Association between hyperinsulinaemia and laminitis severity at the time of pituitary pars intermedia dysfunction diagnosis.

BACKGROUND: Hyperinsulinaemia is the suspected component of insulin dysregulation having the strongest association with laminitis and occurs variably in equids with pituitary pars intermedia dysfunction (PPID). OBJECTIVES: We hypothesised that magnitude of hyperinsulinaemia correlates with laminitis severity in PPID-affected equids. Furthermore, we hypothesised that owners can be unaware of chronic endocrinopathic laminitis. STUDY DESIGN: Cross-sectional study. METHODS: Serum insulin concentrations, owner-reported laminitis history and radiographic evidence of laminitis were determined in 38 client-owned horses and ponies with confirmed PPID. Laminitis severity was classified into four categories (normal [nonlaminitic], mild, moderate or severe laminitis) based on degree of distal phalangeal rotation. Animals were also categorised as normoinsulinaemic (<20 µU/ml), mildly hyperinsulinaemic (20-50 µU/ml) and severely hyperinsulinaemic (>50 µU/ml). One-way ANOVA, t tests and Fisher's exact tests were performed. RESULTS: While owners reported laminitis in 37% of animals, 76% were laminitic based on study criteria (P = 0.01). Owners reported laminitis more frequently in hyperinsulinaemic vs. normoinsulinaemic animals; recognition increased with severity of hyperinsulinaemia (P = 0.03). Mean insulin concentrations were higher in equids with moderate to severe radiographic laminitis (geometric mean 74.1, 95% confidence interval (CI) 38.4-143.1 uU/ml) vs. those classified radiographically as normal to mild (31.9, 95% CI 21.1-48.1 uU/ml P = 0.03). MAIN LIMITATIONS: Dynamic insulin testing was not performed; some normoinsulinaemic animals might have had subtle insulin dysregulation. CONCLUSIONS: Although radiographic abnormalities were present in most animals at the time of PPID diagnosis, chronic laminitis remained unrecognised by many owners. Owner awareness of laminitis increased with severity of hyperinsulinaemia and higher insulin concentrations were detected in association with more severe radiographic changes. The Summary is available in Chinese - See Supporting Information.

Thyroid hormone responses to endurance exercise.

REASONS FOR PERFORMING STUDY: Limited information exists about changes in circulating thyroid hormone concentrations during prolonged endurance exercise in horses. OBJECTIVE: To examine the effects of prolonged exercise on serum iodothyronine concentrations in horses performing endurance exercise of varying distances. METHODS: Serum concentrations of iodothyronines were measured in horses before and after completion of 40, 56, 80 and 160 km endurance rides (Study 1); daily during a 5 day, 424 km endurance ride (Study 2); and before and for 72 h after completion of a treadmill exercise test simulating a 60 km endurance ride (Study 3). RESULTS: In Study 1, 40 and 56 km of endurance exercise had little effect on serum iodothyronine concentrations with the exception of a 10% decrease (P<0.05) in free thyroxine (FT4) concentration after the 56 km ride. In contrast, total thyroxine (T4), total triiodothyronine (T3), FT4 and free triiodothyronine (FT3) concentrations all decreased (P<0.05) after successful completion of 80 and 160 km rides, with decreases ranging from 13-31% and 47-54% for distances of 80 and 160 km, respectively. Further, pre-ride T4 concentration was lower (P<0.05) and FT3 concentration was higher (P<0.05) in horses competing 160 km as compared to horses competing over shorter distances. In Study 2, serum concentrations of T4, T3 and reverse triiodothyronine (rT3) progressively decreased (P<0.05) over the course of the multi-day ride. In Study 3, the greatest decrease (P<0.05) in all iodothyronines was observed at 12 h of recovery, ranging from 25% for FT4 to 53% for FT3, but all thyroid hormone concentrations had returned to the pre-exercise values by 24 h of recovery. CONCLUSION: Endurance exercise results in transient decreases in serum iodothyronine concentrations. POTENTIAL RELEVANCE: These data are important to consider when thyroid gland function is assessed by measurement of serum iodothyronine concentrations in endurance horses.

A herd-level analysis of risk factors for antibodies to Sarcocystis neurona in Michigan equids.

Equine protozoal myeloencephalitis (EPM) is a neurological disease of horses and ponies caused by infection of the central nervous system with the protozoan parasite Sarcocystis neurona. A herd-level analysis of a cross-sectional study of serum antibodies to S. neurona in Michigan equids was conducted, using data collected in 1997 for study that included 1121 equids from 98 Michigan horse farms. Our objective was to identify specific herd-level risk factors associated with seropositivity. We tested associations between herd seroprevalence and various farm-management practices (including feed-storage methods and wildlife control). Multivariable models were developed for three strata based on relative opossum abundance (opossum districts). Herd seroprevalence ranged from 0 to 100% (median=57%). No risk factor was significantly associated with herd seroprevalence at P< or = 0.05 in all opossum districts. Our results suggest that equids living in areas with large opossum populations might be infected with S. neurona from multiple sources.

Comparison of Sarcocystis neurona isolates derived from horse neural tissue.

Sarcocystis neurona is a protozoan parasite that can cause neurological deficits in infected horses. The route of transmission is by fecal-oral transfer of sporocysts from opossums. However, the species identity and the lifecycle are not completely known. In this study, Sarcocystis merozoites from eight isolates obtained from Michigan horses were compared to S. neurona from a California horse (UCD1), Sarcocystis from a grackle (Cornell), and five Sarcocystis isolates from feral opossums from Michigan. Comparisons were made using several techniques. SDS-PAGE analysis with silver staining showed that Sarcocystis spp. from the eight horses appeared the same, but different from the grackle isolate. One Michigan horse isolate (MIH6) had two bands at 72 and 25kDa that were more prominent than the UCD1 isolate and other Michigan horse isolates. Western blot analysis showed that merozoites of eight of eight equine-derived isolates, and the UCD1 S. neurona isolate had similar bands when developed with serum or CSF of an infected horse. Major bands were seen at 60, 44, 30, and 16kDa. In the grackle (Cornell) isolate, bands were seen at 60, 44, 29, and 16kDa. DNA from merozoites of each of the eight equine-derived isolates and the grackle-derived isolate produced a 334bp PCR product (Tanhauser et al., 1999). Restriction fragment length polymorphism (RFLP) analysis of these horse isolates showed banding patterns characteristic for S. neurona. The grackle (Cornell) isolate had an RFLP banding pattern characteristic of other S. falcatula species. Finally, electron microscopy examining multiple merozoites of each of these eight horse isolates showed similar morphology, which differed from the grackle (Cornell) isolate. We conclude that the eight Michigan horse isolates are S. neurona species and the grackle isolate is an S. falcatula species.

The seroprevalence of antibodies to Sarcocystis neurona in Michigan equids.

A cross-sectional study of serum antibodies to Sarcocystis neurona (the etiologic agent of equine protozoal myeloencephalitis, EPM) was performed on Michigan equids. Our objectives were to determine the seroprevalence of antibodies to S. neurona in Michigan equids and to identify specific risk factors for seropositivity. A random, weighted sample of Michigan horse farms (stratified by the state's opossum (Didelphis virginiana) population and the number of equids on each operation) was selected. Ninety-eight equine-operation owners agreed to participate, and blood collection occurred from late March through October of 1997. Data regarding the 98 farms' feeding and management practices were collected, as well as descriptive data for each of the 1121 individual horses. Serum samples were tested for antibodies to S. neurona using a Western blot test. The true seroprevalence of antibodies specific to S. neurona was estimated to be 60%. Chi-square analysis showed that seroprevalence was lowest in the colder parts of the state that had the fewest opossums (P<0.0001). In two multivariable logistic-regression analyses with random effects grouped by herd, age and exposure to pasture were associated with increased odds of seropositivity, and feeding of sweet feed (grains mixed with molasses) was associated with decreased odds of testing positive. No association was found between farm size, animal gender, hay types, horse-housing types or exposure to natural surface water and seropositivity.

Association of sex of fetus, sire, month of conception, or year of foaling with duration of gestation in standardbred mares.

OBJECTIVE: To determine whether sex of fetus, sire, month of conception, or year of foaling was associated with duration of gestation in mares. DESIGN: Epidemiologic retrospective cohort study. ANIMALS: 500 foalings for 296 Standardbred mares. PROCEDURE: Data for reproductive events from 1986 to 1992 were analyzed. Analyses were conducted to determine whether duration of gestation was associated with sex of fetus, sire, month of conception, or year of foaling. RESULTS: Mean duration of gestation was 343.3 days and was significantly greater for colt fetuses (344.4 days) than for filly fetuses (342.2 days). Sire was associated with duration of gestation; gestation after mating with certain sires was consistently less than 340 days in duration, whereas duration after mating with other sires was consistently more than 350 days. Duration of gestation was associated with month of conception, decreasing by about 2.5 d/mo for mares conceiving later during the breeding season. CLINICAL IMPLICATIONS: Duration of gestation is affected by mating to specific sires and by month of conception. Stallions associated with exceptionally prolonged gestations might be used to breed mares early in the breeding season, whereas stallions associated with shorter gestations might be desirable for mares bred later in the breeding season. Preparations for impending parturition should be more effective and efficient with improved information on expected date of parturition.

Risk factors for colic in the Michigan (USA) equine population.

A population-based prospective epidemiological study was conducted to assess risk factors for equine colic. A stratified sample of 3925 equids in 138 randomly selected equine farms in the state of Michigan was monitored in two 12-month rounds of data collection. Incidence densities were used to describe the rate of development of colic in the study population. Mortality rates, case fatality rates and survival rates were used to describe the severity of colic on the study population. Multivariable logistic regressions with random effects (grouped according to farm) were used to identify risk factors associated with occurrence of colic. A total of 3175 equids from 132 farms from the starting population of 3925 equids in 138 farms was used in the multivariable analysis. There were 77 cases of colic reported during the study period in 62 animals. Of these animals, 54 (87%) had one case, 5 (8%) had two cases, 2 (3%) had three cases, and 1 (2%) had seven cases. Of the cases reported, 49 (64%) were non-specific diagnoses, 13 (17%) impaction/acute intestinal obstruction colics, 7 (9%) spasmodic colics, 4 (5%) sand colics, 2 (3%) gas colics, 1 (1%) verminous mesenteric arteritis, and 1 (1%) enteritis due to ingestion of moldy grain. The annual incidence density of colic in the study was 3.5 cases per 100 equid-years. The surgical treatment risk was 17% (13/77). The overall mortality risk due to colic was 0.5 deaths per 100 equids, and the case fatality risk was 13% (10/77). The case fatality risk for cases treated surgically was 31% (4/13), while the case fatality risk for non-surgical colics was 10% (7/69). Risk factors associated with significantly increased likelihood of developing colic were foaling during the study, deworming during the study, increased age, and participation in showing activities. Geldings and equids provided group drinking water from sources other than tanks, buckets and automatic waterers were significantly associated with reduced risk of colic.

Identification of opossums (Didelphis virginiana) as the putative definitive host of Sarcocystis neurona.

Sarcocystis neurona is an apicomplexan that causes equine protozoal myeloencephalitis (EPM) in North and South America. Horses appear to be an aberrant host, because the merozoites continually divide in the central nervous system, without encysting. The natural host species has not previously been identified. The small subunit ribosomal RNA (SSURNA) gene of S. neurona was compared to those of Sarcocystis muris, Sarcocystis cruzi, Toxoplasma gondii, and Cryptosporidium parvum to identify a unique region suitable for a species-specific amplification primer. The S. neurona SSURNA primer was used in a polymerase chain reaction (PCR) assay for the purpose of identifying this organism in feces and intestinal digest of wildlife specimens. Sporocysts were isolated from 4 raccoons (Procyon lotor), 2 opossums (Didelphis virginiana), 7 skunks (Mephitis mephitis), 6 cats (Felis catus), 1 hawk (Accipiter sp.), and 1 coyote (Canis latrans). The S. neurona SSURNA PCR assay and a control PCR assay using protist-specific primers were applied to all sporocyst DNA samples. All sporocyst DNA samples tested positive on the control assay. The SSURNA PCR assay yielded a 484-bp product only when applied to opossum samples. The SSURNA gene of both opossum sporocyst samples was sequenced to determine its relationship to the S. neurona SSURNA gene. The sequence had 99.89% similarity with S. neurona. This suggests that opossums are the definitive host of S. neurona.

Concentrations of estrone sulfate in peripheral serum of pregnant goats: Relationships with gestation length, fetal number and the occurrence of fetal death in utero.

Blood sampling was initiated shortly after breeding and continued weekly through 60 to 72 days post breeding in 20 pregnant and 5 nonpregnant dairy goat does. In does not showing a return to estrus by 72 days, collection of blood was continued at 10- to 14-day intervals until 135 days post breeding. At parturition, the numbers of does delivering one, two, three, four or five kids was four, ten, three, two and one, respectively. Immunoreactive estrone sulfate (ES) was measured in serum by radioimmunoassay (RIA). In nonpregnant does, the mean+/-SD concentration of ES was 0.1+/-0.1 nmol/l (n=36 samples). At 40 to 50 days post breeding, ES concentrations increased dramatically in pregnant does. Statistically, does were classified as pregnant when serum ES increased and remained above 1.1 nmol/l (P<0.05). Serum ES in pregnant does peaked at 65 to 75 days of gestation, remained at a relative plateau through 120 days and then gradually increased for the remainder of the sampling schedule. There were positive correlations between serum ES and the number of kids born in sampling periods of 50 to 55 days and after 90 days of gestation (P<0.05). Fetal loss was documented in two does that were not included in the survey data. One doe delivered two normal kids and two mummified fetuses. Time-trend changes in ES were typical of a normal pregnancy. Another doe had a marked decrease in ES (below 0.8 nmol/l) in samples drawn on Days 94 and 108 of gestation while luteal concentrations of progesterone were maintained. This doe delivered one weak, depressed kid, one stillborn kid and a decomposed fetus at the expected time for parturition.

Cerebrospinal nematodiasis in a goat herd.

During the fall of 1985, 4 Angora goats, from a herd of 40, were examined on a farm in central Michigan. Affected goats were alert but had neurologic deficits consistent with upper and lower moto neuron involvement. Eosinophilic pleocytosis in a cerebrospinal fluid sample from one goat was consistent with cerebrospinal nematodiasis. Parelaphostrongylosis was confirmed in 3 goats by identification of Parelaphostrongylosis tenuis larvae in spinal cord sections. Ivermectin may have influenced the herd's susceptibility to new parasitic infections. Control of parelaphostrongylosis probably is best achieved by removal of susceptible animals from treed swamps coinhabited by white-tailed deer from late summer until after the first killing frost.

Reproductive difficulties in cattle with antibody titers to Haemophilus somnus.

A herd of Holstein cows was examined because of suspected embryonic death. Four cows had embryonic loss, and 2 cows had aborted. Paired serum samples were tested for antibodies to infectious bovine rhinotracheitis virus, bovine viral diarrhea virus, and Haemophilus somnus. Of 16 cows, 8 had antibody titers to H somnus greater than 1:1,024, and 3 had greater than or equal to four-fold changes in antibody titers to H somnus. Haemophilus somnus infection was active in this herd and may have been responsible for the herd's reproductive problems.

Compliance with recommended drug withdrawal requirements for dairy cows sent to market in Michigan.

By examination of computerized individual cow records from January 1981 through June 1985, compliance with premarketing drug withdrawal times was investigated in 23 dairy herds. During this period, 877 cows were culled from 23 herds; 33 cows from 12 herds were in violation of premarketing drug withdrawal times. Six herds had 1 violation, 2 herds had 2 violations, 2 herds had 3 and 4 violations, and 2 herds had 7 and 9 violations. Fifty drugs had been used; 15 drugs were used in violation of drug withdrawal times before cows were sent to market. The most commonly used drugs in violation were oxytetracycline, gentamicin, chloramphenicol, and a combination of lincomycin/spectinomycin. Significant differences between cows in violation and cows not in violation were not observed for age, lactation number, milk production, herd size, or month of culling. However, the 12 herds in violation of premarket drug withdrawal times had significantly (P less than 0.05) more cows culled within 30 days for retained placenta and milk fever, and more cows culled within 30 and 100 days for mastitis, metritis, and displaced abomasum. Although not significant, the 2 herds with 7 and 9 violations had more hired vs family labor than did the other herds with violations.

Responses of dairy cattle to long-term and short-term supplementation with oral selenium and vitamin E1.

In a two-lactation-gestation cycle experiment, 152 Holstein cows with low serum Se and vitamin E were fed total mixed rations and assigned at parturition to four groups (1, control; 2, 500 IU vitamin E/d; 3, 2 mg Se/d; 4, 500 IU vitamin E plus 2 mg Se/d). Supplements were not fed during dry periods. Serum Se and vitamin E were increased within 1 mo by oral supplements. Maximal mean serum Se in cycles 1 (67 ng/ml at 7 mo) and 2 (74 ng/ml at 4 mo) occurred in groups 3 and 4, respectively. Maximal mean serum vitamin E in cycle 1 (3.3 micrograms/ml at mo 8) and 2 (3.03 micrograms/ml at mo 2) occurred in groups 4 and 2, respectively. Selenium treatment of the dams increased Se in colostrum and in serum of presuckle calves. Vitamin E supplementation of dams did not affect vitamin E in serum of presuckled calves. Reproductive performance was not affected by supplement. In an 8-wk study, 24 lactating cows with low serum Se were assigned (6/group) to 0, 2.5, 5, and 10 mg supplemental Se/d. Maximal mean serum Se concentrations of 23, 56, 71, and 79 ng/ml were attained by wk 4 in the above respective groups. These data indicate that 2 to 2.5 mg supplemental Se/cow per d were inadequate for desirable serum Se concentrations and support recent changes in allowed Se supplementation for dairy cattle.

Pregnancy toxemia and ketosis of ewes and does.

Pregnancy toxemia of ewes and does appears to occur when the animal cannot meet the glucose demands of the fetal-placental unit and hypoglycemia develops. There is individual variation in susceptibility, and there may be basic differences in glucose metabolism between susceptible animals and nonsusceptible animals. Increased serum NEFA and ketone body concentrations accompany the disease, but clinical signs do not appear to develop in the absence of hypoglycemia. The diagnosis is based on history, clinical signs, and the finding of ketone bodies in the urine. Numerous metabolic abnormalities develop subsequent to hypoglycemia and hyperketonemia, and these affect the prognosis. Important secondary abnormalities include acidosis, dehydration, and renal failure. Therapy is frequently unsuccessful, but frequent administration of small doses of glucose appears to be beneficial, if the other abnormalities, such as acidosis and dehydration, are controlled. Prevention can be readily achieved by nutritional means and is far more rewarding than therapy. Ewes and does must be fed in relation to their changing energy needs throughout the reproductive cycle.

Descriptive epidemiology of anestrus in Michigan Holstein-Friesian cattle.

Twenty-two Michigan Holstein-Friesian herds were studied to determine the incidence and epidemiology of anestrus. In 3,309 lactations studied, 42% were classified as having exhibited preservice anestrus (no estrus detected by 70 d after calving). Organic reasons (pyometra, cystic follicles, static ovaries) were identified by palpation per rectum for 237 (23%) of the cows with preservice anestrus that were examined by a veterinarian. Postservice anestrus, defined as failure to show estrus within 35 d after an unsuccessful insemination, was identified in 790 (47%) of 1,691 lactations. Veterinary examination identified 104 (20%) of postservice anestrous cows as having this condition because of organic causes. The average cow with preservice anestrus had an increase of 30 d open compared to her herdmates, and the average cow with postservice anestrus had an increase of 37 d open. Anestrous cows produced more milk than their unaffected herdmates in both the current and the previous lactation. Analysis of composite lactation curves indicates that, for preservice anestrus, this additional milk production was obtained gradually over the entire lactation. Anestrous cows were culled at a significantly higher rate than their herdmates. Cows with preservice anestrus were more likely to have begun their lactation in the spring months.

Use of prostaglandin F2 alpha in the treatment of unobserved estrus in lactating dairy cattle.

A field trial was conducted to evaluate the use of prostaglandin F2 alpha (PGF2 alpha) (lutalyse)a in lactating dairy cattle with unobserved estrus in the presence of a functional corpus luteum (CL) and clinically normal reproductive tract. Seventy-three Holstein and 9 Jersey cows, weighing between 340.0 and 772.7 kg, were allotted to treatment and control groups. All treated cows were inseminated within 80 hours after treatment as assigned by this trial. Control cows were inseminated at the first observed estrus. Of the treated cows, 50% showed estrus within 80 hours after treatment. In this trial, 96% of the treated cows and 92% of the control cows were determined to have at least 1 functional CL on the day of treatment. For the treatment group and the control group, mean serum progesterone concentrations were 4.1 ng and 3.5 ng (P less than 0.2, by Student's t test), respectively, on day of treatment and were 0.4 ng and 5.0 ng (P less than 0.005, by Student' t test) on day 5 after treatment. Pregnancy rates were 57% for treated and 47% for control cows (P = 0.5, by X2). Days from treatment to first-observed estrus, treatment to first service, and treatment to conception were significantly reduced in the treatment group compared with these criteria for the control group (P less than 0.05, 0.005, and 0.01 respectively). It was concluded that induction of luteolysis with PGF2 alpha in lactating dairy cattle with unobserved estrus and a palpable functional CL will be an effective addition to reproductive health programs.