Beef Research News
Brought to you by Kansas State University
College of Veterinary Medicine - Agricultural Practices Section
April 2007
Contents:
Meta-analysis of BRD treatment with tulathromycin
Comparison of progestin-based synchronization protocols
Comparison of Neospora caninum serological tests
Validation of beef quality DNA tests
CIDR-based estrus synchronization
programs in beef heifers
Meta-analysis of BRD treatment with tulathromycin
A systematic review of published
literature was performed to evaluate the comparative efficacy of
tulathromycin at resolving bovine respiratory disease in North American
feedlot cattle. A search was conducted to identify all manuscripts
relating to antibiotic treatment of cattle with respiratory disease
revealing 782 potential manuscripts. Relevant studies reported treatment
with tulathromycin of naturally occurring respiratory disease in beef
cattle. Studies which failed to use randomization to minimize bias were
excluded from the review. After relevance screening and quality
assessment, 21 high quality manuscripts were available for analysis. In
the meta-analysis of studies comparing tilmicosin with tulathromycin,
the summary Mantel–Haenszel relative risk was 0.51 (95% confidence
interval 0.45–0.57). It was not possible to calculate a summary Mantel–Haenszel
relative risk comparing florfenicol with tulathromycin as the only three
studies reported this comparison. When using a meta-analysis to combined
data from randomized clinical trials reporting treatment with
tulathromycin or either florfenicol or tilmicosin, tulathromycin was
associated with an approximately 50% reduction in the risk of
re-treatment for bovine respiratory disease compared with treatment with
tilmicosin.
Wellman, N.G., A.M. O’Connor. Meta-analysis of treatment of cattle with
bovine respiratory disease with tulathromycin. J. Vet. Pharmacol. Therap.
2007 doi:10.1111/j.1365-2885.2007.00846.x
Comparison of progestin-based synchronization protocols
This experiment was designed to compare pregnancy rates in postpartum
beef cows resulting from fixed-time AI (FTAI) after treatment with one
of two protocols to synchronize estrus and ovulation. Crossbred, suckled
beef cows (n = 650) at four locations (n = 210; n = 158; n = 88; n =
194) were assigned within a location to one of two protocols within age
group by days postpartum and BCS. Cows assigned to the MGA Select
treatment (MGA Select; n = 327) were fed melengestrol acetate (MGA; 0.5
mg•hd-1•d-1) for 14 d, GnRH (100 µg i.m. Cystorelin) was injected on d
26, and PGF2 (PG; 25 mg i.m. Lutalyse) was injected on d 33. Cows
assigned to the CO-Synch + CIDR protocol (CO-Synch + CIDR; n = 323) were
fed carrier for 14 d, were injected with GnRH and equipped with an EAZI-BREED
Controlled Internal Drug Release insert (CIDR; 1.38 g progesterone) 12 d
after carrier removal, and PG (25 mg i.m. Lutalyse) was injected and
CIDR were removed on d 33. Fixed-time AI was performed at 72 or 66 h
after PG for MGA Select and CO-Synch + CIDR groups, respectively. All
cows were injected with GnRH (100 µg i.m. Cystorelin) at the time of
insemination. Blood samples were collected 8 and 1 d before the start of
MGA or carrier to determine estrous cyclicity status of cows (estrous
cycling versus anestrus) before treatment [progesterone 0.5 ng/mL; (MGA
Select, 185/327, 57%; CO-Synch + CIDR, 177/323, 55%); P = 0.65]. There
was no difference (P = 0.20) between treatments associated with
pregnancy rate to FTAI (MGA Select, 201/327, 61%; CO-Synch + CIDR,
214/323, 66%). There was also no difference (P = 0.25) between
treatments in final pregnancy rate at the end of the breeding period (MGA
Select, 305/327, 93%; CO-Synch + CIDR, 308/323, 95%). These data
indicate that pregnancy rates were comparable after FTAI, following
administration of the MGA Select or CO-Synch + CIDR protocols. Both
protocols provide opportunities for beef producers to utilize AI and
potentially eliminate the need to detect estrus.
Schafer, D.J., J.F. Bader, J.P. Meyer, J.K. Haden, M.R. Ellersieck, M.C.
Lucy, M.F. Smith, D.J. Patterson. Comparison of progestin-based
protocols to synchronize estrus and ovulation before fixed-time
artificial insemination in postpartum beef cows. J. Anim Sci. 2007 doi:
10.2527/jas.2006-836.
Comparison of
Neospora caninum serological tests
A study was conducted to evaluate the performance and agreement of
various commercial and in-house Neospora caninum antibody assays used in
dairy cattle in North America. From 1998 to 2005, three enzyme linked
immunosorbent assays (ELISAs, a competitive ELISA-VMRD Inc., ian
indirect ELISA-Biovet Inc., and another indirect ELISA-Herdchek IDEXX
Corp.), two indirect fluorescent antibody tests (IFATS, VMRD Inc., and
in-house USDA) and one N. caninum agglutination test (NAT, in-house
USDA) were utilized to test 397 randomly selected dairy cattle serum
samples from 34 herds in eastern Canada for antibodies to
N. caninum.
Manufacturer’s cutoff values were used to evaluate test performance and
agreement between tests. One IFAT (VMRD Inc.) performed well
(sensitivity and specificity: 0.97 and 0.97 respectively) using
reference sera (n = 452), therefore, results from this IFAT on the 397
samples could subsequently be used as the reference standard to
calculate test characteristics for the other assays. Sensitivity was >
0.89 for all assays except the NAT, which had a significantly lower
sensitivity (0.66). Specificity was high (> 0.94) for all assays except
for one indirect ELISA (specificity = 0.52). This indirect ELISA did not
perform satisfactorily when used in 1998, but an improved version of the
ELISA performed as one of the best assays in 2004. The performance
characteristics observed for most assays in this study make them useful
for screening antibodies to N. caninum in cattle.
Wapenaar, W., H. Barkema, J. VanLeewen, J. McClure, R. O’Handley, O.
Kwok, P. Thulliez, J. Dubey, M. Jenkins. Comparison of serological
methods for the diagnosis of Neospora caninum infection in cattle. Vet
Parasitology. 2007 143(2): 166-173.
Validation of beef quality DNA tests
Associations between 3 commercially available
genetic marker panels (GeneSTAR Quality Grade, GeneSTAR Tenderness, and
Igenity Tender-GENE) and quantitative beef traits were validated by the
US National Beef Cattle Evaluation Consortium. Validation was
interpreted to be the independent confirmation of the associations
between genetic tests and phenotypes, as claimed by the commercial
genotyping companies. Validation of the quality grade test (GeneSTAR
Quality Grade) was carried out on 400 Charolais x Angus crossbred
cattle, and validation of the tenderness tests (GeneSTAR Tenderness and
Igenity Tender-GENE) was carried out on over 1,000 Bos taurus and Bos
indicus cattle. The GeneSTAR Quality Grade marker panel is composed of 2
markers (TG5, a SNP upstream from the start of the first exon of
thyroglobulin, and QG2, an anonymous SNP) and is being marketed as a
test associated with marbling and quality grade. In this validation
study, the genotype results from this test were not associated with
marbling score; however, the association of substituting favorable
alleles of the marker panel with increased quality grade (percentage of
cattle grading Choice or Prime) approached significance (P 0.06), mainly
due to the effect of 1 of the 2 markers. The GeneSTAR Tenderness and
Igenity TenderGENE marker panels are being marketed as tests associated
with meat tenderness, as assessed by Warner-Bratzler shear force. These
marker panels share 2 common µ-calpain SNP, but each has a different
calpastatin SNP. In both panels, there were highly significant (P <
0.001) associations of the calpastatin marker and the µ-calpain
haplotype with tenderness. The genotypic effects of the 2 tenderness
panels were similar to each other, with a 1 kg difference in Warner-Bratzler
shear force being observed between the most and least tender genotypes.
Unbiased and independent validation studies are important to help build
confidence in marker technology and also as a potential source of data
required to enable the integration of marker data into genetic
evaluations. As DNA tests associated with more beef production traits
enter the marketplace, it will become increasingly important, and likely
more difficult, to find independent populations with suitable phenotypes
for validation studies.
Van Eenennaam, A.L., J. Li, R.M. Thallman, R.L. Quaas, M.E. Dikeman,
C.A. Gill, D.E. Franke, and M.G. Thomas. Validation of commercial DNA
tests for quantitative beef quality traits. J. Anim Sci. 2007 85:
891-900.
CIDR-based
estrus synchronization programs in beef heifers
The objective of the experiment was to compare pregnancy rates resulting
from fixed-time AI (FTAI) following administration of either one of two
controlled internal drug release (CIDR)-based protocols. Heifers at
three locations (Location 1, n=78; Location 2, n=61; Location 3, n=78)
were assigned to one of two treatments within reproductive tract scores
(RTS; 1 to 5, 1 = immature, and 5 = cycling) by age and weight. Heifers
assigned to CIDR Select received a CIDR insert (1.38 g progesterone)
from d 0 to 14 followed by GnRH (100 µg, i.m.) 9 d after CIDR removal (d
23) and PGF2 (PG, 25 mg, i.m.) 7 d after GnRH treatment (d 30). Heifers
assigned to CO-Synch + CIDR were administered GnRH and received a CIDR
insert on d 23, and PG and CIDR removed on d 30. Heifers at location 1
were fitted with a HeatWatch Estrus Detection System transmitter from
the time of PG until 24 d after FTAI to allow for continuous estrus
detection. Artificial insemination was performed at predetermined
fixed-times for heifers in both treatments at 72 or 54 h after PG for
the CIDR Select and CO-Synch + CIDR groups, respectively. All heifers
were administered GnRH at the time of insemination. Blood samples were
collected 10 d before and immediately before treatment initiation (d 0)
to determine pre-treatment estrous cyclicity (progesterone 0.5 ng/mL).
At Location 1, estrous response during the synchronized period was
greater (P = 0.06; 87 vs. 69%, respectively) and the variance for
interval to estrus after PG was reduced among CIDR Select (P < 0.01)
than for CO-Synch + CIDR treated heifers. Fixed-time AI pregnancy rates
were significantly greater (P = 0.02) following the CIDR Select protocol
(62%) compared with the CO-Synch + CIDR protocol (47%). In summary, the
CIDR Select protocol resulted in a greater and more synchronous estrous
response and significantly greater fixed-time AI pregnancy rates
compared with the CO-Synch + CIDR protocol.
Busch, D.C., D.J. Wilson, D.J. Schafer, N.R. Leitman, J.K. Haden, M.R.
Ellersieck, M.F. Smith, D.J. Patterson. Comparison of CIDR-based estrus
synchronization protocols before to fixed-time AI on pregnancy rate in
beef heifers. J. Anim Sci. 2007 85
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