Effect of feeding barley or corn silage with dry-rolled barley, corn, or a blend of barley and corn grain on rumen fermentation, total tract digestibility, and nitrogen balance for finishing beef heifers

Abstract

Five ruminally cannulated heifers were used in an incomplete 6 × 6 Latin square design to determine the effects of cereal silage (barley vs. corn), cereal grain (barley vs. corn vs. a 50:50 blend of barley and corn), and their interaction (S × G) on dry matter intake, ruminal fermentation, total tract digestibility, nitrogen balance, and in situ degradation. Corn silage (CS) or barley silage (BS) was included at 8% of dietary dry matter (DM). Within each silage source, diets contained (DM basis) either dry-rolled barley (BG; 86%), dry-rolled corn (CG; 85%), or an equal blend of barley and corn (BLEND; 85%). Periods were 25 d, with 5 d of dietary transition, 13 d of dietary adaptation, and 7 d of data and sample collection. Samples collected included feed and refusals, total urine and feces, and ruminal fluid. All data were analyzed using the Mixed model of SAS with the fixed effects of silage, grain, and the S × G. Dry matter intake (P ≥ 0.19) and mean ruminal pH (P ≥ 0.096) were not affected by the silage, grain, or S × G. Total short-chain fatty acid concentrations were greater for BLEND than BG or CG (grain, P = 0.003) and for CS (silage, P = 0.009) relative to BS. The molar proportion of acetate was greater for BS-BG and BS-CG (S × G, P < 0.001), while molar proportion of propionate was greater for CS-BG (S × G, P < 0.001) relative to other silage and grain source combinations. Rumen ammonia-N concentration was greater for CG than BG, or BLEND (grain, P < 0.001), and greater for CS compared to BS (silage, P = 0.023). Apparent total tract digestibility of DM, organic matter, neutral detergent fiber, starch, and gross energy were greatest for BG (grain, P ≤ 0.035). Digestible energy content (Mcal/kg) was greater for BG (grain, P = 0.029) than CG and BLEND. Total nitrogen retention (g/d and % of intake) was greatest for CS-BG (S × G, P ≤ 0.033) relative to all other treatments. In situ degradation rates of DM, crude protein, and starch were greater for BG than CG (P ≤ 0.004). The potentially degradable fraction of DM, crude protein, and starch was greater for CG (P ≤ 0.031), while the undegradable fraction was greater for BG (P ≤ 0.046). For silage sources, CS had greater 24 h in situ DM digestibility (P = 0.009) and starch digestibility (24, 48, and 72 h incubations, P ≤ 0.034) relative to BS. Results suggest that while feeding a combination of CS and BG promotes propionate production and greater N retention; few other additive effects were observed.

Effect of Feeding Barley, Corn, and a Barley/Corn Blend on Beef Composition and End-Product Palatability

“…The reason for elevated n-6 fatty acids when feeding the blend are not related to the dietary supply, but instead likely relate to effects on rumen pH. Lower rumen pH was found in blended compared with barley and corn grain-fed steers in the present study, as previously reported by Johnson et al [ 41 ]. Under these conditions, lipolysis of dietary lipids could have been inhibited [ 42 ], reducing PUFA biohydrogenation by rumen bacteria, and allowing for greater bypass of n-6 fatty acids.…”

Effects of Dietary Barley Starch Contents on the Performance, Nutrient Digestion, Rumen Fermentation, and Bacterial Community of Fattening Hu Sheep

“…The reason for decreased starch digestibility in BS-100 could be the sharply reduced ruminal pH, resulting in subacute rumen acidosis in the lambs, which thereby limited starch degradation in rumen and intestine ( 28 , 29 ). However, several studies indicated that increasing dietary barely grain improved the total tract starch digestibility because of its high rumen degradation rate ( 5 , 30 ). The inconsistent results among studies were likely due to differences in diet treatments, dietary starch contents, and experimental animals.…”

“…The inconsistent results among studies were likely due to differences in diet treatments, dietary starch contents, and experimental animals. For example, Johnson et al ( 5 ) reported a greater starch digestibility for barley-based diet than that for corn-based diet at a dietary starch content (ranged from 55.4 to 62.25%) was reported in beef cattle. The current results indicated that partially substitute CS with BS could decrease total tract fiber digestibility for fattening sheep, and total substitute CS with BS would decrease both fiber and starch digestibility for fattening sheep.…”

“…Attention should be paid while choosing cereal grain during diet formulation, as the ruminal degradation rates of starch from different cereal grains can be quite variable. For instance, the degradation rate of starch in corn was lower than that in barley after dry-rolled ( 4 , 5 ). The lower degradation rate of corn starch (CS) compare to the other sources of starch in diets could decrease the risk of subacute ruminal acidosis (SARA) in high production ruminates ( 6 , 7 ).…”

“…Yahaghi et al ( 12 ) reported that substitution of corn with 30% barley improved ruminal pH (6.05 vs. 5.95) compared with the substitution of corn with 70% barley for lambs. Johnson et al ( 5 ) reported higher digestibilities of dry matter (DM), organic matter (OM), CP, neutral detergent fiber (NDF), and starch for the barley grain treatment (85.94% of diet) compared to the corn grain treatment (84.96% of diet), or the combination of barley and corn group (42.72% corn and 42.72% barley of diet). These studies revealed that the varied proportions of the barley and corn may change the content of rumen degradable starch and finally affect the rumen fermentation, nutrient digestibility, and performance of ruminant.…”