Improved Prediction of Ovulation Time may Increase Pregnancy Rates to Artificial Insemination in Lactating Dairy Cattle

A prospective observational study was conducted in two Australian dairy herds to assess the potential for improving pregnancy rates (proportions of inseminations that result in pregnancy) to artificial insemination (AI) if the time of ovulation could be predicted with more certainty. Herd 1 calved year‐round and inseminations were performed during two periods each day. Herd 2 calved during autumn–winter and inseminations were performed only after the morning milking each day. In both herds, the AI to ovulation interval of enrolled cows was determined by trans‐rectal ovarian ultrasonography approximately 0, 12, 24 and 36 h after AI, and pregnancy was assessed by palpation per rectum 35–56 days after AI. Also, in Herd 1 vaginal electrical resistance (VER) measurements were taken at approximately 0, 12, 24 and 36 h after AI, and in Herd 2 cows were fitted with neck mounted activity meters that monitored cow activity count in 2‐h periods. There was substantial variation in the intervals from AI to ovulation within and between herds (mean ± SD 21.2 ± 10.7, n = 102; 14.7 ± 10.4, n = 100 in herds 1 and 2, respectively). Pregnancy rates were higher for inseminations close to, but preceding, ovulation. Using combined herd data (n = 202), the highest pregnancy rate (50.8%) was observed for inseminations between 0 and 16 h before ovulation, a period in which only a modest proportion of inseminations (31.2%) occurred. In contrast, pregnancy rate was significantly lower (28.7%; risk ratio 0.6; 95% CI 0.4–1.0; p = 0.039) for inseminations between 16 and 32 h before ovulation, a period where the highest proportion of inseminations (53.2%) occurred. Thus pregnancy rates could potentially be improved if a greater proportion of inseminations were conducted shortly before ovulation. In Herd 1, mean VER during the peri‐ovulatory period varied with time from ovulation. Lowest values (mean ± SEM, VER = 64.8 ± 1.2, n = 55) occurred approximately 18 h before ovulation and were significantly lower than measurements approximately 6 h before ovulation (67.4 ± 1.0; n = 73; p = 0.003). Further work is required to determine if VER can be used to identify ovulation time and hence the optimal time to inseminate in individual animals. In Herd 2 a modest proportion of inseminations (26.9%) occurred between 24 and 40 h after the onset of increased cow activity where the highest pregnancy rate (67.9%) was observed, whereas a significantly lower pregnancy rate (42.4%; risk ratio 0.6; 95% CI 0.4–0.9; p = 0.036) was observed for inseminations between 8 and 24 h after the onset of increased cow activity where the highest proportion of inseminations (56.7%) occurred. Thus cow activity monitoring may be useful to identify the optimal time to inseminate cows. Results from this study indicate that improved methods of ovulation prediction may allow better insemination timing relative to ovulation and consequently increased pregnancy rates.     

Radiophosphorus (32P) treatment of bone marrow disorders in dogs: 11 cases (1970-1987)

Between March 1970 and February 1987, radiophosphorus (32P) was used to treat bone marrow disorders in 6 dogs; 4 had polycythemia vera and 2 had essential thrombocythemia. Activities of 32P given initially ranged from 2.4 to 3.3 mCi/m2. Four dogs responded well to 32P treatment, with gradual resolution of high RBC or platelet counts. Two of these dogs died of intercurrent disease unrelated to their bone marrow disorder, before blood counts could be stabilized. Two dogs did not respond to the initial 32P treatment nor to additional treatments with 32P, and had clinical signs and blood counts stabilized by use of phlebotomy or chemotherapeutic agents. We reviewed and analyzed 5 other cases of bone marrow disorders in dogs treated with 32P and included the findings from their records with the records of our 6 dogs in this retrospective analysis. Of the 8 dogs with polycythemia vera treated with 32P, 5 were given a single treatment that controlled clinical signs and blood counts for the remainder of the follow-up period. Of the 3 dogs treated for thrombocytosis with 32P, 2 had blood counts that responded to a single treatment.     

Peripheral metabolism of thyroid hormones and iodide in healthy and hyperthyroid cats

The metabolic clearance rate, volume of distribution, and fractional clearance rate of thyroxine (T4), triiodothyronine (T3), and iodide were calculated for 6 healthy and 7 hyperthyroid cats, using single-compartmental and noncompartmental methods of analysis. The mean T4 volume of distribution of the hyperthyroid cats was 32.0% less than that of the healthy cats; it was the only variable that was significantly different (P less than 0.05) between these 2 groups of cats. The mean fractional clearance rate of T4 in the hyperthyroid cats was 53.2% greater than that in the healthy cats, but this difference was not significant. Hyperthyroid cats had no significant differences in T3 or iodide kinetic variables when compared with those in healthy cats. Single-compartmental analysis significantly overestimated T4 kinetic variables of healthy cats and T4, T3, and iodide kinetic variables of hyperthyroid cats when compared with the noncompartmental method of analysis.     

Inherited epidermal dysplasia in Holstein-Friesian calves

Inherited epidermal dysplasia (IED), formerly called baldy calf syndrome, is a lethal disease of calves of Holstein-Friesian ancestry. The disease causes progressive illthrift and skin, horn and hoof lesions, which can be confused with inherited zinc deficiency. The clinicopathological features and ancestry of 10 affected calves in Gippsland, Victoria are described.     

UNEXPECTED TOXICITY FOLLOWING USE OF GEMCITABINE AS A RADIOSENSITIZER IN HEAD AND NECK CARCINOMAS: A VETERINARY RADIATION THERAPY ONCOLOGY GROUP PILOT STUDY

Gemcitabine (2',2'-difluorodeoxycytidine) was given intravenously twice weekly to 10 cats with oral squamous cell carcinoma and 15 dogs with nasal carcinoma undergoing radiotherapy as a radiosensitizing agent. The average total radiation dose was 50 Gy for dogs and 54 Gy for cats given Monday-Friday (planned dose of 54 and 57 Gy, respectively). Dogs received an average of five doses of gemcitabine beginning at 50 mg/m2, and cats received an average of five doses of gemcitabine beginning at 25 mg/m2. Twelve of 15 dogs and five of 10 cats required chemotherapy dose reduction or postponement because of hematologic or normal tissue toxicity. The results herein do not support the use of gemcitabine at the studied dose and schedule, as significant hematologic and local tissue toxicity was observed in the studied patients. Pharmacokinetic data are necessary to best define the efficacy and optimal dose and schedule of gemcitabine in combination with traditional radiotherapy.     

Do Computer‐Assisted,Morphometric‐Derived Sperm Characteristics Reflect DNA Status in Canine Spermatozoa?

It is widely accepted that sperm morphology is a strong indicator of semen quality. As the sperm head mainly comprises the sperm DNA, it is have been proposed that subtle changes in sperm morphology may be related to abnormal DNA content. Semen from four mongrel dogs was used to investigate DNA quality by means of the sperm chromatin structure assay (SCSA), and for computerized sperm morphometry (CASMA). Each sperm head was measured for nine primary parameters [head area (A), head perimeter (P), head length (L), head width (W), midpiece width (w), midpiece area (a), distance (d) between the major axes of the head and midpiece, angle (theta) of divergence of the midpiece from the head axis] and four parameters of head shape [FUN1, L/W; FUN2, 4piA/P(2); FUN3, (L - W)/(L + W); FUN4, piLW/4A]. Significant differences were found in all CASMA-derived parameters among dogs (p < 0.001). Linear regression models including sperm head shape factors 1, 3 and 4 predicted the extent of DNA denaturation (p < 0.001). We conclude that the CASMA analysis can be considered a powerful tool to improve the spermiogram.