Effects of dietary supplemented of γ-amino butyric acid on growth performance, blood biochemical indices and intestinal morphology of yellow-feathered broilers exposed to a high temperature environment

Figures & data

Table 1. Composition and nutrient levels of the basal diet (air dry basis).

Ingredients	Content (%)
Corn	65.40
Soybean meal (43%)	22.63
Corn protein meal	5.00
Soybean oil	3.30
Limestone	1.23
CaHPO4	0.97
DL-Met	0.13
Lys (65%)	0.39
NaCl	0.30
Choline chloride	0.30
Chlortetracycline	0.10
Mineral Premix^a	0.20
Vitamin Premix^b	0.03
Thr (98%)	0.02
Total	100.00
Nutrient levels (g/kg)^c
ME(kcal/kg)	3200
CP (g/kg)	172.10
Ca (g/kg)	7.70
Total phosphorus (g/kg)	5.60
Non phytate phosphorous (g/kg)	3.50
SID Lys^d (g/kg)	10.30
SID Met + Cys^e (g/kg)	5.30

^aThe mineral premix provided the following per kg of diet：Mn 120 mg, Fe 80 mg, Cu 16 mg, Zn 110 mg, Se 0.3 mg, I 1.5 mg and Co 0.5 mg.

^bThe vitamin premix provided the following per kg of diet: Vitamin A (retinyl acetate) 15,000 IU; Vitamin D (cholecalciferol) 3,600 IU; Vitamin E (DL-tocopheryl acetate) 30 IU; Vitamin K 3.0 mg; Vitamin B1 2.70 mg; Vitamin B2 9.60 mg; nicotinic acid 45 mg; Vitamin B6 0.15 mg; folic acid 1.50 mg; and Vitamin B12 0.03 mg.

^cMetabolisable energy and SID amino acid were calculated, whereas all other values were analysed. Nutritive levels obtained from Analysis of Nutritional Value of Feed Ingredients in China (Evonik Industries AG, 2017).

^dSID Lys = Standard ileum digestible Lys.

^eSID Met + Cys = Standard ileum digestible Met and Cys.

Table 2. Effects of dietary supplemented of GABA on the growth performance of yellow-feathered broilers exposed to a high temperature environment from 36–49 d of age.

Items	Groups		SEM	p Value
	Control group	GABA group
36d BW (g/bird)	955	903	3.5	.104
49d BW (g/bird)	1145^b	1218^a	15.3	.015
ADG (g/d/bird)	14^b	22^a	1.9	.004
ADFI (g/d/bird)	51^b	72^a	2.2	.003
F/G^c	3.7^a	3.2^b	0.84	.023
Mortality (%)^d	29^a (21/72)	10^b (7/72)	3.6	.042

^a,bIn the same row, values with different superscripts indicate significant difference (p < .05), and N = 6.

^cF/G = feed: gain ratio in survival broilers.

^dThe number in parentheses indicates the number of dead broilers/total broilers.

BW: body weight; ADG: average daily gain; ADFI: average daily feed intake.

Table 3. Effects of dietary supplemented of GABA on blood biochemical indices of yellow-feathered broilers exposed to a high temperature environment from 36–49 d of age.

Items^c	Groups		SEM	p Value
	Control group	GABA group
GLU (mmol/L)	13.3^a	11.6^b	0.27	.016
TG (mmol/L)	0.44	0.67	0.055	.141
HDL (mmol/L)	1.85	1.72	0.070	.503
LDL (mmol/L)	0.87^a	0.63^b	0.034	.001
T-CHO (mmol/L)	3.8^a	3.0^b	0.11	.001

^a,bIn the same row, values with different superscripts indicate significant difference (p < .05), and n = 6.

^cGLU: glucose; TG: triglyceride; HDL: high density lipoprotein; LDL: low density lipoprotein; T-CHO: total cholesterol.

Table 4. Effects of dietary supplemented of GABA on the activities of serum enzymes of yellow-feathered broilers exposed to a high temperature environment from 36–49 d of age.

Items^c	Groups		SEM	p Value
	Control group	GABA group
ALT (U/L)	2.9	3.1	0.27	.596
AST (U/L)	361^a	270^b	16.4	.008
GGT (U/L)	21.9	21.1	0.64	.666
LDH (U/L)	1680^a	1276^b	45.8	.042
CK (U/L)	5105^a	2344^b	66.3	.032

^a,bIn the same row, values with different superscripts indicate significant difference (p < .05), and n = 6.

^cALT: alanine-amino transferase; AST: aspartate-aminotransferase; CK: Creatine kinase; GGT: γ-glutamyl transferase; LDH: lactate dehydrogenase.

Figure 1. Jejunum mucosal morphology of yellow-feathered broilers exposed to a high temperature environment. C: control group; GABA: GABA group.

Figure 2. Ileum mucosal morphology of yellow-feathered broilers exposed to a high temperature environment. C: control group; GABA: GABA group. The longer villi in the jejunum (Figure 1) and ileum (Figure 2) of GABA group as compared to the control group. Besides, it was obvious that the villi in the GABA group was arranged more tightly than that in the control group, which might increase the amount of villi or the area of absorption.

Table 5. Effects of dietary supplemented of GABA on the intestinal morphology of yellow-feathered broilers exposed to a high temperature environment from 36–49 d of age.

Intestinal Section	Items^c	Groups		SEM	P-value
		Control group	GABA group
Jejunum	Villus length (um)	1373^b	1600^a	62.1	0.016
	Crypt depth (um)	225	239	8.6	0.164
	V/C^c	6.1	6.2	0.25	0.952
Ileum	Villus length (um)	864	1004	23.8	0.057
	Crypt depth (um)	256	250	17.6	0.891
	V/C	3.7	4.0	0.32	0.073

^a,bIn the same row, values with different superscripts indicate significant difference (p < .05), and n = 6.

^cV/C = villus length: crypt depth ratio.