Different responses of two strains of chickens to different training procedures for magnetic directions

In previous conditioning experiments training domestic chickens to magnetic directions, a brown strain solved the task, whereas a white strain seemed unable to do so (Freire et al. Anim Cogn 11:547-552, 2008). To test whether this was possibly caused by loss of magnetic compass orientation in the white chickens, we analyzed the distribution of cryptochrome 1a, the candidate receptor molecule mediating magnetic compass information, in the retinae of Lohmann Browns and White Leghorns and found no difference between the two strains. Yet, subsequent training experiments replicated the former findings: Lohmann Browns used the magnetic field to find an imprinting stimulus hidden behind the screen in a specific magnetic direction, whereas White Leghorns did not solve the task. However, when we altered the training method by training also in a magnetic field with North shifted to geographic East and including a punishment for incorrect choices, the performance of White Leghorns improved to a significant preference for the expected directions. The Lohmann Browns, on the other hand, seemed frightened and chose randomly. Our results thus demonstrate the crucial role of the training method for conditioning to magnetic stimuli, with differences found even between strains of the same species.

Trace mineral nutrition for broiler chickens and prospects of application of organically complexed trace minerals: a review

This review critically examines the literature on the current status of trace mineral nutrition and the effect of organically complexed trace minerals, focusing on copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), on broiler chicken production. The requirements of Cu, Fe, Mn and Zn by broiler chickens need to be redefined due to today’s fast growing birds and the availability of organic trace minerals. Zn is one of the key trace minerals for chickens and although it maintains a relatively stable tissue concentration, dietary deficiency of Zn strongly depresses the feed intake, and hence the growth, of broiler chickens. Based on studies using a semiconventional diet, it is reasonable to conclude that the total Zn requirement for broiler chickens is around 60 mg/kg up until day 14 and 70 mg/kg from 14 day onwards, including the Zn content in the basal diet. However, it is difficult to determine the requirements of other organic trace minerals such as Cu, Fe and Mn because under a Zn adequate condition, it is impossible to produce deficient symptoms of these minerals on the basis of growth response. It also identifies gaps in knowledge of inorganic and organic trace mineral nutrition for the modern broiler chicken.

Different responses in two strains of chickens (Gallus gallus) in a magnetic orientation test

Previous studies demonstrated that layer strain domestic chicks bred for egg production can orient using directional cues from the magnetic field; here we report that chicks from a broiler strain bred for meat production do not use magnetic cues for orientation. We imprinted both strains of chicken on a red ball and subsequently trained them in a featureless testing arena. Between rewarded trials in the geomagnetic field, we inserted unrewarded tests under the following conditions: (1) in the geomagnetic field, (2) in a magnetic field with North shifted by 90 degrees and (3) in a magnetic field with the inclination inverted. The layer chicks made a correct axial response in 75-80% of the tests, shifting their choices following a rotation of magnetic North. Chicks of the broiler strain, in contrast, performed at chance level with between 47 and 60% of choices on the correct axis. This difference between the strains does not appear to be due to substantial strain differences in motivation to perform the task. It therefore appears possible that the selection of the broiler strain has led to the elimination of the specific ability to respond to magnetic cues in the test situation.

Functional genomics of the chicken--a model organism

Since the sequencing of the genome and the development of high-throughput tools for the exploration of functional elements of the genome, the chicken has reached model organism status. Functional genomics focuses on understanding the function and regulation of genes and gene products on a global or genome-wide scale. Systems biology attempts to integrate functional information derived from multiple high-content data sets into a holistic view of all biological processes within a cell or organism. Generation of a large collection ( approximately 600K) of chicken expressed sequence tags, representing most tissues and developmental stages, has enabled the construction of high-density microarrays for transcriptional profiling. Comprehensive analysis of this large expressed sequence tag collection and a set of approximately 20K full-length cDNA sequences indicate that the transcriptome of the chicken represents approximately 20,000 genes. Furthermore, comparative analyses of these sequences have facilitated functional annotation of the genome and the creation of several bioinformatic resources for the chicken. Recently, about 20 papers have been published on transcriptional profiling with DNA microarrays in chicken tissues under various conditions. Proteomics is another powerful high-throughput tool currently used for examining the dynamics of protein expression in chicken tissues and fluids. Computational analyses of the chicken genome are providing new insight into the evolution of gene families in birds and other organisms. Abundant functional genomic resources now support large-scale analyses in the chicken and will facilitate identification of transcriptional mechanisms, gene networks, and metabolic or regulatory pathways that will ultimately determine the phenotype of the bird. New technologies such as marker-assisted selection, transgenics, and RNA interference offer the opportunity to modify the phenotype of the chicken to fit defined production goals. This review focuses on functional genomics in the chicken and provides a road map for large-scale exploration of the chicken genome.

Avian genomics and the innate immune response to viruses

Viral diseases pose a significant threat to the poultry industry. However, there is currently a lack of antivirals and suitable vaccine adjuvants available to the poultry industry to combat this problem. The innate immune system is now recognised to be essential in the response to viral infection. However, in contrast to mammals, the innate immune response in chickens is relatively uncharacterised. The release of the full chicken genome sequence has accelerated the identification of genes involved in the immune response. The characterisation of these genes, including Toll-like receptors and cytokines has led to the identification of potential alternate antivirals and adjuvants.

Manipulation of small RNAs to modify the chicken transcriptome and enhance productivity traits

In recent years there has been a revolution in our understanding of genes and how they come to control the physical outcomes of development. Central to this has been the understanding of the cellular processes of RNA interference (RNAi), for which the Nobel Prize for Physiology or Medicine was awarded in 2006. Coupled with this has been the recognition that microRNAs are key mediators of this process within cells. RNAi whether mediated exogenously by synthetic oligonucleotides or vector-delivered double stranded RNA or endogenously by microRNAs can have a profound and specific effect on gene expression. Elucidating and understanding these processes in the chicken will provide critical information to enable more precise control over breeding strategies for improvement of traits in production poultry, either by direct or indirect means. It will also provide alternative strategies for the control and prevention of important avian diseases.