Beef Research News
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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.
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.
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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