Low protein diets (LPs) constitute a reportedly effective form of nutritional therapy for canine chronic kidney disease and cirrhosis. These diets have long been feared to result in reduced muscle mass due to protein catabolism. This adverse effect, however, remains largely unrecognized in veterinary medicine as there are no easily applicable catabolism indicators. Therefore, we focused on urinary creatinine, a metabolite of protein in the urine, and examined whether its ratio to urinary urea nitrogen (UCrn/UN) can be used to assess protein catabolism. In Experiment 1, we first consecutively fed seven healthy beagles an LP, standard protein (SP), and high protein (HP) diet for 1 week each and then measured the UCrn/UN ratio at 2-h intervals from fasting to 16 h post-prandially. We consequently found that the UCrn/UN ratio was significantly elevated in the LP pre-prandially and at all post-prandial measurement points (P < 0.01). No significant differences were observed between the SP and HP. Analysis of fasting plasma amino-acid concentrations revealed that the concentration of methionine was significantly lower in the LP than in the other diets (P < 0.05). Although the effects of this change in amino-acid concentration were unclear, the UCrn/UN ratio was considered having increased due to a deficiency in protein and/or amino acids during LP feeding. In Experiment 2, we continuously fed five healthy beagles an LP for 18 weeks and then measured the UCrn/UN ratio as described above. We also measured changes in body composition with computed tomography. At weeks 10 and 18, the fasting UCrn/UN ratio was significantly higher than it was prior to the start of the LP; however, post-prandially, the UCrn/UN ratio decreased to the point that the significant difference disappeared. Muscle mass decreased at weeks 10 and 18. These results suggest that the fasting UCrn/UN ratio could be used as an indicator of protein catabolism in LP feeding. Our experiments thus indicate that examination of potential increases in the UCrn/UN ratio 1 week after introduction of LP feeding to healthy dogs could enable detection of body protein catabolism in long-term feeding of LP before muscle breakdown occurs.

Most bovine leukemia virus (BLV)-infected cattle do not have clinical signs (aleukemic AL), but some develop persistent lymphocytosis (PL) and B-cell lymphosarcoma (enzootic bovine leucosis [EBL]). BLV infection is a well-known cause of chronic wasting disease, which is associated with a reduction in milk productivity and immunity in dairy cattle. However, the effect of BLV infection on beef cattle is not clear. The objective of this study was to investigate the effect of BLV infection on the productivity of slaughtered beef cattle. A total of 997 blood samples were collected from cattle in 2 slaughterhouses in Miyazaki prefecture, Japan. BLV-antibodies were tested in these cattle＇s blood samples using enzyme-linked immunosorbent assay (ELISA), to identify BLVinfected cattle. We compared blood parameters and carcass weight between BLV ELISA-positive and ELISA-negative cattle in two age groups : young (≤ 60 months) and elder (> 60 months) groups. The results showed that the proportion of ELISA-positive cattle in the young and elder groups were 22.8% and 24.9%, respectively. The number of white blood cells (WBCs) and lymphocytes in ELISA-positive cattle was significantly higher than that in ELISA-negative cattle in the young group. In addition to the number of lymphocytes, the number of monocytes and neutrophils were also significantly higher in BLV ELISA-positive cattle than in ELISAnegative cattle in the elder group. There was no significant difference in the carcass weight between ELISA-positive and ELISAnegative cattle in both groups. The results of this study suggest that BLV infection has an effect on the host immune response in beef cattle.