Keeping Laying Hens in Furnished Cages and an Aviary Housing System Enhances Their Bone Stability M
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British Poultry Science Volume 46, Number 5 (October 2005), pp. 536–544 Keeping laying hens in furnished cages and an aviary housing system enhances their bone stability M. LEYENDECKER, H. HAMANN, J. HARTUNG1, J. KAMPHUES2, 3 4 1 U. NEUMANN ,C.SU¨RIE AND O. DISTL Institute of Animal Breeding and Genetics, 1Institute of Animal Hygiene and Animal Welfare, 2Institute of Animal Nutrition, 3Clinic for Poultry and 4Farm for Education and Research in Ruthe, University of Veterinary Medicine Hannover, Hannover, Germany Abstract 1. Tibia and humerus breaking strength of Lohmann Silver hybrids kept in conventional cages, furnished cages and an aviary with outdoor run were examined in two production cycles. Each trial lasted a full laying period; feeding, management and healthcare were identical for all hens. In both trials bone strength was investigated at the end of laying months 6, 9 and 14. 2. The objective was to determine if bone strength increases when hens are kept in alternative housing systems, especially in furnished cages, and whether hen age affects bone stability. 3. The results indicated that housing system influenced bone breaking strength, which was consistently higher for hens in the aviary compared to hens in conventional and furnished cages. Furthermore, humerus breaking strength was higher for hens in furnished cages compared to conventional cages. No significant difference regarding tibia breaking strength was found between conventional and furnished cages. 4. Our results showed that lack of exercise contributed to the problem of weak bones more than did calcium depletion from eggshell formation. 5. Tibia breaking strength increased during the last third of the production cycle, whereas humerus breaking strength remained unaffected by hen age. 6. Genetic group affected only tibial bone breaking strength, which was lower overall in genetic group A than in group B, which in turn was lower than group C. 7. The increased bone strength in the aviary and in the furnished cages probably reduced the incidence of recently broken bones in these systems compared to the conventional cages. This increase in bone strength can be regarded as an improvement in welfare. Furnished cages, like the aviary system, might be considered an alternative housing system for laying hens, because both resulted in enhanced bone strength. Downloaded By: [University of Montreal] At: 19:42 25 August 2009 INTRODUCTON defines osteoporosis in laying hens as a decrease in the proportion of fully mineralised struc- In the last 15 years conventional cages for laying tural bone, leading to increased fragility and hens have been intensely criticised in the susceptibility to fracture. High continuous egg European Community, because they provide a production (Cransberg et al., 1998), reduced barren environment which restricts the birds’ mobility (Nightingale et al., 1972) as well as movement and prevents them from performing nutritional deficiencies of calcium, phosphorus natural behaviours such as nesting, perching or cholecalciferol (Wilson and Duff, 1991) can and sand bathing (Duncan and Fraser, 1997). induce osteoporosis. Another major issue in this dispute was the fact Modern laying hybrids kept in conventional that the conventional cage, with its limited space, cages have a high prevalence of bone fractures leads to brittle bones and bone breakage, which (Fleming et al., 1994). These fractures can can result in death (McCoy et al., 1996). This is occur during the laying period as well as assumed to be due to the development of osteo- during depopulation, transport and handling at porosis (Wilson et al., 1992). Whitehead (2000) slaughter. The weakness of the bones of hens Correspondence to: Professor O. Distl, Institute of Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Bu¨nteweg 17p, 30559 Hannover, Germany. Tel: þ49-511-953-8875. Fax: þ49-511-953-8582. E-mail: [email protected] Accepted for publication 11th May 2005. ISSN 0007–1668(print)/ISSN 1466–1799(online) ß 2005 British Poultry Science Ltd DOI: 10.1080/00071660500273094 BONE STRENGTH AND HOUSING SYSTEM 537 kept in conventional cages is estimated to be in one unit and under the supervision of the mainly due to the limited opportunity to exer- same staff, we equalised different management cise. Several studies over nearly 25 years have practices and all other farm effects between shown a consistently higher incidence of bone housing systems, so that any differences would fragility in caged laying hens compared to that of be attributable to housing system. hens kept in alternative housing systems, where the hens were allowed to exercise more (Fleming MATERIALS AND METHODS et al., 1994; Van Niekerk and Reuvekamp, 1994; Leyendecker et al., 2001). The extent of the Housing conditions problem is shown by the fact that recent studies of caged hens indicate that up to 35% of the All three different housing systems were installed losses during the laying period were attributable in parallel in the same experimental building. to bone weakness (McCoy et al., 1996). The conventional cages consisted of a block of In response to welfare concerns a new EU double-decker cages (model ‘Eurovent’, Big directive (CEC, 1999) was issued in 1999 which Dutchman) three tiers high, with solid side bans conventional cage systems from the year partitions and horizontal metal bars in the rear; 2012 onwards in all European Union countries. the droppings were automatically removed on This new legal situation has inspired the conveyor belts. Each cage accommodated 4 hens, development and testing of new egg production with 688 cm2 of floor space (50.2cm 55.0 cm) systems. Compared to conventional cages, these per hen, and with 45 cm height at the front and alternatives are intended to improve the welfare 39 cm height at the back of the cage. Automatic of laying hens. Various comparisons of laying chain feeders supplied feed from a trough at the hens kept in different alternative housing systems front of the cage and water was provided from have been carried out with respect to welfare, in nipple drinkers. particular bone breaking strength. Aviaries are an The furnished cages consisted of a block acceptable alternative with regard to improved of double-decker cages (model ‘Aviplus’, Big bone breaking strength, because they provide Dutchman), which were installed in three tiers. more space for locomotor activities such as A furnished cage had solid side partitions and running, wing flapping and flying, and allow the horizontal metal bars in the rear and the birds to perform natural behaviours such as droppings were automatically removed on con- nesting, perching and sand bathing. Another veyor belts. Each furnished cage (120 cm wide, approach to alleviate the problems of conven- 63 cm deep, 45 cm height at the front and 51 cm tional cages is to keep the birds in furnished height at the back of the cage) was equipped with cages. One of the aims of the furnished cage perches, a family nest and a sand bath, with 10 designs was to enhance hens’ opportunity for hens sharing a cage. Thus, every hen had access exercise and so improve bone strength. In this to 609 cm2 cage surface area, 150.8cm2 nest area system hens’ bone breaking strength is reported and 120 cm2 sand bath area. The nest box to be higher than in conventional cages (1508 cm2) was located in the bottom right (Abrahamsson et al., 1996; Abrahamsson and corner of the cage, separated from the cage Downloaded By: [University of Montreal] At: 19:42 25 August 2009 Tauson, 1997). Even modifications to conven- area by a plastic curtain and the floor was tional cages such as adding perches to the cage covered with artificial turf. The laid eggs rolled have been shown to improve bone strength from the nest out of the back of the cage. Next to (Tauson, 1984). On the basis of the increased the nest box a sand bath (1200 cm2) was situated bone strength of hens kept in cages with perches and was filled up with sawdust once a week. and its positive effects on health, one would During the laying period the sand bath was expect furnished cages to bring some improve- automatically opened 6 h after lights on and ment in this respect. closed at the end of the daily photoperiod. The aim of our study was to compare the Three perches were placed parallel to the feed bone breaking strength of Lohmann Silver trough. A perch length of 15 cm per hen was hybrids (LS) housed throughout two full laying provided. Automatic chain feeders supplied the periods in conventional cages, furnished cages feed from a trough at the front of the cage and and an aviary with outdoor run kept under water was provided from nipple drinkers. Two identical management conditions and feeding claw shortening devices were placed parallel to regimes. The hypotheses being tested were that the feed trough. keeping laying hens in alternative housing The aviary housing system (model ‘Natura’, systems will result in increased bone strength Big Dutchman) was equipped with three central and that the bone stability of hens in furnished tiers. On the two lower tiers the hens were fed cages will be similar to that of hens in the aviary. from a trough with automatic chain feeders and Because all three housing systems were located at water was supplied from nipple drinkers. The top our experimental and teaching farm at Ruthe resting tier had perches and nipple drinkers. 538 M. LEYENDECKER ET AL. The hens had no access to the floor under the layer diet (containing 167.2 g/kg CP, 11.6 MJ ME, lowest tier. Family nest boxes (model ‘Colony- 37.2 g/kg Ca and 5.4 g/kg P). From the begin- Nest’, Big Dutchman) in one tier with an artificial ning of laying month 7 the hens received feed turf floor and automatic egg collection belts with 5% oyster shell content.