Ectoparasite activity during incubation increases microbial growth on avian eggs

We thank Estefanía López for lab work, and Tomás Pérez-Contreras and Emilio Pagani-Núñez for facilitating collection of some of the flies used in manipulations. We also thank Ángela Martínez-García for help with management of ARISA data and Natalia Juárez and Deseada Parejo for the pictures of owls and roller clutches, respectively. We appreciate the comments provided by Dr. Adèle Mennerat and five anonymous referees on earlier versions of the manuscript.All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.While direct detrimental effects of parasites on hosts are relatively well documented, other more subtle but potentially important effects of parasitism are yet unexplored. Biological activity of ectoparasites, apart from skin injuries and blood-feeding, often results in blood remains, or parasite faeces that accumulate and modify the host environment. In this way, ectoparasite activities and remains may increase nutrient availability that may favour colonization and growth of microorganisms including potential pathogens. Here, by the experimental addition of hematophagous flies (Carnus hemapterus, a common ectoparasite of birds) to nests of spotless starlings Sturnus unicolor during incubation, we explore this possible side effect of parasitism which has rarely, if ever, been investigated. Results show that faeces and blood remains from parasitic flies on spotless starling eggshells at the end of incubation were more abundant in experimental than in control nests. Moreover, eggshell bacterial loads of different groups of cultivable bacteria including potential pathogens, as well as species richness of bacteria in terms of Operational Taxonomic Units (OTUs), were also higher in experimental nests. Finally, we also found evidence of a link between eggshell bacterial loads and increased embryo mortality, which provides indirect support for a bacterial-mediated negative effect of ectoparasitism on host offspring. Trans-shell bacterial infection might be one of the main causes of embryo death and, consequently, this hitherto unnoticed indirect effect of ectoparasitism might be widespread in nature and could affect our understanding of ecology and evolution of host-parasite interactionsFinancial support was provided by Spanish Ministerio de Economía y Competitividad and FEDER (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P), by JAE programme to DMG and MRR, and by Juan de la Cierva and Ramón y Cajal programmes to GT. All procedures were conducted under licence from the Environmental Department of the Regional Government of Andalucía, Spain (reference SGYB/FOA/AFR)

Sigmoid model for the evaluation of growth and production curves in laying hens

WOS: 000181722300010The aim of this study was to choose the best predictive model for the accurate description of the average flock growth of laying hens and for the daily egg mass being produced by the layers during the productive period. The calculations were undertaken with the generalised data on the weight growth and daily egg mass, produced by the commercial flock of a Shaver White laying hens breed. The model, represented as the ratio of the polynomials of the third and the second powers, was deduced by the authors for the prediction of the growth and daily egg mass production curves. This Narushin-Takma model was tested for the accuracy of the results prediction in comparison with the following growth models: the logistic, the Gompertz, the von Bertalanffy, the Richards, the Weibull and the Morgan-Mercer-Flodin functions. The egg production model used for comparison were the Adams-Bell, the logistic-curvilinear, the compartmental and the Lokhorst functions. Fitting criteria were estimated as the coefficients of determination R-2 and the final loss L-f of the loss function: sum of observed minus predicted data in the second power. The Narushin-Takma model was found to be the best in description of the both curves, values for R-2 of 0.9997 and for L-f of 0.005 for the evaluation of the body growth data and values for R-2 of 0.996 and L-f of 0.001 for the description of the egg mass producing function. The accuracy of the other models was high and almost the same for all functions. The order of the accuracy for the compared models was as follows: for the body growth curve - the Weibull model, the Gompertz, the von Bertalanffy, the Morgan-Mercer-Flodin, the logistic and the Richards functions; for the egg mass producing curve - the logistic-curvilinear model, the compartmental, the Lokhorst and the Adams - Bell functions. (C) 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Science Ltd