Effects of added chelated trace minerals, organic selenium, yeast culture, direct-fed microbials, and Yucca schidigera extract in horses. Part I: Blood nutrient concentration and digestibility.

The objective of this study was to test the hypothesis that feed additives such as chelated minerals, organic Se, yeast culture, direct-fed microbials, and Yucca schidigera extract would improve nutrient digestibility when included in an equine diet. Horses (Quarter Horse geldings 4.5 to 16 yr of age; mean BW 522 kg ± 46 kg) were acclimated to 100% pelleted diets formulated with (ADD) and without (CTRL) commercially available sources of the aforementioned additives followed by a 14-d collection period of feces and urine. Chelated sources of Cu, Zn, Mn and Co were utilized versus sulfated forms, at a 100% replacement rate. No significant differences among apparent the digestibility of DM, ADF, or NDF (P= 0.665, P = 0.866, P = 0.747, respectively) were detected between dietary treatments. Likewise, no differences in apparent digestibility of Cu (P = 0.724), Zn (P = 0.256), Mn (P = 0.888), Co (P = 0.71), or Se (P = 0.588) were observed. No differences were observed in serum Cu, Mn, or Co concentrations between ADD and CTRL at acclimation or collection time points (P > 0.05). While no difference in serum Zn concentrations were observed between ADD and CTRL groups at acclimation (P > 0.05), they were statistically higher at the collection time period for horses consuming CTRL (P < 0.0001). Whole blood Se concentration was greater in the CTRL group versus the ADD group both at acclimation (P = 0.041) and collection (P = 0.005) time periods. In reference to time, serum Cu concentrations increased (P = 0.012) for animals consuming CTRL, but not ADD (P > 0.05). Serum Zn concentrations of horses consuming both ADD (P = 0.021) and CTRL (P < 0.0001) increased over time from acclimation to collection time points. No time differences (P > 0.05) were observed in serum Mn concentrations. Serum Co concentrations increased over time in horses consuming both ADD (P = 0.001) and CTRL (P = 0.021). From acclimation to collection, whole blood Se concentration increased for horses consuming CTRL (P = 0.01) but not for ADD (P > 0.05). The results of this study indicate no effect on nutrient digestibility due to the inclusion of chelated minerals, organic Se, yeast culture, direct-fed microbials, and Yucca schidigera extract for horses at maintenance.

Effects of added chelated trace minerals, organic selenium, yeast culture, direct-fed microbials, and Yucca schidigera extract in horses: II. Nutrient excretion and potential environmental impact.

The objective of this study was to test the hypothesis that an equine diet formulated with chelated trace minerals, organic selenium, yeast culture, direct-fed microbials (DFM) and Yucca schidigera extract would decrease excretion of nutrients that have potential for environmental impact. Horses were acclimated to 100% pelleted diets formulated with (ADD) and without (CTRL) the aforementioned additives. Chelated sources of Cu, Zn, Mn, and Co were included in the ADD diet at a 100% replacement rate of sulfate forms used in the CTRL diet. Additionally, the ADD diet included organic selenium yeast, DFM, and Yucca schidigera extract. Ten horses were fed the 2 experimental diets during two 42-d periods in a crossover design. Total fecal and urine collection occurred during the last 14 d of each period. Results indicate no significant differences between Cu, Zn, Mn, and Co concentrations excreted via urine (P > 0.05) due to dietary treatment. There was no difference between fecal Cu and Mn concentrations (P > 0.05) based on diet consumed. Mean fecal Zn and Co concentrations excreted by horses consuming ADD were greater than CTRL (P < 0.003). Differences due to diet were found for selenium fecal (P < 0.0001) and urine (P < 0.0001) excretions, with decreased concentrations found for horses consuming organic selenium yeast (ADD). In contrast, fecal K (%) was greater (P = 0.0421) for horses consuming ADD, whereas concentrations of fecal solids, total N, ammonia N, P, total ammonia, and fecal output did not differ between dietary treatments (P > 0.05). In feces stockpiled to simulate a crude composting method, no differences (P > 0.05) due to diet were detected for particle size, temperature, moisture, OM, total N, P, phosphate, K, moisture, potash, or ammonia N (P > 0.05). Although no difference (P = 0.2737) in feces stockpile temperature due to diet was found, temperature differences over time were documented (P < 0.0001). In conclusion, the addition of certain chelated mineral sources, organic Se yeast, DFM, and Yucca schidigera extract did not decrease most nutrient concentrations excreted. Horses consuming organic selenium as part of the additive diet had lower fecal and urine Se concentrations, as well as greater fecal K concentrations.