PSIX-23 - Fecal starch in feedlot cattle as affected by sampling time and storage method

Abstract: Fecal starch analysis is a useful tool for monitoring starch digestibility in beef feeding operations. The aim of this study was to investigate the effects of time of day and feces storage method on fecal starch concentration. A commercial feedlot was asked to participate in this study. For both experiments, fecal samples were collected from 5 pens (replicates) of cattle, which were consuming the finishing diet for about 40 d. Dry-ground corn was the primary energy source, with an inclusion of 32.6% DM in the diet. Corn silage was another source of starch (15.5% DM in the diet). Cattle were fed 4 times a day (0800, 1000, 1330, and 1600 h). Pens had on average, 51 animals and the estimated average weight was 495 kg. Fecal samples (~20 g) were collected from 10 undisturbed piles and composited. In Exp. 1, sampling was performed at 6 different times within day: 0800, 0930, 1100, 1330, 1500, and 1630 h. After sampling, all composite samples were frozen for further analyses. In Exp. 2, fecal samples were collected at 1000 h and subjected to 5 storage methods, as follows: 1) oven dried, 2) dried by an Air Fryer device, 3) frozen, 4) cooled for 24 h in a cooler box at 4^oC and subsequently frozen, and 5) addition of 50 g of 70% alcohol in 100 g of feces. Fecal samples were analyzed for DM and total starch. Data were analyzed using MIXED procedure of SAS, followed by a Tukey test at P ≤ 0.05. Fecal starch was unaffected by sampling time (P = 0.60). Average starch concentration was 4.25% of DM. Regarding storage methods, samples from Air Fryer and those mixed with alcohol had greater starch concentration (5.75 and 5.81% of DM, respectively) than other treatments (4.76, 4.83, and 4.96% of DM for those frozen, oven-dried, and cooled for 24 h, respectively). Overall, time of day did not influence determination of fecal starch concentration. In contrast, storage method influenced fecal starch concentration, but the differences were minimal.