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Research Project: Identification of Host Factors and Immunopathogenesis of Pneumonia in Domestic and Bighorn Sheep

Location: Animal Disease Research

Title: Passive transfer in domestic and bighorn lambs Total IgG in ewe sera and colostrum and serum IgG kinetics in lambs following colostrum ingestion are similar in domestic sheep and bighorn sheep (ovis aries and ovis canadensis)

Author
item Highland, Margaret - Maggie
item Berglund, Alix - North Carolina State University
item Knowles Jr, Donald

Submitted to: Sheep and Goat Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2017
Publication Date: 3/2/2018
Citation: Highland, M.A., Berglund, A.K., Knowles, D.P. 2018. Total IgG concentrations in ewe sera and colostrum and kinetics in lambs following colostrum ingestion is similar in domestic sheep and bighorn sheep (ovis aries and ovis canadensis). Sheep and Goat Research Journal. 32:36-42.

Interpretive Summary: The past decade has witnessed increasing controversy concerning infectious disease interface of domestic sheep and bighorn sheep in the Western United States. Respiratory disease is a population limiting problem in bighorn sheep predominantly due to decreased lamb survival. While respiratory disease outbreaks continue to impact wild bighorn sheep herds, with and without domestic sheep contact, attempts at absolute separation of these two species has become a socioeconomic burden to domestic sheep producers and hobbyists in Western North America due to ongoing loss of public grazing rights and pressures placed on private landowners that have domestic sheep. Published research by other investigators has implied, and perhaps incorrectly, that failure of passive transfer is at least in part responsible for bighorn lamb pneumonia and mortality. Well controlled comparative immunologic investigations, such as this one, are lacking and much needed to understand this disease phenomenon in bighorn sheep. This investigation revealed no significant interspecies difference in total IgG in ewe serum or colostrum, apparent efficiency of absorption of maternal IgG, or waning of IgG following colostrum consumption. The results, interpretation, and discussion provided in this manuscript are not only important concepts in understanding the pathogenesis of respiratory disease in bighorn sheep but also in clarifying the findings of previous and perhaps misleading publications on the topic.

Technical Abstract: Pneumonia is a population-limiting disease of bighorn sheep (BHS; Ovis canadensis) and a recognized disease entity in domestic sheep (DS; Ovis aries) worldwide. Respiratory disease in BHS lambs can persist for years after all-age outbreaks, resulting in suppressed lamb recruitment. It has been suggested that inadequate passive transfer (PT) of maternal antibodies may play a role in BHS lamb pneumonia, although inadequate PT is often associated with illness prior to 4 weeks of age in DS while BHS mortality predominantly occurs >4 weeks of age. The purpose of this study was to analyze PT of total colostral IgG in BHS lambs and DS lambs born and hand-raised under the same environmental conditions. Total IgG concentrations were quantified for ewe serum, colostrum, and lamb sera collected at multiple time points following ingestion of a known quantity of colostrum during a recorded period of time. No significant interspecies differences were observed for total IgG concentrations in ewe sera, colostrum, or lamb sera at 1 day and no significant difference in apparent efficiency of absorption were identified. Waning kinetics of IgG in DS and BHS lamb sera was similar post-colostrum ingestion. BHS lambs produced IgG sooner than DS following waning of maternal IgG and had significantly higher serum IgG at 16, 20, and 24 weeks. Significant differences were observed in birth weight (DS > BHS) and amount of time to ingest colostrum (BHS > DS). In summary, findings of this study, as well as consideration of the age of mortality in wild BHS lambs, do not support inadequate PT of total IgG as a primary contributor in BHS lamb pneumonia.