The study highlights some challenges to disease control in small-scale multispecies poultry farms. Time series of disease-associated mortality were correlated with population size for Muscovy ducks (Kendall’s coefficient τ = 0.49, p-value < 0.01) and with frequency of outdoor grazing for ducks (τ = 0.33, p-value = 0.05). The rate of mortality due to disease did not differ much among species, with birds being less likely to die from disease at older ages, but frequency of disease symptoms differed by species. Ducks had a markedly higher removal rate (broilers: 0.14/week layer/breeders: 0.05/week) than chickens and Muscovy ducks (broilers: 0.07/week layer/breeders: 0.01–0.02/week) and a higher degree of specialization resulting in a substantially shorter life span. Muscovy ducks were kept for long periods and outdoors, while chickens and ducks were farmed indoors or in pens. Median flock population sizes were 16 for chickens (IQR: 10–40), 32 for ducks (IQR: 18–101) and 11 for Muscovy ducks (IQR: 7–18) farm size distributions for the three species were heavily right-skewed. Methodįifty three farms were monitored over a 20-month period, with farm sizes, species, age, arrival/departure of poultry, and farm management practices recorded monthly. This observational study describes the demographic structure and dynamics of small-scale poultry farms of the Mekong river delta region. However, smallholder poultry production is constrained by several issues such as infectious diseases, including avian influenza viruses whose circulation remains a threat to public health. Poultry farming is widely practiced by rural households in Vietnam and the vast majority of domestic birds are kept on small household farms.
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