Ovine lentivirus antibody detection in serum, colostrum and milk using a recombinant transmembrane protein ELISA.

An enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies against ovine lentivirus (OLV) in serum, colostrum, and milk from naturally infected sheep. The assay used OLV recombinant transmembrane envelope protein (rTM) as a test antigen. Matched serum/colostrum and serum/milk samples were collected at 24h, 4 weeks (mid-lactation), and 8 weeks (weaning) post-lambing. Among 129 paired samples collected at 24 h post-lambing, there was overall test agreement (concordance) of 82.9% and a kappa value of 0.658 between serum and colostrum rTM ELISA results. Among 130 mid-lactation samples, the milk ELISA had 100% specificity and 64.9% sensitivity relative to the serum ELISA, there was concordance of 79.2%, and a kappa value of 0.602. At mid-lactation, the serum agar gel immunodiffusion test had a sensitivity of 0.390 and 0.560 relative to the serum and milk rTM ELISAs, respectively. Matched serum and milk rTM ELISA results at weaning were very similar to those at mid-lactation. Finally, increased occurrence and severity of subclinical mastitis at weaning was found in ELISA-seropositive compared with ELISA-seronegative ewes. Both subclinical mastitis and ewe OLV infection had a negative impact on lamb growth and weaning weights. Compared with blood, colostrum and milk are easier and less expensive to sample and store. These results suggest that rTM ELISA testing of colostrum and milk could be used to supplement serologic testing in OLV screening or eradication programs.

Controlled efficacy study of the bioequivalence of Strongid C and generic pyrantel tartrate in horses.

The bioequivalence of Strongid C and generic pyrantel tartrate was determined in a controlled study using 30 horses with naturally acquired endoparasitic infections. Three horses were randomly allocated to each of ten replicates based on quantitative nematode and ascarid egg counts and fecal larvae culture results. Horses within each replicate were randomly assigned to one of three treatment groups. Horses in Treatment Group 1 received only oats; horses in Treatment Group 2 received generic pyrantel tartrate pellets (2.65 mg pyrantel tartrate kg-1) mixed with oats; horses in Treatment Group 3 were fed Strongid C pellets (2.65 mg pyrantel tartrate kg-1) mixed with oats. Horses were treated daily for a 30 day continuous treatment period. At the termination of the study the horses were necropsied and endoparasites recovered, identified, and enumerated. In all instances, no significant difference (P > 0.05) in mean numbers of parasites recovered existed between horses treated with generic pyrantel tartrate and Strongid C. Numbers of gastrointestinal parasites recovered from horses treated with generic pyrantel tartrate or Strongid C were shown to be significantly different (P < 0.05) from numbers of gastrointestinal parasites recovered from non-treated controls for the large strongyles (Strongylus vulgaris, S. edentatus, and Triodontophorus spp.), small strongyles (Cyathostomum spp., Cylicocyclus spp., and Cylicostephanus spp.) and fourth-stage Parascaris equorum. Numbers of adult P. equorum recovered from horses treated with Strongid C were also significantly different (P < 0.05) from those from non-treated controls. Numbers of adult P. equorum recovered from horses treated with generic pyrantel tartrate were not significantly different (P = 0.0761) from those from non-treated controls. The determination of bioequivalence was based upon the 95% confidence interval of the difference between the mean number of parasites recovered from horses treated with generic pyrantel tartrate and the mean number of parasites recovered from horses treated with Strongid C. For all instances in which the numbers of parasites recovered from horses treated with either Strongid C or generic pyrantel tartrate were significantly different from the numbers of parasites recovered from non-treated controls, bioequivalence was demonstrated.

A case-control study of acute ibuprofen toxicity in dogs.

A case-control study used data in the National Animal Poison Control Center database to characterize risk factors for gastrointestinal ulceration and acute renal failure subsequent to the acute ingestion of ibuprofen in the dog. For gastrointestinal ulceration (GIU) subsequent to ibuprofen ingestion, four factors differentiated the 116 cases from the 93 controls. Risk of GIU was lower for dogs where the time from ingestion to intervention was known as opposed to missing (adjusted odds ratio (aOR) = 0.12, p = 0.0001). Risk of GIU was also lower for the Labrador breed (aOR = 0.22, p = 0.004). Risk of GIU was higher for each unit of the logarithm of time to intervention (aOR = 2.63, p = 0.0002) and for the German Shepherd breed (aOR = 5.67, p = 0.14). For acute renal failure (ARF) subsequent to ibuprofen ingestion, two factors differentiated the 80 cases from the 64 controls. Risk of ARF was lower for dogs where the time from ingestion to intervention was known as opposed to missing (aOR = 0.15, p = 0.0001). Risk of ARF was higher for each unit of the logarithm of time to intervention (aOR = 2.16, p = 0.01). Although this study failed to describe a dose-response relationship, it appears that there are significant breed differences in susceptibility to GIU subsequent to ibuprofen exposure. Time to intervention was critical for both GIU and ARF outcomes. Dogs, particularly German Shepherds, ingesting even small amounts of ibuprofen, may need to be managed aggressively.

Risk factors for seroprevalence of ovine lentivirus in breeding ewe flocks in Nebraska, USA.

The prevalence of and risk factors for ovine lentivirus (OLV) infection in 1466 breeding ewes in nine US Meat Animal Research Center (MARC) flocks were determined using a recombinant transmembrane protein (PTM) enzyme-linked immunosorbent assay (ELISA) to detect serum anti-OLV antibodies and define infection. Based on multivariable logistic regression, confinement birth and rearing (odds ratio (OR) = 1.6), older weaning ages (OR = 1.1 week-1), and older age (OR = 1.3-2.5 year-1 beyond age 1 year) were significantly associated with higher OLV prevalence in ewes. Prevalence also varied significantly by flock, with Finnsheep and Texel ewes having the highest prevalences and Booroola Merino and Suffolk ewes having the lowest prevalences. These findings support the hypothesis that management control efforts should concentrate on events early in the life of sheep, as this period is associated with factors which can modulate the risk for OLV infection.

Effect of ewe ovine lentivirus infection on ewe and lamb productivity.

We used a previously described sensitive and specific ovine lentivirus (OLV) recombinant transmembrane (rTM) protein enzyme-linked immunosorbent assay (ELISA) to detect anti-OLV antibodies and define OLV infection in breeding ewes from nine US Meat Animal Research Center (MARC) flocks. We estimated the production impacts of dam rTM ELISA seropositivity on ewe and lamb productivity in the birth-to-weaning interval using production data from 1466 breeding ewes (of which 1242 actually lambed) and their 2452 lambs born in spring 1992 using several multiple linear and logistic regression models. By adjusting for lamb weaning age, gender, type of birth and rearing, birth difficulty, dam age, and flock, the component of ewe or lamb productivity related to ewe OLV infection alone was isolated. The rTM ELISA-negative ewes produced significantly more total weight of weaned lamb per ewe-lambing (3.84 kg) and per ewe ram-exposed (4.95 kg) compared to their OLV-positive flockmates. Negative ewes also weaned 0.11 more lambs per ewe-lambing and 0.09 more lambs per ewe ram-exposed, gave birth to 0.13 more lambs per ewe ram-exposed, and were more likely to lamb after breeding (odds ratio (OR) = 1.9) compared to equivalent OLV-positive ewes. Lambs reared by OLV-negative ewes weighed 0.15 kg more at birth, gained 8 g more per day through weaning, and weighed 0.59 kg more at 56-day weaning. Preweaning mortality was lower (OR = 0.8) among lambs born to OLV-negative compared to OLV-positive ewes, although this difference was not significant. Our results suggest that subclinical OLV infection has important detrimental effects on sheep production which occur in cumulative fashion from breeding through weaning and that OLV control efforts may be financially justified in some sheep flocks.

An evaluation of the haemostatic suture in hysterotomy closure in the mare.

This study was designed to evaluate the haemostatic suture as a means of preventing haemorrhage from the hysterotomy in mares after caesarean section. At 2 university hospitals 1982-1994, 48 mares had caesarean section for dystocia, 10 as an elective, and 8 mares concurrently with colic surgery. The haemostatic suture was used in 31 of 66 mares (47%) and surgery period was significantly (P<0.05) shorter when it was not applied. Anaemia (PCV<30%) was recorded in 13 (22%) of 58 mares, excluding the colic group, and the haemostatic suture did not after this proportion of mares that had anaemia. Anaemia was 5 times more probable following caesarean section than vaginal delivery, evidence that bleeding from the hysterotomy is a serious and common complication of caesarean section in mares. Severe uterine haemorrhage was recorded in 3 mares that had an haemostatic suture (10%) and in 2 mares that did not (6%). The latter two mares died of haemorrhage. The suture, therefore did not eliminate post operative anaemia and severe uterine haemorrhage. If omitted, the hysterotomy should be closed with a full thickness pattern that is sufficiently tight to compress vessels in the uterine wall.

Caesarean section and other methods for assisted delivery: comparison of effects on mare mortality and complications.

Data from 116 mares that had caesarean section or vaginal delivery at 2 university hospitals were analysed in 5 groups, as follows: dystocia corrected by caesarean section, Group DCS (n = 48); elective caesarean section, Group ECS (n = 10); caesarean section concurrently with colic surgery, Group CCS (n = 8); assisted vaginal delivery, Group AVD (n = 22); and controlled vaginal delivery under general anaesthesia, Group CVD (n = 28). Survival rate in all mares that had caesarean section, excluding Group CCS, was 88% (51/58). All mares in Group ECS survived and Group CCS had the lowest survival rate (38%). In 98 mares with dystocia, Groups DCS (15%) and AVD (14%) had significantly lower (P<0.05) mortality rates than Group CVD (29%). There were no differences between groups for duration of dystocia. The placenta was retained in 75 (65%) of 116 mares, and for a longer period following elective caesarean section than following assisted vaginal delivery. Multiple complications (> or = 3) were recorded in 6 mares in Group CVD but not in the other groups. Of the 102 foals delivered from 98 mares with dystocia, 11 (11%) were alive at delivery and 5 (5%) survived to discharge. Survival rate for foals was 38% in Group CCS, and 90% in Group ECS. Under conditions similar to those in this study, it is calculated that caesarean section is preferable to CVD if dystocia is protracted and great difficulty and trauma is involved, even if CVD allows delivery of the foal.

Measurement of upper airway resistance in awake untrained dolichocephalic and mesaticephalic dogs.

A technique for measuring upper airway resistance was developed in awake untrained dolichocephalic and mesaticephalic dogs. Twenty healthy dogs, 10 Collies (group A--dolichocephalic) and 10 mixed-breed dogs (group B--mesaticephalic), were studied. All dogs tolerated the procedure well, and adverse effects were not observed. Mean (+/- SEM) value for upper airway resistance was 7.1 +/- 0.50 cm of H2O/L/L/s. There was a trend toward lower upper airway resistance (R(uaw)) values in group-A dogs, compared with those in group-B dogs. Values of R(uaw) were reproducible for an individual dog. The mean individual dog coefficient of variation for R(uaw) was 7.5%. The overall R(uaw) coefficient of variation for all 20 dogs was 31.4%. This technique for measuring upper airway resistance in dogs is clinically applicable for objectively assessing response to treatment of obstructive upper airway disorders.

Haptoglobin and ceruloplasmin as determinants of inflammation in dogs.

Assay procedures for determining serum haptoglobin concentration and ceruloplasmin oxidase activity in dogs were validated, and reference values were established. Serum haptoglobin concentration is reported as milligrams per deciliter of cyanmethemoglobin binding capacity, whereas serum ceruloplasmin oxidase activity was determined by use of p-phenylenediamine as substrate. Both assays were used to analyze serum samples from 288 dogs. In each dog's case record, clinical history and final diagnosis were evaluated to determine whether the dog had an inflammatory condition. Complete blood cell counts were performed in 265 dogs, using simultaneously collected blood samples. Plasma fibrinogen concentration was determined for 161 dogs. A positive correlation (P less than 0.01) for serum haptoglobin concentration and for ceruloplasmin oxidase activity, compared with WBC counts, segmented neutrophil and band neutrophil counts, and plasma fibrinogen concentration. Ceruloplasmin oxidase activity and haptoglobin concentration were up to 6 times more sensitive than fibrinogen concentration or leukocyte counts in detecting inflammation. Specificity of ceruloplasmin oxidase activity was comparable to fibrinogen concentration and leukocyte counts, whereas haptoglobin concentration was found to be slightly less specific. Specificity of haptoglobin concentration improved slightly (from 0.82 to 0.88) when dogs with a history of glucocorticoid administration were excluded from analysis. Predictive value of a negative test result (haptoglobin concentration less than 125 mg/dl; ceruloplasmin oxidase activity less than 20 IU/L) and predictive value of a positive test result for haptoglobin concentration and ceruloplasmin activity were comparable to or better than fibrinogen concentration or various oxidase leukocyte counts in detection of inflammation in a variety of disease conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal and dental lesions in raccoons from a farming and a recreational area in Illinois.

Dental health was evaluated in two populations of raccoons (Procyon lotor) in western Illinois (USA); one was from a rural agricultural area with low human density and the other from a nearby state park heavily used by humans and raccoons. From 1989 through 1993, 300 raccoons were live-trapped in the agricultural area and 246 raccoons were live-trapped in the park. Oral health was assessed using gingival and calculi indices and by measuring loss of attachment and tooth wear. Raccoons from the park were significantly older and smaller, but not thinner, than raccoons from the farmed area. Gingival and periodontal indices, tooth wear, tooth loss, and caries increased significantly from juveniles to yearlings to adults, at both sites. Males had higher levels of gingivitis and loss of periodontal attachment than females, but were similar on other dental measures. There were no seasonal differences between raccoons in dental indices. Animals with high scores for one oral measure tended to have high values for all indices. Dental health was generally good for juveniles and yearlings from both sites. Among adults, periodontal indices and the prevalence of caries were significantly higher in the park, but prevalence of broken or missing teeth was similar for both populations. There was no association between body condition, and a higher dental score or more missing or broken teeth.

Epidemiologic investigation and control of an epizootic of anaplasmosis in cattle in winter.

An epizootic of anaplasmosis affecting 18 of 90 beef cows in winter on a western Illinois ranch was investigated to determine the probable source and mode of transmission. The cause of the epizootic was Anaplasma caudatum. Cows were classified as sick, convalescent, or carrier on the basis of blood smear, complement fixation, or modified rapid card agglutination test results. Patterns of movement did not suggest a common exposure prior to assembly of cattle at the affected ranch. The combination of clinical stages and temporal pattern of the epizootic was compatible with exposure on one or more occasions after arrival of cattle on the ranch, most likely during herd vaccination or ear tagging. A serologic testing and treatment program was initiated to rid the herd of infection. Seventeen surviving cows were treated 3 times with 20 mg of oxytetracycline/kg, IM, at 5-day intervals. At the end of the 6-month follow-up period, 1 of 17 cows was still serologically positive and was treated with a second regimen of oxytetracycline. We believe that eradication of A caudatum was successful, because no clinical cases of anaplasmosis have been reported on the ranch during the last 3 vector seasons.

Risk factors associated with transmissible gastroenteritis in swine.

Commercial production data base records from 2 Illinois farms, on which epizootic or enzootic transmissible gastroenteritis (TGE) was experienced, were accessed for an epidemiologic study. Risk factors investigated were sow parity, source of sows, location of farrowing crates, and breeding practices. At farm 1, an epizootic was experienced; at farm 2, an epizootic of TGE followed by enzootic TGE was experienced. Initially, crude risk ratios were calculated for these risk factors, and the crude risk ratios were subsequently adjusted for confounders and interactions, using multiple logistic regression techniques. After adjustment, parity-3 sows were 2.3 times more likely to have litters with TGE than were sows of all other parities on farm 1, and parity-1 sows were 2.6 times more likely to have litters that experienced TGE than were sows of all other parities on farm 2. A single boar on each farm was linked to increased likelihood of a sow's litter contracting epizootic TGE on each farm. Enzootic TGE was maintained by the periodic influx of outside-source gilts on farm 2; these gilts were 2.2 times more likely to have litters with TGE than were sows derived from farm 2. Sows housed in farrowing crates located under the cold air inlet of farm 2 were 1.7 times as likely as sows located in other rows to have litters with enzootic TGE.

Case-control study of risk factors for development of pleuropneumonia in horses.

Risk factors for development of pleuropneumonia were determined by reviewing medical records of 45 horses with pleuropneumonia and 180 control horses examined between Jan 1, 1980 and Jan 1, 1990. Factors considered included age, breed, sex, occupation, transport farther than 500 miles within the previous week, racing within the previous 48 hours, viral respiratory tract infection or exposure to horses with viral respiratory tract disease within the previous 2 weeks, and vaccination against influenza or rhinopneumonitis within the previous 6 months. Results indicated that Thoroughbreds were at a greater risk of developing pleuropneumonia than were other horses, and Standardbreds were at a reduced risk. Transport farther than 500 miles and viral respiratory tract disease or exposure to horses with respiratory tract disease were determined to be risk factors for the development of pleuropneumonia.

Frequency and distribution of medial and lateral patellar luxation in dogs: 124 cases (1982-1992).

From the medical records of 124 dogs, patellar luxations were classified as congenital or acquired, medial or lateral, and unilateral or bilateral; were graded 1 to 4; and were subdivided according to size of dog. The 4 breed-size categories were based on guidelines from American Kennel Club standards for adult height and weight. Findings from these records were compared with the results from dogs with other orthopedic problems. A majority of dogs had congenital (91; 82%), as opposed to acquired (17; 15%) patellar luxations. Distribution of dogs with patellar luxations according to breed size included 54 (98%) with medial patellar luxations (MPL) and 1 (2%) with lateral patellar luxation (LPL) in small breeds, 17 (81%) with MPL and 4 (19%) with LPL in medium breeds, 35 (83%) with MPL and 7 (17%) with LPL in large breeds; and 4 (67%) with MPL and 2 (33%) with LPL in giant breeds. Medial patellar luxation was observed in 110 dogs and 14 dogs had LPL. Cases of MPL and LPL in the same stifle or of medial and lateral patellar luxation in contralateral stifles in the same dog were not observed. Surgical correction was performed primarily in dogs with grade-3 and grade-4 patellar luxations. Medial patellar luxations and LPL were detected in all breed categories. Small-breed dogs were admitted almost exclusively with MPL. Lateral patellar luxation was found uncommonly; however, it was observed more often in larger-breed dogs. Prevalence of MPL was greater, when compared with that for LPL, in every size/breed category.

Serologic evidence of Anaplasma marginale infection in Illinois white-tailed deer.

A total of 175 deer and 54 cattle from Crab Orchard National Wildlife Refuge in southern Illinois were tested for antibody to Anaplasma marginale, using the capillary tube agglutination test. A total of 12 (6.9%) deer and 7 (13%) cattle were serologically positive. Serologic prevalence in deer increased from 0 at 6 months of age to 14% at 2 1/2 or more years of age. Cattle less than approximately 1 year of age were not seropositive.

Clinical and histologic evaluation of the prolapsed third eyelid gland in dogs.

Eighteen prolapses of the gland of the third eyelid in 17 Beagles were randomly allocated to 3 groups, which included nontreated (group 1, n = 6), excised (group 2, n = 4), and surgically repositioned (group 3, n = 8) glands. A schirmer tear test (STT) was performed on affected and normal (control) eyes for 5 consecutive days on weeks 0 (baseline), 2, 4, 6, 8, 10, 12, 16, 18, 20, and 24. All prolapsed third eyelid glands were excised and examined histologically. Ten female and 7 male Beagles were used in the prospective study. Mean age at prolapse was 35.1 weeks (range, 6 to 89 weeks). Control STT data revealed a population mean of 22.2 +/- 2.1 mm/min. Complications developed in 4 of 6 eyes when the gland was allowed to remain in a prolapsed position. Complications for group-1 eyes were significantly (P < 0.005) greater than those for eyes in groups 2 and 3 (0 of 12). Comparison of affected and control eye baseline data revealed decreased STT values for eyes with prolapsed glands (P < 0.01). Mean differences between affected and control eyes were 2.2, 2.0, and 3.4 mm/min for groups 1, 2, and 3, respectively. A significant (P < 0.001) decrease in lacrimation (0.2 to 3.1 mm/min) in group-2 eyes was detected after removal of the gland. Tear production for affected eyes of nontreated dogs fluctuated above and below that of control eyes prior to excision of the prolapsed gland of the third eyelid; however, with time, affected and control eye STT values were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of corticosteroid-induced alkaline phosphatase isoenzyme as a screening test for hyperadrenocorticism in dogs.

Quantitative determination of the corticosteroid-induced isoenzyme of alkaline phosphatase (CAP) was evaluated as a screening test for hyperadrenocorticism (HAC) in dogs. A series of 40 dogs with HAC (CAP range, 96 to 14,872 U/L), 30 clinically normal dogs (CAP range, 0 to 38 U/L), and 80 dogs with various diseases (non-HAC) and without history of exogenous glucocorticoid exposure for a minimum of 60 days (CAP range, 0 to 1163 U/L) were used to evaluate the test. Sensitivity and specificity of CAP was calculated at various cutoff points for absolute CAP activity and for CAP activity expressed as a percentage of total alkaline phosphatase activity. A cutoff point of 90 U/L was selected as optimal for use of this assay as a screening test for HAC. A prevalence survey then was done of all canine serum samples submitted to our diagnostic laboratory over a 3-month period, to calculate the predictive values of a positive and a negative test result in a clinical population and to determine the relative frequency and magnitude of CAP activity in dogs that had received glucocorticoids. The predictive values of a positive and a negative test result at the 90 U/L cutoff value were 21.43% (95% confidence limits, 8.3 to 40.95%) and 100% (95% confidence limit > 96%), respectively. It was concluded that CAP isoenzyme activity, determined by routine biochemical analysis by an automated levamisole-inhibition assay, could function as a screening test for HAC; however, the predictive value of a positive test result was too low to recommend the assay as a diagnostic test.(ABSTRACT TRUNCATED AT 250 WORDS)

Economic analysis of a mastitis monitoring and control program in four dairy herds.

Mastitis monitoring and control programs were instituted in 4 Illinois dairy herds for 12 months. Two herds had high mean monthly bulk tank somatic cell counts (> 490,000 cells/ml) and 2 had low mean monthly bulk tank somatic cell counts (< 260,000 cells/ml) at the start of the study. The mastitis monitoring and control programs included mandatory mastitis control measures, as well as individualized control measures that were based on results of bacterial cultures of milk, bulk tank milk analyses, milking machine and milking procedure evaluations, and environmental inspections in each herd. Changes in mastitis prevalence, clinical mastitis incidence, milk yield, and individual cow somatic cell counts were evaluated, and an economic analysis was performed for each herd. Mastitis-associated economic losses during the study period ranged from $161.79 to $344.16/lactating cow in the 4 herds. Gross economic benefits resulted when mastitis-associated losses were lower with the monitoring and control program than predicted without it. There were no gross economic benefits in the herds with low somatic cell counts, and, when the marginal costs of the programs were added, there were large net losses ($84.06 and $113.01/lactating cow) in those herds. Gross economic benefits resulted in both of the herds with high somatic cell counts. However, in 1 of the herds, the marginal costs of the program exceeded the benefits, resulting in a net loss of $12.96/lactating cow. The net loss was attributed primarily to poor producer compliance with recommendations. There was a net economic benefit of $19.11/lactating cow in the other herd with high somatic cell counts, in which producer compliance was better.(ABSTRACT TRUNCATED AT 250 WORDS)

Outbreak of vesicular dermatitis among horses at a midwestern horse show.

Dermatitis consisting of blisters on the nose and other parts of the body was reported among horses at a Midwestern horse show. Some horses also had jaundice, hematuria and anorexia. An outbreak investigation was initiated, and of 239 horses for which information could be obtained, 58 (24%) were found to have been affected. Median duration of illness was 5 days, and all horses recovered. Age, sex, water source, grain source, and stabling location were not associated with illness. The use of wood shavings bedding obtained at the show grounds was the factor most strongly associated with the development of vesicular lesions. Horses that became ill were 43 times more likely to have been bedded on wood shavings obtained from the show grounds than were horses that did not become ill. Among horses bedded on shavings from the show grounds, the risk was further increased by a factor of 5 if the shavings had been wetted. Neither organic nor heavy metal toxicants were identified in the samples of the wood shavings. However, samples did contain plant tissues originating from a tree belonging to the family Simaroubaceae, some species of which are known to cause vesicular eruptions in people.

Risk factors for perinatal and postnatal mortality in lambs.

Factors associated with preweaning mortality in lambs were identified by developing risk profiles with logistic regressions for perinatal and postnatal mortality. Compared with heavy lambs, lambs of low birth weight had almost twice the risk of perinatal mortality (odds ratio [OR] = 1.9) and lambs of average weight had a slightly lower risk (OR = 0.7). Two of four lambing location categories affected perinatal mortality, with lambs born at unmonitored areas at greatest risk (OR = 2.7). Multiple births increased the risk of perinatal mortality (OR = 1.5), especially among Targhee lambs (OR = 4.0). Breed variations in perinatal mortality were significant in Suffolk lambs (OR = 1.9) and Booroola Rambouillet lambs (OR = 2.1). Lambs born weak had an increased risk of postnatal mortality while strong lambs had a decreased risk (OR = 3.7 and 0.6, respectively) if the dam had an adequate milk supply. Poor milk supply increased the risk of postnatal mortality for lambs of average vigour (OR = 3.3), but did not change the risk for weak or strong lambs. Male lambs castrated at 30 days of age were at less risk of postnatal mortality (OR = 0.3) than females. There were slight increases in the risk of postnatal mortality for intact males (OR = 1.3), low birth weight lambs (OR = 1.6), and lambs born in sheds (OR = 1.3). Suffolk lambs (OR = 1.8) and Targhee lambs (OR = 1.6) had a higher risk of postweaning mortality.