Effect of tyrosine and phenylalanine supplementation on the colour and behaviour of chinchillas

The long-tailed chinchilla (Chinchilla lanigera Bennett, 1829) is native to northern Chile and can be found along the foothills of the Andes and the coastal mountains south to Talca, at an elevation of 400–1650 m. Human activities, such as poaching, hunting, grazing of cattle and goats, mining, firewood extraction, and the pet trade, have posed a significant threat to this species for years. Although legislation to protect the species has been in place since 1929, it was not efficiently enforced until the establishment of the Reserva Nacional Las Chinchillas in Auco, Chile in 1983. This species has been included in the CITES Appendix I since 1977. The current wild population is estimated at around 5350 mature individuals, and despite current protection measures, populations continue to decline, and the species is classified as endangered according to the Red List Category & Criteria (Jimenez, 1996; Roach and Kennerley, 2016). Currently, chinchillas are a popular pet and farm animal, but due to ABSTRACT. The purpose of the study was to verify whether increasing the content of tyrosine and phenylalanine in the feed would result in more intense colouration of chinchilla fur and affect the animals’ reactions to behavioural tests. Chinchillas were divided into 3 groups: G-1 fed complete commercial fodder (Tyr 6.91 mg/g, Phe 7.45 mg/g), G-2 fed commercial and experimental fodder (1:1 ratio), and G-3 fed with experimental fodder (Tyr 14.31 mg/g, Phe 21.65 mg/g). During the experiment, the fur colouration type was assessed using two methods: objective, with a colorimeter (CIE L*a*b* colour space: L* – light-dark axis, a* – red-green axis, b* – yellow-blue axis, C* – colour saturation), and subjective, by a qualified chinchilla judge. A behavioural hand test was used to categorise the chinchillas’ responses to human intrusion into their cage. The results from the colorimeter measurements did not show any significant differences in the L* (P > 0.05) component; however, significant differences were observed for the a* (P = 0.0029), b* (P = 0.0218), and C* (P = 0.0342) components in relation to the fur colouration of individual groups. The assessment of the colour type by a qualified specialist found statistically significant differences (P < 0.05) between the initial and final measurements. Spearman’s correlation coefficients between colour type assessment and colour components were mostly low or medium, but with stronger values observed for L* compared to a*, b* or C*. There were no significant effects of the feeding group on the results of the and test. However, a decreasing trend was observed in the hand test results for G-3 from week 5 of the measurements. Received: 7 September 2022 Revised: 23 March 2022 Accepted: 25 March 2022