Use of nylon bag technique in fistulated cattle to assess forage nutrient profiles

Orchard grass is a common forage grown on New England organic dairies. However, other forages may provide more energy and protein while using the same land area. By gaining a better understanding of the nutrient profile of various forages, feeding plans and botanical profiles of paddocks could be modified to improve cattle productivity. The objective of this experiment was to determine the nutrient profile and digestibility of five warm- (sudan grass (SD), millet (ML)) and cool- season (orchard grass (OG), white clover (WC), and meadow fescue (MF)) forages commonly grown in New England. Samples were oven dried and ground using a Wiley mill (4-mm screen). Twenty nylon bags containing 7g DM of forage were inserted into each of 4 lactating ruminally fistulated Holstein cows. Samples were run in technical duplicates within cow. Nylon bags were assessed at 10 incubation periods (0, 1, 2, 3, 4, 6, 7.5, 19.5, 48, and 72 h). Recovered bags were washed, dried, and pooled within incubation period within cow for wet chemistry analysis of DM, CP, ADF, NDF, WSC, and starch. Data were analyzed using PROC MIXED and GLIMMIX of SAS (v9.4) with the effects and contrasts of species, time, and species by time. Species by time interactions were present for starch, DM, CP, ADF, NDF, and WSC. White clover had a greater CP content than other forages from h 0 to 48, but at 72 h the CP content of MF and WC were not different from each other. Compared to the other forages, at h 72, OG had the lowest CP content (P \u3c 0.05). The WSC of all forages decreased as time progressed and were all equivalent at the 72 h incubation time (P \u3c 0.05). However, WC had greater amounts of WSC at h 2 and h 7.5. These results indicate that WC had the highest nutrient profile, but that warm- and cool- season grasses were comparable. Differences in the patterns of ruminal forage degradation and nutrient availability between the grasses and WC samples suggests that using a mixture of these forages may be a practical and feasible strategy to increase the nutritive value of a forage-based diet on organic dairy farms in New England