Effects of High Fiber Energy Supplements on Fermentation Characteristics and In Vivo and In Situ Digestibilities of Low Quality Fescue Hay

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Abstract
High fiber energy sources were compared with corn-soybean meal (C-S) as supplements of low quality fescue hay (FH) in two trials using four mature, open, non-lactating, Angus cows ranging in weight from 375 to 500 kg and each fitted with ruminal and abomasal cannulae. In trial 1, FH was supplemented at a level of 25% of the diet dry matter (DM) with 95% C-5% S, soyhulls (SH), dried corn gluten feed (CGF) or 87% citrus pulp-12.5% soybean meal (CP-S). The FH was ground and mixed with the supplements as a complete feed. Total tract dry matter digestibility (DMD) did not differ (P<.05) among treatments. However, cows fed SH and CG-F had higher (P<.05) neutral detergent fiber digestibility (NDFD) than did those fed C-S. True ruminal organic matter digestion (ROMD) did not differ (P<.05) among treatments; however, microbial OM recovery was higher (P<.05) for CP-S. Microbial crude protein (MCP) recovery was also higher (P<.05) for CP-S than for C-S and CGF and MCP/100 g ROMD was highest (P<.05) for CP-S and lowest (P<.05) for C-S. In trial 2, FH was supplemented at a level of 27.4% of the diet with either 95% C-5% S, SH, CGF or a mix of 50% SH and 50% wheat (SH-W). The FH was fed as long-stem hay and the supplements were meal-fed once daily. No differences (P<.05) were again observed for DMD. The NDFD was again higher (P<.05) for cows fed SH than for those fed C-S. Supplementation with C-S tended (P<.10) to lower in situ DM disappearance of hay incubated for 24 and 48 h. In situ DM disappearance of the test supplements was higher (P<.O5) at 12 and 24 h for CGF and SH-W. The observed negative associative effects on DMD resulted from depressed fiber digestion with high starch supplements. However, these effects do not appear related to ruminal pH, since pH was not affected (P<.05) in either trial. Results are interpreted to indicate that high fiber energy supplements appear to be less susceptible to negative feed interactions by possibly lessening the inhibitory effects of starch digesting bacteria and(or) avoiding potential shifts in the ruminal microflora. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.