Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand: V. Mob and individual-hind risk factors associated with calf rearing to weaning.

A 2-year longitudinal observational study of 15 red deer farms was carried out in New Zealand from March 1992. Both years combined, 3364 adult and 653 yearling hinds were diagnosed pregnant in June by ultrasound scanning and monitored for reproductive success up to weaning. At weaning, pre-rut at approximately 100 days after calving, udders were palpated or observed by the farmer and hinds were categorised as lactating (wet) indicating survival of calf, or not lactating (dry). Farm management practices during calving and early lactation were recorded. Analysis of risk factors associated with progeny survival was done using path analysis (separately for adult and yearling hinds). Adult hinds >3 years old at calving, conceiving before 1 May and having a body-condition score >2 in September had 2.8, 2.4 and 2.9 times significantly higher odds of rearing a calf to weaning than other hinds, respectively. Adult hinds had about 5 times lower odds of rearing a calf to weaning when they were mixed with mature stags during calving. When farmers visited calving paddocks and checked for calving problems, adult hinds had 1.7 times higher odds of rearing a calf to weaning. When the farmer entered calving paddocks at least every second time they observed the hinds, yearling hinds had a twice higher odds of rearing a calf up to weaning. Sunny weather and high maximum temperatures were positively and negatively associated, respectively, with the probability of an adult hind being in lactation at weaning.

Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand: II. Risk factors for adult hind conception.

A 2-year longitudinal observational study of 15 red deer farms was carried out in New Zealand from March 1992. About 2600 adult hinds were individually monitored for reproductive success. After mating, hinds were pregnancy-tested by ultrasound and were classified as having conceived before 1 May, after 1 May or as being not pregnant. Risk factors potentially affecting the probability of conception before 1 May or of conception that year were investigated using path analysis. Final path diagrams were used to formulate a putative management strategy for farmers to achieve the desired reproductive performance from adult hinds. To achieve a high pregnancy rate early in the mating season, farmers should wean calves early, exclude hinds which failed to rear a calf to weaning and hinds with a body condition score < or = 2.0 at mating, join hinds early with one or more sire stags, use only experienced sires for mating, limit the hind: stag ratio, use at least one back-up sire after the peak of mating, keep mating mobs away from disturbance and avoid shifting or handling mating mobs. The farmer should choose paddocks with high green pasture allowance and grazed down to no less than 5 cm high.

Reproductive performance of farmed red deer (Cervus elaphus) in New Zealand: III. Risk factors for yearling hind conception.

A 2-year longitudinal observational study of 15 red-deer farms was carried out in New Zealand from March 1992. Seven hundred yearling hinds were individually monitored for reproductive success. After mating, hinds were pregnancy tested by ultrasound and were classified as having conceived before 1 May, after 1 May, or as being not pregnant. Risk factors potentially affecting the probability of conception before 1 May or of conception that year were investigated using path analysis. To increase the probability of conceiving early, this study suggests yearling hinds should be selected prior to mating for high bodyweight and height. Young stags and hinds should be joined late summer (14 months of age) before mating. Mobs of yearling hinds should not be combined with large mobs of adult hinds. Paddocks with limited gullies, hills and trees should be chosen for mating. Finally, paddocks for mating should be away from human disturbance. To increase the probability of yearling hinds conceiving that year, yearling hinds should be in moderate-to-low body condition (around 2.5), and nutrition during mating should be prioritised to ensure optimal growth rates. Short and/or lightweight hinds may be mated successfully if they are well fed but they generally conceive later. Trees should be limited in the mating paddocks.

Observations of leptospirosis in farmed deer.

AIMS: Slaughterhouse and on-farm surveys were undertaken to investigate some aspects of leptospirosis (Leptospira interrogans) in farmed deer in the lower North Island of New Zealand. METHODS: Blood samples and kidneys were collected at slaughter from 601 l-year and older red and red X Wapiti stags and 21 adult hinds from 53 farms (10 or 12 deer per farm). Serum samples were analysed for up to seven Leptospiral serovars. Gross and histological examinations of kidneys were undertaken. Kidneys from 202 deer were cultured for leptospires. A follow-up postal questionnaire (68% response) indicated one herd had been vaccinated prior to the survey. Serological analyses were also carried out on serum bank samples from a previous on-farm survey involving male and female weaner, yearling and adult red deer from 16 commercial deer farms in March and November. RESULTS: Serological reactions at titres > or = 96 to serovar hardjo were present in 73.6%, pomona in 41.5%, copenhageni in 11.3% and tarassovi in 15.1% of farms from the slaughterhouse survey. Antibodies to serovars australis, ballam and balanica were present in three, one and four of six herds studied, respectively. Titre prevalence to hardjo was higher than that of pomona and other serovars within farms. Cultures for Leptospira were positive in 10 stags from six lines with similar prevalence across age groups. Histological examination showed many gross lesions were associated with mild interstitial cellular infiltration characteristic of subclinical Leptospiral infections. Some sections from culture-positive kidneys contained spirochetes in renal tubules. The on-farm survey showed a 10-30% within-herd prevalence of pomona and hardjo titres in 56% of 3-month-old deer herds, but by 11 months of age, 100% of herds were titre-positive with high prevalences to one or both serovars. Concurrently, herds of 1-year-old and adult deer on the same farms were all seropositive. CONCLUSION: This study has shown that Leptospiral infections are common in farmed deer in the survey area.

A survey of internal parasites and parasite control on North Island deer farms.

AIM: To evaluate internal parasite control practices and their effectiveness, and to investigate relationships between indices of parasitism and production outcomes by analysis of data collected during a deer herd health and production profiling project. METHODS: A longitudinal study of 15 red deer farms in the North Island of New Zealand was carried out from March 1992 to April 1994. Anthelmintic usage was recorded. Sentinel weaner, yearling and adult hinds and stags were blood and faecal sampled in early autumn, winter, spring and summer for serum pepsinogen and faecal egg and larval counts. A descriptive analysis of control programmes and egg and larval counts was produced. In addition, further measurements of parasitism and parasite control, including faecal egg count and faecal larval count data, individual pepsinogen concentrations, timing and numbers of anthelmintic treatments, and a farm calf faecal lungworm larvae count index were firstly subjected to univariate statistical association with production outcomes, followed by stepwise multivariable logistic regression analysis. Timing and numbers of anthelmintic treatments, along with other farm, herd or animal management risk factors, were included into path models. RESULTS: A wide range of anthelmintic programmes in all age groups, within farms between years and between farms was recorded. Weaner deer received three to nine treatments in their first year. Many farmers treated older deer in only one of the years of study. Older stags were treated more often than younger stags. Oxfendazole, ivermectin and moxidectin were the most commonly used anthelmintics. Egg and larval counts varied between properties and between years in some seasons but a higher proportion of deer shed larvae than eggs. In winter the number of weaners shedding eggs was the same as in autumn, but fewer shed lungworm larvae. Counts were lower at 12 months of age. Counts in older stags and hinds were highest in early spring, and counts were higher in yearling stags than in adult stags. Geometric mean pepsinogen concentration was lowest in weaners and rose to adult levels by early spring. Statistical analyses showed a lower weaning weight associated with higher faecal larval count index, and a reduced number of anthelmintic treatments prior to weaning. Weaners grew faster in spring after late winter anthelmintic treatment than those without treatment or with later treatments. There were inverse relationships between both farm mean weaner and adult serum pepsinogen and summer growth of weaners, and weaning percentage of adult hinds, respectively. CONCLUSION: This study has highlighted current parasite control practices, relationships between indices of parasitism and production outcomes, and has identified areas for further research into parasitism in farmed deer.