Effects of Adding Either Fibrolytic Enzymes Or Sodium Butyrate to Feedlot Diets on Rumen Parameters of Angus Cattle

Abstract This study conducted at São Paulo State University feedlot, Dracena campus, Brazil, was designed to evaluate the addition of either sodium butyrate (BUT) or exogenous fibrolytic enzymes (ENZ) on dry matter intake (DMI), ruminal pH, short-chain fatty acids (SCFA), and rumen disappearance rate of Angus cattle. Three Angus steers, cannulated in the rumen (+ 690 kg), were used in a replicated 3 x 3 Latin square, resulting in 6 experimental periods, in a total of 203 days of study. Each experimental period lasted 28 days; 14 days of adaptation diets, and 14 days of the finishing diet containing 85% concentrate (71% finely-ground corn). Cattle were given a 7-day washout interval between periods, where they were allowed to graze. The experimental diets fed to the animals were different only with respect to the feed additives used, according to the treatments: Control (CTL; no feed additives added), ENZ [0.01% of diet dry matter (DM)], and BUT (0.3% and 0.1% of diet DM during adaptation and finishing phases, respectively). The DMI was measured daily, and rumen pH and temperature were measured by data loggers on days 25 and 26 of each experimental period. The rumen fluid samples were collected at 0, 4, 8, and 12 hours after feeding on day 26 of each period to determine the molar proportion of SCFA. The rumen of the animals was emptied on day 27 at 1100 h (3 hours after feeding) and day 28 at 0800 h (before feeding) in each experimental period. The rumen contents were separated into solid and liquid fractions and then weighed. Based on the solid and liquid mass values obtained, as well as the DM intake, the rumen disappearance rate was calculated and expressed in %/h. Data were analyzed by PROC MIXED of SAS (2003), using Tukey's test to compare means when appropriate, considering P ≤ 0.05 as significant. The DMI was not affected (P > 0.76) by treatments in this study. Likewise, no treatment effect was observed on minimum, maximum, and mean ruminal pH (P > 0.23). The pH time below 6.2, 5.6, and 5.2 was not affected by treatments (P > 0.45), as well as pH area under 6.2, 5.6, and 5.2 (P > 0.55). Rumen temperature was lower in cattle fed ENZ when compared with those fed CON and BUT (39.63°C vs. 40.12°C and 40.02°C, respectively; P = 0.04). Furthermore, the molar proportions of SCFA were not affected by treatments (P > 0.71). Cattle consuming ENZ increased ruminal disappearance rate (%/h) when compared with CTL-fed cattle (8.61 vs 6.36; P = 0.05). Thus, the addition of BUT to feedlot diets did not cause any impact on ruminal fermentation parameters; however, the use of ENZ promoted small benefits that deserve further investigation.