Alternative production systems for hens compared with caged housing present both egg marketing opportunities and challenges to management.1 And while many studies have addressed the equipment, behavior, welfare and stressors on birds in alternative production settings vs. cages, little has been reported about the impact of these systems on the nutritional requirements of the hen.
Aviary – Although there were no nutritional treatments applied, a study comparing aviary vs. battery cage housing indicated alternative nutritional parameters might be warranted.2,3 Aviary hens were significantly lighter than those in cages (2021 vs. 2241g), despite having consumed more feed (121 vs. 116g/bird/day) and having a higher feed conversion ratio (FCR). Caged hens also had poorer feather cover (39 per cent of caged hens had denuded areas (5cm2)] vs. 32 per cent among aviary hens. No difference in tibia breaking strength was measured between the two housing systems in these studies.
Production and egg parameters were also evaluated among aviary hens fed either mash or crumbled diets with the same nutrient composition.4 Birds fed the mash diet had a higher FCR and energy consumption than those fed crumbs. Hens fed the crumbs had greater body weight, egg weight and egg mass than those fed mash. These parameters indicated better performance on the higher density crumble diet compared to mash. The same dietary strategies with greater nutrient density may be advantageous for commercial birds housed in aviary settings.
Floor – Because of the greater initial investment required for aviaries and furnished cage systems, most non-cage eggs are produced in floor systems in the United States.5
In a field study comparing three types of layer housing including high-rise (HR), manure-belt (MB), and cage-free floor-raised (FR), air temperature, RH, CO2, and atmospheric NH3 under winter and summer conditions in Iowa were monitored.6 Under winter conditions, the HR and MB houses had more comfortable temperatures (mean 24.6 and 20.6 C, or 76.3 and 69.1 F) and NH3 levels (9 to 24 ppm of NH3, respectively) than the FR houses (mean 15.5 C, or 59.9 F and maximum 85 to 89 ppm of NH3, respectively). The FR house temperature varied more with outside winter conditions. In summer the FR house showed the least increase above ambient conditions (mean 0.3 C) compared to a 4.7 and 1.2 C increase for the MB and HR houses, respectively. Ammonia levels were similar for all housing types during summer conditions (mean 3 to 9 ppm).
Birds housed in alternative floor systems and birds with access to pasture demonstrate significantly greater activity including running and flying. Most often these birds are placed at lower densities per cubic foot or meter than birds in cage systems that are stacked in multiple decks. This results in lower heat production (HP) per unit area and presents the potential for lower house temperatures in cooler climates. To maintain hen body temperature this will require either greater feed consumption or fuel to heat the building so the hen can maintain thermal balance. Taken independently or together both activity and lower housing density can require greater calories per hen per day than hens houses in battery cages.
Colder environmental temperatures are a reality in floor systems without supplemental heat in the winter and when bird density does not maintain house temperatures. In studies evaluating dietary wheat middling for floor layers, the low energy levels of some diets could not maintain production despite great feed consumption in December and January when temperatures averaged only 11 and 15 F.7 Hens fed diets with 89 per cent middlings, had an average feed intake of 136g/hen/day and feed conversion of 4.03 kg/doz eggs over twelve 28-day periods. Today, many floor layers are housed in heated barns, but often additional dietary measures are required to optimize hen performance.8 Elliot (2012) indicated higher density diets including protein, amino acids and energy are necessary for brown layers to get equivalent performance as hens housed in cages.9 Energy density is typically increased by 20kcal/lb in winter for floor layers, and can increase to 30, 40 or even 50kcal/lb if house temperatures cannot be maintained.10
Layers on litter floors fed wheat based diets with access to course wood shavings showed up to 60 per cent greater weight of the gizzard and its contents than caged layers fed the same diets without access to wood shavings.11 No such affect was observed when feeding oat based diets. This indicated the appetite for wood shavings may be dependent on fiber level in the diet. In a second experiment the hens’ appetite for wood shavings and paper was examined for birds fed wheat or oat based diets. Neither the paper or wood affected hen performance. However, the intake of wood shavings or paper by birds fed the wheat-based diet was twice as high as birds fed oat-based diets, and neutral detergent fiber in the gizzard was also elevated compared to birds fed only wheat. Furthermore, birds fed the wheat diet consumed almost twice the amount of wood shavings than those fed the oat diet. In their final study, birds fed a high-fiber diet and a diet containing coarsely ground oat hulls had a negligible amount of feathers in their gizzards compared to hens fed a low-fiber diet and one with finely ground oat hulls. The authors indicated that feather-pecking behavior may be partly related to the feed structure and consistency.
Pasture – In the U.S. pastured hens eggs often sell at a premium price with the claim of enhanced nutritional and health benefits from the eggs. The effect of alfalfa, clover and grass pastures on egg production and composition was examined and compared to sister hens housed in cages.12 In a cross over design three groups of 75 (Hy-Line brown) hens rotated to one of three pastures treatments for 2-week periods and were provided 70g/hen/day commercial hen mash (16.9 per cent CP, 2863 kcal/kg) and were expected to forage for the remainder of their nutritional requirements. Fifty sister hens housed in cages (60in2/bird) were offered the same mash ad libitum (averaging 113g/hen/day intake). At the end of the study body weight was not significantly different between the pasture treatments, but significantly less than hens in the cages (1571 vs. 1821g). Similarly egg production was not maintained by hens on the pasture averaging 72 per cent vs. 85 per cent for hens housed in the cages. It was estimated the pastured hens derived approximately 13.2 per cent of their energy requirement (36 kcal ME) and 21.5 per cent of their CP needs (3.9g) from pasture foraging. However, pastured hens were still lacking dietary protein and energy (2.3g and 35 kcal) on a daily basis to match the caged hens. The authors of the study believe an additional 13g of mash per hen per day would be required to sustain egg production and body weight equal to that of the caged hens. Despite greater linolenic acid in the pasture clover and alfalfa compared to the grass, there were no significant differences in egg linolenic acid levels. When compared to the eggs from caged hens, eggs from pastured hens had greater egg yolk omega-3 fatty acids, vitamin A and E. However, these nutrients can readily be supplemented in the hens diet to derive the same egg levels as pasture treatments for less money.13-16 The authors concluded that if additional mash was provided to pastured hens to maintain hen welfare, body weight and egg production, this would undoubtedly mute the changes in egg composition observed herein.
The nutritional composition of eggs from hens housed in cages vs. sister hens in range paddocks established with bermudagrass, fescue and clover was similarly compared in another study.17 Supplemental feeds for all hens were provided ad libitum in a phase program from 17-82 weeks of age. Eggs from the cage environment had significantly more total fat, monounsaturated fat, and polyunsaturated fat than eggs produced by caged hens. Levels of omega-3 fatty acids were also significantly higher (0.17 per cent vs. 0.14 per cent) in range eggs vs. cage eggs. There was no difference in egg cholesterol, vitamin A or E levels between eggs from the different management systems. Hen body weight was similar at the conclusion of the study (1970g range vs. 2000g caged), egg weight, mass and production were all lower for the range birds and while feed consumption was greater in cages (103 vs. 101g) this indicated little reliance on pasture for the hens’ nutritional requirements.18 Finally egg income minus feed costs was lower for the range treatment ($18.07 vs. 23.70/hen) and labor to care for them was more than 15 times greater than hens housed in cages. The author concluded that no significant nutritional advantage of eggs produced by range hens over hens maintained in cages could be established.
Enriched Cage – In a study to examine the effects of dietary energy on egg production and quality of hens kept in conventional (3/cage) or furnished cages (8/cage), it was determined that higher energy levels improved egg production, reduced feed consumption and improve feed conversion, but there were no interactions with housing type.19 Housing type had no impact on production parameters, and the authors concluded that like previous studies cage type had no impact on egg production or feed conversion ratios.
Several studies have shown a greater incidence of cracked eggs in furnished than in conventional cages. Because hens kept in furnished cages often have greater bone strength, they may lay eggs with weaker shells because the calcium is utilized for bone mineralization. In a similar trial, the effects of added dietary calcium for hens in 3/cage conventional and 8/cage enriched cages.20 Normal calcium was 37-40g/kg diet, and 44-50g/kg diet in the supplemented diets. Dietary calcium had similar effects in both cage systems. Greater limestone increased the laying rate, with no effects on egg quality, specific gravity, or tibia-breaking strength. Based on this study the weakening of eggshells in furnished cages is not caused by a possible calcium shortage resulting from high bone mineralization.
Two studies looking at the influence of conventional (CC) and enriched cages on nitrogen, calcium and phosphorus balance recorded greater feed intake in the CC (95.0 vs. 92.5g/hen/day).21,22 However, this did not result in any greater body weight, egg production, egg weight or mass. In the end manure and egg nitrogen output was not significantly different between hen housing treatments. With greater feed intake, CC hens did have both greater manure calcium and phosphorus excretion compared to hens from enriched cages. Deposition of egg shell calcium (g/hen/day) was also greater in CC vs. enriched cages, but there was no impact on eggshell P deposition or absolute P balance (average -48.3mg/hen/day).
Bird Health – Decreased egg production, egg drop syndrome and cannibalism in free-range flocks in the UK was reported as early as 1986 by Swarbrick.23 A more recent survey of birds raised in alternative systems reported the greatest mortality in the litter and free-range systems compared to conventional cages. Bacterial infections caused the greatest mortality in birds raised on litter and included erysipelas, colibacillosis and pasteurellosis.24 Greater mortality with viral diseases (lymphoid leukosis, Marek’s disease and Newcastle) coccidiosis and red mites was also associated with litter and free-range hens. Many of these diseases and ectoparasites are a result of contact with wild birds and animals that can bring them to domestic poultry with outdoor access. Furthermore, these birds are at risk of predation. Other infections of layers result from direct contact with soil, litter and fomotes (rodents, beetles and equipment) known to carry disease.25
Another study evaluated the effectiveness of diatomaceous earth (DE) as a feed additive to treat for parasites and to increase feed efficiency and egg production in brown organic free-range layers.26 Bovan brown hens fed the DE had significantly lower Capillaria, slightly lower Eimeria and fewer birds with Heterakis. Hens fed the DE were significantly heavier, laid more eggs and consumed more feed that the control hens. Furthermore, dusting with DE reduced mite numbers. Two additional studies both indicated hens in aviary, and enriched cage systems can be plagued by Red mites that might benefit from diatomaceous earth added to the feed.27,28 And finally, according to Sossidou et al. (2011) a high incidence of bone breakage in free range flocks represents a serious issue which compromises welfare benefits one might anticipate.29
This article was presented at the 2012 Midwest Poultry Federation Convention. References are available by request and online at www.canadianpoultrymag.com