[Discussion of actual legal minimum requirements for feeder space and perch length in laying hen husbandry in the light of the body widths measured in Lohmann Selected Leghorn and Lohmann Brown laying hens]

Legal requirements on space and dimensions regarding furnished cages and alternative systems in laying hen husbandry are subject of constant discussion. Further knowledge about basic measures of the hens might help to come to reasonable results in the future. Digital images of Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) laying hens, housed at the Lehr- und Forschungsgut Ruthe, University for Veterinary Medicine Hanover, Foundation, in Big Dutchman Eurovent laying hen cages, were made at three stages (19th, 36th and 58th week) of production. All hens had been taken out of their cages by night and set on a perch in a special cage used to photograph the hens frontally under controlled conditions. Body widths were calculated by a python application Cdisto.py0 2009 Andreas Briese) to mark and measure the body width in the digital images of a total of 156 hens. Mean body widths of 133.77 mm in Lohmann-LSL hens (SD = 9.71; N = 64; mean weight: 1.73 kg) and of 152.55 mm in Lohmann-LB hens (SD = 10.31; N = 92; mean weight: 1.93 kg) respectively were found. Even slight changes in body weights had no effect on the body width. Nonetheless the differences between both hybrids were always statistically significant (Mann-Whitney p0,001). Using these preliminary results on body width in a mathematical model simultanious feeding behaviour becomes only possible if the number of animals is reduced by 10.3% to 89.7% in LSL and by 21.3% to 78.7% in LB breeds in relation to a calculated maximum on base of the minimum space requirements for furnished cages in the EU-Dir 74/1999/EC.