|Akins, Matthew - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/13/2019
Publication Date: N/A
Technical Abstract: Accurate and precise determinations of in-vitro NDF digestibility are critical to proper evaluation of forage nutritive value, and essential for proper diet formulation for dairy cows. The objective of this research was to compare NDF digestibility (NDFD) determined with the ANKOM Daisy Incubator II System (ANKOM) using 2 sample sizes (0.25 or 0.50 g); a further goal was to compare these results with those obtained from a commercial laboratory using traditional methodology without samples restrained within fiber bags. All determinations of NDFD were conducted with NDF determined with heat-stable amylase and sodium sulfite, and corrected for residual ash (asNDFom). Triticale forages (n = 48) were incubated in triplicate for 12, 24, 30, 48, 144, or 240 h by ANKOM methods. For the 30-h incubation, the relationship between 0.25 and 0.50-g sample sizes was explained by a linear model (Y = 1.206 x – 1.1; R2 = 0.933), in which the slope differed from unity (P < 0.001), but the intercept did not differ from 0 (P = 0.661). After a 48-h incubation, a linear model (Y = 1.014 x + 7.1; R2 = 0.964) indicated that the slope did not differ from unity (P = 0.631), but the intercept was greater than 0 (P < 0.001). When compared with results from a commercial laboratory, a linear regression (Y = 1.040 x – 1.8; R2 = 0.861) of the results using the 0.25-g sample size obtained by ANKOM on those from the commercial laboratory indicated the slope did not differ from unity (P = 0.521), nor did the intercept differ from 0 (P = 0.626). A similar relationship was obtained from the 48-h incubation (Y = 1.021 x – 3.4; R2 = 0.866), in which the slope and intercept did not differ from unity and 0 (P = 0.430), respectively. Relationships were poorer for the 0.50-g sample size in ANKOM, particularly for the 30-h incubation, where the slope (0.824) was less than unity (P = 0.002). Generally, NDFD digestibility was greater by ANKOM with the 0.25-g sample size, especially with short incubation times, and agreement with traditional methods was improved relative to those with a 0.50-g sample sealed in fiber bags.