Long term effect of dietary lipid saturation on eggshell quality and bone characteristics of laying hens

Skeletal disorders in laying hens: a systematic review with a focus on non-cage housing systems and hemp-based dietary interventions for bone health

1. The poultry sector is possibly the fastest growing and most flexible of all livestock sectors. At present, the main changes to the table egg production system include the gradual abandonment and closure of all cage-housing systems for laying hens, driven by animal welfare concerns and stricter legislation in many countries. In the future, keeping hens in enriched cage systems may be restricted or phased out in response to evolving animal welfare guidelines and public demand. To meet the welfare and behavioural requirements of the hens, it is desirable to choose housing on litter or housing in aviaries as a substitute for housing in enriched cages.2. The objective of this systematic review was to examine non-cage housing systems and hemp-based dietary interventions in relation to skeletal health in laying hens. This review focussed on the risks associated with alternative housing systems, particularly the increased incidence of bone fractures and the potential of nutritional strategies to mitigate skeletal disorders, including osteoporosis.3. The proportion of hens housed in non-cage alternative housing systems is currently increasing sharply but carries certain risks. One of the most significant concerns is skeletal integrity, as hens in aviaries experience a higher rate of keel bone fractures due to collisions, falls and deviations thought to be related to internal pressure. Numerous studies have shown that the incidence of keel bone damage (i.e. fractures and deviations) was greater in aviaries compared to enriched cage systems.4. Optimal skeletal health can be supported through proper nutrition, which plays a crucial role in bone metabolism. Key nutritional elements, including calcium, vitamins D, E and K, polyunsaturated fatty acids and hemp-based products, have been shown to be beneficial in preventing skeletal disorders and associated fractures due to their specific roles in maintaining bone structure and strength.

A Meta-Analysis on the Significance of Dietary Omega-3 Fatty Acids on Bone Development and Quality in Egg- and Meat-Type Chickens

Poultry egg and meat production continue to be optimized for productivity and efficiency. However, genetic selection focusing on production efficiency has overlooked other aspects critical to bird wellbeing, such as skeletal development. As a result, modern birds are more prone to leg weakness, osteoporosis, and, subsequently, fractures. Dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) enrichment has been proposed to benefit bone development, quality, and strength. However, there is a lack of conclusive and quantitative results across studies. Therefore, a meta-analysis approach was used to evaluate published studies to determine the effects of dietary n-3 PUFA enrichment on bone quality in laying- and meat-type birds. Publications were retrieved from multiple sources (databases and hand searching), and ten studies were selected for inclusion in the final dataset. A model to predict tibial bone ash content (BAC) was developed in Proc MIXED of SAS, treating the study as a random effect. The dietary concentration of n-3 PUFA, n-3 PUFA:n-6 PUFA ratio, calcium (Ca), phosphorus and feeding duration (days) were used as independent variables to predict BAC. The final model included the dietary n-6:n-3 FA ratio and the calcium concentration in the diet. The final model was selected based on the corrected Akaike Information Criteria, the root mean square prediction error (0.999) and its components, and the concordance correlation coefficient (CCC) (0.99). In laying-type birds, BAC was reduced by n-3 PUFA (p = 0.001) but was increased by Ca (p = 0.014). In contrast, in broiler chickens, BAC was increased by n-3 PUFA (p = 0.001) and decreased by Ca (p = 0.014). The influence of n-3 PUFA:n-6 PUFA ratio on tibia BAC in laying-type birds was not statistically significant (p = 0.505), whereas in meat-type birds, the influence of PUFA ratio was significant (p < 0.05). These results may indicate a low biological significance in laying-type birds but not in meat-type birds.

Dietary Soybean Oil Supplementation Affects Keel Bone Characters and Daily Feed Intake but Not Egg Production and Quality in Laying Hens Housed in Furnished Cages

To evaluate dietary soybean oil supplementation on production performance, egg quality, and keel bone health in laying hens. Two hundred and four laying hens at 20 weeks of age (WOA) were distributed into 12 cages containing 17 birds each. Birds were either fed a commercial diet (control group, CON) or a diet supplemented with 3% of soybean oil (SO group). Experiments lasted 17 weeks. Body weight, daily feed intake, production performance and egg quality were measured at 25, 29, 33, and 37 WOA. Birds were subsequently assessed for keel bone status by palpation, and keel was excised to measure bone length, microstructure, bone mineral density (BMD), elements contents, and the expression of osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B ligand (RANKL), collagen type II alpha 1 (COL2α1), periostin (POSTN), and sclerostin (SOST). The results showed that dietary SO supplementation did not affect production performance and egg quality (P > 0.05), but improved body weight of hens at 29 and 37 WOA (P < 0.05), and decreased daily feed intake at 33 and 37 WOA (P < 0.05). Incidence of keel bone damage (especially fracture) was higher in hens of SO group. Keel bone length in birds of SO group was significantly decreased compared to CON (P < 0.05). Keel bone of supplemented hens showed increased trabecular separation at 29 WOA and higher levels of V, Mn, Fe, Se, and Ba at 33 WOA (P < 0.05). Moreover, decreased BMD, trabecular number and thickness were observed in keel bone of laying hens receiving supplementation at 29 and 37 WOA (P < 0.05); decreased levels of Li, Ca, Hg, and TI at 33 WOA and trabecular thickness at 37 WOA (P < 0.05) were also identified. mRNA levels of SOST and RANKL and the ratio of RANKL/OPG mRNA levels were increased in birds fed a SO-supplemented diet (P < 0.05); COL2α1, OPG, and POSTN were downregulated at all sampling points (P < 0.05). Taken together, results indicate that feeding laying hens a diet supplemented with soybean oil can decrease daily feed intake and impair keel bone health but not influence production performance and egg quality.

Algal Oil as Source of Polyunsaturated Fatty Acids in Laying Hens Nutrition: Effect on Egg Performance, Egg Quality Indices and Fatty Acid Composition of Egg Yolk Lipids

The aim of this study was to evaluate the effect of algal oil with very high level of docosahexaenoic acid (DHA, C22:6n-3) used as fat source in the diet for laying hens, on egg yolk lipids fatty acid composition, as well as egg production and egg quality indices, in comparison with other dietary fat sources. The experiment was carried out on 168 ISA Brown hens (25 to 60 wks of age), allocated to 7 groups of 12 replicates (cages), with two birds in each cage. The experimental diets were supplemented with 2% of different fat sources, i.e. soybean oil (SO), coconut oil (CO), rapeseed oil (RO), linseed oil (LO), camelina oil (CAO), fish oil (FO), or algal oil (AO). Laying performance indices, i.e. egg production, mean egg weight, feed intake, feed conversion ratio, or egg and eggshell quality parameters were not affected by used fat sources (P>0.05). Dietary fat sources significantly influenced on egg yolk lipids fatty acids composition. Thus, AO addition caused some changes in the yolk lipid profile that were favorable from the dietary perspective, i.e., increased concentration of eicosapentaenoic acid (EPA) and DHA (P<0.05). However, boiled eggs from hens fed a diet with AO were characterized by an inferior flavour and taste to those from other groups. In conclusion, the results of this experiment, have shown that the use of AO in the laying hens nutrition is an efficient way to increase the deposition of n-3 long chain polyunsaturated fatty acids (n-3 LCPUFAs) in eggs, without negative effect on egg performance, however further researches, aiming to establish optimal AO dietary level that does not adversely affect the organoleptic properties of eggs, are needed.