Dietary Trace Mineral Level and Source Affect Fecal Bacterial Mineral Incorporation and Mineral Leaching Potential of Equine Feces

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.

Higher Concentration of Dietary Selenium, Zinc, and Copper Complex Reduces Heat Stress-Associated Oxidative Stress and Metabolic Alteration in the Blood of Holstein and Jersey Steers

This study investigated the influence of high concentrations of dietary minerals on reducing heat stress (HS)-associated oxidative stress and metabolic alterations in the blood of Holstein and Jersey steers. Holstein steers and Jersey steers were separately maintained under a 3 × 3 Latin square design during the summer conditions. For each trial, the treatments included Control (Con; fed basal TMR without additional mineral supplementation), NM (NRC recommended mineral supplementation group; [basal TMR + (Se 0.1 ppm + Zn 30 ppm + Cu 10 ppm) as DM basis]), and HM (higher than NRC recommended mineral supplementation group; [basal TMR + (Se 3.5 ppm + Zn 350 ppm + Cu 28 ppm) as DM basis]). Blood samples were collected at the end of each 20-day feeding trial. In both breeds, a higher superoxide dismutase concentration (U/mL) along with lower HSP27 (μg/L) and HSP70 (μg/L) concentrations were observed in both mineral-supplemented groups compared to the Con group (p < 0.05). The HM group had significantly higher lactic acid levels in Jersey steers (p < 0.05), and tended to have higher alanine levels in Holstein steers (p = 0.051). Based on star pattern recognition analysis, the levels of succinic acid, malic acid, γ-linolenic acid, 13-methyltetradecanoic acid, and tyrosine decreased, whereas palmitoleic acid increased with increasing mineral concentrations in both breeds. Different treatment groups of both breeds were separated according to the VIP scores of the top 15 metabolites through PLS−DA analysis; however, their metabolic trend was mostly associated with the glucose homeostasis. Overall, the results suggested that supplementation with a higher-than-recommended concentration of dietary minerals rich in organic Se, as was the case in the HM group, would help to prevent HS-associated oxidative stress and metabolic alterations in Holstein and Jersey steers.

Trace Mineral Leaching from Equine Compost

Mineral leaching from compost can be environmentally disruptive. Little information is available regarding trace mineral leaching from equine-sourced compost. The objective of this study was to quantify the mineral content and leaching potential of compost produced from feces of horses fed different amounts and forms (organic or inorganic) of trace minerals. Nine horses were fed three treatments in a 3 × 3 replicated Latin Square design. The dietary treatments were provided as a daily pellet: CON (pellet without added trace minerals), ING (added inorganic trace minerals), and ORG (added organic trace minerals). The added trace minerals were Co, Cu, Mn, and Zn. Feces were collected from each horse after a 16-day feeding period, combined with straw, composted, and then subjected to simulated rainfall to measure mineral mobility. Concentrations of Co, Cu, Mn, and Zn were greater in ING and ORG compared to CON compost (p < 0.05); additionally, ING had greater Zn than ORG compost (p < 0.05). More Cu leached from ING and ORG compared to CON (p < 0.05). The most Zn leached from ING, followed by ORG, and the least amount leached from CON compost (p < 0.05). Dietary trace mineral intake affected the trace mineral concentration in the compost and amount available to leach during rainfall events.