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Title: Interactive effects between genotype, protein nutrition and immune status on the parasite-induced anorexia of sheep
Author: Zaralis, Konstantinos Georgiou
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2008
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Experiments involved two breeds of lambs (Suffolk x Greyface, S, and Scottish Blackface, B) or ewes (Greyface cross, G, and Scottish Blackface, B) that are known to differ in their production potential. Animals were either infected with abomasal nematode Teladorsagia circumcincta and fed ad libitum or non-infected and fed either ad libitum or restrictedly. The first two experiments investigated the effect of a primary and a secondary infection on anorexia and plasma leptin concentrations (PLC) in growing lambs. The results showed that lambs of the S breed were more susceptible to nematode infection than B lambs, Primary infection resulted in anorexia in S lambs but not in B lambs and re-infection tended to affect the food intake of S lambs only. Infection did not result in an acute increase in PLC, but its effect was significant when variation in food intake between treatments was accounted for. These results suggest that anorexia can occur in previously infected lambs, thus the effect of re-infection on anorexia was further investigated. Previously naïve lambs of approximately 3 or 7 months of age were infected with T. circumcincta for either 10 or 7 weeks, respectively. Lambs of experiment I were re-infected either 4 or 8 weeks after the end of the primary infection. The results showed that the breed differences in resistance to infection were not associated with breed differences in the degree of anorexia and infection of 7-month old lambs did not result in anorexia. Re-infection of previously infected lambs did also not result in anorexia when lambs were re-infected 4 or 8 weeks after the end of the primary infection. Nematode (re)infection did not result in an increase of PLC. These results suggest that leptin may be involved in the response of lambs to infection, but it is unlikely that leptin alone is responsible for the parasite induced anorexia in lambs. The last experiment investigated the consequences of protein supplementation on anorexia, and PLC in infected periparturient ewes. Infection resulted in a breakdown of immunity to parasites (PPRI) and a reduction in food intake in both breeds. The breeds differed in the extent of PPRI (G ewes having higher FEC than B ewes), but not in the magnitude of anorexia. Protein supplementation resulted in a reduction in FEC, but had no effect on the magnitude of anorexia. Plasma leptin concentrations changed significantly over time, but were not affected by protein supplementation or infection. It was concluded that infection with T. circumcincta in periparturient ewes resulted in anorexia that is not alleviated by protein supplementation. Leptin is unlikely to be responsible for the anorexia of nematode infection in periparturient ewes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available