A cross-sectional study of 329 farms in England to identify risk factors for ovine clinical mastitis.

The aims of this study were to estimate the incidence rate of clinical mastitis (IRCM) and identify risk factors for clinical mastitis in suckler ewes to generate hypotheses for future study. A postal questionnaire was sent to 999 randomly selected English sheep farmers in 2010 to gather data on farmer reported IRCM and flock management practices for the calendar year 2009, of which 329 provided usable information. The mean IRCM per flock was 1.2/100 ewes/year (CI:1.10:1.35). The IRCM was 2.0, 0.9 and 1.3/100 ewes/year for flocks that lambed indoors, outdoors and a combination of both, respectively. Farmers ran a variety of managements before, during and after lambing that were not comparable within one model, therefore six mixed effects over-dispersed Poisson regression models were developed. Factors significantly associated with increased IRCM were increasing percentage of the flock with poor udder conformation, increasing mean number of lambs reared/ewe and when some or all ewes lambed in barns compared with outdoors (Model 1). For ewes housed in barns before lambing (Model 2), concrete, earth and other materials were associated with an increase in IRCM compared with hardcore floors (an aggregate of broken bricks and stones). For ewes in barns during lambing (Model 3), an increase in IRCM was associated with concrete compared with hardcore flooring and where bedding was stored covered outdoors or in a building compared with bedding stored outdoors uncovered. For ewes in barns after lambing (Model 4), increased IRCM was associated with earth compared with hardcore floors, and when fresh bedding was added once per week compared with at a frequency of ≤2 days or twice/week. The IRCM was lower for flocks where some or all ewes remained in the same fields before, during and after lambing compared with flocks that did not (Model 5). Where ewes and lambs were turned outdoors after lambing (Model 6), the IRCM increased as the age of the oldest lambs at turnout increased. We conclude that the reported IRCM is low but highly variable and that the complexity of management of sheep around lambing limits the insight into generating hypotheses at flock level for risks for clinical mastitis across the whole industry. Whilst indoor production was generally associated with an increased IRCM, for ewes with large litter size indoor lambing was protective, we hypothesise that this is possibly because of better nutrition or reduced exposure to poor weather and factors associated with hygiene.

A longitudinal study of risk factors for teat lesions in 67 suckler ewes in a single flock in England.

A longitudinal study of 67 suckler ewes on a commercial sheep farm near Wolverhampton, England was carried out from March to July 2010. Data on ewe teat lesions and udder and teat conformation were collected together with data on lamb health and weight at lambing and at 14-day intervals until lambs were 8-10 weeks old. Each ewe was examined on 4-5 occasions. Teat lesions were categorised as traumatic or non-traumatic based on appearance. Risk factors for the development of each type of teat lesion were investigated using mixed effect binomial regression models. The incidence of traumatic teat lesions was greatest 3-4 weeks after lambing with 27.9% new cases by udder half. There was an increased risk of traumatic teat lesions in 2 year old ewes (OR 3.5, CI 1.2, 10.5) compared with 6 year old ewes and in ewes with abnormal compared with normal teat placement, a wide or narrow udder width compared with a normal udder width, a heavy total litter weight, body condition score (BCS)<2.5, compared with BCS of 2.5 14-days previously, and in ewes with abnormal udder skin (waxy, dry or chapped) compared with normal udder skin. The incidence of non-traumatic teat lesions was greatest 7-10 weeks after lambing with 21.4% new cases. Non-traumatic lesions were more likely to occur in ewes with BCS=3 compared with BCS of 2.5. The risk factors for traumatic and non-traumatic teat lesions differ. Traumatic lesions are associated with teat and udder morphology, ewe age and BCS, and lamb growth rate, whereas non-traumatic lesions are associated with ewe BCS.

A cohort study of the associations between udder conformation, milk somatic cell count, and lamb weight in suckler ewes.

A cohort study of 67 suckler ewes from 1 farm was carried out from January to May 2010 to investigate associations between udder conformation, udder half milk somatic cell count (SCC), and lamb weight. Ewes and lambs were observed at lambing. Ewe health and teat condition and lamb health and weight were recorded on 4 to 5 further occasions at 14-d intervals. At each observation, a milk sample was collected from each udder half for somatic cell counting. Two weeks after lambing, ewe udder conformation and teat placement were scored. Low lamb weight was associated with ewe SCC >400,000 cells/mL (-0.73 kg), a new teat lesion 14 d previously (-0.91 kg), suboptimal teat position (-1.38 kg), rearing in a multiple litter (-1.45 kg), presence of diarrhea at the examination (-1.19 kg), and rearing by a 9-yr-old ewe compared with a 6-yr-old ewe (-2.36 kg). High lamb weight was associated with increasing lamb age (0.21 kg/d), increasing birth weight (1.65 kg/kg at birth), and increasing number of days the ewe was given supplementary feed before lambing (0.06 kg/d). High udder half SCC was associated with pendulous udders (9.6% increase in SCC/cm of drop) and greater total cross-sectional area of the teats (7.2% increase of SCC/cm(2)). Low SCC were associated with a heavier mean litter weight (6.7% decrease in SCC/kg). Linear, quadratic, and cubic terms for days in lactation were also significant. We conclude that poor udder and teat conformation are associated with high levels of intramammary infection, as indicated by increased SCC and that both physical attributes of the udder and SCC are linked to lamb growth, suggesting that selection of suckler ewes with better udder and teat conformation would reduce intramammary infection and increase lamb growth rate.

Short communication: Preliminary investigation into the effect of freezing and a cryopreservant on the recovery of mastitis pathogens from ewe milk.

The objective of this study was to investigate the recovery of bacteria from ewe milk after freezing for 4 or 8 wk with and without the addition of glycerol as a cryopreservant. A total of 50 udder-half milk samples with a known range of bacterial species were selected, stored, and analyzed in 5 treatment groups: time zero; frozen for 4 wk with, and without, glycerol; and frozen for 8 wk with, and without, glycerol. A lower recovery was observed in all bacterial species studied after freezing. Samples containing fewer than 100 cfu/mL came from ewes with a lower somatic cell count and were more likely to be bacteriologically negative after freezing than those above this threshold. The addition of glycerol increased recovery of gram-negative bacteria after freezing, although this requires further study to draw strong conclusions. The effects on gram-positive species were inconsistent. We conclude that although the addition of glycerol had a small beneficial effect on the sensitivity of detection of bacteria from frozen sheep milk, sensitivity was highest in cultures from fresh milk.