Evaporatranspiration and growth of two contrasting species of eucalypts under non-limiting and limiting water availability

Changes in root zone water storage between 0 and 1 m depth were monitored at 14-day intervals under contrasting canopies ofEucalyptus nitens (a gum) andEucalyptus delegatensis (an ash) during their fourth and fifth years of growth and periods of non-limiting and limiting water availability, respectively. The leaf area index of the gum remained approximately double that of the ash throughout this time. Stem volume growth differed by factors of 1.8 and 2.0 betweenE. nitens andE. delegatensis while total water use differed by factors of 1.1 and 0.9 in two periods, respectively. A cumulative plot of volume growth as a function of total evapotranspiration suggested that stem volume growth ofE. nitens was less sensitive to severe water stress than that ofE. delegatensis.     

AN ABATTOIR SURVEY OF BULL GENITALIA

SUMMARY This paper describes a survey of 504 bull genitalia collected after slaughter at 3 Western Australian abattoirs over 18 months. Details of the gross pathology, histopathology, and microbiology of the genitalia, and physical dimensions of the testicles are presented. The major breeds represented were Hereford (30%), Shorthorn (16%), Friesian (14.3%), and Aberdeen Angus (13.9%). The mean age of 263 bulls (52.6%) was 4.4 years. The mean length and breadth of 469 paired testicles was 10.8 cm and 6.9 cm respectively.     

Practices and opinions of New Zealand beef cattle farmers towards bovine viral diarrhoea control in relation to real and perceived herd serological status

ABSTRACT

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status.

Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control.

Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only.

Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options.     

Effect of susceptible and resistant canola plants on Plasmodiophora brassicae resting spore populations in the soil

Clubroot, caused by Plasmodiophora brassicae, has become a serious threat to canola (Brassica napus) production in western Canada. Experiments were conducted to assess the effect of growing resistant and susceptible canola genotypes on P. brassicae soil resting spore populations under greenhouse, mini‐plot and field conditions. One crop of susceptible canola contributed 1·4 × 10⁸ spores mL^?1 soil in mini‐plot experiments, and 1 × 10¹⁰ spores g^?1 gall under field conditions. Repeated cropping of susceptible canola resulted in greater gall mass compared to resistant canola lines. It also resulted in reduced plant height, increased clubroot severity in susceptible canola, and increased numbers of resting spores in the soil mix.