Behavior, welfare, production and bioenergetics of laying hens in alternative housing systems
Transitioning of egg production systems from conventional cage to alternative housing (e.g., enriched colony, aviary cage-free) is increasingly occurring in various parts of the world, especially in Europe and the United States, to meet animal welfare requirements or legislations. This dissertation had the central goal of providing scientific knowledge or discoveries related to behavior, welfare, production, and bioenergetics of laying hens in alternative housing systems. It covers five experiments that were conducted in controlled environment and commercial settings with the following specific objectives: 1) Develop and validate a UHF RFID system able to evaluate nesting and feeding behaviors of laying hens in an Enriched Colony Housing (ECH) (Chapter 2); 2) Evaluate the impact of feeder space on feeding behavior of individual hens in an ECH (Chapter 3); 3) Investigate nesting behavior and nesting patterns of individual hens in an ECH (Chapter 4); 4) Assess the impact of managing litter floor access and using experienced hens on floor eggs, air quality and welfare of hens in an aviary system (Chapter 5); and 5) Quantify building ventilation rate (VR) and laying-hen bioenergetics in a fully-open aviary house (Chapter 6).
The research described in this dissertation contain the following discoveries: The UHF RFID system was successfully developed and validated. The system allows for assessing the impacts of housing design and/or management practices on behaviors of individual laying hens (Chapter 2). Laying hens (W-36 breed) in the ECH showed similar feeding behaviors when provided a feeder space of 12 or 9.5 cm/hen, and not all hens choose to feed simultaneously (Chapter 3). Hens spent approximately one hour in the nest box during a 16-hr daily light period. However, nesting time during the 6-hr laying period (37.5% of the light period) accounted for 56% of the daily total. Maximum occupancy of the nest box (29% of the hens) occurred within 4-hr after lights-on, when most (83%) of the eggs were laid. There exist considerable hen-to-hen variations in nesting behavior. The same is true for an individual hen from one day to the next, although specific patterns could be noted (Chapter 4). Full litter access (FLA) in the aviary housing system showed a number of shortcomings when compared with part-time litter access (PLA), including much higher incidence of floor eggs, higher ammonia concentration, more presence of caked litter, and greater amount of manure accumulation on the floor which necessitates more frequent removal from the barn. No difference was detected between FLA and PLA in hen welfare, mortality, BW, BW uniformity, or litter bacteria concentration. Inclusion of experienced hens (1.5%) in a young flock did not show benefit of inducing nest-laying behavior (Chapter 5). Mean ventilation rate (VR) of a fully-open aviary house (~ 140,000 Dekalb White laying hens) under the Midwest (Iowa) climate conditions (outside temperature ranging from 3.4 to 28.9°C) was 4.0 ± 0.4 m3 h-1 hen-1, ranging from 0.8 to 9.1 m3 h-1 hen-1. Overall, daily mean total heat production rate (THP) was 7.5 ± 0.2 W kg-1, house-level sensible heat production rate (SHP) was 4.8 ± 0.3 W kg-1 and house-level latent heat production rate (LHP) was 2.7 ± 0.2 W kg-1. THP decreased by 40% in the nighttime or dark period (5.1 ± 0.3 W kg-1) as compared to the daytime or light period (8.5 ± 0.3 W kg-1). Information from this dissertation research is expected to contribute to establishment or improvement of guidelines for housing system design and management to ensure animal welfare and efficient use of resources in alternative laying-hen housing. In particular, the updated bioenergetics data will prove valuable in estimating building ventilation rate using the indirect calorimetry or carbon dioxide (CO2) balance method, and improving the design and operation of ventilation, supplemental heating, and cooling components of the housing.