The welfare of laying hens is often compromised by feather pecking, a phenomenon that leads to injuries, high mortality, and poor performance. In this study, conducted on 16,000 Lohmann Brown, the supplementation of precision glycans capable of modulating gut microbiota metabolism was evaluated. The results showed improved laying persistency, lower mortality, and better feather and footpad conditions. The data obtained suggest that precision glycans may contribute to support welfare of barn-raised hens.
Introduction
In recent years, the transition from cage systems to alternative housing systems has become a priority in Europe, driven by consumer demands and scientific recommendations (EFSA, 2023). However, this transition introduces new management challenges, particularly an increased incidence of feather pecking, a behaviour characterised by the removal of feathers by some individuals at the expense of conspecifics (Dixon, 2008). This behaviour, often associated with stress and frustration due to the inability to express species-specific behaviours, can lead to wounds, pain, cannibalism, and reduced performance (Schreiter et al., 2019). Several factors influence feather pecking, including genetics, lighting management, stocking density, and also nutrition (Rodenburg et al., 2008). In fact, nutritional imbalances or alterations in the intestinal microbiota have been shown to promote this behaviour, as they affect anxiety, locomotor activity, stress response, and the serotonergic and dopaminergic systems, thereby influencing hens’ ability to cope with environmental challenges (Mens et al., 2020; Van der Eijk et al., 2019).
Advances in molecular biology are helping the scientific community to better understand the functioning of the gut microbiota and its metabolic pathways in the animal gut (Sergeant et al., 2014; Glendinning et al., 2020). Substances known as microbiome metabolic modulators have been identified and synthesised; these are able to influence specific metagenomic functions of intestinal bacteria, modifying metabolite production in the gut with the ultimate goal of providing benefits for animals and the environment (Walsh et al., 2021). Within this context, precision glycans represent a novel approach. These carbohydrates, characterised by specific glycosidic linkages, are able to direct microbial metabolism towards more favourable pathways, improving protein utilisation and reducing the production of harmful metabolites (Walsh et al., 2021; Jacquier et al., 2022).
In light of the positive results already observed in broiler chickens in terms of performance and welfare (Jacquier et al., 2022; Bortoluzzi et al., 2023), the present study evaluated whether the addition of precision glycans in laying hens diet could improve performance and reduce reactivity, thereby limiting feather pecking.
Materials and methods
The study was conducted in a commercial farm, involving 16,000 beak-trimmed Lohmann Brown laying hens from 48 to 78 weeks of age, housed in two houses with similar environmental conditions and fed ad libitum:
- the treated group (T) that received a corn- and soybean-based diet supplemented with precision glycans;
- the control group (C) that received the same diet without glycans supplementation.
During the trial, all production parameters (egg production, discarded eggs, mortality rate) were recorded daily. Animal welfare was assessed monthly according to the Welfare Quality® Protocol (2019), which assigns scores to feather condition and lesions in different body areas (head, back, tail, cloaca, and comb), as well as scores for footpad condition. To assess animal reactivity, two behavioural tests were applied: the Novel Object Test (NOT) and the Avoidance Distance Test (ADT). The NOT evaluates hens’ reactions to a novel object introduced into the environment, measuring curiosity or fear based on approach or avoidance behaviour. The ADT measures the distance at which hens move away when an observer approaches, indicating their level of fear or confidence towards humans. Finally, metagenomic analyses of intestinal contents from a sample of animals were performed to evaluate changes in metabolic pathways.
Results
Egg production remained consistent with the genetic line standards, showing a physiological decline due to age. However, from week 72 onward, hens in the treated group showed higher laying persistency, a result of interest in the context of longer production cycles aimed at reducing costs (Bain et al., 2016). No substantial differences were observed in the percentage of discarded eggs, except during periods of heat stress, known to reduce shell quality (Mashaly et al., 2004), when group T showed a lower proportion of rejects. Moreover, cumulative mortality was lower in hens receiving precision glycans (2.9% vs 4.3%), suggesting a positive effect on intestinal and immune health, in line with findings from other studies (Yadav and Jha, 2019; Lobo et al., 2023). The results of the welfare assessments were also in line with previously found outcomes: hens of the treated group exhibited more intact plumage and fewer footpad lesions. This effect is attributed to reduced nitrogen excretion and, consequently, improved litter quality, as demonstrated by a previous study by Jacquier et al. (2022). Welfare assessment results were supported by behavioural tests: hens in group T showed greater curiosity towards the novel object and greater confidence towards humans, reducing their distance from observers. A positive human–animal relationship is a key management factor with beneficial effects on welfare and productivity (Papageorgiou et al., 2023). Moreover, reduced fear and stress have often been associated with a lower propensity for feather pecking in several studies (Uitdehaag et al., 2008; Hüttner et al., 2023). Finally, metagenomic analyses showed improved protein utilisation and confirmed the favourable effect of precision glycans on microbiota metabolic pathways. These metabolic changes translate into improved gut health and a potential reduction in reactivity and, consequently, in undesirable behaviours such as feather pecking.
Conclusions
In the present study, dietary supplementation with precision glycans in laying hens improved laying persistency, reduced mortality and feather pecking, and supported intestinal health. These results pave the way for further investigations into the potential of precision glycans as a tool to optimise welfare and performance in laying hens.
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