Impacts of Rearing Enrichments and Range Use on Production, Behaviour, Health and Welfare of Free-Range Hens

Abstract

<p>Free-range egg production is gaining popularity among consumers in Australia. Free-range pullets are typically reared indoors, but adult hens get outdoor access. This inconsistency in the rearing and adult housing may affect the production, health, behaviour and welfare of freerange hens. Enrichments provided during rearing might increase the adaptation of hens when moved to new adult housing in the free-range system, and thus might improve welfare. Freerange hens consistently show high individual variation in ranging which could result in impacts on their welfare. This dissertation aimed to address the effect of rearing enrichments and range use on the production, behaviour, health and welfare of free-range hens.</p> <p>Chapter 1 of this dissertation provides the background of the study along with an in-depth literature review and justification for the study. The new free-range environment for the pullets when moved to a free-range housing system might be challenging to adapt to, which might affect the egg production and egg quality. Chapter 2 addressed the effect of rearing enrichments on free-range egg production, and egg quality along with hens' nest use behaviour. Enrichments during pullet rearing might also improve the adaptation to stress and welfare of hens across the laying cycle. Individual variation in outdoor ranging may also affect their welfare. Chapter 3 evaluated the effects of rearing enrichments and an imposed environmental stressor on hen welfare and egg quality along with the association of welfare with ranging. The mismatched environments between the indoor pullet rearing and adult housing may increase fearfulness in free-range hens. Rearing enrichments and/or range use may reduce adult fearfulness. Chapter 4 assessed the fearfulness of hens at different age points throughout the laying cycle. Additionally, enrichments in rearing may optimise pullet development and subsequent welfare of adult free-range hens. Outdoor ranging might also contribute to improved health and welfare. Chapter 5 assessed the external and internal health and welfare of hens following rearing enrichments and individual variation in range use. Finally, enrichment in rearing and ranging in adults may also contribute to microbiota variation and gut health of both pullets and adults. Chapter 6 illustrated the caecal microbiota profiles of pullets and adult hens from different rearing enrichment groups and ranging patterns. Chapter 7 described the overall findings, their implications along with the limitations of the current study and future research prospects.</p> <p>To accomplish the research, 1386 Hy-Line Brown^® chicks were reared indoors with three enrichment treatments across 16 weeks including a control group with standard litter housing conditions, a novelty group that were provided with weekly changing novel objects, and a structural group with custom-designed H-shaped structures to enhance navigation and perching. Pullets were moved to a free-range system at 16 weeks and were provided outdoor access daily from 25 until 64 weeks of age. Daily ranging was individually tracked from 25 to 64 weeks via radio-frequency identification technology. In Chapter 2, the daily egg production at different laying locations (large nests, small nests and floor), weekly egg weights and egg abnormalities were recorded from 18 to 64 weeks old. External and internal egg quality parameters were measured at 44, 52, 60 and 64 weeks. In Chapter 3, individual hen welfare was assessed at different age points across their laying cycle and correlated with the hens' respective ranging patterns before each assessment. At 44 weeks, the range area was reduced by 80% for 11 days to induce stress and the changes in ranging behaviour, albumen corticosterone concentrations and egg quality were assessed. In Chapter 4, a total of 135 hens were selected at 62 weeks from the three rearing treatments and two ranging groups (indoor: no ranging, and outdoor: daily ranging) based on individual radio-frequency identification tracking. Individual behavioural tests of tonic immobility, emergence, open field, and novel object (pen level) were carried out on hens along with spectrograms of vocalisations and computer vision tracking of their locomotion in the open field test. In Chapter 5, a total of 307 hens were selected at 65 weeks based on their range use patterns across the last 54 days including indoor, low outdoor and high outdoor range use. The external and internal health and welfare parameters were evaluated via external assessment of welfare and post-mortem evaluation of internal organs and keel bones along with whole-body CT scanning for body composition. In Chapter 6, a total of 45 pullet caecal samples and 91 adult caecal content samples were collected and DNA was extracted for their 16S rRNA sequencing to demonstrate their microbiota profiles.</p> <p>Chapter 2 revealed the novelty hens laid more eggs in the large nest boxes and fewer eggs on the floor than both the structural and control hens (<i>P</i> < 0.0001). The rearing enrichments affected shell reflectivity and yolk colour of eggs with the control hens showing paler colours across time relative to the changes observed in the eggs from enriched hens. Chapter 3 illustrated plumage coverage had a positive relationship with range use across most age points (<i>P</i> < 0.0001). Hens reduced ranging time following the imposed stressor but increased their number of visits with the lowest increase by the structural hens (<i>P</i> = 0.03). Significant interactions between rearing treatment and stressor for albumen corticosterone concentrations showed the structural hens decreased concentrations immediately post-stress, but the control and novelty hens increased (<i>P</i> < 0.006). The stressor increased or decreased values of most egg quality parameters across all rearing groups (all <i>P</i> ≤ 0.02). Chapter 4 demonstrated few effects of rearing treatments on the fearfulness of hens, and the outdoor rangers were less fearful than indoor hens. The latency to step in the open field test negatively correlated with hen feather coverage. Chapter 5 showed the control hens had the lowest feather coverage (<i>P</i> < 0.0001) and a higher number of comb wounds (<i>P</i> = 0.03) than the novelty hens. The high outdoor rangers had fewer comb wounds than the indoor hens (<i>P</i> = 0.04), the shortest toenails (<i>P</i> < 0.0001) and the most feather coverage (<i>P</i> < 0.0001), but lower body weight (<i>P</i> < 0.0001) than the indoor hens. High outdoor ranging decreased both body fat and muscle (both <i>P</i> < 0.0001). The novelty group had lower spleen weights than the control hens (<i>P</i> = 0.01) but neither group differed from the structural hens. The high outdoor hens showed the highest spleen (<i>P</i> = 0.01) and empty gizzard weights (<i>P</i> = 0.04). Chapter 6 revealed the most common bacteria in the pullets were <i>Clostridium, Aldercreutzia, Prevotella, Blautia</i>, and <i>Methanobrevibacter</i>, but in adults they were <i>Ruminococcus, Blautia, Sutterella</i>, and <i>Helicobacter</i>. The microbial diversity was not significant within the group but significantly varied between groups. The <i>Blautia, Sutterella</i>, and <i>Ruminococcus</i> were more predominant in the enriched hens than the control group. Most of the genera identified were more abundant in indoor hens than the high outdoor hens.</p> <p>Overall, this study indicated that rearing enrichments might have some impacts on production parameters in free-range hens. The provision of rearing enrichments and greater range use had positive impacts on hen welfare. Rearing enrichment had minimal effect on fearfulness, but the subsequent ranging had a greater impact. At later ages, rearing enrichments had some effects on hen health and welfare, but subsequent range use had the greatest impact. In addition, rearing enrichments affected the microbiota composition of both pullets and adult hens showing the long-term changes in free-range hens that result from exposure to different types of environments during their rearing period.</p>