Oral administration of L‐citrulline changes the concentrations of plasma hormones and biochemical profile in heat‐exposed broilers

Abstract

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/ head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 AE 1 C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3 0 -triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.

Liver metabolomic analysis in broiler chicks: Profiling the metabolites after oral administration of l‐citrulline

“…Previously, it was confirmed that food intake was not changed but rectal temperature declined by oral l ‐Cit in layer chicks (Chowdhury et al, 2017). However, recently, we have reported that l ‐Cit reduced food intake in 28‐day‐old heat‐exposed broilers (Chowdhury et al, 2021). Therefore, food intake could be influenced by oral l ‐Cit in broilers.…”

“…In the present study, we further confirmed that oral l ‐Cit reduced the rectal temperature in broiler chicks. The reduction in rectal temperature has been suggested to modulate plasma metabolites, namely, glucose (Chowdhury et al, 2017), lactic acid, nonesterified fatty acids, and metabolic hormones (Chowdhury et al, 2021). However, the details of the metabolic changes are yet to be elucidated.…”

L‐Citrulline: A novel hypothermic amino acid promoting thermotolerance in heat‐exposed chickens

“…In another study (Chowdhury, Ouchi, Han, et al, 2021) involving market-age broilers, one group of broilers received a dual dose of orally administered L-Cit (20 mmol/head/administration; 40 mmol/ head in total, using an elastic-plastic needle on a syringe), as a preliminary study had found that a single dose of orally administered L-Cit (20 mmol/head) was not sufficient to provide thermotolerance. They were then exposed to an HT (30 ± 1 C) chamber.…”

“…Therefore, Cit has not been considered to add in the poultry diet. However, recent studies showed that Cit administration can minimize heat stress in chickens (Chowdhury et al, 2017; Chowdhury, Ouchi, Han, et al, 2021; Uyanga, Liu, et al, 2022; Uyanga, Zhao, et al, 2022). Moreover, a concern with dietary Arg supplementation is its potential antagonism with basic amino acids, including Arg, lysine, and histidine, whereas Cit is a neutral amino acid and does not share the same transporters with basic amino acids (Wu & Morris, 1998).…”

“…It has also been reported that the thermoregulatory response to thyrotropin‐releasing hormone is dependent upon stimulation of the hypothalamus‐pituitary–adrenal axis rather than the HPT axis and, as a result, may differ across neonatal stages (Takahashi et al, 2005). However, it has recently been found that exposure of 4‐week‐old broilers (average BW: 1.8 kg) to an HT resulted in increased plasma T3 and decreased T4 (Chowdhury, Ouchi, Han, et al, 2021), which indicates that in market‐age broilers, the HPT axis may have an active role in thermoregulation.…”