Alkali addition and roughage inclusion effect on performance and carcass characteristics of feedlot steers fed diets containing 60% dried distillers grains with solubles

Abstract

Three experiments were conducted to determine the effectiveness of calcium hydroxide (Ca(OH)₂) addition and roughage inclusion on digestibility, performance, and carcass characteristics of steers fed 60% dried distillers grains with solubles (DGS). Statistical analyses for studies were conducted using the MIXED procedures of SAS. In experiment 1, 48 steers (353.5 ± 7.55 kg) were allotted to individual pens and fed 1 of 3 diets (dry matter [DM] basis) containing 60% dried DGS, 20% corn silage, and 4% supplement with: 1) 14.5% corn and no Ca(OH)₂; 2) 14% corn and 2% Ca(OH)₂; and 3) 14.5% additional corn silage and no Ca(OH)₂. Steers fed Ca(OH)₂ consumed the least (P = 0.03) and steers fed added corn silage consumed the most and had the least gain:feed (P = 0.02). Gain and carcass quality were not affected by treatment (P ≥ 0.48). In experiment 2, 112 steers (375.3 ± 19.25 kg) were allotted to pens (four pens per treatment; seven steers per pen) arranged as a 2 × 2 factorial (roughage × Ca(OH)₂) and fed one of four diets (DM basis) containing 60% dried DGS, 17% corn silage, and 4% supplement with: 1) 17.5% corn silage and no Ca(OH)₂; 2) 17% corn silage and 2% Ca(OH)₂; 3) 17.25% corn stover and no Ca(OH)₂; and 4) 17% corn stover and 2% Ca(OH)₂. Added stover decreased average daily gain (ADG) compared to added corn silage (P = 0.04). Ca(OH)₂ increased ADG when steers were fed stover, but not when steers were fed only corn silage (P = 0.05; interaction). In experiment 3, six ruminally cannulated steers (initial body weight = 352 ± 14.8 kg) were randomly allotted to a 6 × 6 Latin square design to determine the effects of roughage inclusion (corn, corn silage, stover) and Ca(OH)₂ addition (0% or 2%) on ruminal characteristics. Feeding stover decreased total volatile fatty acid(s) (VFA) concentration and DM digestibility compared to corn silage or corn (P < 0.01), whereas Ca(OH)₂ resulted in greater total VFA concentrations and DM digestibility (P ≤ 0.02). Stover increased rate of DM degradation (K _d) and rate of particle outflow from the rumen (P ≤ 0.04) but decreased extent of DM digestion and mean retention time (P ≤ 0.02) compared to corn or silage. Ca(OH)₂ increased K _d (P < 0.01) and tended to increase (P = 0.06) liquid passage rate. In conclusion, added roughage did not improve performance of cattle fed 60% dried DGS. Ca(OH)₂ may decrease intake and maintain performance of cattle fed 60% dried DGS with corn silage as the roughage source and increases ADG when corn stover replaces a portion of the corn silage.

Keywords: calcium hydroxide; cattle; digestibility; kinetics; roughage; rumen pH.

Figure 1.

Effect of roughage inclusion on ruminal pH (experiment 3); n = 6. *Differences in ruminal pH due to roughage inclusion (P ≤ 0.05). At 0, 9, 12, and 18 h post-feeding, corn stover inclusion increased ruminal pH, whereas corn silage inclusion resulted in a ruminal pH similar to that of steers fed corn. ^†Differences in ruminal pH due to roughage inclusion (0.05 ≤ P ≤ 0.10). At 6 h post-feeding corn stover inclusion tended to increase ruminal pH.

Figure 2.

Effect of Ca(OH)₂ addition on ruminal pH (experiment 3); n = 6. ^†Differences in ruminal pH due to Ca(OH)₂ addition (0.05 ≤ P ≤ 0.10). At 18 h post-feeding addition of Ca(OH)₂ tended to increase ruminal pH.