Effect of feeding warm-season annuals with orchardgrass on ruminal fermentation and methane output in continuous culture

Abstract

A 4-unit, dual-flow continuous culture fermentor system was used to assess nutrient digestibility, volatile fatty acids (VFA) production, bacterial protein synthesis, and methane (CH) output of warm-season annual grasses. Treatments were randomly assigned to fermentors in a 4 × 4 Latin square design using 7 d for adaptation to treatment and 3 d for sample collection. Treatments were (1) 100% orchardgrass (Dactylis glomerata L.; ORD); (2) 50% orchardgrass + 50% Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz; MIL]; (3) 50% orchardgrass + 50% brown midrib sorghum × sudangrass (Sorghum bicolor L. Moench × S. bicolor var. sudanense; SSG]; or (4) 50% orchardgrass + 25% millet + 25% sorghum × sudangrass (MIX). Fermentors were fed 60 g of dry matter (DM)/d in equal portions of herbage 4 times daily (0730, 1030, 1400, and 1900 h). To replicate a typical 12-h pasture rotation, fermentors were fed the orchardgrass at 0730 and 1030 h and the individual treatment herbage (orchardgrass, Japanese millet, sorghum × sudangrass, or 50:50 Japanese millet and sorghum × sudangrass) at 1400 and 1900 h. Gas samples for CH analysis were collected 6 times daily at 0725, 0900, 1000, 1355, 1530, and 1630 h. Fermentor pH was determined at the time of feeding, and fermentor effluent samples for NH-N and VFA analyses were taken daily at 1030 h on d 8, 9, and 10. Samples were also analyzed for DM, organic matter (OM), crude protein, and fiber fractions to determine nutrient digestibilities. Bacterial efficiency was estimated by dividing bacterial N by truly digested OM. True DM and OM digestibilities and pH were not different among treatments. Apparent OM digestibility was greater in ORD than in MIL and SSG. The concentration of propionate was greater in ORD than in SSG and MIX, and that of butyrate was greatest in ORD and MIL. Methane output was greatest in MIL, intermediate in ORD, and lowest in SSG and MIX. Nitrogen intake did not differ across treatments, whereas bacterial N efficiency per kilogram of truly digestible OM was greatest in MIL, intermediate in SSG and MIX, and lowest in ORD. True crude protein digestibility was greater in ORD versus MIL, and ORD had lower total N, non-NH-N, bacterial N, and dietary N in effluent flows than MIL. Overall, we detected little difference in true nutrient digestibility; however, SSG and MIX provided the lowest acetate to propionate ratio and lower CH output than MIL and ORD. Thus, improved warm-season annual pastures (i.e., brown midrib sorghum × sudangrass) could provide a reasonable alternative to orchardgrass pastures during the summer months when such perennial cool-season grass species have greatly reduced productivity.

Nutritional evaluation and ruminal fermentation patterns of kochia compared with alfalfa and orchardgrass hays and ephedra and cheatgrass compared with orchardgrass hay as alternative arid-land forages for beef cattle in two dual-flow continuous culture system experiments1

“…Ruminal NH 3 -N concentration was greater (P < 0.01) for FK compared with the other forages (Table 4), possibly as a result of highest (P < 0.05) true CP digestibility (Table 3). In agreement with the current study, Dillard et al (2017) also found a positive relationship between true CP digestibility and effluent NH 3 -N concentration when dual-flow continuous culture fermenters were fed 100% orchardgrass. Nevertheless, the accumulation of NH 3 -N in the fermenter fluid not only depends upon the extent of CP digestibility but also on the rate of N utilization by ruminal bacteria (Bach et al, 1999).…”

“…Although FK treatment had increased (P < 0.05) true CP digestibility, which led to an increase (P < 0.01) in ruminal NH 3 -N concentration, it was not followed by improvements in N utilization since bacterial efficiency showed no concurrent increase. Bacterial efficiency averaged 7.84 g of bacterial N per kilogram of OM truly digested, which agrees with data reported by Dillard et al (2017), who found a bacterial efficiency average of 7.32 g in dual-flow continuous culture when fermenters were fed diets containing 100% orchardgrass or Least squares means within the same row with different superscripts differ (P < 0.05).…”

Animal performance and environmental efficiency of cool- and warm-season annual grazing systems

“…However, Ingram (2014) found that when grazed, canola (Brassica napus) had a mean seasonal herbage biomass of 873 kg DM/ha. Dillard et al (2017a) reported greater seasonally accumulated herbage biomass during the fall in monocultures of canola, rapeseed (B. napus L.), and turnip (B. rapa L.) than ARG (1,023 and 242 kg DM/ha, respectively). No difference in fall accumulated herbage biomass was observed among brassica species.…”

“…No difference in fall accumulated herbage biomass was observed among brassica species. Ingram (2014) and Dillard et al (2017a) reported CP concentrations of multiple brassica forage species ranging from 20% to 30%. Furthermore, NDF and ADF concentrations were considerably lower than similar CSA grasses, with brassicas having 46% and 22% less NDF and ADF, respectively, than ARG (19% vs. 35% NDF and 14% vs. 18% ADF, respectively; Dillard et al, 2017a).…”

Evaluation of a single‐flow continuous culture fermenter system for determination of ruminal fermentation and enteric methane production

“…Depending on the CCF apparatus, the volume‐to‐feed ratio of each system varies tremendously. For example, Rusitec systems use 20 g substrate/day per 0.7 L = 29 g/L (Hristov et al, ), while the Dillard et al () system used 60 g substrate/day per 1.1 L = 55 g/L. This results in different dilution rates and retention times within each system, causing large discrepancies among different systems even when using the same diet ingredients.…”