Pituitary responsiveness to GnRH in mares following deslorelin acetate implantation to hasten ovulation

The present experiment characterized the pituitary responsiveness to exogenous GnRH in the first 10 d after ovulation following commercially available deslorelin acetate implantation at the normal dosage for hastening ovulation in mares. Twelve mature, cyclic mares were assessed daily for estrus and three times weekly for ovarian activity starting May 1. Mares achieving a follicle at least 25 mm in diameter or showing signs of estrus were checked daily thereafter for ovarian characteristics. When a follicle >30 mm was detected, mares were administered either a single deslorelin acetate implant or a sham injection and then assessed daily for ovulation. On d 1, 4, 7, and 10 following ovulation, each mare was challenged i.v. with 50 microg GnRH, and blood samples were collected to characterize the LH and FSH responses. The size of the largest follicle on the day of treatment did not differ (P = 0.89) between groups. The number of days from treatment to ovulation was shorter (P < 0.001) by 2.0 d for the treated mares indicating a hastening of ovulation. The size of the largest follicle present on the days of GnRH challenge was larger in the treated mares on d 1 (P = 0.007) but smaller on d 10 (P = 0.02). In addition, the interovulatory interval was longer (P = 0.036) in the treated mares relative to controls by 4.4 d. Concentrations of FSH in plasma of the treated mares were lower (P < 0.05) than control concentrations from d 3 to 12; LH concentrations in the treated mares were lower (P < 0.05) relative to controls on d 0 to 5, d 7, and again on d 20 to 23. Progesterone values were the same (P = 0.99) for both groups from 2 d before ovulation though d 23. There was an interaction of treatment, day, and time of sampling (P < 0.001) for LH and FSH concentrations after injection of GnRH. Both the LH and FSH responses were suppressed (P < 0.009) in the treated mares relative to controls on d 1, 4, and 7; by d 10, the responses of the two groups were equivalent. In conclusion, deslorelin administration in this manner increased the interovulatory interval, consistently suppressed plasma LH and FSH concentrations, and resulted in a complete lack of responsiveness of LH and FSH to GnRH stimulation at the dose used during the first 7 d after the induced ovulation. Together, these results are consistent with a temporary down-regulation of the pituitary gland in response to deslorelin administered in this manner.     

Comparative studies on three isolates of Breda virus of calves

Three isolates of Breda virus of calves were compared morphologically and antigenically. The isolates demonstrated similar morphology and shared common antigens, as determined by enzyme-linked immunosorbent assay and immunoelectron microscopy. On the basis of results of the hemagglutination-inhibition test, enzyme-linked immunosorbent assay, and immunoelectron microscopy, the 3 isolates were further subdivided into 2 serotypes: serotype 1 (Breda virus 1) represented by the Iowa isolate 1; and serotype 2 (Breda virus 2), by the Ohio isolate and the Iowa isolate 2. The 3 isolates caused diarrhea in gnotobiotic calves.     

The protection given by pilus and whole cell vaccines of Bacteroides nodosus strain 198 against ovine foot-rot induced by strains of different serogroups

A highly purified pilus vaccine prepared from cells of Bacteroides nodosus strain 198 provided a high level of protection against homologous challenge and small, not statistically significant, levels of protection against challenge with 4 other strains each from different serogroups. In a second experiment, a partially purified pilus vaccine from strain 198 induced significant immunity to 1 of 4 heterologous strains which were different from those used in the first experiment. In a third experiment a strain 198 whole cell vaccine produced significant immunity against 3 of 6 heterologous strains used in the first 2 experiments. There was no obvious relationship between the colony type, degree of piliation and level of cross-protection obtained against a particular strain. The results provide further evidence that immunogens associated with, but distinct from, the pilus are involved in cross-protection and that cross-protective antigens are common to some, but not all, strains.     

Narthecium asiaticum Maxim. Poisoning of grazing cattle: observations on spontaneous and experimental cases

A total of 39 Holstein cattle were grazed in tracts of wild grassland on account of shortage in pasture grass. Twenty-nine cattle were affected and 26 of them died during a 21-day period. The main signs were depression, anorexia, ascites, and oliguria. There was elevated serum urea nitrogen and sugar and protein in the urine. Pathological examination revealed turbid swelling of the kidney, an increase in the amount of fluid in the body cavity, edema in the perirenal adipose tissue and hemorrhage in various visceral organs and tissues. Histologically, acute tubular necrosis in the kidney, hypoplasia of the erythroblast series in the bone marrow, atrophy and degeneration of the lymphatic tissue and focal necrosis of the liver were observed in many of the cattle. Among cows experimentally fed Narthecium asiaticum Maxim., Polygonum sachalinense Fr. Schum., and Vitis coignetiae Pulliat which were presumed to have been ingested in large amounts by grazing cattle in the field, the cows fed N. asiaticum revealed the clinical, biochemical and pathological changes similar to those noticed in naturally affected cattle. Cows fed P. sachalinense and V. coignetiae showed no distinct systemic symptoms except transient anorexia and hypothermia.     

Effects of exercise conditioning on semen characteristics from hyper- and hypotensive lines of turkeys

Twenty-one male Broad Breasted White turkeys which had been selected for high or low blood pressure were put on an exercise regimen to determine its effect on semen quality. Eleven were from the hypertensive line and 10 from the hypotensive line. Eleven (6 hypertensive and 5 hypotensive) turkeys were placed on an exercise regime of walking (herding) about 1 mile daily for 6 weeks before the experiment began, and then for a further 6 weeks during semen collection. Semen was collected from 11 turkeys on the exercise regime and 10 nonexercised control birds which were kept in their experimental pens during the trial. Both hypertensive and exercised groups showed an improved semen colour score at the first collection period (P less than or equal to 0.09). Only the exercised group showed a significantly (P less than or equal to 0.05) better score than the control group during periods 2 and 3. The hypertensive line showed significantly higher spermatozoa count than the hypotensive line during the first collection period. There was no effect of either exercise or selection for high or low blood pressure on semen volume.     

Enhancement of resistance of lambs to Haemonchus contortus by previous infection with Ostertagia circumcincta

Two experiments were performed to determine whether previous infection of young lambs with Ostertagia circumcincta increased their resistance to the development of Haemonchus contortus and to explore alterations in the microenvironment of the abomasum related to the interaction. The parasitic infections were monitored with periodic fecal egg counts and by recovery and enumeration of parasites at necropsy of the lambs. Alteration of the microenvironment was examined by measurement of serum gastrin concentrations at critical times during both experiments. The results indicated that the numbers of H contortus were significantly (P less than 0.05) less in lambs which had O circumcincta infections before their exposure to H contortus. There was less reduction in lambs from which O circumcincta was removed (anthelmintic therapy) before their exposure to H contortus. Fecal egg counts also were significantly (P less than 0.05) less in the former group of lambs (exposed to both parasites) than those in lambs exposed only to H contortus. Serum gastrin values were significantly (P less than 0.05) increased in lambs infected with O circumcincta and indicated that the interaction observed could be due, in part, to alteration of abomasal pH.     

Sudden death in training and racing Thoroughbred horses

We reviewed case records, necropsy reports, and histologic sections from 25 Thoroughbred racehorses that died suddenly at 3 Chicago racetracks. These were young horses ranging in age from 2 to 5 years. There were more females (n = 16) than males (n = 9), and the incidence of death increased slightly in the spring and summer. Twenty-one of the 25 horses died while racing or training. Only 8 of the 25 horses (32%) had lesions sufficient to account for the death. In 6 of those 8 cases, death was caused by massive thoracic or abdominal hemorrhage. The site or nature of the vascular defect in these cases could not be determined. One horse died of severe preexisting pulmonary disease, and one died of encephalitis and cardiac papillary muscle fibrosis. The cause of death was undetermined in 17 horses (68%). Nearly all horses had pulmonary edema, congestion, and/or hemorrhage. We postulate that these unexplained deaths were a result of exercise-induced acute cardiovascular failure.     

Rocky Mountain spotted fever in dogs and its differentiation from canine ehrlichiosis

Rocky Mountain spotted fever (RMSF) or ehrlichiosis was diagnosed in dogs on the basis of specific immunofluorescent testing for each disease. Comparisons between clinical and laboratory findings were made between the 2 diseases. The incidence of RMSF tended to be more seasonal and it affected younger dogs. Purebred dogs appeared to be more susceptible to both diseases. In general, RMSF had a more rapid and severe course of clinical illness than did ehrlichiosis, but acute ehrlichiosis was difficult to differentiate from RMSF. Both diseases were characterized by fever, depression, lymphadenopathy, and signs of neurologic dysfunction; petechial hemorrhages or other signs of hemorrhagic diathesis were evident only in a small proportion of cases. Anemia, leukopenia, and thrombocytopenia were more common in dogs with ehrlichiosis, whereas those with RMSF more often had leukocytosis and thrombocytopenia. Hypoalbuminemia was found in dogs with both diseases, but those with ehrlichiosis usually had concurrent hyperglobulinemia. High serum alkaline phosphatase activity and serum cholesterol concentration, and low serum calcium concentration were more common in dogs with RMSF than with ehrlichiosis. Rising serum titers or positive direct immunofluorescence for Rickettsia rickettsii in skin biopsy specimens were used to confirm RMSF, whereas a single serum titer for Ehrlichia canis enabled detection of ehrlichiosis. In the absence of neurologic deficits and when dogs were treated with tetracycline, dogs with RMSF made a more rapid and consistent recovery than did dogs with ehrlichiosis.     

Hepatic neoplasia

The clinicopathologic features of hepatic neoplasms such as hepatocellular adenomas, hepatocellular carcinomas, bile duct carcinomas, and hepatic carcinoids are presented. The authors also discuss the diagnostic and therapeutic approaches to hepatic neoplasia.