Submitted to: International Conference on Farm Animal Endocrinology
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2004
Publication Date: July 1, 2004
Citation: Allen,P., Richards, M., Poch, S., Vasilatos-Younken, R. 2004. Ghrelin-growth hormone relationship in the coccidial-infected chicken [abstract]. Biotechnologie, Agronomie Societe et Environnement 8:44.
One of the most costly enteric parasitic diseases of broilers is coccidiosis. Impaired feed consumption is a major consequence of coccidiosis, which negatively impacts growth and feed efficiency. The cause of the inappetance in coccidial infected chicks is unknown. Avian ghrelin has unique properties separate from mammals. In chickens, ghrelin is mainly produced in the proventriculus, and has been shown to inhibit feed intake. This study was conducted to monitor plasma ghrelin and other metabolic hormones during a coccidial infection. At 24 days of age, male chicks were inoculated with sporulated oocysts of Eimeria acervulina (I). A control (C) group received vehicle. Blood samples were taken prior to inoculation (day 0), and on days 4, 8, and 14 post infection. Plasma levels of ghrelin, growth hormone (GH), IGF-I and -II, GLP-1, glucagon and thyroid hormones were determined by RIA. At 4 days post infection, ghrelin and GH concentrations were 3- and 1.7 fold greater respectively in the I chicks than in the C group. This is the period when feed intake was suppressed to the greatest extent. By day 8 ghrelin and GH levels had declined to C levels. On day 4 glucagon levels were elevated in I compared to C chicks. Conversely, IGF-I and triiodothyronine concentrations were lower in I birds on day 4. By day 8 post infection, hormone levels were not different between the two groups, and remained similar through day 14. Infection did not alter IGF-II, GLP-1 or thyroxine. It is evident from this study that coccidial infection elicits a dramatic increase in circulating ghrelin and GH, with a concomitant decrease in feed intake, strongly suggesting that ghrelin maybe acting as a GH secretagogue. Whether ghrelin alone is responsible for inappetance in this situation awaits further study.