘no common letters’.

¹There were six replicates per group of 10 birds; A chick from each replicate was randomly selected for sampling (n = 6).

²Gln = glutamine.

³SEM = standard error of the mean.

⁴The muscles were stored at 2–4°C (24 h) for meat quality analyses; CL = cooking loss; DL = drip loss; WHC = water-holding capacity: The value was the weight of the sample after pressing as a percentage of the weight before pressing.

Table 3. Effects of dietary Gln on measures of sample texture characteristics in breast and thigh muscles of broilers under acute heat stress¹.

Item	Normal temperature	Acute heat stress
	Control	0 g/kg Gln^2	5 g/kg Gln^2	15 g/kg Gln^2	20 g/kg Gln^2	SEM^3
	Breast
Hardness^4 (g)	1254.17a	989.17b	1227.67ab	1221.58ab	1260.83a	87.214
Springiness^4 (mm)	3.75	3.62	3.74	3.76	3.75	0.195
Gumminess^4(g)	575.42a	503.75b	532.75ab	581.08a	579.08a	24.155
Chewiness^4 (mJ)	21.65	17.30	19.95	21.46	21.55	2.831
Cohesiveness^4	0.46	0.51	0.43	0.48	0.46	0.031
	Thigh
Hardness^4 (g)	1274.17a	950.33b	1143.67ab	1287.50a	1295.33a	110.03
Springiness^4 (mm)	2.33a	2.02b	2.16ab	2.33a	2.31a	0.097
Gumminess^4 (g)	670.33a	497.00b	545.83ab	636.33ab	653.17a	50.128
Chewiness^4 (mJ)	15.07a	10.23b	12.03ab	14.52a	14.22a	1.346
Cohesiveness^C	0.53	0.52	0.48	0.49	0.51	0.026

a, b, c – The ‘a,b,c’ footnote implies that rows of means with no letters following them are all significantly (p < 0.05) different as they have ‘no common letters’.

¹There were six replicates per group of 10 birds; A chick from each replicate was randomly selected for sampling (n = 6).

²Gln = glutamine.

³SEM = standard error of the mean.

⁴Hardness: maximum force required to compress the sample for a compression to 50% of the initial sample heigh; Springiness: recover meat original form after removed external force; Gumminess: the product of hardness and cohesiveness; Chewiness: the energy needed to chew a solid sample to a steady state of swallowing; Cohesiveness: extent to which the sample could be deformed prior to rupture.

Table 4. Effects of dietary Gln on MDA and antioxidant enzymes levels in breast and thigh muscles of broilers under acute heat stress¹.

Item	Normal temperature	Acute heat stress
	Control	0 g/kg Gln^2	5 g/kg Gln^2	15 g/kg Gln^2	20 g/kg Gln^2	SEM^3
	Breast
MDA^4 (nmol/mgprot)	0.34b	0.52a	0.43ab	0.41b	0.42b	0.033
CAT^4 (U/mgprot)	0.08b	0.17ab	0.18ab	0.21a	0.23a	0.044
GSH^4 (mg/gprot)	4.76b	4.95b	5.12b	8.31a	8.04a	0.943
GSH-Px^4 (U/mgprot)	2.13c	6.18bc	12.36ab	13.61a	14.08a	2.303
T-AOC^4 (U/mgprot)	0.25b	0.25b	0.28ab	0.30ab	0.36a	0.034
	Thigh
MDA^4 (nmol/mgprot)	0.45b	0.70a	0.64ab	0.41b	0.46b	0.083
CAT^4 (U/mgprot)	0.17	0.25	0.28	0.31	0.33	0.061
GSH^4 (mg/gprot)	5.31b	6.24b	9.83ab	11.92a	11.99a	1.614
GSH-Px^4 (U/mgprot)	3.61c	4.37bc	9.34ab	9.34ab	10.74a	1.819
T-AOC^4 (U/mgprot)	0.42	0.42	0.46	0.69	0.66	0.104

a, b, c – The ‘a,b,c’ footnote implies that rows of means with no letters following them are all significantly (p < 0.05) different as they have ‘no common letters’.

¹There were six replicates per group of 10 birds; A chick from each replicate was randomly selected for sampling (n = 6).

²Gln = glutamine.

³SEM = standard error of the mean.

⁴MDA = malondialdehyde, CAT = catalase, GSH = glutathione, GSH-Px = glutathione peroxidas, T-AOC = total antioxidant capability.

Table 5. Effects of dietary Gln on Gln, Glu, GLS and GS levels in breast and thigh muscles of broilers under acute heat stress¹.

Item	Normal temperature	Acute heat stress
	Control	0 g/kg Gln^2	5 g/kg Gln^2	15 g/kg Gln^2	20 g/kg Gln^2	SEM^3
	Breast
Gln^2 (mmol/gprot)	0.234b	0.186a	0.200ab	0.214ab	0.23b	0.015
Glu^4 (mmol/gprot)	8.408b	2.931a	5.155ab	6.031ab	6.921b	1.322
GLS^4 (ng/mgprot)	1.656b	1.284a	1.381ab	1.572ab	1.701b	0.100
GS^4 (U/mgprot)	0.348	0.367	0.357	0.349	0.347	0.034
	Thigh
Gln^2(mmol/gprot)	0.390b	0.292a	0.380ab	0.386ab	0.388b	0.033
Glu^4 (mmol/gprot)	15.396b	10.505a	14.704ab	14.937ab	15.417b	2.634
GLS^4 (ng/mgprot)	1.539b	1.130a	1.415ab	1.536b	1.545b	0.125
GS^4 (U/mgprot)	0.457c	0.562a	0.551ab	0.496abc	0.463bc	0.032

a, b, c – The ‘a,b,c’ footnote implies that rows of means with no letters following them are all significantly (p < 0.05) different as they have ‘no common letters’.

¹There were six replicates per group of 10 birds; A chick from each replicate was randomly selected for sampling (n = 6)

²Gln = glutamine.

³SEM = standard error of the mean.

⁴Glu = glutamate, GLS = glutaminase, GS = glutamine synthetase.