Effect of maternal environment on yolk immunoreactive corticosterone and its influence on adrenocortical and behavioral activity in chicks of Greater Rhea (Rhea americana)

Maternal corticosterone in avian eggs may modify offspring phenotype in order to increase survival in poor environments. In the Greater Rhea (Rhea americana), we previously found that yolk immunoreactive corticosterone is influenced by the quality of the maternal environment: eggs laid by females of the intensive rearing system (IRS), living in poor captive conditions, had higher yolk immunoreactive corticosterone than those produced by females of the semi-extensive rearing system (SRS), living in better conditions. Here, we evaluate if these different hormone levels are associated with the production of different phenotypes. We collected eggs from the IRS and SRS for hormonal quantification and artificial incubation. Then, half of the chicks selected from each environment were exposed to a capture and restraint protocol, and the rest remained undisturbed and were used as controls. In the IRS, we found that higher yolk immunoreactive corticosterone was associated with the production of chicks that had reduced hatchability, lower hatchling mass and higher baseline fecal glucocorticoid metabolites (FGM) than those produced by SRS females. Moreover, after capture and restraint, IRS chicks did not modify their FGM nor their behaviors compared to their controls, while SRS chicks increased their FGM and spent more time ambulating and less time pecking, compared to their controls. These results indicate that yolk immunoreactive corticosterone could modify offspring phenotype. Although future studies are needed to elucidate their implications for fitness, our results suggest that yolk corticosterone could be mediating an adaptive maternal effect that allows individuals to better cope with poor conditions.

Enzymatic Properties of Rhea Lysozyme

Rhea lysozyme was analyzed for its enzymatic properties both lytic and oligomer activities to reveal the structural and functional relationships of goose type lysozyme. Rhea lysozyme had the highest lytic activity at pH 6, followed by ostrich and goose at pH 5.5-6, whereas the optimum of cassowary was at pH 5. pH profile was correlated to the net charge of each molecule surface. On the other hand, the pH optimum for oligomer substrate was found to be pH 4, indicating the mechanism of rhea catalysis as a general acid. The time-course of the reaction was studied using beta-1,4-linked oligosaccharide of N-acetylglucosamine (GlcNAc) with a polymerization degree of n ((GlcNAc)n) (n=4, 5, and 6) as the substrate. This enzyme hydrolyzed (GlcNAc)6 in an endo-splitting manner, which produced (GlcNAc)3+(GlcNAc)3 predominating over that to (GlcNAc)2+ (GlcNAc)4. This indicates that the lysozyme hydrolyzed preferentially the third glycosidic linkage from the nonreducing end. Theoretical analysis has shown the highest rate constant value at 1.5 s-1 with (GlcNAc)6. This confirmed six substrate binding subsites as goose lysozyme (Honda, Y., and Fukamizo, T., Biochim. Biophys. Acta, 1388, 53-65 (1998)). The different binding free energy values for subsites B, C, F, and G from goose lysozyme might responsible for the amino acid substitutions, Asn122Ser and Phe123Met, located at the subsite B.

Pharmacokinetic behaviour of enrofloxacin in greater rheas following a single-dose intramuscular administration

The pharmacokinetic behaviour of enrofloxacin in greater rheas was investigated after intramuscular (IM) administration of 15 mg/kg. Plasma concentrations of enrofloxacin and its active metabolite, ciprofloxacin, were determined by high performance liquid chromatography. Enrofloxacin peak plasma concentration (C(max)=3.30+/-0.90 microg/mL) was reached at 24.17+/-9.17 min. The terminal half-life (t(1/2lambda)) and area under the curve (AUC) were 2.85+/-0.54 h and 4.18+/-0.69 microg h/mL, respectively. The AUC and C(max) for ciprofloxacin were 0.25+/-0.06 microg/mL and 0.66+/-0.16 microg h/mL, respectively. Taking into account the values obtained for the efficacy indices, an IM dose of 15 mg/kg of enrofloxacin would appear to be adequate for treating infections caused by highly susceptible bacteria (MIC(90)<0.03 microg/mL) in greater rheas.

Pharmacokinetics of enrofloxacin following intravenous administration to greater rheas: a preliminary study

The pharmacokinetic behaviour of enrofloxacin (ENR) and its active metabolite ciprofloxacin (CIP) were determined in six greater rheas following a single intravenous (i.v.) dose of 15 mg/kg bw. Plasma concentrations of ENR and CIP were simultaneously determined by a HPLC/u.v. method. Following i.v. administration, the plasma drug concentrations were best fitted by an open two-compartment model with a rapid distribution phase. The high volume of distribution (V(ss)=5.01 L/Kg) suggests good tissue penetration. ENR presents a high clearance (3.95 L/kg h) explaining the low AUC values (3.57 mg h/L) and a short permanence (t(1/2beta)=2.66 h and MRT=1.23 h). Ciprofloxacin comprised 14% of the total fluoroquinolone (ENR+CIP).

Identification of the major proteins of the organic matrix of emu (Dromaius novaehollandiae) and rhea (Rhea americana) eggshell calcified layer

1. The eggshell is a composite consisting of 95% calcite and an organic matrix. 2. While many proteins of the chicken eggshell matrix have already been identified, little is known about the matrix of other birds. 3. Isolation of the emu and rhea eggshell matrix and analysis of its major constituents showed that the predominant components were C-type lectin-like proteins related to those of ostrich, chicken and goose. 4. Serum albumin, vitelline membrane outer layer protein I (VMO-I) and the turpentine-induced acute phase serum protein 18-B were identified as minor components of the emu shell matrix. Both eggshell matrices also contained a novel proline- and alanine-rich protein. 5. Like ostrich, and unlike chicken and goose, both emu and rhea eggshell matrix contained two different C-type lectin-like proteins as major components, indicating that the occurrence of two proteins of this family may be widespread among ratites.