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

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin; CAVADINI, JASON - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 3/12/2020
Citation: Coblentz, W.K., Akins, M.S., Cavadini, J.S. 2020. Fermentation characteristics and nutritive value of baled grass silages made from meadow fescue, tall fescue, or an orchardgrass cultivar exhibiting a unique non-flowering growth response. Journal of Dairy Science. 103(4):3219-3233. https://doi.org/10.3168/jds.2019-17387.
DOI: https://doi.org/10.3168/jds.2019-17387

Interpretive Summary: The production of baled silages continues to be a popular form of forage conservation, particularly with small and mid-sized dairy and or beef producers. A total of 47 large-round bales (4 x 4-ft) of orchardgrass, meadow fescue, or tall fescue were made with or without engagement of a factory-installed bale-cutting mechanism on the baler. Bales were made at either high (58.3%) or ideal (44.9%) moisture, based on recommendations for baled silages. Bale-cutting increased initial wet and dry bale weights by 4.1 and 4.7%, respectively, but had no effect on forage nutritive value, and little effect on silage fermentation. Bale-cutter engagement tended to increase concentrations of fermentation acids in cut silages, which led collectively to a final pH reduction of 0.07 pH units compared to long-stem silages. A unique non-flowering (vegetative) growth response by first-cutting orchardgrass forage produced sharply greater 30-hour fiber digestibilities compared to meadow or tall fescue, which could not be explained on the basis of typical detergent analysis of fiber composition. Meadow fescue corroborated a commonly reported advantage over tall fescue with respect to fiber digestibility, but was not comparable to orchardgrass exhibiting the unique non-flowering growth response. Cutting mechanisms have useful purposes, such as easing the mixing of baled silages into blended diets, but can't be justified on the basis of improved silage fermentation.

Technical Abstract: The production of baled silages continues to be a popular form of forage conservation. Our research objectives were to compare the (baled) silage fermentation characteristics and nutritive value of perennial cool-season grass [meadow fescue (Schedonorus pratensis (Huds.) P. Beauv.), orchardgrass (Dactylis glomerata L.), and endophyte-free tall fescue (Schedonorus phoenix (Scop.) Holub]. Twenty-four plots (0.23 ha) were arranged in a randomized complete block design with 6 plots/block; within each block, 2 plots were assigned randomly to each forage type, and one of those was designated to have the bale-cutting mechanism engaged, while the other plot was baled without cutting. Within each plot, there were 2 bales produced, one was packaged at relatively high moisture (58.3%), while the other moisture was considered ideal (44.9%) for this silage type. Bale-cutting for 1.2 ×1.2-m silage bales (n = 47) increased initial wet and dry bale weights by 4.1 and 4.7%, respectively. Modest increases in bale density for cut bales had no practical effect on measures of nutritive value, either on a pre- or post-ensiled basis. Cutter engagement tended (P = 0.058) to increase concentrations of VFA in silages, and numerically increased production of lactic acid (3.40 vs. 3.03%; P = 0.117), leading collectively to a pH reduction of 0.07 pH units (5.54 vs. 5.61). Although not statistically significant (P = 0.204), this numerical improvement in silage acidity was generally consistent with past studies. A unique non-flowering (vegetative) growth response by the first-cutting orchardgrass forage in this study resulted (P < 0.001) in yields of DM for orchardgrass (2977 kg DM/ha) that were only 52 to 53% of those observed for meadow (5580 kg DM/ha) or tall fescue (5763 kg DM/ha), which did not differ (P = 0.515). Despite the unique vegetative nature of orchardgrass, concentrations of NDF, ADF, and ADL 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 sharply greater (P < 0.001) NDF digestibility (56.2%) compared to meadow (44.9%) or tall fescue (40.8%), which also differed (P = 0.002). Meadow fescue corroborated a commonly reported advantage over tall fescue with respect to NDF digestibility, but was not comparable in this respect to orchardgrass exhibiting a unique non-flowering growth response.