Fecal Ph Variables of Beef Steers Consuming Grower Or Finisher Diets Containing Saccharomyces Cerevisiae

Abstract The effects of live-yeast and diet type (grower or finisher) offered to beef steers on fecal pH variables were evaluated. Ruminally-cannulated Angus-crossbred steers (n = 8; BW = 550 ± 20 kg) were used in a duplicated 4 × 4 Latin Square design, on a 2 × 2 factorial treatment arrangement, with factors described as follows: A) presence of live-yeast [Saccharomyces cerevisiae (CNCM I-1077), at 2 × 1010 CFU/g); and B) diet type. Diets (DM basis) contained 3% yellow-grease and min/vitamin supplement-adjusted. The grower [40% low-quality alfalfa-hay (LQ-hay), 35% steam-flaked corn (SFC), 20% wet corn gluten feed (WCGF)] and finisher (65% SFC, 20% WCGF, 8% LQ-hay)] diets were offered to ad libitum intake, once daily at 0700 h. Live-yeast treatment and control (soybean meal as carrier only) were pre-weighed (0.25 g, as is) within gel-capsules and kept at room temperature until introduced directly into the rumen (via ruminal cannula) twice daily (0700 and 1800 h). Four periods of 35 d (28 d of adaptation and 7 d of collection) were used. Fresh fecal samples (50 ± 1 g, as is) were collected via rectal finger-stimulation 4 times per day (every 6 h), during 6 consecutive days, while sampling time was adjusted by advancing 1 h daily so that all the 24 h period after feeding became represented by collections. Samples were suspended with deionized water (to complete 100 g, total) into a plastic container with cap and immediately measured using a pH electrode. The statistical model used animal as experimental unit, the fixed effects of diet, live-yeast, and diet × live-yeast. Square, period, and animal(square) were used as random effects, except by pH average (repeated measures), in which animal(treatment) was also included. For fecal pH average, no 3-way, treatment × time, or diet × time interactions were observed (P ≥ 0.86), except by a treatment × diet interaction, in which animals offered live-yeast on a grower diet had greater (P = 0.04) fecal pH compared with those offered live-yeast on a finisher diet (6.63 vs. 6.55). Regardless of treatments, collection time was meaningful (P = 0.01), where the greatest fecal pH average (6.70) was reached at 14 h, while the least (5.52) was reached at 8, 15, and 22 h after feeding. The fecal pH average across all treatments was 6.58, and it was used to calculate area and time under such threshold. The area (147, min × pH-delta) and the time (730 min) under the curve (pH 6.58), maximum (6.98), minimum (6.22), and the pH magnitude of change (0.76) were not affected (P ≥ 0.37) by treatments. Fecal pH was cyclic and seemed to be positively affected by dietary live-yeast inclusion when offered to beef steers consuming a grower diet.