Titanium dioxide has been used as a marker for determining digestibility indirectly, but some authors have expressed difficulty measuring TiO₂ concentrations in fecal material. We developed an accurate and precise method to determine TiO₂ concentrations in equine feces. The method includes dry-ashing samples, digestion with (NH₄)₂SO₄ in concentrated sulfuric acid, followed by the addition of H₂O₂ to produce a yellow to orange color that can be read spectrophotometrically. Accuracy was tested by spike-recovery and precision was tested by examining the CV between duplicates of 449 individual samples. The method described here was compared to a previously published method by examining CV between duplicates of samples analyzed using both methods and comparing them using a paired t-test. Titanium dioxide spike recovery averaged 106% and the CV between duplicates averaged 4.0%, with 79% of sample pairs having a CV of < 5%. When compared to a previously published method, the method described here had lower CV between duplicates (P < 0.0001). The method described here provides an accurate and precise quantitative analytical procedure for TiO₂ in equine fecal samples.

Inorganic P is often added to growing horse diets because organic P, or phytate-P, is believed to have lower digestibility. If horses can efficiently digest organic P, then the need for inorganic P may be reduced. Much of the P in grain-based concentrates fed to growing horses is in the form of phytate-P. Little is known about the ability of growing horses to degrade phytate-P or whether horse age affects mineral digestion in horses. The objective of this study was to examine the effect of age on P, Ca, and Mg digestibility as well as phytate-P degradation. Four yearling geldings and 4 mature geldings were fed a diet of alfalfa cubes, timothy cubes, and a pelleted concentrate. The diet contained 0.28% total P and 17.4% of that P was in the phytate form. There was a 14-d diet adaptation period followed by a 4-d fecal collection period. Apparent total tract P digestibility was higher for yearlings than mature geldings (P = 0.036; 7.7 and –6.6% for yearlings and mature geldings, respectively). Phytate-P disappearance was 94.8% and did not differ between ages (P = 0.190). Apparent Ca digestibility was lower in mature geldings (P = 0.043), but apparent Mg digestibility did not differ between ages (P = 0.414). Phytate is broken down in the gastrointestinal tract, but the low P digestibilities suggest that either degradation occurs after the site of P absorption or liberated P is recycled back into the gastrointestinal tract. Yearlings can utilize organic P as well as mature horses; therefore, diets without inorganic P are acceptable for growing horses. Copyright © 2015. American Society of Animal Science .

Minerals excreted in feces have the potential to leach or runoff to water-ways, negatively impacting water quality. This study examined the effect of dietary trace mineral levels, and their source, on the leaching potential of minerals from equine feces. Nine horses were used in a replicated 3 × 3 Latin Square, with three dietary treatments provided as pellets: no added trace minerals (CON), added inorganic trace minerals (ING), and added organic trace minerals (ORG). Supplemental trace minerals included Co, Cu, Mn, and Zn. Horses were allowed ad libitum access to forage and fed their treatment pellets for 16 days prior to fecal sample collection. Estimated dietary mineral intake exceeded requirements for supplemented minerals. Regardless of the source, adding dietary trace minerals increased the fecal leaching potential of Cu, Zn, and P (p < 0.05). More Co leached from ORG compared to ING, while Zn leached in greater amounts from ING compared to ORG (p < 0.05). Fecal bacterial Zn content was greater (p < 0.05) for ORG compared to ING. Negative correlations were observed between bacterial mineral content and leaching for several minerals. Supplementing trace minerals in forms that increase microbial incorporation may provide a strategy to control fecal mineral leaching.

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.

Dairy calves in the Southwest regions of the United States are typically raised individually in wooden hutches with 1.23 m² of space. The objective of the study was to determine if increased space allowance in wooden hutches influences measures of innate immunity and behaviors of Holstein bull calves pre- and postcastration. Calves were randomly assigned at 4 d of age to conventional (CONV; 1.23 m² of space; n = 18), moderate (MOD; 1.85 m² space; n = 17), or maximized space allowance (MAX; 3.71 m² space; n = 19) in hutches. Calves were surgically castrated at 24 d of age. Peripheral whole blood samples were collected at -1, +1, +5, and +12 d of castration. Accelerometer loggers (n = 16 calves per treatment) were used from -3 to +5 d of castration to assess standing behaviors. All calves decreased total standing duration the day of castration versus precastration. Overall, MAX spent the most time in the stand position postcastration versus CONV and MOD. Within treatments, MOD and MAX had increased plasma cortisol 1 d postcastration versus precastration. A treatment × time tendency was observed for cortisol at 12 d postcastration; MAX had the least circulating cortisol. A treatment × time tendency for circulating haptoglobin (Hp) was observed and Hp was greatest among CONV 1 d pre- and 12 d postcastration. Compared with precastration, CONV had increased Hp at 1, 5, and 12 d, whereas MOD had increased Hp at 5 d, and Hp remained similar within MAX. A treatment × time tendency for tumor necrosis factor-α (TNF-α) from lipopolysaccharide-stimulated whole blood was observed; at 1 d postcastration, MOD had the most TNF-α, whereas MAX had the least. Within MAX, calves had increased TNF-α from precastration to 5 d postcastration. A treatment × time interaction was observed for whole blood bactericidal activity against Escherichia coli (WB anti-E). The CONV tended to have the greatest WB anti-E at d -1, but at d 1 and 5 postcastration, CONV had the least WB anti-E. Overall, MAX had less intensity of neutrophil oxidative burst versus CONV and MOD. The lower response of neutrophil oxidative burst and slower Hp secretion after castration is indicative that the wound site likely had less microbial exposure. The findings of this study suggest that calves housed with more space are potentially at less risk of too much inflammation after castration, which may likely be due to the effects of increased space on hide cleanliness and increased standing time.