Growth Rates of Thoroughbred Foals and In Vitro Gut Health Parameters When Fed a Cereal or an All-Fiber Creep Feed

Traditions and the economic advantage when producing big athletic Thoroughbred (TB) yearlings for sale encourage owners to feed high levels of cereals. Such diets can predispose gastric ulceration and developmental orthopedic diseases, impacting negatively on future careers. This study aimed to (1) determine if an all-fiber creep feed (total mixed fiber ration [TMFR] would sustain equal growth rates in TB foals versus a cereal-based stud cube (SC) and (2) compare pH and lactate produced by SC and TMFR in in vitro foregut and hindgut conditions. Eight TB foals in matched-pairs were fed SC or TMFR for 18 weeks. Weight gain (average daily gain [ADG]), height at wither and hip, heart girth, and body length were recorded weekly. Similar growth rates were recorded for all measurements. The ADG of TMFR and SC were 1 and 1.1 kg per head per day, respectively. In vitro foregut incubation of SC and TMFR at 37°C in pepsin HCl solution for 6 hours produced higher pH 5.84 (TMFR) compared with 5.33 (SC) (P < .05). Gas production measured fermentation rate, acidity, and lactate from TMFR and SC, incubated with fecal inoculum from the foals on the same diet. Fermentation rates and lag times were equal for both feeds; total gas produced at t50 and y50 were greater (P < .05) for SC. Lactate and pH levels were lower and higher, respectively, for the TMFR. This study showed that similar growth in TB foals was achieved on the TMFR feed and that potentially better gut health, denoted by higher pH and lower lactate levels, could be maintained by fiber compared with cereal feed. •Similar average daily gain in Thoroughbred foals fed a high-fiber versus cereal diet.•Fiber feed maintained higher pH than cereal feed in in vitro stomach conditions.•Less lactate on fiber feed compared with cereal feed in fore and hindgut conditions.•One kilogram average daily gain was achieved on high-fiber diets.