Huntley, Selene J. (2013) Longitudinal studies of intramammary infection in suckler ewes. PhD thesis, University of Warwick.

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Abstract

Four longitudinal studies were conducted. The first study investigated the
longitudinal pattern of udder half somatic cell count (HSCC) and intramammary
infection (IMI) in 48 UK suckler ewes over the first 10 weeks of lactation. This was
the first study to demonstrate that HSCC of suckler ewes followed a quadratic and
cubic relationship with days in lactation over the first 10 weeks of lactation. Udder
half somatic cell count was also explained by presence of bacteria. Ewes older than 6
years of age had significantly higher HSCC than younger ewes.
The second study investigated the relationships between udder conformation, SCC
and lamb weight. Whilst accounting for lamb age and birth weight, significantly
lower lamb weight was associated with a ewe SCC of >400,000 cells/ml (-1.7 kg), a
traumatic teat lesion (bite, tear or chapping) 2 weeks previously (-1.1 kg), and a ewe
body condition score (BCS) of <2.5 before lambing (-1.3kg). Higher HSCCs were
observed in ewes with a lower suspended udder, and older ewes in poorer body
condition. The findings from this study make an important contribution to the
knowledge of the impact of udder health of suckler ewes by demonstrating that udder
conformation is associated with IMI and that IMI and teat damage are negatively
associated with lamb weight.
The third study investigated the effect of dry cow therapy (DCT) on subclinical
mastitis in a lowland flock with a low incidence of clinical mastitis by recording
HSCC and lamb weights in the following lactation. To the author’s knowledge, there
are no published reports of the effect of broad spectrum DCT on subclinical mastitis
in suckler ewes in the literature. No significant effect was found between the use of
DCT and HSCC or lamb weight in the subsequent lactation.
The fourth study was a randomised controlled trial to assess the effect of DCT on
clinical mastitis in a suckler flock with a high level of clinical mastitis. Dry cow
treatment significantly reduced the incidence of clinical mastitis over one year, with
a 70% reduction of clinical mastitis in ewes that received treatment from 6.2% to
1.8%. This was the first field trial to investigate and demonstrate the clinical benefit
of the use of a broad spectrum DCT in suckler ewes.
These studies have enhanced our knowledge of longitudinal patterns of infection and
demonstrated the importance of udder health for optimising production of suckler
ewes. Factors to control for when using SCC as a tool to measure intramammary
infection were described.

Item Type:	Thesis (PhD)
Subjects:	S Agriculture > SF Animal culture
Library of Congress Subject Headings (LCSH):	Udder -- Diseases -- Longitudinal studies, Mastitis -- Longitudinal studies, Ewes
Official Date:	January 2013
Dates:	Date Event January 2013 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Green, Laura E.
Sponsors:	English Beef & Lamb Executive (EBLEX)
Extent:	214 leaves : charts.
Language:	eng

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