Mortality in free range flocks – final report executive summary
From Poultry Hub
Mortality in free range flocks can be caused by numerous factors including feather pecking and/or cannibalism, disease, predators and management (diet, housing, strain, rearing, light levels, vaccinations, flock size and density). There is limited scientifically sound information on causes of mortality in free range flocks in Australia and we will start to address this. This pilot study provides survey data on what producers believed were the causes of mortality and preliminary epidemiological data on causes of mortality in an intensive, albeit of limited geographical range, survey.
A survey of all free-range producers in Australia was undertaken to indicate causes of mortality in the industry and to tailor the epidemiological survey to ensure temporal/locality issues were covered. Fourteen free range producers replied to the nationwide survey, five from Queensland, one from New South Wales, and four each from South Australia and Victoria. Fowl cholera was named as the most important cause of mortality in Queensland. New South Wales and Victoria recorded spotty liver as one of their most important causes of mortality with South Australia giving it a low rank and Queensland producers not considering it a problem at all. It is to be thought that, similar symptoms shown by both fowl cholera and spotty liver might have confused producers in their presumption. Queensland and Victoria had problems with predators (foxes/crows and dogs/hawks, respectively) with Victoria also recording heat stress as an important cause of mortality. Egg peritonitis, prolapse/ protusion, cannibalism and vent pecking were all seen as important causes of mortality in all states.
In 2006, five flocks of birds from free range farms in Southeast Queensland undertook an intensive epidemiological survey which included a detailed survey, serology and faecal samples of the flock, ongoing mortality records and gross pathology of all mortalities. Flock sizes of the five farms ranged from 1500 – 3500 with all hens (Bond Brown, Bond Black and Hyline Brown) allowed to range in daylight hours regardless of weather conditions. All farms had conventional sheds fixed in one location and fitted with individual nest boxes and perches. All farmers reported that they had vaccinated their flocks for infectious bronchitis (IB), Newcastle disease virus (NDV) and egg drop syndrome (EDS). Overall, all flocks had a positive average NDV, IB and EDS titre throughout the survey; however farms 4 and 5 did not have a uniform distribution of the titres and therefore not a good protection for their flocks. Reproduction tract lesions such as oophoritis, salpingitis, egg peritonitis, and salpingoperitonitis were the most frequently encountered necropsy findings, presumably causing death of laying hens. Cannibalism was the second most common cause of mortality. A follow-up investigation was carried out in 2008 to collect sterile samples from fresh sacrificed birds showing similar symptoms to previous trial for further microbiological tests. It was shown that 85% of birds sacrificed had similar reproductive tract problems. From samples collected (61 in total), 20 did not show presence of any bacteria; gram positive cocci were found in 30 (or 49%) of all samples, while 11 (or 18%) of isolates were gram negative cocci or rods. It is common in commercial poultry that egg laying can be interrupted by stress or an infectious disease. The frequency with which Staphylococcus spp. was isolated suggests an aetiological relationship with encountered lesions. However, only S. aureus is considered to be pathogenic in poultry. To date isolates from live birds have not been associated with human infections or food intoxications. Economic losses occur to producers because egg production drops and mortality increases. Bird welfare could also be compromised.
The nationwide survey questionnaire return rate was disappointing with only fourteen producers returning completed surveys. The survey was developed in consultation with free range producers and an opportunity for the industry itself to have a major input into the direction of free-range research in Australia. Apparently, the survey caused concern that we were unfairly targeting the free range industry and therefore in turn helping the cage layer industry. Recommendations include improvement of hygienic conditions and biosecurity, approval of more antibiotics and anthelmintics for use in laying hens, and a detailed investigation into the microbial population of the reproduction tract in free range, barn and cage laying hens with the possibility of developing probiotics.
Further information
- Nagle, T and Shini, S 2008 Pilot trial – Mortality in free range flocks ISBN 1 921010 26 6 Final Report, Australian Poultry CRC Pty Ltd
See also
- Research project: Mortality in free range flocks
- Optimising liveability of free-range layers
- Backyard/general poultry references
- The egg
- Chicken
External links
- Free Range Egg & Poultry Association of Australia Inc. is a national representation of state based associations practicing and promoting free range egg and broiler farming.
- Free Range Egg & Poultry Australia is a members' organisation for free range producers. The FREPA website provides information on FREPA standards, membership, accreditation and FAQs.
- Free Range Poultry Association of Queensland Inc. is a not-for-profit association of free range egg and poultry meat farmers.
