The USDA-ARS Livestock Behavior Research Unit in conjunction with the Department of Animal Science, Purdue University has recently published results of two studies to evaluate behavior of laying hens in relation to housing. In the first paper¹ a conventional battery cage system was compared to a European-style furnished cage. This alternative has been adopted in Germany since it is considered to be an acceptable alternative to conventional cages to promote welfare.
Furnished cages have solid metal walls, perches, a dust bathing area, scratch pad and nest box. The results obtained in Indiana apparently favored furnished cages with respect to “higher levels of comfort behavior expressed by the birds.” The authors concluded that furnished cages “may be a favorable alternative system for battery cages in housing birds for egg production.”
Questioning the conclusions
On closer review the following facts are apparent:
- The comparisons involved 100 hens each which is inadequate in relation to extrapolating to a commercial-scale unit.
- The hens were housed in a conventional cage at 100 in² per bird. This is in excess of the current 76 in² specified in the UEP Program.
- Conclusions were based on computerized evaluation of surveillance videos depicting behaviors including feeding, drinking, walking, preening, pecking and alteration in behavior. There is no established correlation between specific behaviors and stress, other than the previous observations made by European researchers. The numerical differences between battery cages and furnished cages varied markedly within treatment according to age. The differences between the treatments, despite some significant values, do not appear persuasive.
- There was no attempt made to correlate behavior with a physiological measure such as plasma corticosterone level or lymphocyte to heterophil ratio.
- It is noted that six birds (6%) among the treatment in furnished cages demonstrated pododermatitis. If this observation is consistently associated with this housing system, additional work is necessary to develop a cage floor which is more conducive to the well-being of flocks. Commercial experience does not show any obvious prevalence of pododermatitis in either first or second cycle hens in conventional U.S. cages with a floor slope of less than 6 degrees.
Study of feeder space
The second article² evaluated the effect of feeder space on the behavior of hens housed in conventional cages. Trough space ranged from 2.3 inches to 4.8 inches per hen. Intuitively the number of hens feeding simultaneously related to the allocation of feed space with obvious competition evident at the two lowest feed space levels evaluated. There was no significant interaction with number of hens feeding and the time of day or feed space allocation.
The authors derived conclusions from observations of feeding frequency including “hens with less feeder space utilize more food in less time, perhaps reflecting increased feed wastage” although there was no data quantifying actual feed consumption. The only practical concept derived from the study is that hens tend to increase feed intake in anticipation of darkness. Generally feeding periods are spread evenly through the illuminated period of the day and it is therefore possible that the frequency of operating feeders could be adjusted to conform to the physiologic need of flocks. This is especially the case with light-weight pullets during the period following onset of production and during hot weather.
Lack of commercial application
The significant omission in both trials was the failure to quantify commercial parameters such as egg production, feed intake, egg mass or conversion or to extend this data to financial return. Studies on housing which show effects on behavior have implications for welfare and the formulation of policy. The egg industry which indirectly funds studies on housing, management and behavior should be in a position to make value judgment decisions on investment and production practices based on both scientific observation and performance parameters.
There is a concern that welfare standards recommended by panels of scientists may be unduly influenced by fragmentary research and studies which do not relate to the commercial situation. Researchers should be more attuned to the needs of the industry and should consult with their scientific colleagues actually involved in production and primary breeding when designing and executing studies which have potential application to the commercial situation.