Fermentation characteristics and nutritive value of baled grass silages made from meadow fescue, tall fescue, or an orchardgrass cultivar exhibiting a unique nonflowering growth response

Abstract

Throughout central Wisconsin, many soils are poorly drained, and perennial cool-season grasses are often planted as monocultures or in mixed stands with alfalfa because of the poor persistence of alfalfa under these growing conditions. Our objectives were to compare the fermentation characteristics and nutritive value of perennial cool-season grasses {meadow fescue [Schedonorus pratensis (Huds.) P. Beauv.], orchardgrass (Dactylis glomerata L.), and endophyte-free tall fescue [Schedonorus phoenix (Scop.) Holub]} conserved as baled silages with or without particle-size reduction, and at 2 moisture concentrations. Twenty-four plots (0.23 ha) were arranged in a randomized complete block design with 6 plots/block. Within each of the 4 field blocks, one of the 6 plots was assigned randomly to each of the (3 × 2) factorial combinations of forage type and bale cutting engagement (cut or uncut). The baler cutting mechanism consisted of 15 cutting knives, thereby creating a theoretical length of cut of about 8.1 cm. Generally, sufficient forage was available to produce 2 bales/plot; therefore, one bale was packaged at relatively high moisture (58.3%), whereas the other bale was made at an ideal moisture (44.9%) for this silage preservation method. Theoretically, bale cutting can increase bale weights and densities by reducing particle size, thereby allowing inclusion of additional forage within the same-sized bale. In this experiment, bale-cutting within 1.2 × 1.2 m silage bales (n = 47) increased initial wet and dry bale weights by 4.1 and 4.7%, respectively, but had no practical effect on measures of nutritive value, either on a pre- or postensiled basis. Cutter engagement tended to increase total volatile fatty acids in silages, thereby resulting in a pH reduction of 0.07 pH units (5.54 vs. 5.61). A unique nonflowering growth response by the first-cutting orchardgrass forage resulted in yields of dry matter for orchardgrass (2,977 kg of dry matter/ha) that were only 52 to 53% of those observed for meadow (5,580 kg of dry matter/ha) or tall fescue (5,763 kg of dry matter/ha), which did not differ. Despite the unique vegetative nature of orchardgrass, concentrations of neutral detergent fiber, acid detergent fiber, and acid detergent lignin determined before ensiling exhibited limited variability across forages (60.9 to 62.7%, 35.2 to 36.4%, and 2.75 to 2.99%, respectively). However, a 30-h in vitro incubation determined that orchardgrass exhibited greater neutral detergent fiber digestibility (56.2%) compared with meadow (44.9%) or tall fescue (40.8%), which were also statistically distinct.