Rumen Degradation of Canola Products
Rumen Degradability of Canola Meal
The rumen degradability and solubility of CM has
been studied extensively (Ha et al. 1986 {1144}; Broderick et
al. 1988 {1081}; Kirkpatrick and Kennelly 1989 {1066}; McAllan
et al. 1988 {1111}; Kirkpatrick and Kenelly 1985 {1200}; Rooke
1985 {1208}) (table 9). Most studies used the in situ
technique to determine rumen degradability of CM (Mustafa 1996).
It is evident from the literature that CM is rapidly degraded
in the rumen and is considered a poor source of rumen undegradable
protein. After a 24 hr incubation CM and 2 RSM reported solubility
values of 89.1 to 94.0% CP compared to FM at 28.8% (% CP) (Voigt
et al. 1990 {1042}).
There is a large variation in the kinetic CM parameters
and in the measurement of effective degradability (tables 9 +
10). The soluble protein (a) content of CM ranges from 18.6 to
29.8% (Kirpatrick and Kennelly 1987 {1125}; Khorasani et al. 1994
{858}; Tuori 1992 {29.8}). The proportion of potentially degradable
protein (b) ranges from 56.7 to 84.9% (Khorasani et al. 1994 {858};
Tuori 1992 {961}). The rate of degradation of the b fraction
has been reported (c) to vary from 2.48 to15.7%/hr (Liu et al.
1993 {905}; Cheng et al. 1993 as cited by Christensen and McKinnon
1993). The degree of variation in the different protein fractions
and in the degradation rate constant, is in part a reflection
of the diet. Cheng et al. (1993 as cited by Christensen and McKinnon
1993) reported a potentially degradable protein fraction (b) for
CM of 72.5% on hay based diets and 59.6% on concentrate based
diets.
The amount of CM protein that actually disappears in the rumen, the effective degradability, is in part a function of the turnover rate of rumen contents. Table 9 provides a summary of measurements of the effective degradability DM (EDDM) and CP (EDCP) fractions of CM assuming a rumen turn-over rate of 5%/hr. Khorasani et al. (1994 {858}) reported similar values for effective degradable CP for SBM and CM. In agreement, Kendall et al. (1991 {1004}) reported an average EDCP of 51.5% for five CM samples and 51.5% for SBM. Ha and Kennelly (1984 {1226}) reported EDCP of CM, SBM and dehydrated alfalfa to be 65.8, 53.6 and 41.4%, respectively. Mustafa et al. (1996 {2061}) reported EDCP for regular, low and high fiber CM to be 74.9, 75.3 and 72.5%, respectively. Cheng et al. (1993 as cited by Christensen and McKinnon 1993) reported EDCP of CM was 62.5% with a concentrate diet and 74.9 and 72.3% on a hay and straw diet, respectively. A decrease in EDCP, but not EDDM with increasing concentrate was also reported by Petit (1992 {949}). The type of diet effects the amount of EDCP and must be a consideration when incorporating a protein supplement into a ration (Christensen and McKinnon 1993). Conversely, Murphy and Kennelly (1987 {1120}) reported no difference in EDCP values with an increasing CP concentration or protein source. Kendall et al. (1991 {1004}) reported similar ruminal CP degradation values for three samples of CM and lower values for two other CM samples obtained from five different processors in Western Canada. The variability was attributed to the differences in processing conditions (Khorasani et al. 1994 {858}; Kendall et al. 1991 {1004}). Variability of EDCP is related to the diet, the processing conditions and the turnover rate of rumen contents.
| Table 9. Characterization of CM DM and protein: Soluble (a) and potentially degradable (b) and the rate constant (c %/hr) for the disappearance of fraction b. | |||
| Reference | Rumen kinetic parameterx | ||
| DM | a (%) | b (%) | c (%) |
| Seoane et al. 1992 {956} | 31.4 | 62.6 | 6.9 |
| Liu et al. 1993 {905}z | 29.8 | 65.3 | 2.78 |
| Liu et al. 1993 {905}y | 23.2 | 71.5 | 2.09 |
| Mustafa et al. 1996 {2061} | 18.8 | 77.9 | 13.5 |
| CP | |||
| Seoane et al. 1992 {956} | 26.5 | 68.1 | 9.7 |
| Liu et al. 1993 {905}z | 28.0 | 72.0 | 2.48 |
| Liu et al. 1993 {905}y | 14.4 | 85.6 | 1.69 |
| Tuori 1992 {961}untreated | 7.4-29.8 | 65.4-84.9 | 5-11.8 |
| Tuori 1992 {961}Opex | 1.8-13.2 | 72.1-95.6 | 5.9-14.7 |
| Ha and Kennelly 1984 {1226} | 22.8 | 65.9 | 9.3 |
| Trial 2 | 24.9 | 74.5 | 6.8 |
| DePeters and Bath 1986 {1142} | 21.5 | 70.2 | 7.6 |
| Kirpatrick and Kennelly 1987 {1125} | 18.6 | 77.1 | 9.0 |
| Cheng et al. 1993w | |||
| Trial 1 hay diet | 19.9 | 72.8 | 15.7 |
| Trial 2 straw diet | 19.4 | 75.4 | 11.8 |
| Trial 3 grain diet | 21.8 | 59.3 | 13.0 |
| Khorasani et al. 1994 {858} | 18.6 | 56.7 | 11.2 |
zThe protein supplement was RSM not CM.
yThe RSM had been treated with FA (0.6%/meal CP).
xa=soluble CP (%CP), b=degradable CP (%CP), c=degradation rate of b fraction (%/h)
was cited by Christensen and McKinnon 1993.
| Table 10. Summary of the effective degradability of CM DM and protein fractions (rumen outflow rate 5%/hr) | ||
| Reference | ||
| DM | CP | |
| Seoane et al. 1992 {956} 12 h | 59.0 | 63.8 |
| Tuori 1992 {961}untreated | 49.8-65.3 | |
| Tuori 1992 {961}Opex | 38.9-64.2 | |
| Broderick et al. 1988 {1081} | 52, 75w | |
| Ha and Kennelly 1984 {1226} | ||
| Trial 1 | 57.1 | 65.8 |
| Trial 2 | 57.7 | 65.5 |
| Kirpatrick and Kennelly 1987 {1125} | ||
| Trial 1 {1125} | 63.0 | 63.2 |
| Trial 2 {1125} | 64.2 | 72.0 |
| Kendall et al. 1991 {1004} | 53.5 | 51.5 |
| Boila and Ingalls 1992 {950} | 60.6 | 67.3 |
| Cheng et al. 1993y | ||
| Trial 1 hay diet | 74.9 | |
| Trial 2 straw diet | 72.3 | |
| Trial 3 grain diet | 62.5 | |
| Khorasani et al. 1994 {858} | 57.8 | |
| Murphy and Kennelly 1987 {1120}z | 68.1 0.85 | 74.2 1.17 |
| Khorasani et al. 1993 {899} | 81.3 | |
| Mustafa et al. 1996 {2061} | 72.3 | 74.9 |
zmean standard error.
yas cited by Christensen and McKinnon 1993.
win vitro system.