The effects of dietary tryptophan (TRP) supplementation on behavioural response, body weight, feed intake and winter fur development were assessed in silver fox pups from 28 July until 5 December 1997. Ten males and 10 females received a commercial fox ration (control) and 10 males and 10 females the same ration supplemented with TRP (1.2 g/MJ ME). Dietary TRP supplementation increased the intake of protein and gross energy in September and November and total DM in September. Male foxes also consumed more feed and gained more weight than females throughout the trial. Dietary TRP supplementation did not affect liveweight gain, initiation of winter fur growth or fur quality in the test groups. There was a trend toward later priming of fur in the TRP supplemented group. The number of contacts with the novel object increased and the latency time until contact with the tidbit and the novel object reduced towards the end of the experiment. In the tidbit test, dietary TRP supplementation reduced the latency time of the females (40.4 s) compared with non-supplemented females (58.0 s), TRP-supplemented males (51.7 s), and non-supplemented males (47.6 s, P=0.001). In the novel object test, the latency time of the TRP females (32.5 s) was likewise reduced compared with the control group females (46.9 s) and TRP group males (44.0 s) being comparable to the control group males (38.5 s, P=0.029). It appears that dietary TRP supplement reduces fear and enhances exploratory behaviour in the female silver fox. This is attributed to the female being more sensitive to the imbalance between TRP and other large neutral amino acids, the supplement leading to increased brain serotonin synthesis.
|Publication Title||Applied Animal Behaviour Science|
|Author Address||Department of Animal Science, Nova Scotia Agricultural College, PO Box 550, Truro, Nova Scotia, B2N 5E3, Canada.|
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