Cone, J.W.

Guedes, C.

Rodrigues, M.A.M.

English

Name not available

Ruminal degradability of neutral detergent fibre and neutral detergent insoluble nitrogen of feed supplements

Wageningen Yield 

215 
 
Ruminal degradability of neutral detergent fibre and neutral detergent insoluble nitrogen of  
feed supplements 
Cristina Guedes1, Miguel Rodrigues1, John Cone2, Ana Lourenço1, Severiano Silva1, Arnaldo Dias-da-Silva1 
1CECAV-UTAD, Vila Real, Portugal, 2WUR, Wageningen, Netherlands 
Email:cvmguedes@sapo.pt 
 
Introduction In ruminant feeding, the prediction of metabolizable protein requires accurate estimates of feed protein 
degradation in the rumen. Some common feed protein sources have a high concentration of neutral detergent insoluble 
nitrogen (N-NDF) whose degradation may be dependent on neutral detergent fibre (NDF) degradation and, consequently, 
on rumen cellulolytic activity. This may lead to an underestimation of the undegraded protein that reaches the small 
intestine, particularly when animals are fed high starch diets. The objective of this study was to verify if there is a 
relationship between the ruminal degradability of the NDF and N-NDF of eight feed supplements currently used in 
ruminant feeding with the in sacco technique. 
 
Materials and methods Twelve samples of eight feed supplements (dried distillers’ maize, corn gluten feed, coconut meal,  
palm kernel meals, sunflower meal, groundnut meal, cottonseed meal and dehydrated lucerne) were used in this study. 
Samples (1 mm) were analysed for dry matter (DM) and crude protein (CP) according to AOAC (1990) and NDF and N-
NDF according to Van Soest et al. (1991). Samples (4 mm) were incubated in sacco (46 µm pore size; Ørskov et al., 1980) 
for 2, 4, 8, 16, 24, 48, 72 and 96 h. The daily ration of the 3 cannulated rams consisted of meadow hay, beet pulp and soya 
bean meal making 50:35:15 on DM basis.  Residues from individual animals were analysed for N-NDF and NDF. 
Degradation data were analysed using the exponential model: p=a+b(1-exp(-ct)) where p is the degradation, t is the time of 
incubation, a is the soluble and/or rapidly degradable fraction, b is the potential degradable fraction and c is the constant 
rate of degradation. One-way ANOVA analysis was used to compare degradation constants between feeds. 
 
Results Chemical composition of feed supplements (Table1) is in good agreement with current tabulated values. The N-
NDF fraction represents a large proportion of the CP (higher than 50%) in palm kernel meals and coconut meals. 
Differences in the degradation constants between feed supplements for NDF and N-NDF were found (Table 1). As 
expected, the soluble and/or rapidly degradable fraction was low for both NDF and N-NDF, representing the losses of small 
particles from the bags. Higher (P<0.05) degradation rates were observed for sunflower meal for both NDF and N-NDF. 
The correlation between degradation rate for NDF and N-NDF was significant (r=0.814; n=12; P<0.001). These data show 
that the N-NDF degradation rate is lower than the degradation rate of NDF for all the feeds studied, confirming that the 
degradation of N-NDF depends on the NDF degradation. This probably indicates that a large amount of feed protein may 
be affected by the lower ruminal cellulolytic activity when animals are fed high starch diets. 
 
Table 1 Chemical composition and degradation constants of NDF and N-NDF 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Conclusions These results show that the N-NDF degradation constants varied greatly between feed supplements. Our data 
also indicates that the degradation of the N-NDF fraction seems to be dependent of on the NDF degradation. 
 
References 
AOAC 1990. Official methods of analysis. 14th ed., AOAC, Washington DC, USA. 
Ørskov, E.R., Deß Hovell, F.D. and Mould, F., 1980. Tropical Animal. Production, 5: 195-213. 
Van Soest, P.J., Robertson, J.B. and Lewis, B. A. 1991. Journal of Dairy Science, 74: 3583-3587. 
  Degradation constants 
 Chemical composition NDF N-NDF 
 CP NDF N-NDF a  b c a b c 
Feed supplements (%DM) (%) (%/h) (%) (%/h) 
Coconut meal 1 22.5 58.7 2.72 2.7b 58.0b 3.52ab 4.5cd 48.7cd 2.00a 
Coconut meal 2 21.3 62.5 2.51 2.3b 61.7b 3.88b 3.3bc 45.2c 2.15a 
Palm kernel meal 1 16.3 72.2 1.71 1.1a 57.4b 3.11a 6.2e 31.1a 2.63b 
Palm kernel meal 2 17.5 73.2 1.81 0.8a 59.6b 4.02b 2.0a 30.2a 2.91bc 
Sunflower meal 30.0 45.6 0.91 2.5b 57.7b 6.77d 5.2d 60.2e 4.65e 
Groundnut meal 1 52.8 24.2 1.38 2.2b 62.4b 5.86c 5.5d 58.5e 3.61d 
Groundnut meal 2 43.9 31.6 0.99 2.2b 68.0cd 5.71c 3.0ab 57.6e 3.58d 
Cottonseed meal 43.1 26.8 0.65 3.0b 65.3bc 5.65c 2.8ab 50.9cd 3.17c 
Dehydrated lucerne 13.7 46.9 0.33 3.6c 59.3b 4.97c 2.0a 43.3bc 2.81bc 
Dried distillered maize 1 26.9 47.2 2.14 3.3c 71.7d 3.18a 9.7g 39.3b 2.91bc 
Dried distillered maize 2 28.8 48.2 2.21 3.7c 67.8c 3.21a 7.8f 29.0a 2.76b 
Corn gluten feed 21.9 36.7 0.86 4.1c 45.9a 4.17b 9.7g 35.1a 3.12c 
Probability   0.007 <0.001 0.002 0.033 <0.001 0.005 
Values in the same column with different letter are significant different (P<0.05).


Ruminal degradability of neutral detergent fibre and neutral detergent insoluble nitrogen of feed supplements

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