Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol83.Issue3-4.Mar2000:
Animal Feed Science and Technology
83 (2000) 273±285
The effect of animal species on in sacco degradation
of dry matter and protein of feeds in the rumen
K.S. Nandraa, R.C. Dobosb, B.A. Orchardc,*, S.A. Neutzed,
V.H. Oddyb, B.R. Cullisc, A.W. Jonesa
a
Elizabeth Macarthur Agricultural Institute, PMB 8, Camden, NSW 2570, Australia
b
NSW Agriculture Beef Industry Centre, Armidale, NSW 2350, Australia
c
Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650, Australia
d
Novartis Animal Health, Australasia Pty Ltd, 140-150 Bungaree Rd., Pendle Hill, NSW 2145, Australia
Received 17 November 1998; received in revised form 3 August 1999; accepted 11 November 1999
Abstract
A study was undertaken on lucerne (LUC), ryegrass (RG), kikuyu (KIK), soybean meal (SBM),
wheat grain (WG) and meat and bone meal (MBM) to determine the effect of animal species (sheep
versus cattle) on in sacco degradation of dry matter (DM) and protein. The approach of cubic
smoothing splines ®tted as a linear mixed model was used for the analysis of degradability of DM
and protein of feeds.
The quickly degradable DM (QDDM), cumulative slowly degradable DM (CSDDM), total
degradable DM (TDDM) and rate of degradation of slowly degradable DM of LUC, RG, KIK, SBM
and WG in the rumen of sheep and cattle were not different (p > 0.05). The QDDM, CSDDM
and TDDM of these forages and concentrates ranged from 22.9 to 57.6, 35.3 to 54.9 and 70.2 to
92.9 (g/100 g).
Estimates of in sacco quickly degradable protein (QDP), cumulative slowly degradable protein
(CSDP), total degradable protein (TDP), rate of degradation of slowly degradable protein of LUC,
RG, KIK and SBM were similar (p > 0.05) for sheep and cattle. For the WG a vertical shift was
found in the species cubic splines ®tted to logit transformed protein degradation data. This resulted
in QDP of 52.0 and 43.8 g/100 g, CSDP of 41.6 and 48.0 g/100 g and TDP of 93.6 and 91.6 g/100 g
for sheep and cattle, respectively.
In sacco degradation of DM and protein of MBM was irregular for both sheep and cattle,
consistent with extreme heterogeneity of the concentrate. # 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Degradability; In sacco; Protein; Dry matter; Sheep versus cattle
*
Corresponding author.
E-mail address: orcharb@agric.nsw.gov.au (B.A. Orchard).
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 2 9 - 7
274
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
1. Introduction
Information about the extent and rate of dry matter (DM) and protein degradation of
ruminant feeds in the rumen is crucial to match feed inputs to animal requirements. While
there is some information available regarding differences between sheep and cattle in
their ability to digest feed, there is little information on the degradation of components of
feed dry matter and protein in the rumen. The rumen in sacco technique has been adopted
as the standard method for determining DM and protein degradation. Sheep or cattle are
used depending on the facilities of the various research establishments. It is important to
understand the applicability of results obtained from one species, to the other species.
Playne et al. (1978) speculated that cattle had higher microbial activity and therefore faster
DM degradation relative to sheep. Few differences were observed between sheep and cattle
by (érskov et al., 1983) when comparing the in sacco degradation of dry matter of feeds after
9 or 24 h incubation. Prigge et al. (1984) have demonstrated that mature ruminant species
generally degrade feeds similarly. Huntington and Givens (1997) concluded that mature
ruminant species (sheep and cattle) when fed at maintenance, degrade DM of hay, soybean
meal and ®sh meal similarly as measured by the in sacco technique.
In a recent European ring test involving 23 laboratories, Madsen and Hvelplund (1994)
observed a large variation in in sacco estimates of protein degradability. There was no
apparent difference between sheep and cattle in in sacco rumen protein degradability,
although a possible species effect could have been masked by other factors in the
procedure varying among laboratories.
The present study was designed to determine whether in sacco degradability of DM
and protein, of some forages and concentrates differ between sheep and cattle fed the
same basal diet to maintain live weight.
2. Materials and methods
2.1. Animals and basal diet
Nine rumen cannulated Merino wethers (3±4 years old, mean live weight 55 kg) and
three rumen cannulated heifers (mean live weight 444 kg) were individually housed and
were offered 0.9 and 6.0 kg/day, respectively of the same diet, half at 0730 h and half at
1530 h. These quantities of feed were calculated to approximately maintain live weight
(Oddy, 1983). The diet consisted of 60% lucerne chaff (5±7 cm chop length) (904 g DM/
kg, 890 g organic matter (OM)/kg DM, 346 g acid detergent ®bre (ADF)/kg DM, 29.8 g
N/kg DM, estimated metabolisable energy (ME) concentration of 7.2 MJ/kg DM) and
40% calf pellets consisting mainly of cereal grain and roughage (912 g DM/kg, 910 g
OM/kg DM, 102 g ADF/kg DM, 32.3 g N/kg DM, estimated ME concentration of
9.6 MJ/kg DM) (Oddy et al., 1983).
2.2. Sample preparation
Samples of lucerne (Medicago sativa) (LUC), ryegrass (Lolium rigidum) (RG) and
kikuyu (Pennisetum clandestinum) (KIK) were dried in a forced draught oven at 558C.
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
275
Table 1
Experimental design for the degradability study
Species
animal
Period 1
(27 March 1995)a
Period 2
(3 April 1995)a
Period 3
(10 April 1995)a
Period 4
(18 April 1995)a
Heifer 1
Heifer 2
Heifer 3
Sheep 1
Sheep 2
Sheep 3
Sheep 4
Sheep 5
Sheep 6
Sheep 7
Sheep 8
Sheep 9
1,2,3
1,2,3
1,2,3
1
1
1
2
2
2
3
3
3
4,5,6
4,5,6
4,5,6
4
5
6
4
5
6
4
5
6
1,2,3
1,2,3
1,2,3
2
2
2
3
3
3
1
1
1
4,5,6
4,5,6
4,5,6
5
6
4
5
6
4
5
6
4
a
Feed types: 1, lucerne; 2, kikuyu; 3, ryegrass; 4, soybean meal; 5, meat and bone meal; 6, wheat.
Dried forages and concentrates (soybean meal (SBM), meat and bone meal (MBM) and
wheat grain (WG)) were ground through a Christie and Norris hammermill (Checley
Everitt & Associates, Victoria, Australia) ®tted with 4 and 2.25 mm screens, respectively.
A `test' sieving was done on the concentrates by shaking the feeds for 3 h on a 0.45 mm
sieve. Where losses were >5% (soybean meal and wheat), the feed was sieved in this
manner to remove ®ne particles before incubation in bags.
2.3. In sacco degradability study
The protocol for the measurement of in sacco degradability of feeds was similar to that
recommended by the Agricultural and Feed Research Council (AFRC, 1992), the only
difference being that cannulated animals were offered feed only twice daily.
Approximately 2 g sieved feed was weighed into each dacron bag (80 mm 120 mm,
36±38 mm pores). Bags were made of polyester single thread woven with welded
crossheads (Allied Screen Fabrics, Hornsby, New South Wales, Australia).
Table 1 presents the experimental design for this study of in sacco protein and dry
matter degradation in the rumen of sheep and cattle. Samples from the three forages and
three concentrates were placed in dacron bags in the rumen of three cattle and nine sheep
on four occasions (periods) at weekly intervals commencing 27 March 1995. The total
duration of the in sacco study was six weeks, two weeks adaptation period followed by
four weeks degradation studies. In any one period, each heifer received three test feeds
and each sheep one test feed, with the test feed allocation outlined in Table 1. Some
attempt was made to balance the allocation of the feed types to animals between periods,
though the particular allocation of feed types to animals and periods is not optimal in the
presence of animal or period effects. Six bags per test feed, were inserted in the rumen
simultaneously. Bags inserted in the rumen containing forages were withdrawn after 4, 8,
12, 24, 48 and 72 h, while those containing concentrates were withdrawn after 2, 4, 8, 12,
24 and 48 h. Bags were hand-rinsed brie¯y under cold tap water, then washed for 30 min
276
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
on a cold rinse cycle in a washing machine. The value at time zero was obtained by
washing the bag and test feed contents without incubation. The bags were then fully dried
at 558C in a forced-draught oven. Disappearance of DM was measured as the loss of
weight of the bag contents and the material left in the bag at each incubation time was
analysed for nitrogen content.
2.4. Chemical analyses
Organic matter of the basal diet was determined after ignition in a muf¯e furnace for
3 h at 6008C and the acid detergent ®bre (ADF) of the basal diet was estimated by re¯ux
according to Faichney and White (1983). The nitrogen content (N) of the basal diet, the
test feeds and the residue left in the nylon bags after incubation in the rumen of sheep and
cattle was determined by the combustion analyser method (Sweeney, 1989) using a
LECO FP-428.
Crude protein (CP, g/100 g DM) was calculated as N (g/100 g DM) 6.25. The CP
content of LUC, RG, KIK, SBM, MBM, WG was 23.00, 23.00, 25.81, 51.69, 51.56 and
12.50, respectively.
2.5. Statistical methods
Five of the six test feeds were considered for statistical analysis. MBM was not
included in this analysis because the degradation of MBM was irregular, consistent with
extreme heterogeneity (Fig. 1a and b).
Table 2 presents the decomposition of the terms in the analysis of the degradation data.
This is consistent with the experiment design being a cross-over design with animals,
periods, animal periods and animal periods samples being the strata in the design.
`Samples' represent a factor notionally randomized to sampling times within an animal
for a particular period.
Modelling of the degradation of DM or protein is via the cubic smoothing spline,
which is a smooth (that is, continuous in the ®rst derivative over the domain of de®nition)
function comprising piece-wise cubic polynomials between sampling times. The
decomposition of the terms in the animal period sample strata follows from Verbyla
et al. (1999).
Preliminary plots of the residuals of percent dry matter and protein degradation
indicated severe variance heterogeneity. This was ameliorated by use of the logit
transformation. The signi®cance of all ®xed terms was assessed using Wald tests and the
signi®cance of random terms was assessed using residual maximum likelihood ratio tests
(Verbyla et al., 1999). All analyses were performed using ASREML (Gilmour et al.,
1999).
érskov and McDonald, 1979 de®ne the exponential decay function f(t) eÿkt to be the
fraction of the feed which still remains in the rumen after t hours given k, the rate of
passage from the rumen. Using this rate of passage k, and denoting the percentage
degraded at time t by p(t), the corrected rate of disappearance is given by f(t) dp(t)/dt and
the cumulative slowly degradable protein up to time t (CDSP(t) or, CDSP for short) is
then obtained using
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
277
Fig. 1. (a) Original dry matter degradation data for sheep and cattle. (b) Original protein degradation data for
sheep and cattle.
278
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 2
Sources of variation in the linear mixed model analysis of degradation data
Term
Decomposition
Fixed or
Random (F/R)
Final model
protein
Final model
DM
constant
F
***
***
species
animalc1
F
R
b
***
**
periodc2
R
***
Constant
Animal
Period
Animal period
feed
species feed
animal periodc3
animal period feed (group)c4
F
F
R
R
***
***
***
Animal period samples
linear (ta)
spline (t)
deviations (random (t))d,e
species linear (t)
species spline (t)
deviations (species random (t))d,f
animal linear (t)c1
animal spline (t)
deviationsd
period linearc2
period spline (t)
deviationsd
feed linear (t)
feed spline (t)
deviationsd
species feed linear (t)
species feed spline (t)
deviationsd
animal period linear (t)c3
animal period spline (t)
deviationsd
group linear (t)c4
group spline (t)
F
R
R
F
R
R
R
R
R
R
R
R
F
R
R
F
R
R
R
R
R
R
R
***
**
***
*
***
***
***
***
R
***
***
*
Error
due to soybean meal within animal period
error
*
p < 0.05, **p < 0.01, ***p < 0.001, respectively.
`t' represents time of incubation in the rumen.
b
`' indicates the ®xed effect was included because of marginality constraints.
c1±4
indicate pairs of terms for which a covariance may be included.
d
Denotes terms estimating `deviations' which estimate systematic deviation at the particular mean level.
e
Represents deviations at the overall mean level.
f
Represent systematic deviations at the species mean level and so forth.
a
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
CSDP
Z
0
t
f u
dp u
du
du
279
(1)
In this study, the cumulative slowly degradable protein (CSDP) has been calculated
using f(t) eÿkt for k 0.02/h and with p(u) representing the equation of the backtransformed logit cubic spline ®tted for either an individual test feed or a particular
species by test feed combination. The accuracy of the results of this integration depends
on the precision of the S-PLUS (Version 3.4, Release 1) `integrate' function (Statistical
Sciences, 1995). The rate of disappearance of slowly degraded protein (SDP) has been
calculated using
dSDP
dp t eÿktÿg t g0 t
f t
dt
dt
1 eÿg t 2
where g(t) represents the particular test feed or test feed by species logit spline.
The total degradable protein (TDP) in the rumen at a particular ¯ow rate (k 0.02)
was calculated as the sum of the quickly degraded protein (QDP) (or zero hour protein)
and the CSDP. An analysis analogous to that performed for protein degradation was
performed for dry matter degradation with comparable calculations for total degradable
dry matter (TDDM), quickly degradable dry matter (QDDM) and cumulative slowly
degradable dry matter (CSDDM).
3. Results
3.1. Protein degradation
The salient features of the ®nal model were an interaction of feed type with the linear
component of the cubic smoothing spline, an interaction between species and feed type,
and some evidence of a differential curvature in the cubic smoothing spline between feeds
(see Table 2). The ®tted curves from this model are presented in Fig. 2. The feed type by
species interaction resulted in a signi®cant (p < 0.01) difference between sheep and cattle
for wheat only.
The value of QDP for each test feed is given in Table 3, which also includes the value
of QDP for each species by feed curve. The corresponding values for CSDP from (1) and
TDP are also presented.
While the values of QDP, CSDP and TDP varied between feeds, there were no
differences between sheep and cattle for LUC, RG, KIK and SBM. The difference in the
QDP between cattle and sheep for WG (43.8 and 52.0 g/100 g, respectively) may re¯ect a
`lag' in protein degradation for cattle but this was not included in the analysis as there
was insuf®cient data in the 0±4 h period. The calculated CSDP of WG at a rumen out¯ow
rate of 0.02 per hour appears somewhat higher in cattle (48.0 g/100 g) than in sheep
(41.6 g/100 g), but the TDP of WG for cattle and sheep are similar (91.8 and 93.6 g/
100 g, respectively).
The rate of degradation of SDP for the test feed curves and for the feed curves of each
species, with fractional rumen out¯ow rate k of 0.02 per hour, is presented in Table 4. The
280
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Fig. 2. Protein degradation curves for sheep and cattle on the logit and percentage scale.
281
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 3
Quickly degradable protein (QDP), cumulative slowly degradable protein (CSDP) at fractional out¯ow rate of
0.02 per hour and corresponding total degradable protein (TDP) measured as percentage of total protein
Overall feed
QDP
CSDPa
TDP
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
39.9
28.5
20.6
47.9
55.3
45.0
53.8
66.3
44.8
78.7
84.9
82.3
86.9
92.7
Heifer by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
40.6
28.0
21.9
43.8
55.3
44.6
54.1
65.6
48.0
78.7
85.2
82.1
87.5
91.8
Sheep by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
39.1
29.1
19.5
52.0
55.3
45.4
53.6
67.0
41.6
78.7
84.5
82.7
86.5
93.6
a
CSDP was calculated assuming the cubic spline to be linear passed the ®nal data point and using t ! 1,
suf®cient for consistency to 0.0001.
Table 4
Rate of degradation (percentage per hour) of slowly degradable protein in the rumen at fractional out¯ow rate of
0.02 per hour
Overall feed
Hours
0
2
4
8
12
24
48
72
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.03
3.27
3.89
6.04
2.97
3.95
3.48
4.65
5.50
2.99
3.51
3.40
4.87
4.32
2.57
2.29
2.75
3.90
2.06
1.85
1.24
1.83
2.84
0.85
0.60
0.18
0.44
0.43
0.09
0.11
0.04
0.06
0.02
0.01
0.02
0.02
0.01
±
±
Heifers by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.05
3.23
4.06
5.96
2.98
3.95
3.44
4.79
5.64
2.99
3.50
3.38
4.93
4.60
2.57
2.27
2.76
3.84
2.30
1.85
1.22
1.85
2.25
0.97
0.60
0.18
0.44
0.04
0.10
0.11
0.04
0.06
0.02
0.01
0.02
0.01
0.01
±
±
Sheep by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.00
3.32
3.72
6.04
2.97
3.94
3.50
4.50
5.29
2.98
3.52
3.41
4.78
4.02
2.57
2.32
2.74
3.95
1.84
1.85
1.26
1.81
2.42
0.74
0.60
0.19
0.43
0.46
0.07
0.11
0.04
0.06
0.03
0.01
0.02
0.02
0.01
±
±
282
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Fig. 3. Dry matter degradation curve for test feeds on the percentage scale.
maximum degradation rate of protein occurred in the 0±4 h period after bag insertion. No
differences are apparent in the rate of degradation of SDP at different times between
sheep and cattle for LUC, RG, KIK or SBM. However, for WG the rate of degradation of
SDP appears to be somewhat higher in cattle between 2 and 24 h after insertion of the
feed bags, as compared to sheep.
3.2. Dry matter degradation
The important features of the ®nal model for DM degradation included a
signi®cant (p < 0.001) interaction of feed type with the linear component of the cubic
smoothing spline and signi®cantly different (p < 0.001) curvature due to feed type
(Table 2).
In the model for DM degradation there was no evidence of species or species by feed
differences (p > 0.05). The DM degradation curves for each test feed are given in Fig. 3.
While the estimated values of quickly degradable dry matter (QDDM), cumulative
slowly degradable dry matter (CSDDM), and total degradable dry matter (TDDM) and
rate of degradation of SDDM, varied between test feeds, no difference for these
parameters between sheep and cattle for LUC, RG, KIK, SBM and WG was evident.
Therefore, Tables 5 and 6 present the overall QDDM, CSDDM, TDDM and rate of
degradation of SDDM (with k 0.02 per hour) for the test feeds only.
283
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 5
Quickly degradable dry matter (QDDM), cumulative slowly degradable dry matter (CSDDM) at rumen out¯ow
rate of 0.02 per hour and corresponding total degradable dry matter (TDDM) measured as percentage of total
DM
Overall feed
QDDM
CSDDMa
TDDM
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
22.9
32.5
31.0
33.8
57.6
48.7
37.7
45.3
54.9
35.3
71.6
70.2
76.3
88.7
92.9
a
CSDDM was calculated assuming the cubic spline to be linear passed the ®nal data point and using t ! 1,
suf®cient for consistency to 0.0001.
Table 6
Rate of degradation (percentage per hour) of slowly degradable dry matter in the rumen at a fractional rumen
out¯ow rate of 0.02 per hour
Overall feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
Hours
0
2
4
8
12
24
48
72
1.32
2.01
1.47
4.12
7.22
1.41
2.26
1.55
4.08
5.25
1.60
2.74
1.77
3.59
2.91
2.01
2.32
2.16
3.04
0.81
1.91
1.08
1.88
2.07
0.37
0.72
0.17
0.55
0.34
0.12
0.10
0.06
0.07
0.03
0.03
0.04
0.01
0.04
±
±
4. Discussion
4.1. Parametric model
The traditional approach to the analysis of degradation curves is to ®t a nonlinear model, typically the exponential model (érskov and McDonald, 1979).
There has been evidence to suggest that the exponential model may not be entirely
appropriate (McDonald, 1981; Dhanoa et al., 1995; Huntington and Givens, 1997; Lopez
et al., 1999).
All of the competing models are continuous and smooth, in the sense that they are
all functions of the incubation time which exhibit continuity in the ®rst derivative.
The biological basis for these models is essentially empirical, with the choice of
model determined by statistical rather than entirely biological reasons (Lopez et al.,
1999).
The cubic smoothing spline represents a semi-parametric alternative which avoids
choosing a parametric model. The estimation of all key biological parameters such as
CSDDM and CSDP is straightforward. The additional advantage of the cubic smoothing
spline is that other relevant sources of variation such as animal and period effects can be
easily incorporated in the cubic smoothing spline's linear mixed model formulation
(Verbyla et al., 1999).
284
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
4.2. Degradability
Following the ring tests, the Technical Committee on responses to nutrients (AFRC,
1992) made no de®nitive recommendation regarding the species of animal to be used for
protein degradability. Therefore, the present study focused on determining species
differences for protein degradability of concentrates and forages.
Although feed and feed species were signi®cant in the ®nal model for protein
degradation in the rumen, the only test feed for which these terms were associated with a
signi®cant vertical shift in logit curves was WG. No signi®cant species differences were
evident for protein degradation for the forages studied (LUC, RG and KIK). In the case of
SBM, signi®cant heterogeneity of variance was detected but was not associated with any
species differences in protein degradability.
For the forage and concentrate feeds examined (except MBM), parameters for DM
degradation were independent of the species of animal (sheep or cattle). There was no
signi®cant species effect and no interaction of species with either feed or period.
Therefore, a single curve for each test feed from either sheep or cattle (on the logit scale)
may be used to represent the DM degradation in the rumen. The results of the present
study are in accordance with the ®ndings of Huntington and Givens (1997) who found no
differences between host species on in sacco DM disappearance of hay, SBM and ®sh
meal. Uden and van Soest (1984) also found that mature ruminant species degrade the
®bre fraction of feeds similarly.
5. Conclusions
The ®ndings of this planned study have quanti®ed no difference between sheep and
cattle in the in sacco degradability of DM for LUC, RG, KIK, SBM and WG. In sacco
degradability of protein (QDP, CSDP and TDP) of LUC, RG, KIK and SBM were also
found to be similar in cattle and sheep.
For WG, there were species differences in the in sacco degradation characteristics of
protein, the nature of which was a vertical shift in the logit scale degradation splines.
Future work needs to examine the difference in the in sacco degradability of protein of
various grains.
Acknowledgements
The authors wish to acknowledge the assistance of Ms. K. Riley in the animal house
and Dr. R. Hegarty for his valuable comments for the preparation of the manuscript.
References
Agricultural and Food Research Council (AFRC), 1992. Nutritive requirements of ruminant animals: Protein.
AFRC Technical Committee on Responses to Nutrients. Report No. 9. Nutr. Abstr. and Rev. (Series B) 62,
pp. 787±835.
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
285
Dhanoa, M.S., France, J., Siddons, R., Buchanan-Smith, J.G., 1995. A non-linear compartmental model to
describe forage degradation kinetics during incubation in polyester bags in the rumen. Br. J. Nutr. 73, 3±15.
Faichney, G.L., White, G.A., 1983. Methods for the analysis of feeds eaten by ruminants. Commonwealth
Scienti®c and Industrial Research Organisation, Melbourne, Victoria, pp. 4±9.
Gilmour, A.R., Cullis, B.R., Welham, S.J., Thompson, R., 1999. ASREML Reference Manual. N.S.W.
Agriculture Biometrics Bulletin No. 3., NSW Agriculture, Orange, Australia, pp. 7±46.
Huntington, J.A., Givens, D.I., 1997. Studies on in situ degradation of feeds in the rumen. 1. Effect of species,
bag mobility and incubation sequence on dry matter disappearance. Anim. Feed Sci. Technol. 64, 227±241.
Lopez, S., France, J., Dhanoa, M.S., Mould, F., Dijkstra, J., 1999. Comparison of mathematical models to
describe disappearance curves obtained using the polyester bag technique for incubating feeds in the rumen.
J. Anim. Sci. 77, 1875±1888.
Madsen, J., Hvelplund, T., 1994. Prediction of in situ protein degradability in the rumen. Results of a European
ringtest. Livest. Prod. Sci. 39, 201±212.
McDonald, I.M., 1981. A revised model for the estimation of protein degradability in the rumen. J. Agric. Sci.
Cambr. 96, 251±252.
Oddy, V.H., 1983. Feed requirements of sheep and cattle during drought using a Metabolizable Energy system.
AG Bulletin 3. Department of Agriculture NSW, Australia, pp. 12±13.
Oddy, V.H., Robards, G.E., Low, S.G., 1983. Prediction of in vivo dry matter digestibility from the ®bre and
nitrogen content of a feed. In: Robards, G.E., Packham, R.G. (Eds.), Feed Information and Animal
Production. Commonwealth Agricultural Bureau: Slough, United Kingdom, pp. 395±398.
érskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation
measurements weighted according to rate of passage. J. Agric. Sci. Cambr. 92, 449±503.
érskov, E.R., Hughes-Jones, M., Elimam, M.E., 1983. Studies on degradation and out¯ow rate of protein
supplements in the rumen of sheep and cattle. Livest. Prod. Sci. 10, 17±24.
Playne, M.J., Khumnalthong, W., Echevarria, M.G., 1978. Factors affecting the digestion of oesophageal ®stula
samples and hay samples in nylon bags in the rumen of cattle. J. Agric. Sci. 90, 193±204.
Prigge, E.C., Baker, M.J., Varga, G.A., 1984. Comparative digestion rumen fermentation and kinetics of forage
diets by steers and wethers. J. Anim. Sci. 59, 237±245.
Statistical Sciences, 1995. S-Plus Guide to Statistical and Mathematical Analysis version 3.3. Seattle: StatSci, a
division of MathSoft Inc., 24±18 to 24±19.
Sweeney, R.A., 1989. Generic combustion method for determination of crude protein in feeds: collaborative
study. J.A.O.A.C. 72, 770±774.
Uden, P., van Soest, P.J., 1984. Investigations of the in situ bag technique and a comparison of the fermentation
in heifers, sheep, ponies and rabbits. J. Anim. Sci. 58, 213±221.
Verbyla, A.P., Cullis, B.R., Kenward, M.G., Welham, S.J., 1999. The analysis of designed experiments and
longitudinal data by using smoothing splines. Applied Statistics 48, 269±311.
83 (2000) 273±285
The effect of animal species on in sacco degradation
of dry matter and protein of feeds in the rumen
K.S. Nandraa, R.C. Dobosb, B.A. Orchardc,*, S.A. Neutzed,
V.H. Oddyb, B.R. Cullisc, A.W. Jonesa
a
Elizabeth Macarthur Agricultural Institute, PMB 8, Camden, NSW 2570, Australia
b
NSW Agriculture Beef Industry Centre, Armidale, NSW 2350, Australia
c
Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650, Australia
d
Novartis Animal Health, Australasia Pty Ltd, 140-150 Bungaree Rd., Pendle Hill, NSW 2145, Australia
Received 17 November 1998; received in revised form 3 August 1999; accepted 11 November 1999
Abstract
A study was undertaken on lucerne (LUC), ryegrass (RG), kikuyu (KIK), soybean meal (SBM),
wheat grain (WG) and meat and bone meal (MBM) to determine the effect of animal species (sheep
versus cattle) on in sacco degradation of dry matter (DM) and protein. The approach of cubic
smoothing splines ®tted as a linear mixed model was used for the analysis of degradability of DM
and protein of feeds.
The quickly degradable DM (QDDM), cumulative slowly degradable DM (CSDDM), total
degradable DM (TDDM) and rate of degradation of slowly degradable DM of LUC, RG, KIK, SBM
and WG in the rumen of sheep and cattle were not different (p > 0.05). The QDDM, CSDDM
and TDDM of these forages and concentrates ranged from 22.9 to 57.6, 35.3 to 54.9 and 70.2 to
92.9 (g/100 g).
Estimates of in sacco quickly degradable protein (QDP), cumulative slowly degradable protein
(CSDP), total degradable protein (TDP), rate of degradation of slowly degradable protein of LUC,
RG, KIK and SBM were similar (p > 0.05) for sheep and cattle. For the WG a vertical shift was
found in the species cubic splines ®tted to logit transformed protein degradation data. This resulted
in QDP of 52.0 and 43.8 g/100 g, CSDP of 41.6 and 48.0 g/100 g and TDP of 93.6 and 91.6 g/100 g
for sheep and cattle, respectively.
In sacco degradation of DM and protein of MBM was irregular for both sheep and cattle,
consistent with extreme heterogeneity of the concentrate. # 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Degradability; In sacco; Protein; Dry matter; Sheep versus cattle
*
Corresponding author.
E-mail address: orcharb@agric.nsw.gov.au (B.A. Orchard).
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 2 9 - 7
274
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
1. Introduction
Information about the extent and rate of dry matter (DM) and protein degradation of
ruminant feeds in the rumen is crucial to match feed inputs to animal requirements. While
there is some information available regarding differences between sheep and cattle in
their ability to digest feed, there is little information on the degradation of components of
feed dry matter and protein in the rumen. The rumen in sacco technique has been adopted
as the standard method for determining DM and protein degradation. Sheep or cattle are
used depending on the facilities of the various research establishments. It is important to
understand the applicability of results obtained from one species, to the other species.
Playne et al. (1978) speculated that cattle had higher microbial activity and therefore faster
DM degradation relative to sheep. Few differences were observed between sheep and cattle
by (érskov et al., 1983) when comparing the in sacco degradation of dry matter of feeds after
9 or 24 h incubation. Prigge et al. (1984) have demonstrated that mature ruminant species
generally degrade feeds similarly. Huntington and Givens (1997) concluded that mature
ruminant species (sheep and cattle) when fed at maintenance, degrade DM of hay, soybean
meal and ®sh meal similarly as measured by the in sacco technique.
In a recent European ring test involving 23 laboratories, Madsen and Hvelplund (1994)
observed a large variation in in sacco estimates of protein degradability. There was no
apparent difference between sheep and cattle in in sacco rumen protein degradability,
although a possible species effect could have been masked by other factors in the
procedure varying among laboratories.
The present study was designed to determine whether in sacco degradability of DM
and protein, of some forages and concentrates differ between sheep and cattle fed the
same basal diet to maintain live weight.
2. Materials and methods
2.1. Animals and basal diet
Nine rumen cannulated Merino wethers (3±4 years old, mean live weight 55 kg) and
three rumen cannulated heifers (mean live weight 444 kg) were individually housed and
were offered 0.9 and 6.0 kg/day, respectively of the same diet, half at 0730 h and half at
1530 h. These quantities of feed were calculated to approximately maintain live weight
(Oddy, 1983). The diet consisted of 60% lucerne chaff (5±7 cm chop length) (904 g DM/
kg, 890 g organic matter (OM)/kg DM, 346 g acid detergent ®bre (ADF)/kg DM, 29.8 g
N/kg DM, estimated metabolisable energy (ME) concentration of 7.2 MJ/kg DM) and
40% calf pellets consisting mainly of cereal grain and roughage (912 g DM/kg, 910 g
OM/kg DM, 102 g ADF/kg DM, 32.3 g N/kg DM, estimated ME concentration of
9.6 MJ/kg DM) (Oddy et al., 1983).
2.2. Sample preparation
Samples of lucerne (Medicago sativa) (LUC), ryegrass (Lolium rigidum) (RG) and
kikuyu (Pennisetum clandestinum) (KIK) were dried in a forced draught oven at 558C.
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
275
Table 1
Experimental design for the degradability study
Species
animal
Period 1
(27 March 1995)a
Period 2
(3 April 1995)a
Period 3
(10 April 1995)a
Period 4
(18 April 1995)a
Heifer 1
Heifer 2
Heifer 3
Sheep 1
Sheep 2
Sheep 3
Sheep 4
Sheep 5
Sheep 6
Sheep 7
Sheep 8
Sheep 9
1,2,3
1,2,3
1,2,3
1
1
1
2
2
2
3
3
3
4,5,6
4,5,6
4,5,6
4
5
6
4
5
6
4
5
6
1,2,3
1,2,3
1,2,3
2
2
2
3
3
3
1
1
1
4,5,6
4,5,6
4,5,6
5
6
4
5
6
4
5
6
4
a
Feed types: 1, lucerne; 2, kikuyu; 3, ryegrass; 4, soybean meal; 5, meat and bone meal; 6, wheat.
Dried forages and concentrates (soybean meal (SBM), meat and bone meal (MBM) and
wheat grain (WG)) were ground through a Christie and Norris hammermill (Checley
Everitt & Associates, Victoria, Australia) ®tted with 4 and 2.25 mm screens, respectively.
A `test' sieving was done on the concentrates by shaking the feeds for 3 h on a 0.45 mm
sieve. Where losses were >5% (soybean meal and wheat), the feed was sieved in this
manner to remove ®ne particles before incubation in bags.
2.3. In sacco degradability study
The protocol for the measurement of in sacco degradability of feeds was similar to that
recommended by the Agricultural and Feed Research Council (AFRC, 1992), the only
difference being that cannulated animals were offered feed only twice daily.
Approximately 2 g sieved feed was weighed into each dacron bag (80 mm 120 mm,
36±38 mm pores). Bags were made of polyester single thread woven with welded
crossheads (Allied Screen Fabrics, Hornsby, New South Wales, Australia).
Table 1 presents the experimental design for this study of in sacco protein and dry
matter degradation in the rumen of sheep and cattle. Samples from the three forages and
three concentrates were placed in dacron bags in the rumen of three cattle and nine sheep
on four occasions (periods) at weekly intervals commencing 27 March 1995. The total
duration of the in sacco study was six weeks, two weeks adaptation period followed by
four weeks degradation studies. In any one period, each heifer received three test feeds
and each sheep one test feed, with the test feed allocation outlined in Table 1. Some
attempt was made to balance the allocation of the feed types to animals between periods,
though the particular allocation of feed types to animals and periods is not optimal in the
presence of animal or period effects. Six bags per test feed, were inserted in the rumen
simultaneously. Bags inserted in the rumen containing forages were withdrawn after 4, 8,
12, 24, 48 and 72 h, while those containing concentrates were withdrawn after 2, 4, 8, 12,
24 and 48 h. Bags were hand-rinsed brie¯y under cold tap water, then washed for 30 min
276
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
on a cold rinse cycle in a washing machine. The value at time zero was obtained by
washing the bag and test feed contents without incubation. The bags were then fully dried
at 558C in a forced-draught oven. Disappearance of DM was measured as the loss of
weight of the bag contents and the material left in the bag at each incubation time was
analysed for nitrogen content.
2.4. Chemical analyses
Organic matter of the basal diet was determined after ignition in a muf¯e furnace for
3 h at 6008C and the acid detergent ®bre (ADF) of the basal diet was estimated by re¯ux
according to Faichney and White (1983). The nitrogen content (N) of the basal diet, the
test feeds and the residue left in the nylon bags after incubation in the rumen of sheep and
cattle was determined by the combustion analyser method (Sweeney, 1989) using a
LECO FP-428.
Crude protein (CP, g/100 g DM) was calculated as N (g/100 g DM) 6.25. The CP
content of LUC, RG, KIK, SBM, MBM, WG was 23.00, 23.00, 25.81, 51.69, 51.56 and
12.50, respectively.
2.5. Statistical methods
Five of the six test feeds were considered for statistical analysis. MBM was not
included in this analysis because the degradation of MBM was irregular, consistent with
extreme heterogeneity (Fig. 1a and b).
Table 2 presents the decomposition of the terms in the analysis of the degradation data.
This is consistent with the experiment design being a cross-over design with animals,
periods, animal periods and animal periods samples being the strata in the design.
`Samples' represent a factor notionally randomized to sampling times within an animal
for a particular period.
Modelling of the degradation of DM or protein is via the cubic smoothing spline,
which is a smooth (that is, continuous in the ®rst derivative over the domain of de®nition)
function comprising piece-wise cubic polynomials between sampling times. The
decomposition of the terms in the animal period sample strata follows from Verbyla
et al. (1999).
Preliminary plots of the residuals of percent dry matter and protein degradation
indicated severe variance heterogeneity. This was ameliorated by use of the logit
transformation. The signi®cance of all ®xed terms was assessed using Wald tests and the
signi®cance of random terms was assessed using residual maximum likelihood ratio tests
(Verbyla et al., 1999). All analyses were performed using ASREML (Gilmour et al.,
1999).
érskov and McDonald, 1979 de®ne the exponential decay function f(t) eÿkt to be the
fraction of the feed which still remains in the rumen after t hours given k, the rate of
passage from the rumen. Using this rate of passage k, and denoting the percentage
degraded at time t by p(t), the corrected rate of disappearance is given by f(t) dp(t)/dt and
the cumulative slowly degradable protein up to time t (CDSP(t) or, CDSP for short) is
then obtained using
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
277
Fig. 1. (a) Original dry matter degradation data for sheep and cattle. (b) Original protein degradation data for
sheep and cattle.
278
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 2
Sources of variation in the linear mixed model analysis of degradation data
Term
Decomposition
Fixed or
Random (F/R)
Final model
protein
Final model
DM
constant
F
***
***
species
animalc1
F
R
b
***
**
periodc2
R
***
Constant
Animal
Period
Animal period
feed
species feed
animal periodc3
animal period feed (group)c4
F
F
R
R
***
***
***
Animal period samples
linear (ta)
spline (t)
deviations (random (t))d,e
species linear (t)
species spline (t)
deviations (species random (t))d,f
animal linear (t)c1
animal spline (t)
deviationsd
period linearc2
period spline (t)
deviationsd
feed linear (t)
feed spline (t)
deviationsd
species feed linear (t)
species feed spline (t)
deviationsd
animal period linear (t)c3
animal period spline (t)
deviationsd
group linear (t)c4
group spline (t)
F
R
R
F
R
R
R
R
R
R
R
R
F
R
R
F
R
R
R
R
R
R
R
***
**
***
*
***
***
***
***
R
***
***
*
Error
due to soybean meal within animal period
error
*
p < 0.05, **p < 0.01, ***p < 0.001, respectively.
`t' represents time of incubation in the rumen.
b
`' indicates the ®xed effect was included because of marginality constraints.
c1±4
indicate pairs of terms for which a covariance may be included.
d
Denotes terms estimating `deviations' which estimate systematic deviation at the particular mean level.
e
Represents deviations at the overall mean level.
f
Represent systematic deviations at the species mean level and so forth.
a
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
CSDP
Z
0
t
f u
dp u
du
du
279
(1)
In this study, the cumulative slowly degradable protein (CSDP) has been calculated
using f(t) eÿkt for k 0.02/h and with p(u) representing the equation of the backtransformed logit cubic spline ®tted for either an individual test feed or a particular
species by test feed combination. The accuracy of the results of this integration depends
on the precision of the S-PLUS (Version 3.4, Release 1) `integrate' function (Statistical
Sciences, 1995). The rate of disappearance of slowly degraded protein (SDP) has been
calculated using
dSDP
dp t eÿktÿg t g0 t
f t
dt
dt
1 eÿg t 2
where g(t) represents the particular test feed or test feed by species logit spline.
The total degradable protein (TDP) in the rumen at a particular ¯ow rate (k 0.02)
was calculated as the sum of the quickly degraded protein (QDP) (or zero hour protein)
and the CSDP. An analysis analogous to that performed for protein degradation was
performed for dry matter degradation with comparable calculations for total degradable
dry matter (TDDM), quickly degradable dry matter (QDDM) and cumulative slowly
degradable dry matter (CSDDM).
3. Results
3.1. Protein degradation
The salient features of the ®nal model were an interaction of feed type with the linear
component of the cubic smoothing spline, an interaction between species and feed type,
and some evidence of a differential curvature in the cubic smoothing spline between feeds
(see Table 2). The ®tted curves from this model are presented in Fig. 2. The feed type by
species interaction resulted in a signi®cant (p < 0.01) difference between sheep and cattle
for wheat only.
The value of QDP for each test feed is given in Table 3, which also includes the value
of QDP for each species by feed curve. The corresponding values for CSDP from (1) and
TDP are also presented.
While the values of QDP, CSDP and TDP varied between feeds, there were no
differences between sheep and cattle for LUC, RG, KIK and SBM. The difference in the
QDP between cattle and sheep for WG (43.8 and 52.0 g/100 g, respectively) may re¯ect a
`lag' in protein degradation for cattle but this was not included in the analysis as there
was insuf®cient data in the 0±4 h period. The calculated CSDP of WG at a rumen out¯ow
rate of 0.02 per hour appears somewhat higher in cattle (48.0 g/100 g) than in sheep
(41.6 g/100 g), but the TDP of WG for cattle and sheep are similar (91.8 and 93.6 g/
100 g, respectively).
The rate of degradation of SDP for the test feed curves and for the feed curves of each
species, with fractional rumen out¯ow rate k of 0.02 per hour, is presented in Table 4. The
280
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Fig. 2. Protein degradation curves for sheep and cattle on the logit and percentage scale.
281
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 3
Quickly degradable protein (QDP), cumulative slowly degradable protein (CSDP) at fractional out¯ow rate of
0.02 per hour and corresponding total degradable protein (TDP) measured as percentage of total protein
Overall feed
QDP
CSDPa
TDP
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
39.9
28.5
20.6
47.9
55.3
45.0
53.8
66.3
44.8
78.7
84.9
82.3
86.9
92.7
Heifer by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
40.6
28.0
21.9
43.8
55.3
44.6
54.1
65.6
48.0
78.7
85.2
82.1
87.5
91.8
Sheep by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
23.4
39.1
29.1
19.5
52.0
55.3
45.4
53.6
67.0
41.6
78.7
84.5
82.7
86.5
93.6
a
CSDP was calculated assuming the cubic spline to be linear passed the ®nal data point and using t ! 1,
suf®cient for consistency to 0.0001.
Table 4
Rate of degradation (percentage per hour) of slowly degradable protein in the rumen at fractional out¯ow rate of
0.02 per hour
Overall feed
Hours
0
2
4
8
12
24
48
72
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.03
3.27
3.89
6.04
2.97
3.95
3.48
4.65
5.50
2.99
3.51
3.40
4.87
4.32
2.57
2.29
2.75
3.90
2.06
1.85
1.24
1.83
2.84
0.85
0.60
0.18
0.44
0.43
0.09
0.11
0.04
0.06
0.02
0.01
0.02
0.02
0.01
±
±
Heifers by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.05
3.23
4.06
5.96
2.98
3.95
3.44
4.79
5.64
2.99
3.50
3.38
4.93
4.60
2.57
2.27
2.76
3.84
2.30
1.85
1.22
1.85
2.25
0.97
0.60
0.18
0.44
0.04
0.10
0.11
0.04
0.06
0.02
0.01
0.02
0.01
0.01
±
±
Sheep by feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
2.73
4.00
3.32
3.72
6.04
2.97
3.94
3.50
4.50
5.29
2.98
3.52
3.41
4.78
4.02
2.57
2.32
2.74
3.95
1.84
1.85
1.26
1.81
2.42
0.74
0.60
0.19
0.43
0.46
0.07
0.11
0.04
0.06
0.03
0.01
0.02
0.02
0.01
±
±
282
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Fig. 3. Dry matter degradation curve for test feeds on the percentage scale.
maximum degradation rate of protein occurred in the 0±4 h period after bag insertion. No
differences are apparent in the rate of degradation of SDP at different times between
sheep and cattle for LUC, RG, KIK or SBM. However, for WG the rate of degradation of
SDP appears to be somewhat higher in cattle between 2 and 24 h after insertion of the
feed bags, as compared to sheep.
3.2. Dry matter degradation
The important features of the ®nal model for DM degradation included a
signi®cant (p < 0.001) interaction of feed type with the linear component of the cubic
smoothing spline and signi®cantly different (p < 0.001) curvature due to feed type
(Table 2).
In the model for DM degradation there was no evidence of species or species by feed
differences (p > 0.05). The DM degradation curves for each test feed are given in Fig. 3.
While the estimated values of quickly degradable dry matter (QDDM), cumulative
slowly degradable dry matter (CSDDM), and total degradable dry matter (TDDM) and
rate of degradation of SDDM, varied between test feeds, no difference for these
parameters between sheep and cattle for LUC, RG, KIK, SBM and WG was evident.
Therefore, Tables 5 and 6 present the overall QDDM, CSDDM, TDDM and rate of
degradation of SDDM (with k 0.02 per hour) for the test feeds only.
283
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
Table 5
Quickly degradable dry matter (QDDM), cumulative slowly degradable dry matter (CSDDM) at rumen out¯ow
rate of 0.02 per hour and corresponding total degradable dry matter (TDDM) measured as percentage of total
DM
Overall feed
QDDM
CSDDMa
TDDM
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
22.9
32.5
31.0
33.8
57.6
48.7
37.7
45.3
54.9
35.3
71.6
70.2
76.3
88.7
92.9
a
CSDDM was calculated assuming the cubic spline to be linear passed the ®nal data point and using t ! 1,
suf®cient for consistency to 0.0001.
Table 6
Rate of degradation (percentage per hour) of slowly degradable dry matter in the rumen at a fractional rumen
out¯ow rate of 0.02 per hour
Overall feed
Kikuyu
Lucerne
Ryegrass
Soybean meal
Wheat
Hours
0
2
4
8
12
24
48
72
1.32
2.01
1.47
4.12
7.22
1.41
2.26
1.55
4.08
5.25
1.60
2.74
1.77
3.59
2.91
2.01
2.32
2.16
3.04
0.81
1.91
1.08
1.88
2.07
0.37
0.72
0.17
0.55
0.34
0.12
0.10
0.06
0.07
0.03
0.03
0.04
0.01
0.04
±
±
4. Discussion
4.1. Parametric model
The traditional approach to the analysis of degradation curves is to ®t a nonlinear model, typically the exponential model (érskov and McDonald, 1979).
There has been evidence to suggest that the exponential model may not be entirely
appropriate (McDonald, 1981; Dhanoa et al., 1995; Huntington and Givens, 1997; Lopez
et al., 1999).
All of the competing models are continuous and smooth, in the sense that they are
all functions of the incubation time which exhibit continuity in the ®rst derivative.
The biological basis for these models is essentially empirical, with the choice of
model determined by statistical rather than entirely biological reasons (Lopez et al.,
1999).
The cubic smoothing spline represents a semi-parametric alternative which avoids
choosing a parametric model. The estimation of all key biological parameters such as
CSDDM and CSDP is straightforward. The additional advantage of the cubic smoothing
spline is that other relevant sources of variation such as animal and period effects can be
easily incorporated in the cubic smoothing spline's linear mixed model formulation
(Verbyla et al., 1999).
284
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
4.2. Degradability
Following the ring tests, the Technical Committee on responses to nutrients (AFRC,
1992) made no de®nitive recommendation regarding the species of animal to be used for
protein degradability. Therefore, the present study focused on determining species
differences for protein degradability of concentrates and forages.
Although feed and feed species were signi®cant in the ®nal model for protein
degradation in the rumen, the only test feed for which these terms were associated with a
signi®cant vertical shift in logit curves was WG. No signi®cant species differences were
evident for protein degradation for the forages studied (LUC, RG and KIK). In the case of
SBM, signi®cant heterogeneity of variance was detected but was not associated with any
species differences in protein degradability.
For the forage and concentrate feeds examined (except MBM), parameters for DM
degradation were independent of the species of animal (sheep or cattle). There was no
signi®cant species effect and no interaction of species with either feed or period.
Therefore, a single curve for each test feed from either sheep or cattle (on the logit scale)
may be used to represent the DM degradation in the rumen. The results of the present
study are in accordance with the ®ndings of Huntington and Givens (1997) who found no
differences between host species on in sacco DM disappearance of hay, SBM and ®sh
meal. Uden and van Soest (1984) also found that mature ruminant species degrade the
®bre fraction of feeds similarly.
5. Conclusions
The ®ndings of this planned study have quanti®ed no difference between sheep and
cattle in the in sacco degradability of DM for LUC, RG, KIK, SBM and WG. In sacco
degradability of protein (QDP, CSDP and TDP) of LUC, RG, KIK and SBM were also
found to be similar in cattle and sheep.
For WG, there were species differences in the in sacco degradation characteristics of
protein, the nature of which was a vertical shift in the logit scale degradation splines.
Future work needs to examine the difference in the in sacco degradability of protein of
various grains.
Acknowledgements
The authors wish to acknowledge the assistance of Ms. K. Riley in the animal house
and Dr. R. Hegarty for his valuable comments for the preparation of the manuscript.
References
Agricultural and Food Research Council (AFRC), 1992. Nutritive requirements of ruminant animals: Protein.
AFRC Technical Committee on Responses to Nutrients. Report No. 9. Nutr. Abstr. and Rev. (Series B) 62,
pp. 787±835.
K.S. Nandra et al. / Animal Feed Science and Technology 83 (2000) 273±285
285
Dhanoa, M.S., France, J., Siddons, R., Buchanan-Smith, J.G., 1995. A non-linear compartmental model to
describe forage degradation kinetics during incubation in polyester bags in the rumen. Br. J. Nutr. 73, 3±15.
Faichney, G.L., White, G.A., 1983. Methods for the analysis of feeds eaten by ruminants. Commonwealth
Scienti®c and Industrial Research Organisation, Melbourne, Victoria, pp. 4±9.
Gilmour, A.R., Cullis, B.R., Welham, S.J., Thompson, R., 1999. ASREML Reference Manual. N.S.W.
Agriculture Biometrics Bulletin No. 3., NSW Agriculture, Orange, Australia, pp. 7±46.
Huntington, J.A., Givens, D.I., 1997. Studies on in situ degradation of feeds in the rumen. 1. Effect of species,
bag mobility and incubation sequence on dry matter disappearance. Anim. Feed Sci. Technol. 64, 227±241.
Lopez, S., France, J., Dhanoa, M.S., Mould, F., Dijkstra, J., 1999. Comparison of mathematical models to
describe disappearance curves obtained using the polyester bag technique for incubating feeds in the rumen.
J. Anim. Sci. 77, 1875±1888.
Madsen, J., Hvelplund, T., 1994. Prediction of in situ protein degradability in the rumen. Results of a European
ringtest. Livest. Prod. Sci. 39, 201±212.
McDonald, I.M., 1981. A revised model for the estimation of protein degradability in the rumen. J. Agric. Sci.
Cambr. 96, 251±252.
Oddy, V.H., 1983. Feed requirements of sheep and cattle during drought using a Metabolizable Energy system.
AG Bulletin 3. Department of Agriculture NSW, Australia, pp. 12±13.
Oddy, V.H., Robards, G.E., Low, S.G., 1983. Prediction of in vivo dry matter digestibility from the ®bre and
nitrogen content of a feed. In: Robards, G.E., Packham, R.G. (Eds.), Feed Information and Animal
Production. Commonwealth Agricultural Bureau: Slough, United Kingdom, pp. 395±398.
érskov, E.R., McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation
measurements weighted according to rate of passage. J. Agric. Sci. Cambr. 92, 449±503.
érskov, E.R., Hughes-Jones, M., Elimam, M.E., 1983. Studies on degradation and out¯ow rate of protein
supplements in the rumen of sheep and cattle. Livest. Prod. Sci. 10, 17±24.
Playne, M.J., Khumnalthong, W., Echevarria, M.G., 1978. Factors affecting the digestion of oesophageal ®stula
samples and hay samples in nylon bags in the rumen of cattle. J. Agric. Sci. 90, 193±204.
Prigge, E.C., Baker, M.J., Varga, G.A., 1984. Comparative digestion rumen fermentation and kinetics of forage
diets by steers and wethers. J. Anim. Sci. 59, 237±245.
Statistical Sciences, 1995. S-Plus Guide to Statistical and Mathematical Analysis version 3.3. Seattle: StatSci, a
division of MathSoft Inc., 24±18 to 24±19.
Sweeney, R.A., 1989. Generic combustion method for determination of crude protein in feeds: collaborative
study. J.A.O.A.C. 72, 770±774.
Uden, P., van Soest, P.J., 1984. Investigations of the in situ bag technique and a comparison of the fermentation
in heifers, sheep, ponies and rabbits. J. Anim. Sci. 58, 213±221.
Verbyla, A.P., Cullis, B.R., Kenward, M.G., Welham, S.J., 1999. The analysis of designed experiments and
longitudinal data by using smoothing splines. Applied Statistics 48, 269±311.