Buchwalder, 2011 – Assessment of colony nests for laying hens in conjunction with the authorization procedure

Pretesting farm animal housing systems that are intended for mass production is a practical way to increase and ensure product quality of livestock systems. The Swiss authorization procedure requires new systems and equipment for farm animals to show improvement with regard to animal welfare. For this purpose, a method to test hen colony nests was developed and subsequently applied to assess the suitability of five commercial nests. First, we developed a “minimal nest” that fulfilled the minimum requirements of the Swiss Animal Welfare Regulations (development phase). In a second step consisting of five experiments, the minimal nest was offered in combination with one of the commercial nests (assessment phase). For approval, the hens’ preference for the commercial nest must be better than or equal to their preference for the minimal nest. The experiments were carried out with eight (development phase) or nine (assessment phase) groups of 20 hens and spanned the 18th to the 26th (development phase) or 28th (assessment phase) week of age. The numbers of eggs in the nests and on the floor were registered daily, and the behaviour and positions of the hens were recorded during the last two weeks of the experiments. The hens significantly preferred an open litter box to a minimal nest with an open front side (59% vs. 36% of the eggs, p < 0.03), while the minimal nest in which the front side was covered by a plastic curtain was significantly more attractive than the open litter box (86% vs. 12% of the eggs, p < 0.001). One of the commercial nests was significantly preferred over the minimal nest with the plastic curtain (78% vs. 17% of the eggs, p < 0.01), whereas two of the commercial nests were significantly less favored than the minimal nest (39% vs. 58% of the eggs, p < 0.01; 16% vs. 82% of the eggs, p < 0.002). No significant differences were found for the other two commercial nests (42% vs. 56% of the eggs, p = 0.33; 29% vs. 65% of the eggs, p = 0.17). Behavioural and positional data for the laying hens are also presented. Seclusion seems to be an essential factor for hens searching for a nest site. With regard to the authorization procedure, the commercial nests that were preferred or rated similarly to the minimal nest may become definitively authorized, whereas the disliked nests are likely to be disapproved. Investigations on commercial farms are needed for final assessment.