May 7, 2014
During fattening liver size increases up to 10-fold.15 Lipogenesis exceeds secretion, so the resulting liver contains more than 50% fat.15 The liver has reduced function to the extent that blood flow is reduced and hepatocyte function is impaired.16,17 It is reported these effects would progress and cause death if force feeding was continued,18 but that they are also reversible.20
Increased liver weight is accompanied by a substantial overall live weight gain (in the range of 85%).21 Obesity influences behavior as fattened ducks are less active and exhibit increased panting in an effort to avoid over-heating.8 The ducks' plumage may develop a wet or greasy appearance. Anecdotal observations by members of the European Scientific Committee on Animal Health and Welfare suggest fattened ducks also demonstrate abnormalities in standing posture and gait.18 Mortalities have been attributed to some ducks becoming immobile and therefore unable to access water.19
Limited mortality figures are available for ducks used in the production of foie gras and it is difficult to find a reasonable baseline for comparison in terms of breed, age, housing, and duration of force feeding. The European Scientific Committee on Animal Health and Animal Welfare review18 indicates that mortality during the force feeding period is typically 2 to 4%; the Institut Technique de l'AVIculture (Technical Institute of Poultry Farming) reports a figure of 2 to 5%.21 Given that this relates to the 2- to 4-week fattening phase of production, this phase seems to result in mortality equivalent to the entire 12-week production period of ducks grown for meat, including the vulnerable post-hatching period.
Foie gras production practices may interact with other general rearing practices with consequences for animal welfare. For example, in the United States ducks are fattened in group pens, which provide opportunities for social behavior. However, it has been suggested that the increased effort required to capture and restrain ducks in pens might cause them to experience more stress during force feeding. Also, although injuries and fatalities during transport and slaughter occur in all types of poultry production, fattened ducks are more susceptible to conditions such as heat stress. The relatively new Mulard breed used in foie gras production seems to be more prone than its parent breeds to fear of people,22 developing lesions in the area of the sternum when kept in small cages, and to bone breakage during transport and slaughter.23
Some of these risks can be mitigated by effective management. There is evidence of industry efforts to use modern feeding equipment, improve feed tube design and provide ducks with a familiar handler. Other refinements might include immediate identification and removal of injured animals and moderation of feeding levels to strike a balance between product yield and animal welfare.
The few empirical studies that have been conducted would benefit from validation of method, more robust use of controls, and independent replication. There is a clear and pressing need for research that focuses on the condition of ducks during fattening, including the actual incidence and severity of animal welfare risks on the farm. This would allow deficits to be accurately identified and ameliorated. Until this occurs, estimates of the welfare condition of ducks used to produce foie gras will be approximate, based upon the severity of the manipulations (force feeding) and resultant deviations from normal health (marked obesity).
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