Previous research indicated that there were significant differences in rumen-undegraded protein (RUP) among canola meals (CM). These differences could influence the nutritional value of CM. The objective of this study was to evaluate the effects of feeding CM with different RUP on ruminal fermentation, nutrient digestion, and microbial growth using a dual-flow continuous-culture system. Diets were randomly assigned to 6 fermenters in a replicated 3 × 3 Latin square with three 10-d experimental periods consisting of 7-d for adaptation and 3-d for sample collection. Treatments were solvent soybean-meal (SBM); low-RUP CM (LCM); and high-RUP CM (HCM). Fermenters were fed 72 g/d, divided in 4 feedings. Diets were prepared as 3 concentrate mixes that were combined with orchardgrass hay and wheat straw. Liquid and solid flow rates were adjusted to 11 and 5.5%/h, respectively. Samples were collected for digestibility, ruminal fermentation, and microbial growth. Statistical analyses were performed using SAS. Orthogonal contrasts were used to compare effects of different protein sources (SBM vs. LCM + HCM), and (LCM vs. HCM). Partial data are presented in the table below. Ruminal NH₃-N, total VFA concentration, molar proportion of acetate, propionate, butyrate, and isobutyrate were not affected by treatments. Molar proportion of valerate was greater when SBM was fed, whereas molar proportions of isovalerate, and total BCVFA were lower for CM diets (Table 1). Isovalerate, an intermediate product of leucine degradation, is associated with protein degradation; therefore, this may indicate that CM diets had higher RUP than SBM. Table 1. Effects of feeding canola meals (with different RUP LCM and HCM) on ruminal fermentation

Item	Treatment			SEM	Contrast P-values
SBM	LCM	HCM	SBM vs. LCM + HCM	LCM vs. HCM
NH3-N, g/d	0.51	0.57	0.53	0.02	NS	NS
Total VFA, mmol	122.6	116.2	116.6	2.54	NS	NS
Acetate, %	64.6	65.4	66.5	1.25	NS	NS
Propionate, %	19.9	20.7	21.1	0.86	NS	NS
Butyrate, %	11.7	10.9	9.4	0.64	NS	NS
Isobutyrate, %	0.44	0.48	0.44	0.02	NS	NS
Valerate, %	1.5	1.6	1.6	0.03	0.02	NS
Isovalerate, %	1.3	1.1	1.1	0.08	0.02	NS
Acetate:Propionate	3.3	3.2	3.2	0.18	NS	NS
Total BCVFA, mmol	2.1	1.8	1.8	0.11	0.04	NS