The Effect of Organic Trace Mineral Supplementation in the Form of Proteinates on Performance and Sustainability Parameters in Laying Hens: A Meta-Analysis

Abstract

The effect of supplementing organic trace minerals (OTM), in the form of mineral proteinates (Bioplex^® Cu, Fe, Mn, and Zn, Alltech Inc., Nicholasville, KY, USA), in the diets of laying hens was examined using Comprehensive Meta-Analysis (CMA) statistical software. The impact on production performance, egg quality traits, and sustainability parameters related to the carbon footprint of egg production was assessed. Data were obtained from 32 global studies, comprising 107 dietary assessments of 30,992 laying hens. Overall pooled effect size (raw mean difference) of production performance when dietary organic trace minerals were supplemented either in basal diets, partial replacement of inorganic trace minerals (ITM), or total replacement of ITM, indicated that use of Bioplex minerals resulted in 2.07% higher hen-day production (HDP), whilst feed conversion ratio (FCR) was lower by 51.28 g feed/kg egg and 22.82 g feed/dozen eggs, respectively. For egg quality traits, daily egg mass was 0.50 g/hen/day higher and egg weight was 0.48 g per egg greater when Bioplex minerals were incorporated in the diet. The mean difference in egg loss was -0.62%. Eggshell thickness was greater by 0.01 mm, and a higher eggshell strength of 0.14 kgf was observed. Eggshell weight was heavier by 0.20 g, eggshell percentage was higher by 0.15%, and Haugh unit was 1 point higher (0.89). We also carried out a meta-regression of the effects of the study factors (location, year of study, hen breed/strain, age of hens, number of hens, and study duration) on the overall pooled effect size of the production performance and egg quality traits in response to supplementary OTM inclusion, and it indicated that certain factors had a significant (p < 0.05) impact on the results. Finally, a life cycle assessment (LCA) model was selected to evaluate the impact of feeding organic trace mineral proteinates on the carbon footprint (feed and total emission intensities) of the egg production using the data generated from the meta-analysis. Results showed that the inclusion of OTM proteinates resulted in an average drop in feed and total emission intensities per kg eggs of 2.40% and 2.50%, respectively, for a low-global-warming-potential (GWP) diet and a drop of 2.40% and 2.48% for feed and total emissions, respectively, based on high-GWP diet. Based on the overall results, the inclusion of organic trace mineral proteinates in layer diets can benefit production performance and egg quality traits while contributing to a lower carbon footprint.

Keywords: carbon footprint; laying hen; meta-analysis; organic trace minerals; proteinate; sustainability.

Figure 1

PRISMA flow diagram describing the literature search strategy and study selection for the meta-analysis.

Figure 2

The structure and system boundary of the egg production system considered in the life cycle assessment (adapted from Salami et al., 2022 [53]).

Figure 3

Funnel plots of standardised mean differences against their inverse standard errors and the associated significance (p-value for Egger’s test) for testing the publication bias of studies included in the meta-analysis for production performance parameters: feed intake, hen-day production, and feed conversion ratio. Open circles represent individual study comparisons included in the meta-analysis.

Figure 4

Funnel plots of standardised mean differences against their inverse standard errors and the associated significance (p-value for Egger’s test) for testing the publication bias of studies included in the meta-analysis for egg quality traits: egg mass, egg weight, egg loss, eggshell thickness, eggshell strength, eggshell weight, and eggshell percentage. Open circles represent individual study comparisons included in the meta-analysis.