Effects of nitrogen fertilization and maturity of bromegrass on in situ ruminal digestion kinetics of fiber.

Abstract

Four ruminally cannulated, nonlactating Holstein cows (593 kg) were fed bromegrass hay diets within a 4 X 4 Latin square. Treatments were arranged factorially and consisted of bromegrass fertilized with 0 or 89 kg N/ha and harvested in the late-boot or full-head stage of maturity. Total tract digestibility of DM (57.6 vs 51.1%), NDF (68.8 vs 63.0%), ADF (51.1 vs 46.0%) and cellulose (63.4 vs 53.5%) decreased with increasing maturity (P less than .05). These forages also were placed in dacron bags for determination of in situ digestion kinetics. Rate, extent of digestion, and lag times were determined for DM and fiber components using linear regression of log-transformed data or a nonlinear fitting procedure. Treatment effects generally were consistent between methods of calculating kinetic data; however, numerical results often differed greatly. Extents of in situ ruminal digestion (72 h residue) for NDF, hemicellulose and cellulose were lower (P less than .05) for full-head than for late-boot-stage bromegrass. Extent of digestion calculated using the nonlinear method followed similar trends. Nitrogen fertilization had no effect on extent or total tract digestibilities of fiber components of DM. In situ disappearance rates (calculated using both methods) for fiber fractions and DM generally were almost always affected less by maturity than by fertilization. Particles of N-fertilized bromegrass had more (P less than .05) bacterial N associated with them during the first 12 h in situ than did particles of unfertilized brome. Surface area equations based on lignification of NDF accurately estimated fiber digestion and suggested that lignification was the primary reason DM and NDF digestibilities decreased with advanced maturity. Due to the relatively low DM intakes of these diets (11 kg/d), rate of passage, not rate of digestion, was of principle importance in determining extent of digestion of these diets.

Importance and Effect of Nitrogen on Crop Quality and Health

“…yield and nitrogen concentration in the forage are increased. Increased water concentration and decreased soluble carbohydrates are commonly observed after nitrogen fertilization of grasses (Messman et al, 1991;Brink and Fairbrother, 1992).…”

“…Van Soest (1982) reported that as nitrogen fertilization increases lignin production, digestibility may be reduced. Others (Messman et al, 1991: Puoli et al, 1991 found that the rate of neutral detergent fiber digestion and with it animal feed intake was increased upon nitrogen fertilization. Nitrogen fertilization of forages was more likely to increase digestibility of warm-season grasses because of their lower nitrogen content as compared to cool-season grasses (George and Hall, 1983).…”

The effect of supplemental concentrate feed on live weight gain of yearling heifers over grazing season in subirrigated rangelands of East Anatolia

“…These general increases were related to the plant growing stage because as plant growth advanced cellulosic content increased (6,25). The decreases in NDF and ADF content on the sampling date of 3 July and after the beginning of August were related to the increasing contribution of legumes to the allowed forage because legumes always have lower NDF and ADF contents than grasses (26).…”

Changes in Leaf Area Index, Forage Quality and Above-Ground Biomass in Grazed and Ungrazed Rangelands of Eastern Anatolia Region

“…As the CP concentration decreases, the ADF and NDF contents increase together with the advancing plant maturity (Messman et al 1991;Lacefield et al 1999;Linn ve Martin 1999). In the ungrazed site, similar results with respect to CP, ADF and NDF contents can be attributed to plant maturity, whereas the unchanging CP content and increasing ADF and NDF contents in grazed area can be ascribed to the grazing effects.…”