Ž .
grday SEM s 5 when flavored pomace was not paired with cellulose, and 163 grday Ž
. SEM s 5 when flavored pomace was paired with cellulose.
Lambs were tested for preference during 20 min, as described for Experiment 1 Ž
. Table 2 .
2.2.4. Trial 4 The objective of this trial was to determine if duration of exposure influenced
Ž preference for grape pomace–starch relative to grape pomace. From days 1 to 15 Period
. Ž
. Ž
. 1 , lambs 35 kg BW from Experiment 1 Trial 4 were offered two novel foods — a
70–30 mixture of grape pomace–starch and grape pomace — simultaneously from 0800 h to 0820 h. Refusals were collected and intake of each food was calculated.
Ž .
From days 16 to 21 Period 2 , lambs were offered 500 g of each food described Ž
above, but the amount of exposure was increased to from 20 minrday to 8 hrday 0800 .
h to 1600 h daily . At 1600 h, refusals were collected and weighed and lambs received 1500 g of alfalfa pellets.
On day 22, lambs were offer both foods for only 20 min. Intake of each food was Ž
. recorded and compared with the last day of Period 1 Table 2 .
2.2.5. Trial 5 The objective of this trial was to determine if lambs generalized an aversion from a
grain high in starch to another food that contained starch. After Trial 4, lambs were Ž
. treated with LiCl as described for Trial 2; lambs consumed 372 g SEM s 51 of milo
prior to receiving LiCl, and no milo following the LiCl infusion. After LiCl infusions, Ž
. lambs in the LiCl–Milo group did not eat milo, whereas Controls ate 363 g SEM s 32 .
3. Statistical analyses
3.1. Experiment 1 Food intake during preference tests was analyzed as a split-plot design with animals
Ž .
nested within group naive and experienced . Group was the between-subject factor and Ž w
x w
treatment received during conditioning 1 milo supplementation or 2 no supplementa- x.
tion was the within-subject factor. Alfalfa intake was analyzed as a repeated measures
Ž .
design; daily days 1, 2, 3 intake was the repeated measure. Means were compared with LSD tests.
3.2. Experiment 2 Food intake in Trials 1–3 and 5 was analyzed as a split-plot with lambs nested within
Ž w
x w
x. groups. Group 1 or 2 Trials 1 and 3 ; LiCl–Milo or Control Trials 2 and 5
was the Ž
. between-subject factor; test foods pomace–starch; pomace–cellulose; Trials 1 and 2 ,
Ž period preference test before LiCl administration; preference test after LiCl administra-
. Ž
tion; Trials 2 and 5 and treatment received during conditioning cellulose infusions; no .
cellulose infusions, Trial 3 were the within-subject factors in the split-plot. Day was the repeated measure in Trial 1.
Food intake in Trial 4 was analyzed as a split-plot design. Lambs and test foods Ž
. Ž
. pomace–starch; pomace were whole-plot factors and day repeated measure was the
sub-plot. Intake of the test foods during the last day of Period 1, and the day after Period 2, was analyzed as a split-plot with lambs and test foods as the whole plot and day as the
sub-plot.
4. Results
4.1. Experiment 1 4.1.1. Trial 1
The objective of this trial was to determine if lambs acquired a preference for Ž
. flavored straw eaten immediately after they ate an energy supplement milo . Lambs did
not differ in initial preference for the flavors to be associated with milo during Ž
. Ž
. conditioning: 12 vs. 11 g experienced group and 12 vs. 10 g naive group for
Ž .
treatments 1 and 2, respectively P .05; SEM s 3 . Similarly, no preference was
Ž .
evident after conditioning with milo Fig. 1A, Trial 1 , as reflected in non-significant Ž
. treatment and group by treatment effects P 0.05 .
4.1.2. Trial 2 The objective of this trial was to determine if restricting the supply of energy from
the basal diet increased preference for flavored straw eaten after lambs consumed milo. Lambs in the experienced group preferred the flavored straw consumed after milo
Ž .
ingestion Fig. 1A, Trial 2; treatment by group interaction P - 0.1 . When lambs were offered milo along with the flavored straw in the second preference test, they strongly
Ž preferred milo to flavored straw 194 g vs. 5 g and 4 g for milo, flavored straw paired
with milo, and flavored straw not paired with milo, respectively, P - 0.001; Fig. 1B, .
Ž Trial 2 . Preferences did not differ between groups group and treatment by group
. interaction; P 0.05 .
4.1.3. Trial 3 This trial determined lambs’ preference for flavored straw eaten after an infusion of
milo into the rumen, rather than after eating milo. Lambs strongly preferred the flavored Ž
straw paired with intraruminal infusions of milo 46 g vs. 10 g for Treatments 1 and 2, .
respectively, P - 0.001, SEM s 5.77 , and preferences did not differ between groups Ž
. group effect and treatment by group interaction; P 0.05; Fig. 1A, Trial 3 . When
lambs received milo and flavored straw in the second preference test, they preferred Ž
milo flavored straw paired with milo flavored straw not paired with milo 197 g vs. .
16 g and 3 g, respectively, P - 0.001; Fig. 1 B, Trial 3 . Preferences did not differ Ž
. between groups group effect and treatment by group interaction; P 0.05 .
Ž Prior ingestion of milo affected intake of alfalfa. Intake of alfalfa during a 1-h
. period was higher after lambs ate 200 g of milo, or received 200 g of milo by infusion,
Ž than when no milo was offered: 799, 797, and 688 g, respectively
P - 0.001; .
SEM s 24 .
Ž . Ž
. Fig. 1. Experiment 1. A Mean SEM intake of flavored straw by lambs during preference tests after four
Ž .
Ž .
Ž conditioning periods. During conditioning even days milo was ingested Trials 1, 2 and 4 or infused Trial
. 3 into the rumen before straw consumption. One group of lambs had previous experience with straw and milo
Ž .
Ž .
Ž .
Ž .
Exp. , and another group had moderate Trial 1 or no Trial 4 experience Naive with those foods before Ž
. Ž . Ž
. conditioning. Means differed only for Exp. Trial 2 P - 0.1 . B Mean SEM intake of flavored straw and
Ž .
milo by lambs during two preference tests conducted after Trials 2 and 3. During conditioning even days , Ž
. Ž
. milo was ingested Trial 2 or infused Trial 3 into the rumen before straw consumption. One group of lambs
Ž .
Ž .
had experience with straw and milo Exp. , and another group had less experience with those foods Naive Ž
. before conditioning. Milo intake was higher than straw intake in both trials P - 0.001 , and preference of
Ž .
flavored straw paired with milo flavored straw not paired with milo in Trial 3 P - 0.001 .
4.1.4. Trial 4 The objective of this trial was to determine if the complete lack of experience with
flavored straw and milo affected the acquisition of a preference for flavored straw, when
Ž .
Ž .
Ž .
Fig. 2. Experiment 2 Trial 1 . Mean SEM intake of pomace–starch and pomace–cellulose 70–30 when Ž
. both foods were novel to all lambs. Means differed for all days P - 0.001 .
straw ingestion immediately followed milo ingestion. No preference was found after Ž
. conditioning with milo Fig. 1A, Trial 4 , as reflected in non-significant treatment or
Ž .
group by treatment effects P 0.05 . 4.2. Experiment 2
4.2.1. Trial 1 This trial determined if lambs discriminated between novel foods of different energy
densities. Lambs strongly preferred the pomace–starch to the pomace–cellulose mixture
Ž .
Ž .
Fig. 3. Experiment 2 Trial 2 . Mean SEM intake of pomace–starch and pomace–cellulose before and after Ž
. LiCl was administered 300 mgrkg BW to two groups of lambs. The Milo–LiCl group received milo before
Ž .
LiCl infusions whereas the Control group received only LiCl. Intake of pomace–starch differed P - 0.001 Ž
. between groups after LiCl administrations when the proportion pomace–starch was 70–30 P - 0.001 .
Ž .
81 g vs. 5 g, respectively; P - 0.001; SEM s 5 . This preference was evident from the first day of exposure and increased throughout days, as evidenced by a significant test
Ž .
food by day interaction P - 0.001; Fig. 2 . Preferences did not differ between groups Ž
. group and test food by group effects P 0.05 .
4.2.2. Trial 2 The objective of this trial was to determine if lambs generalized an aversion from a
Ž .
Ž .
familiar grain milo to a novel food pomace that contained starch. After pairing milo
Ž . Ž .
Ž .
Ž .
Fig. 4. Experiment 2 Trial 4 . A Mean SEM intake of pomace–starch 70–30 and pomace by lambs. Both foods were offered for 20 minrday and they were both novel to all lambs. Means differed on days 9, 11,
Ž . Ž .
Ž .
Ž .
12, 14 and 15 P - 0.001 . B Mean SEM intake of pomace–starch 70–30 and pomace by lambs. Both Ž
. foods were offered for 8 hrday. Means differed on all days P - 0.001; day 3 P - 0.05 .
with LiCl, lambs still preferred pomace–starch to pomace–cellulose, but the pattern of Ž
. preference changed group by food by period interaction; P - 0.05; Fig. 3 . Intake of
Ž .
the pomace–starch mix decreased in both groups after the LiCl treatment P - 0.001 , but intake of pomace–starch was lower for lambs in the Milo–LiCl group than for lambs
Ž .
in the Control group P - 0.001; Fig. 3 . When the proportion of starch was increased from 70–30 to 30–70 in the pomace–
Ž .
starch mix, no differences were found in the intake of the test foods P 0.05; Fig. 3 . Ž
Preferences did not differ between groups group and test food by group effects; .
P 0.05 . 4.2.3. Trial 3
The objective of this trial was to determine if low preferences for pomace–cellulose mix were due mainly to the oral or to the post-ingestive effects of cellulose. Lambs did
not differ in preference for flavored pomace prior to conditioning: 47 g vs. 45 g for Ž
. Treatments 1 and 2, respectively P .05; SEM s 9 . Cellulose conditioning did not
Ž affect the development of preferences for flavored pomace 72 g vs. 84 g for Treatments
. 1 and 2, respectively; P 0.05; SEM s 12 .
4.2.4. Trial 4 The objective of this trial was to determine if lambs discriminated between novel
foods of different energy densities and if the amount of exposure affected their response. There were no differences in intake of pomace and pomace–starch mix during the first 8
Ž .
days of exposure P 0.05; Fig. 4 . Intake of grape pomace was higher than intake of Ž
. grape pomace–starch on days 9, 11, 12, 14 and 15
P - 0.001 , which caused a Ž
. significant test food by day interaction
P - 0.05; Fig. 4 . Average intake of the Ž
pomace–starch mix and pomace across the first 15 days did not differ 24 g vs. 31 g,
Ž .
Ž .
Ž .
Fig. 5. Experiment 2 Trial 4 . Mean SEM intake of pomace–starch 70–30 and pomace by lambs on the Ž
. Ž
. last day of 20-min exposures Period 1 and after 8-h exposures Period 2 . Mean intake decreased for pomace
Ž .
and increased for pomace–starch P - 0.001 .
Ž .
Ž .
Fig. 6. Experiment 2 Trial 5 . Mean SEM intake of pomace–starch and pomace before and after LiCl Ž
. administration 300 mgrkg BW to two groups of lambs. The Milo–LiCl group received milo before LiCl
infusions whereas the Control group only LiCl. Intake of pomace–starch did not differ between groups Ž
. P 0.05 .
. respectively; P 0.05; SEM s 5 . When exposure increased to 8 hrday, intake of
pomace was higher than intake of the pomace–starch mix on the first 2 days, but this Ž
pattern reversed from day 3 to the end of the trial food by day interaction P - 0.001; .
Fig. 4 . Average intake of the pomace–starch mix was higher than intake of grape Ž
. pomace 252 g vs. 191 g; P - 0.1; SEM s 22 .
When we compared the last 20 min preference test of Period 1 with the 20 min preference test performed after Period 2, intake of the pomace–starch mix increased
Ž .
Ž .
P - 0.001 , whereas intake of pomace decreased P - 0.05 after Period 2, as reflected Ž
. in a significant test food by day interaction P - 0.001; Fig. 5 .
4.2.5. Trial 5 The objective of this trial was to determine if lambs generalized an aversion from a
Ž .
Ž .
familiar grain milo to a novel food pomace that contained starch. Intake of the Ž
. pomace–starch mix decreased after LiCl administrations from 104 g to 70 g , but intake
Ž .
of pomace did not change across days 33 g to 28 g . There were significant differences Ž
. Ž
. due to day P - 0.05 and food by day P - 0.05 , but no differences between groups,
Ž .
group by food, group by day, or group by food by day interactions P 0.05; Fig. 6 .
5. Discussion
