Peter R. Wilson

Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand: I. Descriptive data

A longitudinal observational study of 15 red deer (Cervus elaphus) farms was carried out in New Zealand for 2 years from Mar 1992. Management of hind mobs and their composition during mating, calving, and weaning were recorded. About 2700 hinds were individually monitored for live weight, body condition score and reproductive success. All hinds were pregnancy tested in June by ultrasound and classified as having conceived before May 1, after May 1, or as being not pregnant. Calving dates and dam-offspring pairs were recorded on four farms. The lactational status of hinds and live weight of calves were recorded at weaning. Mean pre-mating live weights of yearling hinds were 81.3-82.8 kg and of adult hinds 98.0-98.7 kg, respectively, for each year of study. The percentage of yearling and adult hinds conceiving before May ranged from 8.3 to 95.0% and from 77.6 to 98.4%, respectively, between farms. Overall, the proportion of yearling and adult hinds not pregnant was 15.3% and 3.2%, respectively. Pregnancy rates at scanning of adult hinds within mating mobs were generally over 90%, and 41.7% of mating mobs had 100% pregnancy rates. In contrast, the pregnancy rates of yearling hind mobs were more variable, with five mobs below 50%, and 34.1% of mating mobs achieving 100% pregnancy rate. Estimated in utero loss rates from pregnancy diagnosis to calving were 0.66 and 0.79% for yearling and adult hinds, respectively. From four farms, median calving dates of yearling and adult hinds were Dec 13 and Nov 30, respectively. Overall, calf survival rates to weaning of yearling and adult offspring were 84.1 and 91.6%, respectively, while the reproductive efficiencies (number of calves weaned per hind mated) were 70 and 83.6%, respectively. Farm mean weaner live weights standardised on Apr 1 ranged from 42-59 kg and 39-51 kg for stags and hinds, respectively. These data are currently the best estimates of reproductive parameters of New Zealand red deer herds, and highlight a wide variability in reproductive indices between farms.

Studies of hormone secretion in romney rams: Luteinizing hormone, testosterone and prolactin plasma profiles, LH/testosterone interrelationships and the influence of seasons

Abstract In a study of hormone secretion patterns in rams remote sampling techniques were utilized for collecting jugular blood samples each 20 min for 24 h from adult Romney rams. Five animals were sampled during the summer, four during the winter, and plasma LH, testosterone and prolactin levels were estimated by specific radioimmunoassays.

Sero-Prevalence and Risk Factors for Leptospirosis in Abattoir Workers in New Zealand

Leptospirosis is an important occupational disease in New Zealand. The objectives of this study were to determine risk factors for sero-prevalence of leptospiral antibodies in abattoir workers. Sera were collected from 567 abattoir workers and tested by microscopic agglutination for Leptospira interrogans sv. Pomona and Leptospira borgpetersenii sv. Hardjobovis. Association between prevalence and risk factors were determined by species specific multivariable analysis. Eleven percent of workers had antibodies against Hardjobovis or/and Pomona. Workers from the four sheep abattoirs had an average sero-prevalence of 10%–31%, from the two deer abattoirs 17%–19% and the two beef abattoirs 5%. The strongest risk factor for sero-positivity in sheep and deer abattoirs was work position. In sheep abattoirs, prevalence was highest at stunning and hide removal, followed by removal of the bladder and kidneys. Wearing personal protective equipment such as gloves and facemasks did not appear to protect against infection. Home slaughtering, farming or hunting were not significantly associated with sero-prevalence. There is substantial risk of exposure to leptospires in sheep and deer abattoirs in New Zealand and a persisting, but lower risk, in beef abattoirs. Interventions, such as animal vaccination, appear necessary to control leptospirosis as an occupational disease in New Zealand.

Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand: IV. Biological markers as risk factors for yearling and adult hind conception

A 2-year observational study of 15 red deer (Cervus elephus) farms was carried out in New Zealand from March 1992. In each year of study, approximately 1650 hinds were individually monitored for reproductive success. During farm visits in March 1992 and 1993, five yearling and five adult hinds per farm were randomly selected and blood sampled to define their haematological, biochemical and blood mineral profile. Faecal samples were taken for parasite egg and larvae count. Biological markers potentially affecting the probability of conception before May 1 or of conception that year were investigated separately using multivariable logistic regression analysis. Adult hinds with low serum phosphorus concentrations were more likely to conceive before May 1. Lower conception rates were observed in yearling hinds when blood glutathione peroxidase, serum vitamin B12, and serum albumin concentrations were low, and when faecal lungworm larval counts were high. While these associations have yet to be proven as causal, data suggests that monitoring and maintaining adequate blood elements, and controlling internal parasites in yearling hinds, may assist farmers to achieve optimum reproductive performance in farmed red deer herds.

Foetal ageing in farmed red deer using real-time ultrasonography

Mating dates of 35 adult farmed red deer hinds were recorded and at approximately weekly intervals from the commencement of mating until the end of October 1989, rectal ultrasonographic scans, which were recorded on video, were taken using a 5 MHz linear transducer. Measurements of foetal length, head length, head diameter, nose length, eye diameter, neck diameter, chest diameter, chest depth, umbilical cord diameter, amniotic sac length and width, placentome diameter and uterine diameter were recorded from appropriate scans, and age-estimation equations were computed by regression analysis. All equations were significant (P < 0.001). The earliest dimension measurable was uterine diameter but these measurements were variable and no longer feasible after 45 days pregnancy. Placentomes could be measured from 24 days gestation but placentome dimensions were also variable. The most accurate estimates of foetal age were by measurement of amniotic sac length (37–56 days), crown-rump length (24–59 days) and head length (42–84 days). Accurate foetal ageing was not possible beyond 150 days gestation when pregnancy could only be detected by the presence of placentomes or foetal extremities. n nThe accuracy of pregnancy detection prior to day 20 was 35%, between 20 and 30 days 71%, between 31 and 40 days 98%, 41–130 days 100%, and for pregnancies of 131 days or more the accuracy was 95%.

Evaluation of a SYTO9 real-time polymerase chain reaction assay to detect and identify pathogenic Leptospira species in kidney tissue and urine of New Zealand farmed deer

A SYTO9 real-time polymerase chain reaction assay for detection of pathogenic Leptospira spp. based on amplification of DNA gyrase subunit B (gyrB) gene has been optimized and evaluated for sensitivity and specificity on kidney and urine samples of New Zealand farmed deer. The detection limit was 103 cells/ml (2–10 copies/reaction). Comparison of the assay on deer kidneys (n = 268) with culture as the gold standard revealed a sensitivity and specificity of 85% and 99.2%, respectively. For deer urine (n = 113), the assay was compared with known inoculated samples and revealed a sensitivity and specificity of 96.7% and 100%, respectively. The assay was applied for quantifying pathogenic leptospires shed naturally in deer urine and revealed a detectable concentration of 3.7 × 103 to 1.7 × 106 cells/ml. To assess the assay’s capability for identifying pathogenic Leptospira spp., 14 field isolates of L. borgpetersenii serovar Hardjo-bovis and L. interrogans serovar Pomona were amplified for polymerase chain reaction (PCR) product, purified, and sequenced. When compared with the National Center for Biotechnology Information database, sequence data matched with L. borgpetersenii serovar Hardjo-bovis in 13 samples and L. interrogans serovar Pomona in 1 sample, which was consistent with the microscopic agglutination test (MAT). Sequence analysis of purified PCR product amplified directly from kidney and urine samples also yielded serovar-comparable MAT results. Results suggest that the assay is rapid, sensitive, and specific for detection of pathogenic leptospires in deer clinical samples. The developed assay can also be used for estimating the concentration of leptospires and identifying Leptospira spp. in combination with DNA sequencing.

Estimation of flock/herd-level true Mycobacterium avium subspecies paratuberculosis prevalence on sheep, beef cattle and deer farms in New Zealand using a novel Bayesian model.

The study aimed to estimate the national- and island-level flock/herd true prevalence (HTP) of Mycobacterium avium subsp. paratuberculosis (MAP) infection in pastoral farmed sheep, beef cattle and deer in New Zealand. A random sample of 238 single- or multi-species farms was selected from a postal surveyed population of 1940 farms. The sample included 162 sheep flocks, 116 beef cattle and 99 deer herds from seven of 16 geographical regions. Twenty animals from each species present on farm were randomly selected for blood and faecal sampling. Pooled faecal culture testing was conducted using a single pool (sheep flocks) or two pools (beef cattle/deer herds) of 20 and 10 samples per pool, respectively. To increase flock/herd-level sensitivity, sera from all 20 animals from culture negative flocks/herds were individually tested by Pourquier(®) ELISA (sheep and cattle) or Paralisa™ (deer). Results were adjusted for sensitivity and specificity of diagnostic tests using a novel Bayesian latent class model. Outcomes were adjusted by their sampling fractions to obtain HTP estimates at national level. For each species, the posterior probability (POPR) of HTP differences between New Zealand North (NI) and South (SI) Islands was obtained. Across all species, 69% of farms had at least one species test positive. Sheep flocks had the highest HTP estimate (76%, posterior probability interval (PPI) 70-81%), followed by deer (46%, PPI 38-55%) and beef herds (42%, PPI 35-50%). Differences were observed between the two main islands of New Zealand, with higher HTP in sheep and beef cattle flocks/herds in the NI. Sheep flock HTP was 80% in the NI compared with 70% (POPR=0.96) in the SI, while the HTP for beef cattle was 44% in the NI and 38% in the SI (POPR=0.80). Conversely, deer HTP was higher in the SI (54%) than the NI (33%, POPR=0.99). Infection with MAP is endemic at high prevalence in sheep, beef cattle and deer flocks/herds across New Zealand.

Bayesian estimation of the sensitivity and specificity of individual fecal culture and Paralisa to detect Mycobacterium avium subspecies paratuberculosis infection in young farmed deer.

A Bayesian latent class model was used to estimate the sensitivity and specificity of an immunoglobulin G1 serum enzyme-linked immunosorbent assay (Paralisa) and individual fecal culture to detect young deer infected with Mycobacterium avium subsp. paratuberculosis. Paired fecal and serum samples were collected, between July 2009 and April 2010, from 20 individual yearling (12–24-month-old) deer in each of 20 South Island and 18 North Island herds in New Zealand and subjected to culture and Paralisa, respectively. Two fecal samples and 16 serum samples from 356 North Island deer, and 55 fecal and 37 serum samples from 401 South Island deer, were positive. The estimate of individual fecal culture sensitivity was 77% (95% credible interval [CI] = 61–92%) with specificity of 99% (95% CI = 98–99.7%). The Paralisa sensitivity estimate was 19% (95% CI = 10–30%), with specificity of 94% (95% CI = 93–96%). All estimates were robust to variation of priors and assumptions tested in a sensitivity analysis. The data informs the use of the tests in determining infection status at the individual and herd level.

Molecular epidemiology of Mycobacterium avium subsp. paratuberculosis isolated from sheep, cattle and deer on New Zealand pastoral farms

The present study aimed to describe the molecular diversity of Mycobacterium avium subsp. paratuberculosis (MAP) isolates obtained from sheep, cattle (beef and dairy) and deer farms in New Zealand. A total of 206 independent MAP isolates (15 beef cattle, 89 dairy cattle, 35 deer, 67 sheep) were sourced from 172 species-mobs (15 beef cattle, 66 dairy cattle, 31 deer, 60 sheep). Seventeen subtypes were identified, using a combination of variable number of tandem repeats (VNTR) and short sequence repeat (SSR) methods. Rarefaction analysis, analysis of molecular variance (AMOVA), Fst pairwise comparisons and proportional similarity index (PSI) were used to describe subtype population richness, genetic structure and potential associations between livestock sectors and New Zealand two main islands (North and South). The rarefaction analysis suggests a significantly higher subtype richness in dairy cattle herds when compared to the other livestock sectors. AMOVA results indicate that the main source of subtype variation is attributable to the livestock sector from which samples were sourced suggesting that subtypes are generally sector-specific. The pairwise Fst results were similar, with low Fst values for island differences within a livestock sector when compared to between sector analyses, representing a low subtype differentiation between islands. However, for a given island, potential associations were seen between dominant subtypes and specific livestock sectors. Three subtypes accounted for 76% of the isolates. The most common of these was isolated from sheep and beef cattle in the North Island, the second most frequent subtype was mainly isolated from dairy cattle (either island), while the third most common subtype was associated with deer farmed in the South Island. The PSI analysis suggests similarities in subtypes sourced from sheep and beef cattle. This contrasted with the isolates sourced from other livestock sectors, which tended to present sector-specific subtypes. Sheep and beef cattle were mainly infected with MAP Type I, while dairy cattle and deer were almost exclusively infected with MAP Type II. However, when beef cattle and deer were both present at farm level, they harboured similar subtypes. This study indicates that cross-species transmission of MAP occurs on New Zealand farms although close contact between species appears to be required, as in the case of sheep and beef cattle which are commonly grazed together in New Zealand.

Effectiveness of a commercial leptospiral vaccine on urinary shedding in naturally exposed sheep in New Zealand

L. borgpetersenii serovar Hardjo and L. interrogans serovar Pomona are endemic in New Zealand sheep. An effective vaccine and vaccination strategy would protect both humans and livestock. Four to 12 lambs were selected from each of eight farms (total=84, vaccinated group), while four to 16 lambs (total=98) served as unvaccinated controls. A commercial Hardjo/Pomona vaccine was given at 1-6 weeks of age, 5-11 weeks later and 33-67 weeks later on seven farms and at 18 weeks of age and 5 weeks later on the eighth farm. Vaccinates and controls were grazed together. Blood was regularly collected from the control group to assess flock exposure. Urine was collected from both groups 26-82 weeks after the second vaccination and tested by quantitative PCR. Seroprevalence in controls at the time of urine sampling ranged from 2.7 to 98.2% for Hardjo and from 0 to 54.1% for Pomona with seroconversion occurring 13 to 67 weeks after the second vaccination in all but one farm where exposure had happened by the time of vaccination. The shedding prevalence adjusted for clustering in farms was 45.1% [95% CI 17.6-72.7] (for an observed number of 50/98) in the control animals and 1.8% [95% CI 0.0-10.1] (for an observed number of 5/84) in the vaccinated animals. The vaccine was 100% effective on five farms where animals were vaccinated before 12 weeks of age and before natural exposure occurred, but the effectiveness was 80% [0-97] on one farm where the lambs were exposed before vaccination and 65% [9-87] to 80% [0-97] on one farm where the animals were fully vaccinated by 24 weeks of age. The overall vaccine effectiveness was 86.3% [63.6-94.8%] despite maternal antibodies in some flocks at first vaccination. Vaccination timing seemed to be crucial in achieving optimum reduction in shedding in urine in vaccinated sheep.