Canola meals from different plants over two production years differ in rumen-undegraded protein
Lactation trials showed improved production and N efficiency when dietary soybean meal was replaced with equal CP from canola meal. Three canola meal samples were collected from each of 12 Canadian production plants over 2 years (total = 72) and analyzed for chemical composition and ruminal protein degradability. The Michaelis-Menten inhibitor in vitro method was used to quantify protein degradation rates and rumen-undegraded protein (RUP), assuming passage rates of 0.16/h and 0.06/h for soluble and insoluble proteins. Differences among plants were assessed using the SAS Mixed model; LS-means for plants over both years, and for each year, are reported in the table. Although CP concentration and NDIN and RUP proportions were unaffected by year (P ≥ 0.21), NDF and soluble N were lower (P ≤ 0.01) in canola meal produced in 2011 than 2012. Proportions of NDIN ranged from 18 to 28% of total N but were unaffected by plant (P = 0.15). However, differences were detected among plants in CP and NDF concentrations (P ≤ 0.03) and proportions of soluble N and RUP in total N (P < 0.01). Plant x year interactions (P ≤ 0.04) also were found for concentrations of CP and NDF and proportions of NDIN and RUP, but not for soluble N (P = 0.19). Results indicated that differences in canola meal RUP concentration were consistent over 2 production years and, depending on plant of origin, ranged from 38 to 50% of CP, a difference of 30%.
Table 1. Mean composition of canola meals from 2 production years
|Plant||CP, % of DM||NDF, % of DM||NDIN, % TN||Sol-N, % TN||RUP, % TN|
|Prob-Plant||< 0.01||0.03||0.15||< 0.01||< 0.01|
|Plant*Year||< 0.01||< 0.01||0.04||0.19||< 0.01|
a-f Means within columns with different superscripts differ (P < 0.05).
Inhibitor in vitro