As cholesterol deficiency（CD）of Holstein-Friesian cows is an autosomal recessive disorder, clinical symptoms should not occur in heterozygous individuals. However, the serum total cholesterol（TC）level in healthy heterozygous bulls has been reported to be lower than that in wildtype animals. In the present study, serum TC and milk production of healthy heterozygous cows were evaluated to clarify the effect of heterozygosity on milk production. A total of 93（14.9%） among 718 clinically healthy cows on five farms were found to be heterozygous. The serum TC level of the heterozygous group was significantly lower than that of the wild-type group. In one of the two farms where milk production data were available, the corrected 305-day milk yield of heterozygous cows was significantly lower than that of wild-type cows. In another farm, the corrected 305-day milk yield of heterozygous cows was numerically lower than that of wild-type cows. The corrected 305-day milk fat, protein and solids-not-fat percentages were higher or significantly higher in the heterozygous group compared with wild-type cows. There were no differences in open period or insemination frequency between the two groups.
To determine the most effective antimicrobial agent for urologic diseases in cattle, we performed antibiotic susceptibility testing for pathogenic bacteria in Japanese Black cattle with urinary tract infection（UTI）. A total of 53 bacterial strains were isolated from 30 cattle with UTI at our hospital in a 9-year period from 2010 to 2019.
Sixteen bacterial strains were isolated from the urine samples of eight cattle（female: 6; male: 2）with simple UTI. Common bacterial isolates were Trueperella pyogenes（19%）, Staphylococcus spp.（13%）, Aerococcus viridans（13%）, and Corynebacterium spp.（6%）among Gram-positive bacteria and Escherichia coli（25%）, Proteus mirabilis（12%）, and Klebsiella pneumoniae（6%）among Gramnegative bacteria. Thirty-seven bacterial strains were isolated from the urine samples of 22 cattle （bull or steer）with UTI complicated with urolithiasis. Common bacterial isolates were P. mirabilis （40%）, E. coli（21%）, and P. vulgaris（3%）among Gram-negative bacteria and Staphylococcus spp. （17%）, Corynebacterium spp.（8%）, and A. viridans（8%）among Gram-positive bacteria.
The in vitro susceptibility rate of the isolates varied across the commonly prescribed antimicrobials for UTI. The susceptibility rates of Gram-positive bacteria other than Staphylococcus spp. to ampicillin and cefazolin exceeded 80%, while those of Gram-negative bacteria to ampicillin were low. Furthermore, the susceptibility rates of P. mirabilis, Corynebacterium spp., and T. pyogenes to marbofloxacin and enrofloxacin exceeded 80%, but that of E. coli to marbofloxacin and enrofloxacin was 72% and 55%, respectively.
The results of the present study revealed that the causative bacteria greatly differed between simple and complicated UTIs. Among the approved antimicrobials for cattle in Japan, ampicillin and cefazolin are recommended as the first-line antibacterials for simple UTI, and cefazolin for complicated UTI. Marbofloxacin may be the most effective second-line antibacterial for P. mirabilis and E. coli.
A 29-month-old Holstein dairy cow presented with astasia and shock-like symptoms after calving. Autosomal recessive cholesterol deficiency（CD）was suspected from markedly low serum total cholesterol（6 mg/dℓ）. A PCR test confirmed homozygosity for the gene responsible for CD. Marked emaciation, anemia and muddy stool were noted on physical examination, and acanthocytes were found in the blood smear. Decreased body fat was notable during necropsy. All of these findings were consistent with those of homozygous calves previously reported. Although most homozygous individuals with CD are reported to die by the age of 6 months, the present report confirmed that some cows with CD can survive to the first calving.