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Animals : an open access journal from MDPI2020; 10(1); doi: 10.3390/ani10010140

The Effect of Diet Composition on the Digestibility and Fecal Excretion of Phosphorus in Horses: A Potential Risk of P Leaching?

Abstract: The main horse phosphorus excretion pathway is through the dung. Phosphorus originating from animal dung and manure has harmful environmental effects on waters. The number of horses has increased in many countries, and several studies have pointed that leaching of P from horse paddocks and pastures are hotspots for high P leaching losses. The hypothesis was that feeding regimes might influence phosphorus digestibility and excretion in feces, and therefore the environmental impact of horse husbandry. A digestibility experiment was conducted with six horses fed six forage-based diets to study phosphorus utilization and excretion in feces. The study method was a total collection of feces. The experimental design was arranged as an unbalanced 6 × 4 Latin Squares. Phosphorus intake increased with an increasing concentrate intake. All studied diets resulted in a positive P balance and, the P retention differed from zero in all except the only-hay diet, in which the intake was lower compared to the other diets. The digestibility of P varied from 2.7 to 11.1%, and supplementing forage-diets with concentrates slightly improved P digestibility (p = 0.024), as it also improved the digestibilities of crude protein (p = 0.002) and organic matter (p = 0.077). The horses excreted an average of 20.9 ± 1.4 g/d P in feces. Excretion was smallest (20.0 g) in horses on a hay-only diet (p = 0.021). The average daily phosphorus excretion resulted in 7.6 kg P per year. The soluble P part of the total P in feces accounted for about 88% of the P excreted in feces, and is vulnerable to runoff losses and may leach into waters. Thus, horse dung may pose a potential risk of P leaching into the environment if not properly managed, and is not less harmful to the environment than that from other farm animals. Supplementation with inorganic P should be controlled in the diets of mature horses in light work to decrease the excretion of P in feces.
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Publication Date: 2020-01-15 PubMed ID: 31952257PubMed Central: PMC7022629DOI: 10.3390/ani10010140Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates how the diet composition of horses influences the digestibility and excretion of phosphorus, identifying a potential risk to the environment due to phosphorus leaching. Specifically, it focuses on how different feeding regimes yield varying degrees of phosphorus intake, and how these differences might increase P runoff from horse manure, which could have harmful consequences to surrounding water bodies.

Research Methodology

  • The study was conducted using six horses, whereby a total collection of their feces was acquired for the experiment.
  • A series of six different forage-based diets were implemented to understand how each diet affects phosphorus consumption, digestion, and excretion in horses.
  • The research made use of an unbalanced 6 × 4 Latin Squares experimental design, a renowned research method for animal studies.

Key Findings

  • Phosphorus intake in horses increased with higher consumption of concentrates in their diet.
  • All diets resulted in positive P balance. However, phosphorus retention varied, with the only-hay diet being the exception where intake was less compared to the other diets.
  • The digestibility of phosphorus ranged between 2.7% and 11.1%. Also, supplementing forage-based diets with concentrates led to a slight improvement in phosphorus digestibility.
  • On average, horses excreted approximately 20.9 ± 1.4 g/d of phosphorus in their feces, but this quantity was smallest (20.0 g/d) in horses exclusively on a hay diet.
  • Such level of excretion accounts for approximately 7.6 kg/year of phosphorus, most of which (about 88%) remained soluble in feces, hence susceptible to losses via runoff or leaching into waters.

Implications of the Study

  • This study highlights how horse dung could pose serious environmental risks due to potential phosphorus leaching, especially if not properly managed.
  • The findings imply that this environmental impact is not lesser compared to that from other farm animals.
  • This study suggests that the supplementation of inorganic phosphorus in horse diet should be controlled, particularly in mature horses in light work, to decrease intestinally excreted phosphorus through manure.

Cite This Article

APA
Saastamoinen M, Särkijärvi S, Valtonen E. (2020). The Effect of Diet Composition on the Digestibility and Fecal Excretion of Phosphorus in Horses: A Potential Risk of P Leaching? Animals (Basel), 10(1). https://doi.org/10.3390/ani10010140

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 10
Issue: 1

Researcher Affiliations

Saastamoinen, Markku
  • Production Systems, Natural Resources Institute Finland (Luke), FI-31600 Jokioinen, Finland.
Särkijärvi, Susanna
  • Production Systems, Natural Resources Institute Finland (Luke), FI-31600 Jokioinen, Finland.
Valtonen, Elisa
  • Department of Animal Science, University of Helsinki, FI-00790 Helsinki, Finland.

Grant Funding

  • YM 126/481/2012 / Finnish Ministry of Environment

Conflict of Interest Statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Citations

This article has been cited 3 times.
  1. Maier I, Kienzle E. A Meta-Analysis on Quantitative Calcium, Phosphorus and Magnesium Metabolism in Horses and Ponies. Animals (Basel) 2024 Sep 25;14(19).
    doi: 10.3390/ani14192765pubmed: 39409714google scholar: lookup
  2. Saastamoinen M, Särkijärvi S, Suomala H. Protein Source and Intake Effects on Diet Digestibility and N Excretion in Horses-A Risk of Environmental N Load of Horses. Animals (Basel) 2021 Dec 15;11(12).
    doi: 10.3390/ani11123568pubmed: 34944342google scholar: lookup
  3. Saastamoinen M, Särkijärvi S, Valtonen E. Erratum: Saastamoinen, M.; Särkijärvi, S.; Valtonen, E. The Effect of Diet Composition on the Digestibility and Fecal Excretion of Phosphorus in Horses: A Potential Risk of P Leaching? Animals 2020, 10, 140. Animals (Basel) 2020 Feb 12;10(2).
    doi: 10.3390/ani10020285pubmed: 32059580google scholar: lookup
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