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ABSTRACT Global advances in reproductive biotechnology have allowed for the transfer of embryos from donor females with high genetic merit to recipients using the cryopreservation technique, which preserves an embryo of excellent quality and viability, thereby achieving a feasible pregnancy rate. The objective of this study was to evaluate the quality and viability of Holstein embryos that have been cryopreserved for more than 40 years under glycerol freezing. The embryos were transferred to the recipient heifers using a non-surgical method. Two 17-month-old Holstein heifers (360 kg live weights) which were clinically healthy and reproductively active were used as the recipients. Two bovine embryos of Grade 1 quality were thawed and evaluated for their morphology. Of the two embryo transfers, one pregnancy was achieved, resulting in the birth of a calf. Therefore, embryos frozen in liquid nitrogen and glycerol as a cryopreservative for more than 40 years maintained their quality and viability to produce a live calf.

Importance: Enrofloxacin preparations are available for administration daily or every 3 days. This study presents clinical evidence to define which preparation is adequate to treat clinical cases of bovine respiratory disease (BRD) in calves., Objective: To correlate the pharmacokinetics/pharmacodynamics (PK/PD) ratios of three pharmaceutical preparations of enrofloxacin with their clinical efficacy in treating BRD., Methods: The PK/PD ratios of three enrofloxacin preparations were determined in healthy calves. Then, 48 BRD-affected calves initially treated IV with 2.2 mg/kg of flunixin-meglumine, were randomly assigned to treatment with: enrofloxacin dihydrate-hydrochloride (enro-C) 10% water suspension daily (10 mg/kg subcutaneous for three to six days); enro-C with alginate (enro-C/Al), and reference enrofloxacin (enro-R), both intended for treatment every 72-h in two occasions (10 mg/kg)., Results: The highest maximum plasma concentration (Cmax)/minimum inhibitory concentration (MIC) ratio was obtained with enro-C and the highest area under the curve (AUC) 0-72 /MIC ratio with enro-R, and enro-C/Al exhibited an AUC 0-72 /MIC smaller, but Cmax/MIC higher than enro-R. Based on repeated statistical measurements, clinical progress revealed that the best outcomes were observed with enro-C ( p < 0.05), and no statistical differences resulted by comparing enro-C/Al with enro-R., Conclusions and Relevance: If the priority in calves affected by BRD is to speed up their recovery, and despite the more significant amount enro-C injected, using of lower doses of enrofloxacin as in the long-acting preparations is unsustainable. This study demonstrates that the clinical efficacy of enrofloxacin in cattle is optimally linked to Cmax/MIC rather than to AUC/MIC, which occurs better when injecting enro-C., Competing Interests: The authors declare no conflicts of interest., (© 2025 The Korean Society of Veterinary Science.)