Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2012
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Lactation trials have shown that production and N efficiency were improved when dietary soybean meal was replaced with equal crude protein (CP) from canola meal. Three or four canola meal samples were collected from each of 12 Canadian production plants (total = 37), and analyzed for differences in chemical composition and in vitro and in situ ruminal protein degradability. In situ incubations were conducted at 0 and 12 h only, and estimated rates used to compute rumen-undegraded protein (RUP) assuming first-order degradation and a ruminal passage of 0.06/h. The Michaelis-Menten inhibitor in vitro (MMIIV) method was used as described by Colombini et al. (J. Dairy Sci., 94:1967-1977, 2011) to quantify degradation rates and RUP, assuming passage rates of 0.16/h and 0.06 for the soluble and insoluble protein fractions. Differences among plants were assessed using the general linear model of SAS. Although fraction B3 (neutral detergent-insoluble nitrogen minus acid detergent-insoluble nitrogen) was unaffected, there were differences among plants in CP and neutral detergent fiber (NDF) contents of canola meals produced. There also were differences among plants in RUP estimated by MMIIV: the sole expeller meal had the highest RUP (47.4%), but meals from 4 other plants had similar RUP values (43.0-46.3%). The RUP estimates from the other 7 meals were lower, including 4 that were different from the 4 meals with the highest RUP values. Estimates of RUP made using in situ methods tended to rank the meals differently from the MMIIV assay. Results indicated that, depending on the plant of origin, canola meal RUP may range from 37 to 47%, a difference greater than 25%.