Ž .
during 9 consecutive days. At 1200 all lambs received alfalfa pellets 1400 grlambrday Ž
that provided approximately 80 of their daily digestible energy requirements NRC, .
1985 . 2.6.2. IndiÕidual tests
After conditioning, and immediately before being tested for straw consumption, Ž
. lambs in Group 1 were given intraruminal infusions of a starch 100 grlambrday and
Ž .
lambs in Group 2 received infusions of water 250 mlrlambrday . We recorded the time each lamb spent eating straw during 5 min. Lambs were observed individually and
bouts of inactivity were excluded from calculations of feeding time. We determined the amount of straw ingested as the difference between the weight of food offered and that
Ž .
remaining after 5 min. These data were used to calculate intake rate grmin . At noon all lambs were offered alfalfa pellets, as described during conditioning.
2.6.3. IndiÕidual tests without infusions Lambs were tested as described before but without starch or water administrations.
2.7. Statistical analyses Straw intake, intake rate, number of bites, bite rate, bite size and active feeding time
Ž were analyzed as a split-plot design with lambs nested within groups. Group 1: starch
. or 2: no starch was the between-lamb factor. Pairs of lambs were the between-subject
Ž .
factor when lambs were conditioned as a pair Conditioning; Trial 2 . When tests were Ž
. repeated on different days — Trial 1: 3 days; Trial 2: 4 days Conditioning — Pairs ;
Ž .
Ž .
Trial 3: 2 days Individual Tests after Periods 1 and 2 ; Trial 4: 9 days Conditioning — day was the repeated measure in the analysis. Means were compared using the LSD
test.
3. Results
3.1. Initial indiÕidual tests There were no differences in straw intake between groups of lambs before applying
Ž . Ž
. the treatments starch, water
P 0.05 . All the measurements recorded during testing Ž
. were low and variable Table 1 .
3.2. Trial 1 During Trial 1, lambs’ ability to ingest wheat straw was not affected by infusing
Ž .
starch into the rumen P 0.05 . Intake values and active feeding times were still low Ž
. and variable for both groups of lambs Table 1 . For instance, several lambs in Groups 1
Ž .
Ž .
n s 4, 1, and 0 and 2 n s 3, 3, and 4 consumed - 1 g of straw during tests 1, 2 and 3, respectively.
Table 1 Straw intake, rate of straw intake, number of bites, bite rate and active feeding time by two groups of lambs
that received or not intraruminal infusions of starch associated with straw ingestion Straw
Rate of No. of
Bite Intake
Active intake
straw intake bites
rate per bite
feeding time Ž .
Ž .
Ž .
Ž .
Ž .
g grmin
bitesrmin grbite
min Initial individual
c
Tests G1
4 3.4
15 7.3
0.35 2.7
G2 5
5.4 14
7.8 0.67
1.9 S.E.M.
1.9 2.2
4.5 1.7
0.20 0.7
Trial 1 Starch
6 5.7
10 6.9
0.97 1.5
No starch 4
9.8 6
6.7 1.47
1.3 S.E.M.
1.2 3.4
2.3 0.9
0.52 0.5
Trial 2 Conditioning Pairs
a a
a
Starch 22
4.3 33
6.6 0.67
5.0
b b
b
No starch 5
0.9 17
3.5 0.29
4.9 S.E.M.
4.2 0.8
6.1 1.2
0.05 0.04
Individual Tests
a a
a a
Starch 8
2.3 13
3.8 0.59
3.1
b b
b b
No starch 2
1.0 5
2.8 0.31
2.0 S.E.M.
1.9 0.5
2.8 0.5
0.07 0.7
Trial 3 Individual Tests
a a
a a
a
Starch 24
5.4 29
6.7 0.86
4.3
b b
b b
b
No starch 5
1.4 10
2.6 0.54
3.7 S.E.M.
3.1 0.6
4.1 0.7
0.09 0.5
Without infusions
a a
a a
Starch 14
2.8 30
6.0 0.49
5.0
b b
b b
No starch 2
0.6 8
1.9 0.54
4.3 S.E.M.
1.8 0.4
4.2 0.9
0.16 0.4
d
Trial 4 Individual Tests
a a
Starch 21
5.4 –
– –
3.9
b b
No starch 9
2.6 –
– –
3.1 S.E.M.
4.6 0.9
– –
– 0.7
Without infusions
a a
Starch 19
4.3 –
– –
4.0
b b
No starch 6
2.5 –
– –
2.1 S.E.M.
4.7 1.1
– –
– 0.7
a,b
Ž .
Pairs of means within a column lacking a common superscript differ P -0.1 .
c
G1: Group to be conditioned with infusions of starch during Trials 1 to 4. Group 2: Group to be conditioned with infusions of water during Trials 1 to 4.
d
Not measured.
3.3. Trial 2 3.3.1. Conditioning — pairs
In Trial 2, we increased the exposure to straw by conditioning animals in pairs. Lambs also had further experience with the postingestive consequences of starch and
this treatment began to affect straw consumption. Pairs of lambs that received intrarumi- Ž
. nal infusions of starch had higher intakes, intake rates P - 0.05 and larger bite sizes
Ž .
Ž .
P - 0.001 than lambs that had infusions of water Table 1 . The number of bites and Ž
. bite rate also increased, but the differences were not significant P 0.05; Table 1 .
3.3.2. IndiÕidual tests Ž
. Ž
. Lambs given starch ate more P - 0.05 straw, at a faster rate P - 0.1 , than lambs
Ž .
Ž .
given water Table 1 . Lambs supplemented with starch also took more bites P - 0.1 Ž
. Ž
. of larger sizes P - 0.05 than lambs infused with water Table 1 .
3.4. Trial 3 3.4.1. Conditioning — groups
The number of lambs consuming straw during conditioning declined toward the end of the 40-min interval, particularly for the Group that was not infused with starch. The
Ž .
Fig. 1. Number of lambs ingesting straw secured in wooden frames; 30 cm height during two conditioning Ž
. periods of 4 days each. Lambs were conditioned as two groups Groups 1 and 2 during 40 minrday. The
number of lambs consuming straw was recorded every 2 min. Group 1 received intraruminal infusions of Ž
. Ž
. starch 100 grlambrday and Group 2 intraruminal infusions of water 250 mlrlambrday before consuming
straw.
number of lambs consuming straw in the 2-min scans was in general higher for the Ž
. group infused with starch than for the group infused with water Fig. 1 .
3.4.2. IndiÕidual tests The effects of infusing starch became stronger in Trial 3 as lambs had further
experience ingesting straw and receiving starch infusions. Lambs conditioned with Ž
. Ž
. starch consumed more straw
P - 0.01 and took more bites P - 0.01 than lambs Ž
. conditioned with water Table 1 . Moreover, after the second period of conditioning
Ž .
Ž .
Period 2 , lambs infused with starch increased straw intake from 21 to 27 g; P - 0.05 Ž
. Ž
and number of bites from 24 to 35; P - 0.05 compared to Period 1 Group by day .
interaction, P - 0.05 . Ž
. Lambs given starch ate more straw per unit of time P - 0.001 , maintained a more
Ž .
Ž .
rapid rate of biting P - 0.01 , and took larger bites P - 0.05 than lambs given water. Ž
Thus, active feeding time was the only variable not affected by the treatments P 0.05; .
Table 1 . 3.4.3. IndiÕidual tests without infusions
Ž .
Lambs given starch continued to display higher intakes P - 0.001 , intake rates
Ž .
Ž .
Ž .
P - 0.001 , number of bites P - 0.001 and bite rates P - 0.01 than lambs given Ž
. water, even after starch was no longer administered Table 1 . Bite size and active
Ž .
feeding time did not differ between groups P 0.05; Table 1 .
Ž .
Fig. 2. Intake of straw 1–2 cm particle size by two groups of lambs during 9 days of conditioning. Lambs in Group 1 received intraruminal infusions of starch and lambs in Group 2 intraruminal infusions of water
Ž .
immediately before straw consumption. Means differed after day 3 P -0.05 .
3.5. Trial 4 3.5.1. Conditioning
Groups did not differ in straw intake during the first 3 days of conditioning Ž
. P 0.05; Fig. 2 . After day 3, intake of straw was higher for lambs infused with starch
Ž .
Ž . Ž
Group 1 than for lambs infused with water Group 2 Group by day interaction,
. P - 0.05; Fig. 2 . Average intake of straw across days was 44 g for lambs in Group 1
Ž .
and 27 g for lambs in Group 2 P 0.05; S.E.M.s 10 . 3.5.2. IndiÕidual tests
Lambs conditioned with starch ate more straw at higher rates than lambs conditioned Ž
. with water P - 0.10; Table 1 .
3.5.3. IndiÕidual tests without infusions Ž
. Ž
. Lambs treated with starch ate more straw P - 0.10 , at faster rates P - 0.15 , and
Ž spent more time feeding during the 5-min tests than lambs treated with water P - 0.10;
. Table 1 , even when starch infusions were suspended.
4. Discussion
