Guanidino-Acetic Acid: A Scarce Substance in Biomass That Can Regulate Postmortem Meat Glycolysis of Broilers Subjected to Pre-slaughter Transportation

Abstract

The different substances in biomass can regulate the metabolism and reproduction of broilers. Guanidino-acetic acid (GAA) is a natural feed additive that showed a potential application in dietary for broilers, while its amount is scarce in biomass. The objective of the present study was to investigate the effects of dietary supplemented with GAA on muscle glycolysis of broilers subjected to pre-slaughter transportation. A total of 160 Qiandongnan Xiaoxiang chickens were randomly assigned into three treatments, including a basal control diet without GAA supplementation (80 birds) or supplemented with 600 mg/kg (40 birds) or 1,200 mg/kg (40 birds) GAA for 14 days. At the end of the experiment, the control group was equally divided into two groups, thus resulting in four groups. All birds in the four groups aforementioned were separately treated according to the following protocols: (1) no transport of birds of the control group fed with the basal diet; (2) a 3-h transport of birds of the control group fed with the basal diet; (3) a 3-h transport of birds fed with diets supplemented with 600 mg/kg GAA; and (4) a 3-h transport of birds fed with diets supplemented with 1,200 mg/kg GAA. The results demonstrated that 3-h pre-slaughter transport stress increased corticosterone contents and lowered glucose contents in plasma (P < 0.05), decreased pH_{24 h} (P < 0.05), and resulted in inferior meat quality evidenced by elevating the drip loss, cooking loss, and L^∗ value (P < 0.05). Meanwhile, 3-h pre-slaughter transport stress decreased the contents of Cr and ATP in muscle (P < 0.05) and elevated the ratio of AMP:ATP and the glycolytic potential of muscle (P < 0.05). Moreover, 3-h pre-slaughter transport resulted in a significant elevation of mRNA expressions of LKB1 and AMPKα2 (P < 0.05), as well as the increase in protein abundances of LKB1 phosphorylation and AMPKα phosphorylation (P < 0.05). However, 1,200 mg/kg GAA supplementation alleviated negative parameters in plasma, improved meat quality, and ameliorated postmortem glycolysis and energy metabolism through regulating the creatine-phosphocreatine cycle and key factors of AMPK signaling. In conclusion, dietary supplementation with 1,200 mg/kg GAA contributed to improving meat quality via ameliorating muscle energy expenditure and delaying anaerobic glycolysis of broilers subjected to the 3-h pre-slaughter transport.

Keywords: AMPK signaling; broiler; guandino-acetic acid; postmortem glycolysis; transport stress.

FIGURE 1

Effects of dietary GAA supplementation on the contents of glycose (A) and corticosterone (B) plasma of Qiandongnan Xiaoxiang Chicken experienced transport stress (n = 10 per treatment). Results are expressed as the mean value and standard error. Means within the same row with different superscripts differ significantly (n = 10 per treatment, P < 0.05). Control, broilers fed the basal diet without transport stress; T3h, broilers fed the basal diet and experienced a 3 h transport; T 3h + 0.06% GAA or T 3h + 0.12% GAA, broilers fed the basal diet supplemented with GAA at 600 or 1,200 mg/kg and experienced a 3 h transport. GAA, guanidine acetic acid.

FIGURE 2

Effects of dietary GAA supplementation on concentrations of glycogen (A), lactic acid (B), and glycolytic potential (C) in pectoralis major muscle of Qiandongnan Xiaoxiang Chicken experienced transport stress (n = 10 per treatment). Results are expressed as the mean value and standard error. Means within the same row with different superscripts differ significantly (n = 10 per treatment, P < 0.05). Control, broilers fed the basal diet without transport stress; T3h, broilers fed the basal diet and experienced a 3 h transport; T3h + 0.06% GAA or T3h + 0.12% GAA, broilers fed the basal diet supplemented with GAA at 600 or 1,200 mg/kg and experienced a 3 h transport. GAA, guanidine acetic acid; glycolytic potential = 2 × [glycogen] + [lactic acid].

FIGURE 3

Effects of dietary GAA supplementation on activities of HK (A), PK (B), and Fructose 2,6-niophosphate (C) in pectoralis major muscle of Qiandongnan Xiaoxiang Chicken experienced transport stress (n = 10 per treatment). Results are expressed as the mean value and standard error. Means within the same row with different superscripts differ significantly (n = 10 per treatment, P < 0.05). Control, broilers fed the basal diet without transport stress; T3h, broilers fed the basal diet and experienced a 3 h transport; T3h + 0.06% GAA or T3h + 0.12% GAA, broilers fed the basal diet supplemented with GAA at 600 or 1,200 mg/kg and experienced a 3 h transport. GAA, guanidine acetic acid; HK, hexokinase; PK, pyruvate kinase.

FIGURE 4

Effects of dietary GAA supplementation on mRNA expressions of LKB1 (A), AMPKα1 (B), AMPKα2 (C), and protein abundances of phosphorylation LKB1 (D) and phosphorylation AMPKα (E) in pectoralis major muscle of Qiandongnan Xiaoxiang Chicken experienced transport stress (n = 10 per treatment). Results are expressed as the mean value and standard error. Means within the same row with different superscripts differ significantly (n = 10 per treatment, P < 0.05). Control, broilers fed the basal diet without transport stress; T3h, broilers fed the basal diet and experienced a 3 h transport; T3h + 0.06% GAA or T3h + 0.12% GAA, broilers fed the basal diet supplemented with GAA at 600 or 1,200 mg/kg and experienced a 3 h transport. GAA, guanidine acetic acid; LKB1, liver kinase B1; AMPKα1, adenosine 5′-monophosphate-activated protein kinase α1; AMPKα2, adenosine 5′-monophosphate-activated protein kinase α2; phosphorylation LKB1, phospho-liver kinase B1; phosphorylation AMPKα, phospho-adenosine 5′-monophosphate-activated protein kinase α (including α-1 and -2).