Trace Mineral Leaching from Equine Compost

Analysis of current equine feeding practices in the Netherlands and identification of potential nutrient leaching and environmental contamination factors

The aim of this study was to estimate the potential for nutrient leaching based on current feeding practices of horses in the Netherlands. An online survey of horse owners collected data on the demographics of the horses (n = 274) and feeding practices. The median age was 8 years, the majority being warmblood and geldings with a mean bodyweight of 542.4 ± 101.9 kg. Most horses (85 %) had access to a limited area of pasture (<200m2 per horse), with a median grazing time of 10 hours. Grass hay was the predominant conserved forage offered (77 %) within diets. Concentrate feeds were provided to most horses (93.8 %) as well as the dietary supplements (80 %). The majority of the horses were offered high levels of metabolizable energy (ME) (90 %), starch (mean 2.4 ± 0.8 g/kg bw) and sugar intake (mean 1.4 ± 1.2 g/kg bw) compared to NRC recommendations. The estimated potential nitrogen excretion per horse per day was 228 ± 134 g, or 8.47 kg of nitrogen per ton of manure. Consequently, the estimated daily fecal excretion rates of microminerals for each horse were as follows: Copper (Cu) at 141.0 ± 151.3 mg, Zinc (Zn) at 593.1 ± 504.4 mg, Manganese (Mn) at 957 ± 541.2 mg, and Cobalt (Co) at 2.3 ± 3.5 mg. The analysis indicated that many equine diets in the Netherlands offered excess ME, CP and the minerals Cu, Zn, Mn and Co. To mitigate these concerns, it is crucial to promote sustainable feeding practices and better educate horse owners.

Dietary Transitions Toward Sustainable Horse Feeding

Sustainability is the balancing act of optimizing the use of current resources without compromising the current or future environment. Within the agriculture sector the primary focus of sustainability has been to reduce environmental pollution, specifically greenhouse gasses (GHG) emissions, nitrogen emissions, and leaching. For the equine industry the first step towards sustainability is the documentation and critique of current feeding and management practices to permit modifications to enable the industry meet social and legislative obligations. As a monogastric hindgut fermenter on a per kg bodyweight basis the horse has relatively lower GHG emissions compared to ruminants. However, there are several opportunities to further reduce the environmental impact of the equine industry. The majority of these relate to subtle changes, or consideration of, improving feed conversion, using alternative ingredients, and management of fecal material associated with intensive husbandry. To initiate the journey towards sustainability this review documents opportunities with current equine feeding and management practices to reduce the environmental impacts of the equine industry.