The dysbiosis of ovine foot microbiome during the development and treatment of contagious ovine digital dermatitis

BACKGROUND

Contagious Ovine Digital Dermatitis (CODD) is an emerging and common infectious foot disease of sheep which causes severe welfare and economic problems for the sheep industry. The aetiology of the disease is not fully understood and control of the disease is problematic. The aim of this study was to investigate the polybacterial aetiopathogenesis of CODD and the effects of antibiotic treatment, in a longitudinal study of an experimentally induced disease outbreak using a 16S rRNA gene amplicon sequencing approach.

RESULTS

CODD was induced in 15/30 experimental sheep. During the development of CODD three distinct phenotypic lesion stages were observed. These were an initial interdigital dermatitis (ID) lesion, followed by a footrot (FR) lesion, then finally a CODD lesion. Distinct microbiota were observed for each lesion in terms of microbial diversity, clustering and composition. Porphyromonadaceae, Family XI, Veillonellaceae and Fusobacteriaceae were significantly associated with the diseased feet. Veillonellaceae and Fusobacteriaceae were most associated with the earlier stages of ID and footrot rather than CODD. Following antibiotic treatment of the sheep, the foot microbiota showed a strong tendency to return to the composition of the healthy state. The microbiota composition of CODD lesions collected by swab and biopsy methods were different. In particular, the Spirochaetaceae family were more abundant in samples collected by the biopsy method, suggesting that these bacteria are present in deeper tissues of the diseased foot.

CONCLUSION

In this study, CODD presented as part of a spectrum of poly-bacterial foot disease strongly associated with bacterial families Porphyromonadaceae, Family XI (a family in Clostridiales also known as Clostridium cluster XI), Veillonellaceae and Fusobacteriaceae which are predominately Gram-negative anaerobes. Following antibiotic treatment, the microbiome showed a strong tendency to return to the composition of the healthy state. The composition of the healthy foot microbiome does not influence susceptibility to CODD. Based on the data presented here and that CODD appears to be the severest end stage of sheep infectious foot disease lesions, better control of the initial ID and FR lesions would enable better control of CODD and enable better animal welfare.

The impact of early life nutrition and housing on growth and reproduction in dairy cattle

Contentious issues in calf rearing include milk feeding practices and single versus group housing. The current study was performed on a high producing 170 Holstein cow dairy farm, to investigate the impact of nutrition and housing on growth and reproduction. Heifer calves (n = 100) were allocated in birth order to one of two commonly used management strategies. All calves received 3-4 litres of dam specific colostrum within 6 hours of birth. Group A calves were group housed from birth and fed milk replacer (MR) ad libitum via a computerised machine utilising a single teat, with weaning commencing at 63 days of age. Group R calves were initially housed in individual pens and received 2.5 litres of MR twice daily via a bucket until 21 days of age when they were group housed and fed 3 litres of MR twice daily via a group trough with weaning commencing at 56 days. From 12 weeks of age onwards, calves in both dietary groups were subject to common nutritional and husbandry protocols. All breeding of heifers was via artificial insemination with no hormonal intervention. Calves were weighed, body condition scored and morphometric measures recorded weekly up till 12 weeks of age then monthly until conception. Pre-weaning growth rates (kg/day) were significantly higher in Group A calves compared to Group R (0.89, 95% CI 0.86-0.93 vs 0.57, 95% CI 0.54-0.6 kg/day P < 0.001) with the most marked differences observed during the first three weeks of life (0.72, 95% CI 0.61-0.82 vs 0.17, 95% CI 0.08-0.26 P < 0.001). Whilst Group A calves gained body condition score (BCS) throughout the pre-weaning phase, Group R calves lost BCS during the first 4 weeks of life. Data suggested that Group R calves supported skeletal growth during this period by catabolising body tissue. Group A calves had a greater risk of disease than group R calves during the pre-weaning phase (diarrhoea: odds ratio 3.86, 95% CI 1.67-8.9; pneumonia: odds ratio 5.80, 95% CI 2.33-14.44) although no calves died during this period. Whilst pneumonia had a significant impact on growth during the study duration (P = 0.008), this was not the case for diarrhoea. Whilst univariate analysis failed to show any statistically significant group differences (P > 0.050) in any of the mean values of measured reproductive parameters, multivariable Cox regression suggested that there was a weak trend (P = 0.072) for Group A animals to achieve first service earlier than their Group R counterparts (62.6 weeks versus 65.3 weeks). Irrespective of dietary group, the hazard for achievement of all measured reproductive parameters, apart from time to puberty, was 20-40% less for heifers borne from multiparous dams compared to heifers from primiparous dams.

Inter-observer agreement for clinical examinations of foot lesions of sheep

In sheep, the diagnosis of foot lesions is routinely based on physical examination of the hoof. Correct diagnosis is important for the effective treatment, prevention and control of both infectious and non-infectious causes of lameness. Therefore, the aim of this study was to evaluate the level of inter-observer agreement for clinical examination of ovine foot lesions. Eight observers of varying experience, training and occupation performed foot examinations on a total of 1158 sheep from 38 farms across North England and Wales. On each farm, a group of two to four observers independently examined a sample of 24 to 30 sheep to diagnose the presence or absence of specific foot lesions including white line lesions (WL), contagious ovine digital dermatitis (CODD), footrot (FR), inter-digital dermatitis (ID) and toe granuloma (TG). The inter-observer agreement of foot lesion assessments was examined using Fleiss kappa (κ), and Cohen's κ examined the paired agreement between the test standard observer (TSO) and each observer. Scoring differences with the TSO were examined as the percentage of scoring errors and assessed for evidence of systematic scoring bias. With the exception of WL (maximum error rate 33.3%), few scoring differences with the TSO occurred (maximum error rate 3.3%). This suggests that observers can achieve good levels of reliability when diagnosing most of the commonly observed foot conditions associated with lameness in sheep.

184 PRELIMINARY FINDINGS ON CARBOHYDRATE METABOLISM OF INTACT EQUINE CUMULUS-OOCYTE COMPLEXES DURING IN VITRO MATURATION

Production of equine embryos in vitro is gaining popularity, and many differences exist in composition of in vitro maturation (IVM) media. Metabolism of the cumulus-oocyte complex (COC) is essentially unknown in the horse. Here, we describe preliminary data on carbohydrate metabolism of the equine COC during IVM. COC, collected by scraping of the granulosa layer of all visible follicles of abattoir-derived ovaries, were held overnight (12–18 h) at room temperature (~20°C) and then placed in Maturation Medium (M199 with Earle’s salts, 10% FBS, with 25 μg mL–1 gentamicin and 5 mU mL–1 FSH). They were incubated singly in 10-μL droplets under mineral oil for 30 h at 38.3°C in 5% CO2 in air. Control droplets without COC were incubated in the same dish. After incubation, COC were removed and spent media kept at –80°C for later analysis. Oocytes were denuded of cumulus cells by pipetting in the presence of hyaluronidase and evaluated by light microscopy at 500×. Those with a visible polar body were classified as metaphase II (MII); oocytes with an intact oolemma and no polar body were classified as immature intact (INT) and those with an irregular or unapparent oolemma, or shrunken cytoplasm, were classed as degenerating (DEG). To adjust for variation in cumulus cell number, the stripped cumulus cells were frozen at –20°C and later analysed for DNA content using Picogreene. The spent media was analysed for depletion of glucose and appearance of lactate on a BMG Fluostar spectrophotometer using an enzyme-linked ultrafluorometric method. Data were expressed as pmol/ng DNA/hr and analysed by t-test, x2 and logistic regression. Thirty COC were cultured and analysed; 14 were classified as MII, 2 INT and 14 DEG. Seven COC (23%) depleted all the available glucose, indicating that the rate of glucose consumption in those 7 complexes was ≥1866 pmol/COC per hour. DNA content was positively correlated with glucose depletion (P = 0.02). In the COC that did not deplete available glucose, the ratio of glucose consumption:lactate production was 1.82, indicating that the major fate of exogenous glucose was production of lactate by glycolysis. In the 7 oocytes that depleted all the glucose, the ratio of glucose consumption:lactate production was 1.22. One explanation for this may be that when glucose was no longer available, it was conserved for other pathways. It was noteworthy that these COC had more cumulus cells (P < 0.01) and the maturation rate was 4/7 (57%). In the group of COC that did not deplete all of the glucose, there was no significant difference in glucose consumption (13.17 v. 12.25 pmol/ng DNA per hour; P > 0.4) or lactate production (21.48 v. 20.28 pmol/ng DNA per hour; P > 0.4) between COC in which the oocyte reached MII (10/23; 43%), and those which contained a degenerated oocyte at the end of culture, respectively. To the best of our knowledge, this is the first report documenting the metabolism of equine COC. These data underline the importance of further studies to determine optimal conditions for in vitro maturation of equine COC, especially in terms of glucose availability.

Digital dermatitis treponemes associated with a severe foot disease in dairy goats

A UK dairy goat herd was assessed after reports of a severe lameness problem of unknown aetiology. A lameness prevalence estimate was produced and individual clinical examination of 15 randomly selected lame goats was performed. Fifteen animals had foot lesions closely resembling contagious ovine digital dermatitis (CODD) in sheep. Eight of the goats examined presented with typical CODD lesions and seven showed what appeared to be a more severe CODD with under-running of the sole. Ten biopsy samples were obtained from the foot lesions and tested by PCR for the three previously isolated digital dermatitis (DD) Treponema phylogroups and culture of treponemes was attempted. Ninety per cent of the biopsy samples were positive for Treponema medium/Treponema vincentii-like spirochaetes and Treponema phagedenis-like DD spirochaetes and 80per cent were positive for Treponema pedis. Spirochaetes were successfully isolated from 50 per cent of lesion samples. Three isolates were identified as belonging to the T. phagedenis-like spirochaetes and two were identified as T. pedis. The frequent isolation of similar treponemes to those isolated from bovine digital dermatitis and CODD lesions and the identification of these DD-associated phylotypes in the vast majority of lesions support the hypothesis that this novel foot condition is associated with infection by DD treponemes, and given the similarities to CODD, it suggests a causal role.

Comparison of oestrus detection methods in dairy cattle

Sixty-seven Holstein-Friesian cows, from 20 days postpartum, were recruited into the study and fitted with both a pedometer (SAE Afikim) and a Heatime neck collar (SCR Engineers) and allocated a heat mount detector (either scratchcard [Dairymac] or KaMaR [KaMaR]) or left with none, relying only on farm staff observation. Common production stressors and other factors were assessed to determine their impact on the ability of each method to accurately detect oestrus and to investigate effects on the frequency of false-positive detections. Only 74 per cent of all potential oestrus periods (episodes of low progesterone) were identified by combining information from all methods. There was no difference between the methods in terms of sensitivity for detecting 'true oestrus events' (approximately 60 per cent), with the exception of scratchcards, which were less efficient (36 per cent). Pedometers and KaMaRs had higher numbers of false-positive identifications. No production stressors had any consequence on false-positives. The positive predictive values for neck collars or observation by farm staff were higher than those of other methods, and combining these two methods yielded the best results. Neck collars did not detect any of the nine oestrus events occurring in three cows with a body condition score (BCS) of less than 2, and the efficiency of correctly identifying oestrus was also reduced by high milk yield (odds ratio [OR]=0.34). Pedometer efficiency was reduced by lameness, low BCS or high milk yield (OR=0.42, 0.15 or 0.30, respectively).

Height measurement in horses and ponies: optimising standard protocols

Standard and modified measuring sticks were used to record height at the withers and a 'non-contact' laser was used to measure withers and loin heights. Sixty horses and ponies, ranging in height (115 to 155 cm) and body condition score (BCS) (moderate to obese) were measured by each method at 10-minute intervals for 40 minutes. Measurement series were repeated over three successive days. Unique regression models were constructed for method-specific data. Coefficients of variation were similar for stick and laser methods (0.002 to 0.004 per cent). Models were not influenced by day of measurement or BCS. Withers height decreased significantly (0.48 cm, 95 per cent confidence intervals -0.61 to -0.36 cm, P<0.001) over the first 20 minutes. In living animals, laser-derived measurements of withers height at T(20) exceeded stick measurements by approximately 1 cm (P<0.001). Loin height remained similar across time. Some alteration in relaxed withers height is an inevitable consequence of changes in muscle tone at the scapulothoracic synsarcosis.

Comparing the Fatty Acid Composition of Organic and Conventional Milk

During a 12-mo longitudinal study, bulk-tank milk was collected each month from organic (n = 17) and conventional (n = 19) dairy farms in the United Kingdom. All milk samples were analyzed for fatty acid (FA) content, with the farming system type, herd production level, and nutritional factors affecting the FA composition investigated by use of mixed model analyses. Models were constructed for saturated fatty acids, the ratio of polyunsaturated fatty acids (PUFA) to monounsaturated fatty acids, total n-3 FA, total n-6 FA, conjugated linoleic acid, and vaccenic acid. The ratio of n-6:n-3 FA in both organic and conventional milk was also compared. Organic milk had a higher proportion of PUFA to monounsaturated fatty acids and of n-3 FA than conventional milk, and contained a consistently lower n-6:n-3 FA ratio (which is considered beneficial) compared with conventional milk. There was no difference between organic and conventional milk with respect to the proportion of conjugated linoleic acid or vaccenic acid. A number of factors other than farming system were identified which affected milk FA content including month of year, herd average milk yield, breed type, use of a total mixed ration, and access to fresh grazing. Thus, organic dairy farms in the United Kingdom produce milk with a higher PUFA content, particularly n-3 FA, throughout the year. However, knowledge of the effects of season, access to fresh grazing, or use of specific silage types could be used by producers to enhance the content of beneficial FA in milk.