- This study involved the use of the two-choice preference test to
determine the taste reactions of buck and doe Columbian black-tailed
deer (Odocoileus hemionus columbianus) to ascending concentrations of
water extracts of Douglas fir, red alder, cascara, western hemlock
and bitterbrush; to an ethanol extract of Douglas fir, and to the organic
acids - citric, malic, quinic, and succinic. Also, the water extracts
of Douglas fir and western hemlock, the Douglas fir ethanol extract,
and acetic and malic acids were tested in the presence of butyric acid.
Responses to Douglas fir and western hemlock water extracts and the
Douglas fir ethanol extract were also determined while in the presence
of an odorous extract of fish, PF Extract (Fraction G).
Animals were separated by sex, and penned in groups of two or
three animals per pen. All groups were fed pelleted alfalfa hay and
pelleted concentrate, ad libitum.
Each response was determined by expressing the intake of the
test solution at a given concentration as a percent of the total fluid
intake for two, 24-hour periods. Responses were plotted graphically
by sex and compared to threshold values for intake. In preliminary
tests with water, a 95% confidence interval was established from a
theoretical mean intake of 50%. The upper confidence level was 56%
intake, with the lower level being 44% intake. Thus, intake of test
fluid from 44% to 56% intake was described as the nondiscrimination
zone. The preference threshold was set at 80% intake, and the rejection
threshold at 20% intake.
The sensitivity levels (the point at which discrimination first
occurred) of the bucks for the water extracts were (ml extract/100 ml
water): Douglas fir, 0. 63; red alder, 0. 05; cascara, 0. 0125; western
hemlock, 0. 48; and bitterbrush, 0. 025. The sensitivity for the ethanol
extract of Douglas fir was 0. 14. All sensitivity responses were preference
reactions. The sensitivity levels of the does for the water
extracts were (ml/100 ml): Douglas fir, 0. 05; red alder, 0. 05; cascara,
2. 24; western hemlock, 0. 20; and bitterbrush, 0. 025. The sensitivity
for the ethanol extract of Douglas fir was 0. 10. All sensitivity
responses were preference reactions except the response to red alder
The preference threshold (test fluid 80% or more of total fluid
intake) was crossed by the bucks in response to the water extracts of Douglas fir at 1.52 ml/100 ml, western hemlock at 1.48 ml/100 ml,
and bitterbrush at 0. 34 ml/ 100 ml. The preference threshold was
crossed by the does in response to the water extracts of Douglas fir
at 2.94 ml/100 ml and western hemlock at 1.52 ml/ 100 ml. The does
exhibited the only 20% rejection response to the browse extracts, with
the ethanol extract of Douglas fir prompting rejection at 2. 96 ml/100ml.
The sensitivity level of the bucks for citric acid was 0.072 ml/
100 ml; for -malic acid 0.004 ml/100 ml; for quinic acid 0. 434 ml/
100 ml; and for succinic acid 0. 00063 ml/100 ml. All sensitivity
responses were preference reactions except the response to quinic
acid. The sensitivity levels exhibited by the does were all rejections
at levels of 0. 0016 ml/ 100 ml for citric and succinic acids and 0.00063
ml/100 ml for malic and quinic acids.
The preference threshold was exhibited by the bucks in response
to malic acid at 0.01 m1/100 ml. The responses of the bucks crossed
the rejection threshold at 2.50 ml/ 100 ml for citric acid and 0. 442
ml /100 ml for succinic acid. Responses of the does that first crossed
the rejection threshold were prompted by citric acid at 0.504 ml/100
ml, malic acid at 0. 120 ml/ 100 ml, quinic acid at 0. 395 ml/100 ml,
and succinic acid at 0. 060 ml/100 ml.
The presence of butyric acid in cotton patches at the top of the
fluid containers had no influence on the taste response of the bucks to
the test solutions. Also, butyric acid had no influence on the taste
responses of the does to test solutions of acetic acid and Douglas fir
water extract, but resulted in an increase (P < 0. 05) in the intake of
malic acid and a decrease (P < 0. 05) in the intake of western hemlock
extract and Douglas fir ethanol extract.
The presence of PF Extract (Fraction G) did not influence the
taste response of the bucks to western hemlock extract, but resulted in
a decreased response to test solutions of both Douglas fir extracts.
PF Extract had no influence on the response of the does to the test