Page 64 - Revista Anual - Nº19

sis (MLSA) genotyping. Two dairy herds with prevalent
S. uberis infections were followed in a 6 month period, in DOENÇA RESPIRATÓRIA BOVINA
order to collect and characterize isolates from cows with
persistent infections. These herds, located in Portugal
(Barcelos and Maia regions), had similar management Association of preweaning and weaning serum cor-
practices, with the herd from Barcelos being smaller tisol and metabolites with ADG and incidence of
and having a better milking parlor management, since respiratory disease in beef cattle.
infected cow segregation was immediate. A total of 54 The objectives of this experiment were to determine the
S. uberis isolates were obtained from 24 different cows association of circulating cortisol, lactate, and glucose
from the two herds. To overcome operator-dependent at, and prior to, weaning with ADG and incidences of
analysis of the dot blots and increase the technique’s bovine respiratory disease (BRD) in beef cattle. A blood
consistency and reliability, the hybridization signals were sample was collected approximately 3 wk prior to wea-
converted into probability values, with average probabi- ning and at weaning from genetically diverse steers
lities higher than 0.5 being considered positive results. and heifers ( = 451). Cattle were weighed periodically
These data allowed to confirm the isolates’ identity as S. throughout the study and ADG was calculated for the
uberis using taxa-specific markers and to determine the preweaning period (152 ± 15 d), the receiving period (45
presence of virulence- and antibiotic resistance-related d postweaning), the finishing period (200 d), and total
genes. In addition, MLSA allowed to disclose the most postweaning ADG. Incidences of BRD were recorded
prevalent S. uberis clonal lineages in both herds. Seven and analyzed as a binary trait. Lung lesions were recor-
different clusters were identified, with Barcelos showing ded at slaughter. Preweaning serum cortisol concentra-
a high clonal diversity and Maia a dominant lineage in- tions were positively associated ( = 0.040) with receiving
fecting most cows, suggesting distinct epidemiological ADG and explained 0.74% of the variance of receiving
patterns, with S. uberis displaying an environmental ADG. Preweaning glucose concentrations were positi-
or contagious transmission pattern depending on the vely associated ( < 0.001) with preweaning ADG and
herd. Overall, this work showed the utility of dot blot and negatively associated with receiving ( = 0.003), finishing
MLSA to characterize population structure and epide- ( = 0.008), and total postweaning ADG ( = 0.002) and ex-
miological patterns of mastitis-causing S. uberis. This plained 2.0% of the variance in total postweaning ADG.
approach allowed to disclose prevalent virulence patter- Variation in preweaning serum glucose concentrations
ns and clonal lineages of S. uberis in two distinct herds, could be indicative of variation in milk consumption, and
and gain insights on the impact of herd management therefore indicate calves receiving less milk grow slo-
practices on pathogen population structure. wer prior to weaning, but experience compensatory gain
Albuquerque, P. et al; Front Microbiol. 2017 Jan 24;8:54 postweaning. Cattle that were diagnosed with BRD ( =
130) grew slower during the receiving phase ( = 0.004),
Presence of Mycobacterium avium subs. paratuber- but total postweaning ADG was not different from cattle
culosis DNA in milk used to feed calves in Portugal. not diagnosed with BRD ( = 0.683). Additionally, cattle
This Technical Research communication describes re- that were diagnosed with BRD in the feedlot tended (
sults of a study aimed at detecting the presence of Map = 0.062) to have slightly lower preweaning serum glu-
in milk fed to calves, and identifying possible risk factors cose concentrations. Using a logistic regression analy-
for that presence. A questionnaire was performed on 37 sis, none of the serum variables measured at or before
dairy farms and waste milk samples were collected on weaning were predictive of developing BRD ( > 0.180).
3 occasions separated by a minimum of 1 week. For Weaning serum glucose concentrations tended to be
farms not feeding waste milk, bulk tank milk samples predictive of the presence of lung lesions at weaning (
were collected instead. A real time PCR for the detec- = 0.060). These data indicate that glucose measured
tion of the IS900 sequence was performed for the de- early in life is associated with growth rate, and could
tection of Map. A majority of farms (89·2%) fed waste indicate that carbohydrate metabolism could contribute
to variation in ADG.
milk, with only one pasteurising the milk before feeding Foote, AP. et al; J Anim Sci. 2017 Nov;95(11):5012-5019
it to calves. Results of the PCR showed that 51·5% of
the farms that were feeding waste milk had a positive Herd-level prevalence of the ultrasonographic lung
result for Map on that milk. None of the studied risk fac- lesions associated with bovine respiratory disease
tors were significantly associated with the presence of and related environmental risk factors.
Map in milk samples, possibly due to the small number Bovine respiratory disease complex (BRD) is a major
of farms entering the study. However, the prevalence of calf disease during the preweaning period. Thoracic ul-
positive samples for Map on PCR was 3·5 times higher trasound (TUS) has been recently described as a re-
for farms that bought in animals from a single origin and liable tool for assessing BRD-associated lung lesions.
1·9 times higher for farms that bought from multiple far- The objectives of this study were to define the herd-le-
ms, when compared with closed farms. Having a calving vel prevalence of lung consolidation assessed by TUS
area for multiple cows also increased the risk of a posi- (CONSTUS). A total of 39 Québec dairy herds were ran-
tive Map result by 1·5 when compared with single pens. domly chosen to participate in this cross-sectional study.
The risk of having a positive Map result on waste milk Between 6 and 12 preweaned calves were examined
was 1·6 times higher for farms feeding that milk to male for signs of CONSTUS defined by any site with ≥3 cm
calves and 1·4 for farms feeding to both male and fema- consolidated lung tissue during 1 visit in summer and 1
le calves, when compared with farms not feeding waste visit in winter. Herd questionnaire focused on calf health
milk. This study highlights paratuberculosis as one of and housing data [airborne bacteria (aerobic, coliform,
the potential risks of feeding waste milk to calves, and yeasts and mold counts), air drafts, temperature, hygro-
the need for mitigation strategies to be in place to avoid metry, and ammonia levels] were also collected during
unnecessary disease transmission. these visits looking for potential association with CONS-
Leão, C. et al; J Dairy Res. 2017 May;84(2):124-127. TUS prevalence. The median herd-level of CONSTUS