Skip to main content
ARS Home » Research » Publications at this Location » Publication #65124
Title: EFFECT OF EWE OVINE LENTIVIRUS INFECTION ON EWE AND LAMB PRODUCTIVITY

Author
item Keen, James
item HUNGERFORD, LAURA - UNIVERSITY OF ILLINOIS
item LITTLEDIKE, E - OMAHA COL HLTH CAREERS
item WITTUM, THOMAS - OHIO STATE UNIVERSITY
item Kwang, Hwei Sing

Submitted to: Preventive Veterinary Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ovine lentivirus (OLV) is a slow onset viral pathogen of sheep which infects many U.S. flocks. The virus has an incubation period of 3 to 5 years before the clinical disease syndrome (consisting of pneumonia, arthritis, mastitis, emaciation, and death) is observed. The production and financial impacts of OLV are controversial and previous North American studies have not found major differences between OLV-positive and -negative flockmates. In this study, a new enzyme immunoassay was used to detect OLV-infected sheep and to compare production among OLV-positive and -negative flockmates. OLV-negative ewes were found to produce about 11 more pounds of weaned lamb and 0.1 more weaned lambs than positive ewes. Negative ewes also gave birth to more lambs and were twice as likely to lamb compared to OLV-positive ewes. Also, lambs born to OLV-negative ewes weighed more at birth, gained weight faster, and weighed more at weaning compared to lambs from OLV-positive ewes. These results suggest that subclinical OLV has important detrimental effects on sheep production and that OLV control efforts may be financially justified in some flocks.

Technical Abstract: A sensitive and specific ovine lentivirus (OLV) recombinant transmembrane (rTM) protein enzyme-linked immunosorbent assay (ELISA) was used to detect anti-OLV antibodies and define OLV infection in breeding ewes from nine U.S. Meat Animal Research Center (MARC) flocks. The production impacts of dam rTM ELISA seropositivity on ewe and lamb productivity in the birth to weaning interval were estimated using production data from 1466 breeding ewes (of which 1242 actually lambed) and their 2452 lambs born in spring 1992 using multiple linear and logistic regression models. By adjusting for lamb weaning age, gender, type of birth and rearing, birth difficulty, dam age, and flock, the component of ewe or lamb productivity related to ewe OLV infection alone was isolated. The rTM ELISA-negative ewes produced significantly more total pounds of weaned lamb per ewe lambing (3.84 kg.) and per ewe exposed to rams (4.95 kg) compared to their OLV-positive flockmates. Negative ewes also weaned 0.11 more lambs per ewe lambing and 0.09 more lambs per ewe exposed, gave birth to 0.13 more lambs per ewe exposed, and were more likely to lamb after breeding (odds ratio [OR] = 1.91) compared to equivalent OLV-positive ewes. Lambs reared by OLV-negative ewes weighed 0.15 kg more at birth, gained 0.008 kg more per day, and weighed 0.59 kg more at 56-day weaning. Preweaning mortality tended to be lower (OR = 0.79) among lambs born to OLV-negative compared to OLV-positive ewes, although this difference was not detected statistically. These results suggest that subclinical OLV infection has important detrimental effects on sheep production which occur in cumulative fashion from breeding through weaning and that OLV control efforts may be financially justified in some sheep flocks.