Erna Dewil

The prophylactic effect of vitamin C supplementation on broiler ascites incidence and plasma thyroid hormone concentration

In a two-factorial experiment, 420 1-day-old male commercial broiler chickens were randomly divided and fed a basal diet with or without vitamin C (500 parts/10(6)). Half of the birds within each group receiving the same kind of feed were fed a T(3 )supplemented diet from day 1, in order to increase the ascites incidence. Weekly body weight and feed intake were measured. Venous blood samples were taken from 10 birds per group weekly from day 14 on, for haematocrit measurements, blood gas analysis, measurement of thyroid hormones and lactate/pyruvate ratios. Ascites mortality was recorded daily. Dietary T(3) significantly increased ascites mortality. Adding vitamin C to the feed significantly reduced ascites mortality while it had no effect on performance parameters. Plasma thyroid hormone levels were significantly reduced by dietary vitamin C administration, but neither haematocrit nor blood gas levels were influenced.

Different characteristics in chick embryos of two broiler lines differing in susceptibility to ascites

1. The relationship between the length of incubation, hatching, hypoxic condition, thyroid hormones and the occurrence of ascites were studied in embryos of 2 broiler lines differing in susceptibility to the ascites syndrome. 2. Both the time of external pipping (ep) and hatching of embryos from the ascites-resistant (AR) broiler line was earlier compared to the ascites-sensitive line (AS). The interval between internal pipping (ip) and ep was the same between the lines, but the interval between ep and hatching was shorter in the resistant line. 3. The T3 and T4 concentrations in plasma of the AS line were lower compared to the AR line. 4. Analyses of partial pressures of oxygen (pO2) and carbon dioxide (pCO2) in the air cell of the egg revealed that at day 18 the AS embryos had lower pO2 and higher pCO2 concentrations compared to the AR embryos. 5. The delay in hatching of the AS embryos might induce a more pronounced and/or extended hypoxic environment, thereby creating an environment that evokes ascites.

Different CO2 levels during incubation interact with hatching time and ascites susceptibility in two broiler lines selected for different growth rate

Embryos from ascites sensitive (AS) and resistant lines (AR) were subjected during the third week of incubation to a high CO2 (0.4%) (HC) or normal CO2 level of 0.2% (NC) in the incubators. The effect on embryonic and hatching parameters and growth, ascites sensitivity and related physiological parameters was followed. At NC conditions AR embryos hatch earlier than AS ones but this difference completely disappeared under HC condition, since hatching time of the AS line was reduced. Moreover, AS embryos showed slightly lower T4 and T3 levels than AR embryos. Embryos of both lines incubated at HC had higher plasma T3 concentrations than those incubated at NC. Chickens that had been incubated at HC level showed less ascites mortality than those incubated at NC. RV/TV ratios were higher in NC birds compared with HC ones. It is concluded that different ventilation levels during incubation interact with total incubation time and thereby influence ascites susceptibility.

In ovo treatment with an aromatase inhibitor masculinizes postnatal hormone levels, abdominal fat pad content, and GH pulsatility in broiler chickens

Vorozole, a selective aromatase inhibitor, was administered in ovo to test the specific embryonic role of estrogen in conferring the sex distinction in GH release and body phenotype in broilers. On Day 6 of incubation, eggs were injected with saline or with different concentrations of vorozole. Postnatal blood samples were analyzed for T3, T4, GH, estradiol (E2), and testosterone (T). At the age of 4 wk, control and vorozole-treated birds were cannulated, and serial blood samples were withdrawn every 10 min for 5 hr, wherein GH pulsatility characteristics were determined using deconvolution analysis. The proportional abdominal fat pad weight was reduced significantly in the treated groups, especially in female birds. The vorozole treatment increased plasma T3, E2, T, and GH concentrations, and decreased T4. The frequency of the GH pulses was lower and the interval between the bursts (min) was higher in the vorozole-treated group, as were the mass secreted per burst (ng/ml), the amplitude (ng/ml/min) and the production rate (ng/ml/5 hr). In conclusion, early in ovo treatment with a potent aromatase inhibitor is able to increase the mean serum T3 and GH concentration and masculinize the GH pulse pattern, resulting in an economically favorable decrease in abdominal fat pad content in male and female broilers at slaughter age.

The regulation of GH-dependent hormones and enzymes after feed restriction in dwarf and control chickens

The principal objective of this study was to examine the GH-dependency of IGF-I and IGF-II changes in the chicken. To this end, the regulation of GH-dependent hormones and enzymes were studied in undernourished normal and dwarf chickens. The dwarf chickens examined exhibit a Laron-type dwarfism and have been shown to be GH receptor deficient. Thus, they provide an interesting model to determine the GH-dependency of IGF-I and IGF-II changes. Short (1 day) and long-term (7 days) feed restriction was imposed on growing normal and dwarf chickens to follow the subsequent endocrine changes. Since short-term feed restriction of dwarf chickens resulted in decreased plasma IGF-I, it appears that this is not a GH-dependent effect. However, with longer term undernutrition, IGF-I was not decreased in dwarf chickens. So, after a longer restriction period, the regulation of these factors appears to become more GH-dependent. IGF-II was not depressed at all by feed restriction in the dwarf chicken, suggesting a degree of GH-dependency.