Effects of selected feed additives on the in vitro digestibility and ruminant utilization of medium-quality roughages

Abstract

Experiments were conducted to study the in vitro dry matter disappearance (DMD) and volatile fatty acid (VFA) production patterns using Coastal Bermudagrass hay (CBH) ensiled with individual and combinations of several feed additives. These investigations were followed by total collection digestion trials using unensiled CBH, CBH ensiled with water or aqueous solutions of hydrochloric acid (HCl) or sodium hydroxide (NaOH). A performance testing trial with cottonseed hulls and Bospro, a feed additive for ruminants, was conducted using lactating dairy cows. Increasing levels of Bospro in a ration containing 50% air-dry CBH and 50% air-dry milo grain did not result in statistically significant differences in the mean in vitro DMD values. The production of acetic acid and the ratio of acetic to propionic acid were depressed as the Bospro levels were increased but the reverse was evident with propionic, butyric, and isovaleric acids. The highest DMD at the end of the 24 or 48 hr of fermentation was obtained with CBH ensiled with 2.6% HCl for 3 or 6 weeks. Ensiling CBH with urea as well as NaOH improved the DMD values significantly (P<0.05) as compared with the control ration. Lowest DMD was obtained for CBH samples with ensiled with sodium chlorite. The molar per cent of acetic acid and the ratio of acetic to propionic acid at the end of the 24 hr of fermentation were highest for CBH ensiled with brewers' yeast and water and lowest for CBH ensiled with brewers' yeast, milo grain, and water..