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Aims: To investigate the epidemiology of Yersinia species in healthy goats in New Zealand, in particular to determine the prevalence of farms with infected goats, the prevalence of infected goats on those farms, the serotypes involved, and potential risk factors for carriage., Methods: A cross-sectional study of the prevalence of Yersinia infection in infected flocks in a study population of thirty commercial goat farms in the Manawatu region of New Zealand., Results: Infection was detected on 60% of farms in an initial study. In a prevalence study on 18 infected farms, the study population comprised 6770 animals (mean of 376, median of 175 and range of 36 to 1295 goats/farm). Of 902 goats (296 < 1 year, 178 1 to 2 years, and 428 > 2 years) sampled from the study population, 135 (73 < 1 year, 21 1 to 2 years, and 41 > 2 years) were excreting Yersinia spp, giving an overall prevalence of 14.97% (95% confidence interval [CI]; 12.8 to 17.4) with individual farm prevalences ranging from 0.0 (+ 7.9) to 58.14% (95% Cl, 43.3 to 71.6). Goats < 1 year were more likely to be infected than 1-2 year and > 2 year old animals (relative risk [RR] = 2.1; 95% Cl, 1.3 to 3.3) and 2.6 (95% Cl, 1.8 to 3.6) respectively), but there was no significant difference between risks for 1 to 2 year and > 2 year goats (RR = 1.2; 95% CI, 0.7 to 2.0). Yersinia enterocolitica was the most common species isolated in the youngest age group, with prevalence declining with increasing age, while other species were more common in the older age groups., Conclusion: Yersinia infections were common in goats in the study region, with younger animals apparently more susceptible to infection and in particular to infection with Y enterocolitica. The prevalence on infected farms appeared to decrease as flock size increased and to increase as stocking rates and the number of paddocks grazed increased.

Objective: To determine the temporal pattern of Yersinia infections in three goat flocks and examine the influence of management and seasonal factors on the incidence of those infections over a 1-year period., Methods: A longitudinal study involving monthly culture of faeces for Yersinia spp. from age groups of randomly selected goats on three farms in the Manawatu region of New Zealand., Results: The incidence of excretion of potentially pathogenic Yersinia (Yersinia pseudotuberculosis and Y enterocolitica biotypes 2, 3 and 5) peaked in winter and fell in summer. In contrast, environmental Yersinia (Y enterocolitica biotype 1A, Y frederiksenii, Y intermedia and Y rohdei) showed no clear pattern of seasonal variation. Pathogenic Yersinia were more prevalent in young animals than in adults, while environmental Yersinia were more prevalent in adults. The same type was isolated from the same animal in two or more successive months in about 20 to 25% of cases, and in the remaining cases there was a gap of at least one month between successive isolations, with many animals yielding a particular type on only a single occasion. A notable difference was that with the potentially pathogenic types, no animal had more than one period of time when it was found to be excreting a particular type, suggesting that immunity develops following exposure. In contrast, it was common for environmental types to be isolated from the same animal throughout the study period. Two goats were suspected to have developed clinical yersiniosis but all remaining infected animals showed no clinical signs of infection., Conclusions: Asymptomatic Yersinia carriage was common in goats in New Zealand, with a clear seasonal and age group pattern of infection with potentially pathogenic types. There was evidence that immunity developed to potentially pathogenic types. This is the first time that Y rohdei has been isolated from goats.

Objective: To analyse data from a study of deer herd health and productivity to identify potential risk factors for the occurrence of dystocia., Design: A 2-year longitudinal observational study of 14 red deer farms was carried out in New Zealand. About 2700 hinds were monitored each year for individual characteristics including body condition score (BCS), and reproductive performance. Grazing and calving management practices were recorded. During calving, farmers recorded calving difficulties (dystocia) that needed human assistance or caused the death of the hind. Risk factors potentially affecting the occurrence of dystocia were identified and analysed by multivariable statistical techniques., Results: The percentage of hinds with dystocia was 0.52% (95% CI 0.32 to 0.78). Hinds with a post-winter BCS over 3.5 were 2.7 times as likely to experience dystocia as hinds scoring 3.5 or less. Given the same BCS class, bodyweight gain in late pregnancy was associated with an increased risk of dystocia. Grazing steep paddocks in the last trimester of pregnancy decreased the risk of dystocia in hinds with a BCS over 3.5., Conclusions: The risk of dystocia on red deer farms may be reduced if key individual animal, management and environmental factors are optimal.

Objective: To compare the profitability of three anthelmintic strategies in growing lambs in flocks with nematodes resistant to benzimidazole anthelmintics., Method: A partial-budgeting analysis was carried out by means of a stochastic simulation model, which allows inputs to be described as distributions rather than as fixed values, and hence permits variation between farms to be considered in the analysis., Results: The results show that control of nematode parasites by use of an effective anthelmintic provides the highest net returns, yielding a margin over ineffectively treated lambs of A$114 per 100 lambs on average. Suppressive treatment based on the administration of two controlled-release capsules and monthly with moxidectin resulted in an average loss of A$131 per 100 lambs in comparison with animals treated with an ineffective anthelmintic. Analysis of the results from capsule-treated lambs did not take into account the unmeasured benefits associated with less contamination of pastures. Sensitivity analysis using a stochastic model indicates that apart from the effect of treatment on weight gain variation in carcase price greatly influences the profitability of all the parasite control programs examined., Conclusion: The results suggest that it is economically important for farmers to adjust their strategy in the presence of anthelmintic resistance. But as a result of uncertainty in the factors influencing economic return, the expected economic benefit is likely to vary substantially.

Information routinely supplied during the conduct of a dairy herd health program was analysed to evaluate the performance of artificial breeding in Victoria. A comparison was made between 60 to 90-day non-return rates (supplied by artificial breeding centres) and pregnancy rates (determined by manual pregnancy diagnosis) for first artificial inseminations in 108 herd years in which both items were available in the 1973 and 1974 breeding seasons. The values were 69.3% and 58.2% respectively (P less than 0.001). Non-return rates and conception rates were found to decline as herd size increased. Pregnancy rates to first artificial and natural services did not differ significantly from each other but pregnancy rates were significantly more variable to natural than artificial service (P less than 0.001). The mean pregnancy rate to artificial insemination for all herd years studied was 57.5% and the pregnancy rate to natural service was 58.0%.

A health program for dairy herds is defined as a planned and coordinated approach to achieving and maintaining optimal health and productive efficiency of livestock. A program is described, which has been developed over a period of eight years to fulfill this definition in providing veterinary services to commercial dairy herds. It is demonstrated that clinical veterinary services to participating herds did not satisfactorily achieve the stated aim and therefore an alternative approach was developed. This approach is centred around the concept of performance targets, and each herd is monitored closely by means of a computer-based health and productivity monitoring system in order to detect deviation from target performance. When such deviations occur, the monitoring system is used to diagnose the nature of the problem. The detailed targets adopted in this study are described and the examinations which are undertaken on cattle are outlined. These examinations are aimed at correcting problems, or at confirming satisfactory performance. Further details of the findings of the study are outlined in following papers.

This paper reports those findings concerning property management from the 1977-78 survey of tick control in Queensland, which could effect efficient tick control and also presents a profile of the cattle industry in the tick infested areas at the time of the survey. The average property size was 400 hectares and the average number of cattle on the properties was 726.4. Larger properties tended to have crossbred Zebu cattle. The average number of paddocks per property was 7.2. The most popular stabilised crossbred Zebu breed was Santa Gertrudis but the most common type of cattle was crossbred Zebu, which was on 30% of properties. There were negligible numbers of crossbreed Zebu cattle on dairy properties. Control of other external parasites may result in additional dippings in areas where they occur. Although fence maintenance appears to be carried out regularly it is clear that the effectivness of tick control measures, such as pasture spelling and dipping which depend on clean musters, could be affected by the occurrence of fire, floods and other natural disasters on half the properties in the tick infested areas. There is no evidence from results in the survey that attention to other farming activities (mainly cropping) prevents producers from paying sufficient attention to tick control. In fact cropping often provides the opportunity for producers to rotate cattle around pastures. Producers appear to consider the cost of tick control is a burden and they expect assistance from the Government to reduce these costs. They do not appear to have considered how they can reduce the costs themselves.

A study of mastitis prevalence in 10 herds which participated in a herd health program is reported for varying periods, up to a maximum of 10 years. The program was based on teat dipping with idophor or sodium hypochlorite teat dip, regular maintenance of the milking machine, and selective dry period treatment of quarters which were classified as infected on the basis of California Mastitis Test score and bacteriological examination of milk samples taken before drying off. The procedures reduced mastitis prevalence (measured in cows being dried off), incidence of clinical mastitis, and disposal of cows due to mastitis. Results obtained were similar to those found in short-term studies of control programs based on teat dipping and dry period therapy. The only significant difficulty which arose in maintaining the control program over 10 years was loss of enthusiasm by farmers for teat dipping. This was usually induced by teat irritation problems apparently caused by teat dipping. The use of a monitoring procedure for mastitis prevalence was important in persuading farmers to return to the use of teat dip.

Disease incidence data was collected from 9 dairy herds which participated in a herd health program. A total of 11,534 cow years was analysed. In common with other Australian data, the important clinical diseases were mastitis and infertility. There was an average level of 43.4 disease incidents per year per 100 animals at risk. An average of 18.6% of the herd left each year. This comprised 1.5% through death and 17.1% through sale. Disease accounted for the disposal of 9.8% of animals, and management reasons for 8.8%. These findings are similar to those of other studies in Australia and in other countries, but the results in this study were based on a longer period and on closer surveillance.

A health program service was implemented on 9 farms, for periods ranging up to 7 years. Reproductive performance was substantially improved, when performance indicators were compared with values for the herds prior to commencement of the service. On average, the mean calving to conception intervals for the herds were reduced by 24 days over their periods of participation in the program, from an initial value of 119 days. The intercalving interval was reduced by an average of 27 days. This improvement was associated with a reduction in the mean dry period length of 20 days, from an initial value of 117 days. There was a tendency for the lactation lengths to be reduced to an undesirable extent due to slow adaptation by management to the improvement in reproductive performance, but the problem was corrected late in the study. The improvement in performance was attributed to improved oestrus detection, correction of temporary nutritional deficiencies, and prompt treatment of genital tract disorders in individual animals. Results for a range of performance indicators related to reproductive function are reported in detail.

The economic benefit obtained from 2 schemes for the strategic control of helminthiasis in weaned lambs has been assessed in the Western District of Victoria. The results were compared with those from sheep in control groups which were given a single anthelmintic treatment during an outbreak of helminthosis. Mortality in sheep receiving the critical treatment scheme of 2 appropriately timed anthelmintic treatments was 12%, compared with 22% in the group receiving the traditional series of summer and autumn treatments, and 26% in the control group. As a result of this difference in mortality rate, the critical treatment scheme was the most profitable control strategy at 1970-71 prices, yielding a net benefit of $70 per 100 sheep in comparison with the control group which received no strategic treatment. This is 538% return on funds invested in anthelmintic treatment. The benefit from this scheme was not unduly affected by variation in wool or sheep prices, nor to possible differences in mortality rate within the expected range. The traditional treatment scheme also yielded positive net returns, but the results were adversely affected by a small change in mortality rate and therefore could not be recommended for routine use on commerical farms.

The results of a survey on tick control carried out in 1977-78 indicate that tick resistant cattle have been introduced for their heat and drought tolerance and their ability to grow more rapidly than European cattle, especially in the extensive grazing country of Northern and Central Queensland. In South-eastern Queensland acceptance of tick resistant cattle has been slower because producers believe they are more difficult to manage than European cattle. A need for more publicity to be given to the different handling methods required by these animals was shown. Some producers cull their less resistant crossbred Zebu cattle and others could be encouraged to do so. Pasture spelling appears to be quite common especially in the Costal North; it is being carried out for pasture management rather than as a tick control measure. Producers in Central and South-eastern Queensland, who do not spell pastures, feel that it reduces the carrying capacity.

The development of flukes that resulted from a challenge dose of 175 F. hepatica metacercariae was compared in 4 groups of sheep that were maintained under grazing conditions on fluke-free pasture. One group had been previously uninfected and all subgroups of each of the other 3 groups had been exposed to one of a range of previous doses of metacercariae. The preliminary infections of 2 of the 3 groups had been terminated respectively after 7 and 14 weeks. The third previously infected group had received its preliminary infection as 2 doses of metacercariae, 7 weeks apart. The latter infection had been terminated after 14 weeks. No appreciable differences in the mean numbers, length, prepatent period or fecundity of flukes, established as a result of the challenge dose of metacercariae, were detected between the control group and the 3 previously infected groups. It was concluded that under the conditions of the present experiment no evidence was detected that would suggest that previous infection with F. hepatica conferred any significant resistance to a future challenge.

The development of a computerised data handling and analysis system to aid the operation of a health and management program for commercial dairy herds is described. The aims for the system are outlined, and the development of the system over a period of 8 years to meet these aims is described. The documentation used in the current system is described in relation to the various procedures involved in the operation of the dairy herd health program. Two features which make this system unique are its use for the selection of problem and high risk cows for examination and treatment, and the provision of analyses of recent performance in a number of facets of health and production, which aid in the identification of emerging problems. It is considered that future improvements in the system will be in the areas of milk production recording and calf rearing and disease recording.

An experiment was described in which guinea pigs were used as tracer animals in an attempt to assess the longevity of Fasciola hepatic metacercariae on pasture at Werribee, Victoria. The metacercariae had been encysted on both an irrigated and non-irrigated area at various times during 1976. It was determined that, under the conditions of the experiment, metacercariae can survive and remain viable for up to 10 weeks during the winter. It was also determined that longevity during the summer was greatly reduced, and was of the order of only 1 week. The significance of these findings, with respect to the epidemiology of the disease, was discussed.

Survey results concerning chemical control of the cattle tick (Boophilus microplus) in Queensland are reported in detail, and differences due to region, breed and type of enterprise are discussed. The results show that chemical control was more intensive in Zebu and Zebu crossbred cattle than could be justified economically and that a minority of producers with European cattle carried out strategic dipping. Owners of plunge dips did not make regular use of testing facilities, available from the Department of Primary Industries or the chemical companies.