Objective: To investigate prevalence of BLV and its association with hematological alterations in targeted dairy farms experiencing productivity issues in Korea. Methods: This study investigated five dairy farms reporting decreased milk yield, recurrent mastitis, poor conception rates, and delayed postpartum recovery. Eighty lactating cows underwent physical examination, body condition scoring, hematological and biochemical analyses, and polymerase chain reaction testing for BLV. Results: Overall BLV detection rate among these herds was 70% (56/80), with intra-herd positivity ranging from 57.1 to 90.0%. Lymphocytosis was observed in 31% of the cows.Multivariable generalized estimating equations analysis confirmed that higher lymphocyte counts were the strongest independent predictor of BLV status (adjusted odds ratio, 2.70;p = 0.005), demonstrating a robust association between hematological alterations and BLV positivity. Conclusions and Relevance: BLV infection is highly prevalent in the investigated Korean dairy farms with productivity problems. While these results may not represent the nationwide average due to selection bias, they emphasize the need for nationwide BLV surveillance and implementation of control measures in Korea.

Background: A definite diagnosis should be made in the bovine practice field, however, it was difficult to perform laboratory analysis immediately. Currently, three types of portable blood gas analyzers are available in Korea. Objectives: This study aimed to evaluate the correlations among these three analyzers. Methods: Seventy-two plasma samples from Holstein-Friesian cows were used for blood gas analysis, and three instruments (EDAN i15 Vet, VETSCAN i-STAT, and EPOC) were operated simultaneously. Moreover, plasma calcium levels were compared between these portable analyzers and blood chemistry device, which is usually used in a laboratory environment.Pearson analysis was performed to confirm the correlation of each parameter produced with the three instruments and blood chemistry analyzer. Results: As results, high correlation was observed in parameters of pH, pO2 , potassium ion, ionized calcium, and glucose (p < 0.001, r > 0.7). In addition, pCO 2 showed a moderate correlation among the three analyzers (p < 0.001, r > 0.5), and there was no correlation among all instruments for sodium ions. There was also a high correlation between ionized calcium from the three portable devices and total calcium from the biochemistry analyzer (p < 0.001, r > 0.9). Conclusions In conclusion, there was a high correlation between results from the three different blood gas analyzers used in the bovine clinical field in Korea. Thus, a consistent diagnosis can be made even with different equipment if the operator is aware of the strengths and weaknesses of each piece of equipment and operates it properly.