2. Materials and methods
Ž Twenty-four lambs Finn–Targhee–Columbia–Polypay crossbreeds of both sexes;
. average weight 25 kg were purchased at 6 weeks of age and moved to the Green
Canyon Ecology Center in Logan, UT. The same lambs were used in all three trials. At 3 months of age, lambs were blocked by weight and assigned to separate outdoor pens.
Ž .
Ž .
Pens 2.4 = 9.8 m were situated in two adjacent rows 12 pensrrow that shared a Ž
common shelter area. The shelter area was an aluminum canopy 1.8 m wide and 1.7 m .
from the ground supported by metal legs that provided shade for lambs during mid-day heat. Inside each pen were three metal panels, placed on alternating sides of the pen, that
extended 3r4 of the width of the pen. The panels created a maze-like environment with three distinct foraging locations approximately 3.3 m apart. Throughout the trials, lambs
had access to trace mineral salt with Bovatec and water, located at the furthest end of the pen from the shelter. The basal diet was offered at the opposite end of the pen from the
shelter, adjacent to the water, so that lambs became accustomed to feeding at the location most distant from the shelter.
2.1. Pre-treatment The objective of the pre-treatment was to familiarize lambs with the foods to be used
Ž during the trials. Lambs were offered increasing amounts of Food P high protein, low
. Ž
. energy and Food E high energy, low protein and decreasing amounts of alfalfa pellets
Ž .
and barley, formerly their basal diet, over a 10-day period trial days 1 to 10 .
Table 1 Characteristics of foods used in Trials 1, 2, and 3
Item Basal diets
Novel foods P
E soybean
wheat Ž .
Food ingredients grape pomace
30 30
– –
ground rolled barley –
20 –
– cornstarch
– 50
– –
bloodmeal 50
– –
– ground alfalfa pellets
20 –
– –
1
Ž .
Digestible energy Mcalrkg, as fed basis 2.211
3.07 3.48
3.41
1
Ž .
Digestible protein , as fed basis 31
2 42
11
1
Ž .
Crude protein , as fed basis 47
6 45
14
1
Ž .
Each food was ground to 1 mm and mixed. Calculated values for digestible energy DE , digestible Ž
. Ž
. Ž
. protein
DP , and crude protein CP
are based on values as fed basis
obtained from the Nutrient Ž
. Ž
. Requirements of Sheep NRC, 1985 : barley 3.26 Mcalrkg DE, 10 DP 12 CP ; alfalfa 2.41 Mcalrkg DE,
Ž .
Ž .
Ž 12 DP 17 CP ; cornstarch 4.18 Mcalrkg DE, 0 DP 0 CP . Values for bloodmeal 2.6 Mcalrkg DE,
. Ž
. 57 DP, 80 CP and grape pomace 1.09 Mcalrkg DE, 1.6 DP, 12 CP are from the National Academy
Ž .
of Sciences 1972 .
Food P was a ground mixture of blood meal, grape pomace, and alfalfa that contained Ž
. Ž
. 47 crude protein CP and 2.211 Mcalrkg digestible energy DE . Food E was a
ground mixture of cornstarch, grape pomace, and rolled barley that contained 6 CP Ž
. and 3.07 Mcalrkg DE Table 1 . Food P provided 212 g CPrMcal DE, whereas Food E
provided 20 g CPrMcal DE. Lambs growing at a moderate rate require 179 g CP and Ž
. 3.95 Mcal DE NRC, 1985 .
On days 11 to 15, lambs were given ad libitum access to Foods P and E to determine Ž
. the amounts consumed. On average, lambs consumed 40 Food P range 19 to 53
Ž .
and 60 Food E range 47 to 81 . Lambs were ranked in descending order
according to the proportion of Food E consumed and alternatively assigned to two treatments: basal diet of Food P or Food E.
On days 16 and 17, lambs to be fed Food P as their basal diet were offered a mixture of 30 Food E and 70 Food P, whereas lambs to be fed Food E were fed a mixture of
Ž .
90 Food E and 10 Food P 1600 grlambrday . On days 18 and 19, lambs were fed Ž
. a basal diet of either Food P or Food E 1200 grlambrday , and on day 20, and
thereafter, lambs were fed 1100 grlambrday of their respective basal diets. Lambs had access to their basal rations throughout the day and night, except during daily trials.
2.1.1. Protein status Blood samples were drawn from the jugular vein of each lamb on day 19, just prior
Ž .
Ž .
to Trial 1 see below , and serum assayed for blood urea nitrogen BUN . Blood urea Ž
. nitrogen is an indicator of protein status Hays, 1994 .
2.1.2. Locations We used a wooden box at each foraging location to hold two plastic food containers.
Boxes were located on the side of the panel furthest from the sheltered area of the pen. Ž
. There were three locations: location nearest the sheltered area near , location midway
Ž .
from the shelter to the end of the pen mid , and location furthest from the sheltered area Ž
. far . Prior to the experiments, familiar foods were placed in the boxes at all three
locations so lambs were accustomed to feeding at the three locations. Immediately prior to daily trials, lambs were confined to the sheltered area of their
individual pen while foods were placed at the three locations. Lambs were then allowed to eat a 15-min meal. Twelve lambs in adjacent pens were fed at 0730 h, whereas the
other 12 lambs were fed at 0800 h. The order in which groups of 12 lambs were allowed to eat was alternated daily.
2.2. Trial 1: familiar foods at constant locations The objective of Trial 1 was to determine whether sheep fed at locations with food
that complemented the macronutrient content of their basal diets during a 15-min meal. Ž
. On days 20 and 21, lambs were offered 225 g of food at all three locations Table 2 .
Lambs did not consume all of the food at any location during the 15-min trials in Trial 1 or in Trials 2 and 3. Thus, all foods were offered ad libitum in all trials.
Table 2 Locations of Foods P and E during Trials 1, 2, and 3
TrialrDay Location
Near Mid
Far Trial 1
1 1
1
days 20, 21 P
PqE E
Trial 2 day 22
PqE E
P day 23
P PqE
E day 24
E P
PqE day 25
PqE E
P Trial 3
days 26 to 28 novel foods
no food PqE
1
Ž .
P and E refer to foods high in protein and low in energy Food P or high in energy and low in protein Ž
. Food E . See Table 1 for food ingredients and chemical characteristics.
2.3. Trial 2: familiar foods at different locations The objective of Trial 2 was to determine if sheep changed foraging locations when
Ž .
we changed the locations of foods that complemented their basal diet Table 2 . Lambs were offered 100 g of Foods P and E at each location for 15 min on days 22 and 23 to
familiarize them with the procedure of changing foods at all three locations. They were offered 225 g of foods P and E at each location for 15 min on days 24 and 25. We
measured food intake only on days 24 and 25.
2.4. Trial 3: noÕel and familiar foods at constant locations The objective of Trial 3 was to determine the response of nutrient-imbalanced lambs
Ž .
to familiar and novel foods. From days 26 to 28, two familiar foods Foods P and E and Ž
. Ž
two novel foods ground wheat and soybean meal were offered 225 grfood, 15 .
minrday at two locations. Familiar foods were placed at the furthest location from the sheltered area and novel foods at the nearest location to determine if novelty or distance
from the shelter had a greater influence on the lambs’ foraging behavior; no food was Ž
. offered at the mid location Table 2 .
2.5. Statistical analyses Ž
. Data for Trials 1 and 2 were analyzed with the MIXED procedure of SAS 1996 .
Ž .
There were two treatments low-protein and low-energy basal diets and lambs were Ž
considered a random factor. The data for Trial 3 intake of Foods E and P and novel .
Ž .
foods offered at two locations were analyzed by MIXED SAS, 1996 as a split-plot. Ž
. When F-ratios were significant
P - 0.05 , means were compared with LSD .
0.05
Contrasts were done on effects outlined in our objectives and hypotheses.
3. Results
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