68 Effect of a marine-sourced calcium on fecal pH in horses

Abstract

Lithothamnium calcareum (LC) is a red, marine algae containing calcite in its cell walls. LC has been touted for its gastroprotective effects in horses attributed to the increased surface area of its honeycomb structure allowing greater acid-buffering capacity versus calcium carbonate. Effects on the equine hindgut have not been evaluated. This pilot study aimed to determine if LC (CalseaPowder, Nuwen, France) fed to horses at a rate of 4.6g/kg finished feed would alter fecal pH. Twelve mature horses (12.5 yrs ± 1.4, mean ± SEM, 6 mares, 6 geldings) in moderate exercise in the Ohio State ATI equine program participated in a randomized crossover study. Horses were maintained on 1.2-ha fields and brought into the barn for feeding and riding sessions. Horses transitioned onto the control feed over 2 wks (CON: SAFE ‘N EASY Performance, BUCKEYE Nutrition, Dalton, OH, 1.2% total Ca, 100% added was CaCO 3 ), formulated to meet or exceed NRC 2007 requirements for mature horses in light-moderate work. Horses were randomly assigned to receive either CON or CAL (CON + LC , 1.2% total Ca, added 74% CaCO 3 , 26% calcite) during the first test period then crossed over for the second. Horses acclimated to CON or CAL for 2 wks and were offered 0.5 kg feed per 100 kg bodyweight, divided into 2 feedings (0700 and 1600). Horses had access to mixed grass forage to supplement pasture, fresh water and salt ad libitum . At the end of the first 2-week trial period, horses were brought into stalls bedded with sawdust and observed. All fecal samples were collected immediately upon defecation (within 1–3 h post feeding) from the middle of the top of the manure pile to avoid bedding contamination and analyzed. Within 5 min, approximately 10 mL of fecal water was squeezed through cheesecloth from freshly defecated samples and stirred for 60s. Fecal water pH was then measured in duplicate with a calibrated pH meter. Diets were switched and the protocol repeated with 2 wk acclimation. Statistical analyses utilized R version 3.6.3, with significant differences declared when P ≤ 0.05. A linear mixed effect model was used with pH vs. diet and horse as a random effect. A Dunnett post-hoc comparison between the 2 diet groups was applied. There was no effect of period ( P = 0.66). There was an effect of diet ( P < 0.001). Horses consuming CAL had higher fecal water pH (6.87 ± 0.2; mean ± SD) compared with CON (6.69 ± 0.2). LC may be useful in supporting hindgut health in horses, especially when such changes in pH become clinically relevant (e.g., acidosis). Future work should examine the effects of different doses of LC on hindgut pH and its effects on the microbial population.