1Facultad de Medicina Veterinaria y Zootecnia,
Universidad Veracruzana.
Circunvalación y Yañez,
Col.
Unidad Veracruzana, 91710,
Veracruz,
Veracruz,
México
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The aim of this study was to epidemiologically
characterize the appearance of clinical bovine respiratory disease
complex (BRDC) in a Mexican feedlot. A retrospective study on 260211
records registered over a year and collected
from animals housed in
210 pens
was performed. In the
study period, a total of 67467 steers were housed, with an
incoming monthly
average of 5190 ± 1252. There were 12783 BRDC clinical cases (18.9% of
total steers), representing between 84.5 and 99.9% of all disease cases
identified monthly in the pens (95.18 ± 5.10% sick animals per month).
Other conditions requiring animal medication were lameness, diarrhea,
and balanoposthitis. The average weight at BRDC first treatment was
335.71 ± 9.78 kg, but sick animals lost 15 kg. in average between the
weight on arrival and the weight at first treatment. Average rectal
temperature in animals affected by BRCD was 39.34 ± 0.940C
and 39.23 ± 0.670C in relapsed steers. During the studied
period 400 animals died (0.15% of the total), but only 105 died from
BRCD (0.04% of the total). Overall monthly BRDC deaths represented 26.5%
of total deaths, but the proportion of monthly deaths due to BRDC to the
total number of deaths ranged between 0.22% and 48.1%, with higher
values between July and September, 2010. BRDC lethality rate had an
average value of 0.82% during the period, ranging monthly between 0.17
and 2.21 %. The average success of a first treatment against BRDC was
92.4%. Average monthly relapsed animals were 67 ± 41.3, ranging between
31 and 172 cases in April and February, respectively. Almost twice the
number of sick animals was observed in winter (34%) than in fall, which
had the lowest proportion of cases (18.1%); spring (22.4%) and summer
(25.5%) had intermediate levels. The feedlot had only five animal
suppliers, but most steers came from southern
Veracruz
(54.6%, 35190/67467). The percentage of BRDC sick animals by provenance
of origin ranged from 3.68% (Tuxtepec, Oaxaca) to 19.15% (Chiapas).
According to provenance, the number of relapsed animals ranged from one
(Tuxtepec, Oaxaca) to 493
(south of Veracruz), but animals from
more distant places (Tabasco and Chiapas), exhibited the highest value
(between 7.65 and 7.85%). The heaviest and the lightest steers
were more prone to BRDC relapse than animals in an average weight. Only
11 animals required a third treatment, five of which were treated in
February. In conclusion, most susceptible steers to BRDC illness were
those transported over larger distances, those which arrive in winter,
as well as the heaviest and the lightest.
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