Prevalence of megabacteria in budgerigar colonies

Objective To measure the prevalence of megabacteria in budgerigar-breeding colonies and to evaluate possible methods to reduce the prevalence.
Design A monitoring study over several years.
Sample population Two budgerigar ( Melopsittacus undulatus ) colonies with over 300 birds each.
Procedure The prevalence of megabacteria in the faeces in two budgerigar breeding colonies, colony 1 and 2, was determined by faecal examination of each bird. Following an initial survey (1990), most of the birds that were scored 2+ or more were culled and a management practice was implemented to discriminate against positive birds. Consecutive yearly surveys (1991, 1992) were conducted on the young birds bred in these colonies. The prevalence of megabacteria in colony 2 was also evaluated in 1994 and 1996 after all the birds were treated with amphotericin B administered in drinking water.
Results The prevalence of megabacteria in the two colonies was significantly (P < 0.001) different. Overall the prevalence of megabacteria adjusted for colony differences was significantly higher (P < 0.025) in males compared to females. Age was not an influencing factor. After the initial survey, the prevalence in the offspring did not significantly (P > 0.05) decrease in the following two annual breeding seasons but by inference it did significantly decrease after amphotericin B treatment.
Conclusion The practice of culling most birds with more megabacteria in faeces and discriminating against positive birds when selecting birds for breeding or culling birds on show quality does not decrease megabacteria prevalence in the offspring. However, a reduction in prevalence does occur with administration of amphotericin B. Birds may have amphotericin B-resistant organisms and these birds need to be identified and culled.     

Changes in productivity and profitability of wool-growing farms that follow recommendations from agricultural and veterinary studies

Objective To estimate the changes in productivity and profitability in a group of wool-growing farms as they adopted major recommendations from agricultural and veterinary studies.
Farms Four wool-growing farms in south western Victoria were selected from the clients of the Mackinnon Project, a farm consultancy service run from the University of Melbourne. Each farm had closely followed recommended procedures, kept comprehensive financial and physical records and had been clients for at least 5 years. The comparison group was the South Western Victoria Monitor Farm Project (SWVMFP), about 45 farms in the same region as the study farms that were monitored annually by Agriculture Victoria.
Procedure For a 7-year period, the financial and physical performance of both groups of farms was estimated. Stocking rate, wool production, gross farm income, farm operating costs, net farm income and return on assets were compared.
Results Mean gross farm income of the four study farms steadily rose from 86% of the average SWVMFP farm before the adoption of recommendations to an average of 155%. During the same period, net farm income rose from 70% to 207% of the average of the SWVMFP. Return on asset of the four farms rose irregularly from 26% to 145% of the average of the SWVMFP. Farm operating costs on the four farms were higher than for the SWVMFP group, but the ratio of costs remained relatively constant.
Conclusion The adoption of proven research results was associated with large increases in net farm income. An increase in gross income, rather than a reduction in costs was the main reason for this. Research results offer a way to increase the financial viability of wool-growing farmers, many of whom are currently unable to maintain their lifestyle, resources and infrastructure.     

Evaluation of deniotrification in two shallow-placed low pressure distribution systems

Nitrate removal by biological denitrification was examined in two shallow-placed low pressure distribution (LPD) systems located in soils that were unsuitable for conventional disposal systems because of shallow depth to restrictive soil horizons in an Edom soil or to fractured shale in a Penn-Bucks soil. Four independent LPD subsystems were installed in the Edom soil with actual loading rates of 2.3, 2.9, 4.6, and 8.9 L d^–1 m^–2 while three subsystems were installed in the Penn-Bucks soil with actual loading rates of 3.6, 7.2 and 15.3 L d^–1 m^–2. Maximal rates of nitrate loss through denitrification were determined in the laboratory based on the acetylene block procedure, while actual field denitrification rates were estimated based on nitrate:chloride ratios. In the Edom soil, all four LPD subsystems demonstrated the same potential rates of denitrification in laboratory tests, while field estimates of nitrate loss ranged from 2% to 21% over the four subsystems. These low field denitrification rates were attributed to lower-than-designed loading rates which maintained aerobic conditions. In the Penn-Bucks soil, the subsystem dosed at 15.3 L d^–1 m^–2 failed within six months of installation and was not used further. The subsystem loaded at the rate of 7.2 L^–1 m^–2 yielded higher rates of denitrification under laboratory studies as compared to the subsystem loaded at 3.6 L d^–1 m^–2, and a similar trend was observed in field nitrate losses through denitrification which were 71% and 65%, respectively. These high denitrification rates (compared to the Edom subsystems) indicated that anaerobic conditions were present in the Penn-Bucks subsystems.