Potential of Combined Yeast Culture and Enzymatically Hydrolysed Yeast to Improve In Vitro Dry Matter and Nutrient Degradability of Different Feedstuffs

Abstract

Live yeast cultures have been a popular additive in ruminant feeds to improve fermentation efficiency, rumen, and intestinal health. However, very little is known about inactive yeast culture and hydrolysable yeast cells on nutrient digestibility in ruminants. Therefore, this study was conducted to determine the effects of a combined yeast culture and enzymatically hydrolysed yeast (YC+EHY) on in vitro dry matter and nutrient digestibility. Seven chemically contrasting substrates, including the leaves and petiole of forage plants (Trichanthera gigantea, Gliricidia sepium, Leucaena leucocephala, and Brachiaria arrecta), agriculture by-products (soybean meal and rice hulls), and a commercial concentrate feed, were incubated in vitro with and without YC+EHY to determine dry matter (DM), crude protein (CP), neutral detergent fibre (NDF), and acid detergent fibre (ADF) digestibility after 24 and 48 h of incubation. A second experiment evaluated in vitro CP degradability by incubating substrates for 0, 2, 4, 8, 16, 24, and 48 h with and without YC+EHY. Incubation with YC+EHY reduced 24 h DM and CP digestibility in soybean meal and G. sepium by 16.2% and 38.5%, respectively. Conversely, the ADF digestibility of B. arrecta incubated with YC+EHY increased by 32%. In vitro ruminal DM and nutrient digestibility were unaffected by YC+EHY after 48 h of incubation. The rate of CP degradability in the commercial concentrate and rice hull inoculated with YC+EHY increased sharply between 16 and 24 h post-incubation and generally plateaued afterwards. Similarly, YC+EHY significantly increased CP degradability in L. leucocephala after 8 and 16 h of incubation. The 16 h CP degradation in T. gigantea without YC+EHY was significantly higher. It was therefore concluded that YC+EHY has potential to improve ruminal ADF digestibility and modify ruminal CP degradation dependent on the type of substrate.