Supplemental L-arginine and vitamins E and C preserve xanthine oxidase activity in the lung of broiler chickens grown under hypobaric hypoxia

The effects of l-Arg, vitamin C (VC), and vitamin E (VE) on xanthine- (XO) and NAD(P)H-oxidase (NOX) activities, and nitric oxide (NO) availability of hypoxic broilers were evaluated. Chickens were kept in wire cages with free access to feed and water. One-day-old chicks were assigned to 1 of 3 diets: control (CTL; ME 3,200 kcal/kg, CP 23%), high Arg (HA; CTL + Arg 0.8%), or high Arg plus VE and VC (AEC; HA + 200 IU of VE/kg of feed + 500 mg of VC/L of water), and grown under hypobaric hypoxia (HYP) from d 7 to 30. A fourth group of birds was fed the CTL diet and grown under normoxia (CTL-NOR). At d 30, chickens were euthanized, their lungs fixed in vivo, excised, and processed for cyto- and histochemistry. The enzymes XO and NOX were localized and activities assessed histochemically and in lung homogenates. The NO depletion was assessed through nitrotyrosine immunocytochemistry colloidal gold particles (NTY). The XO and NOX localized in cell membranes and within vesicles of pulmonary vessel endothelial cells. The XO activity was higher in CTL-NOR birds (586 ± 43 reflectance units) than in both AEC-HYP (456 ± 39) and HA-HYP birds (394 ± 31), whereas CTL-HYP birds had the lowest XO activity (313 ± 27). The NO depletion was not affected by dietary or hypoxia conditions in clinically healthy birds; nevertheless, hypoxic birds that developed pulmonary hypertension had higher NTY levels (less NO, 145 ± 19) than hypoxic but clinically healthy birds (56 ± 11). Thus, the concurrent supplementation of Arg, VE, and VC restored XO activity without affecting NOX activity or NO availability. The dual role of XO, which produces superoxide and uric acid, may have buffered the effects of superoxide in broiler chickens grown under hypobaric hypoxia.

Effects of arginine and antioxidant vitamins on pulmonary artery reactivity to phenylephrine in the broiler chicken

The effects of supplemental l-arginine (Arg), vitamin E (VE), and vitamin C (VC) on vascular reactivity to phenylephrine (PE) were examined in clinically healthy hypoxemic male broiler chickens. One-day-old chicks were housed in wire cages and randomly allocated to 1 of 3 dietary treatments: control (CTL; n = 80; 3,200 kcal of ME/kg, 23% CP, 1.55% Arg and 40 IU of VE/kg of feed), high-Arg (HA; n = 40; CTL + 0.8% Arg), or high-Arg and high antioxidant-vitamin diet (AEC; n = 40; HA + 200 IU of VE/kg of feed and 500 mg of VC/kg of feed). At d 14, 40 CTL birds and all the HA and AEC birds had a primary pulmonary bronchus surgically occluded (PBO). Forty CTL broilers underwent surgery without occluding the bronchus (SHAM). Pulmonary artery (PA) rings were mounted for isometric tension recordings 14 to 21 d postsurgery. The HA-PBO and AEC-PBO PA were immersed in Krebs-Henseleit buffer plus a vehicle (VehCtl) or Krebs-Henseleit buffer plus supplemental Arg, or Arg, VE, and VC (A-E-C). Maximal contractile response to PE of the CTL-SHAM PA (16 ± 14 mg/mg of dry tissue) was one-tenth compared with that of the CTL-PBO PA (159 ± 13 mg/mg), whereas the PA contractility in the supplemented groups was one-ninth compared with those of the CTL-PBO (17.9 ± 13.0 mg/mg, 17.90 ± 13.0 mg/mg for the HA-PBO+Arg and AEC-PBO+A-E-C treatments, respectively). Supplementing the bath with Arg did not change the maximal response to PE compared with the vehicle control (16.7 ± 12.2 mg/mg for HA-PBO-VehCtl). However, supplementing the bath with A-E-C produced a one-fourth reactivity compared with that of the vehicle control (80.7 ± 13.0 mg/mg for AEC-PBO-VehCtl). The PBO increased PA reactivity to PE, but supplemental Arg plus VE and VC significantly reduced it. Differential reactivity responses to PE may have been the result of protective effects of Arg, VE, and VC, implicating oxidative stress in endothelial dysfunction as well as in the upregulation of smooth muscle contractility.

L-arginine and antioxidant vitamins E and C improve the cardiovascular performance of broiler chickens grown under chronic hypobaric hypoxia

Two hundred broiler chicks were randomly assigned to 3 dietary treatments: control [CTL; 3,200 kcal of ME/kg, 23% CP, 1.55% Arg, and 40 IU of vitamin E (VE)/kg of feed], high-Arg (HA; CTL+0.8% Arg), or high-Arg and high antioxidant-vitamin diet (AEC; HA+200 IU of VE/kg of feed and 500 mg of vitamin C/L of water). The chicks were housed in wire cages in hypobaric chambers simulating 3,000 m above sea level. From d 28 to 42, clinically healthy birds were selected for cardiovascular performance (n=7 to 12/treatment). After surgery, pulmonary arterial pressure (PAP) and mean arterial pressure (MAP) readings were taken at 180, 120, and 60 s (basal values) before an epinephrine (EPI) challenge and then at 30, 60, 120, 180, 300, 600, and 1,200 s after the challenge, followed by a second EPI challenge with similar sample readings. There were no differences in the basal PAP values among chicken groups. The PAP increased within 30 s after both EPI challenges in all groups. It took 180 s after the first EPI challenge for the CTL chickens to return to the basal PAP values, whereas HA and AEC chickens returned to basal PAP values in 120 s. After the second EPI challenge, it took 60, 180, and 300 s for the AEC, HA, and CTL groups, respectively, to return to basal PAP values. The MAP response pattern to the EPI challenges mimicked that of PAP, but there were no differences among treatments in MAP at any sampling point. Supplemental Arg, VE, and vitamin C did not reduce ascites incidence in hypoxic broilers. In conclusion, supplemental Arg improved the pulmonary vascular performance of hypoxic broiler chickens and its effects were further improved by the addition of the antioxidant VE and vitamin C. Arginine and antioxidant vitamins may have played synergistic roles to increase NO bioavailability and reduce oxidative stress damage, thus improving cardiopulmonary performance.

Maternal dietary n-3 fatty acids alter cardiac ventricle fatty acid composition, prostaglandin and thromboxane production in growing chicks

The effects of feeding n-6 and n-3 fatty acids to broiler hens on cardiac ventricle fatty acid composition, and prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) production of hatched chicks were investigated. Fertile eggs obtained from hens fed diets supplemented with 3.5% sunflower oil (Low n-3), 1.75% sunflower+1.75% fish oil (Medium n-3), or 3.5% fish oil (High n-3) were incubated. The hatched chicks were fed a diet containing 18:3 n-3, but devoid of longer chain n-6 and n-3 fatty acids for 42 days. Arachidonic acid content was lower in the cardiac ventricle of High n-3 and Medium n-3 compared to Low n-3 birds for up to 2 weeks (P<0.002). Long chain n-3 fatty acids were higher in the cardiac ventricle of chicks from hens fed High and Medium n-3 diets when compared to chicks from hens fed the Low n-3 diet. Differences in long chain n-3 fatty acids persisted up to four weeks of age (P<0.001). Peripheral blood mononuclear cells (PBMNC) of 7-day-old High n-3 broilers produced significantly lower PGE2 and TXA2 than PBMNC from Low n-3 and Medium n-3 birds. These results indicate that maternal dietary n-3 fatty acids increases cardiac ventricle n-3 fatty acids while reducing arachidonic acid and ex vivo PGE2 and TXA2 production during growth in broiler chickens.

A preliminary estimate of the heritability of plasma troponin T in broiler chickens

1. Male and female broiler chickens of a pure line were selected over one generation for low or high plasma, cardiac-derived troponin T concentrations at 12 h of age. 2. Heritability of plasma troponin T was moderately high (h2 = 0.38 +/- 0.06), and there was no difference in mean body weights of parents (G0) of the 2 lines at 4 and 19 weeks of age. 3. This preliminary study suggests that broiler breeder companies will be able to select for resistance against heart damage and ascites.

Characterisation of embryonic cardiac-derived troponin T in broiler chicks bled one to 168 hours after hatching

Troponin T, a cardiac-specific protein released only from damaged or injured heart tissue and cells, was measured in the sera from fowl chicks bled one, 12, 24, 48, 96 and 168 hours after hatching. A peak troponin T response was observed 12 hours after hatching in two experiments conducted six months apart. In the second experiment the heterophil/lymphocyte (H/L) ratios were also increased at one and 12 hours after hatching. The data suggest that the troponin T response in chicks bled 12 hours after hatching, together with the raised H/L ratios at the same age, may indicate a physiological stress reaction to the process of hatching, rather than a process which is under direct genetic control.