Technical Note: Collection and preparation techniques change nutrient composition of masticate collected from esophageally fistulated cattle 1

Two experiments determined effects of collection and preparation techniques on nutrient composition of masticate samples from esophageally fistulated cattle. In Exp. 1, 12 esophageally fistulated cattle were maintained on 2 precollection diets, high CP (24% CP; n = 6) or low CP (7.7% CP; n = 6), for 8 d. On d 9, the esophageal plug was removed, screen bottom bags were attached, and each cow was offered fresh grass. Immediately after fresh grass sample collection was complete, dry grass (hay) was offered and a sample was collected. Blood samples were collected and analyzed for serum urea nitrogen concentration. Masticate samples of both fresh and dry grass were divided and each was either squeezed by hand until no more saliva could be removed or remained unsqueezed. In Exp. 2, 10 esophageally fistulated cattle were fitted with either screen (n = 5) or solid (n = 5) bottom collection bags after removal of the esophageal plug and presented grass hay, fresh grass, alfalfa hay, or fresh alfalfa. In Exp. 1, the precollection diet did not affect (P = 0.49) CP content of masticate even though serum urea nitrogen tended to be greater (P = 0.08) for high- vs. low-CP precollection diets. Forage harvest type offered (fresh vs. hay) interacted (P = 0.01) with preparation technique (squeezed vs. unsqueezed) for CP, where CP decreased in squeezed fresh samples (P < 0.001) but not in squeezed grass hay samples (P = 0.98). In Exp. 2, ingestion greatly increased levels of ash (P < 0.001). Crude protein was greater (P < 0.004) before ingestion for all samples except grass hay (P = 0.43). Levels of NDF were similar before and after ingestion (P > 0.15) for all samples except fresh alfalfa, which was greater after ingestion (P = 0.002). Ingestion status did not affect in vitro OM disappearance (IVOMD; P > 0.34) except for grass hay, which was greater after ingestion (P < 0.001). Bag type (screen vs. solid) did not affect ash and NDF (P > 0.31), except for fresh alfalfa, which were greater (P < 0.03) for solid bottom bags. Bag type did not affect alfalfa CP (P = 0.71) but did affect grass CP, which was lower (P = 0.02) for solid bottom bags. Bag type did not affect IVOMD (P > 0.33). More (P = 0.01) fresh forage than hay was recovered through the esophageal opening. Previous diet did not impact masticate samples but squeezing impacted CP levels of high-quality forage and therefore should not be performed. Nutrient values should be reported on an OM basis.