Development of indices to estimate fat reserves in the wild American mink (Neovison vison)

Abstract

Insight into body fat dynamics of wild mustelids could help to monitor changes in their nutritional status. Adipose tissue depots of wild American mink (Neovison vison, n = 50) were dissected to determine how fat was distributed throughout the body and to develop practical and reliable indices to estimate percent body fat in harvested mink. The average percent body fat of mink caught between July and April was 6.2 %, which is very low compared to previously studied farm-bred mink (adult females in summer = 20 %, subadult males in winter = 38 %). Most of the dissected adipose tissue was located in the subcutaneous (SC) fat layer (≈81 %) confirming earlier data on farmed mink. The total fat masses were higher in the subadults/adults than in the juveniles and in the male mink compared to the females. The mass of the SC fat layer was the best predictor for total fat mass (R 2 = 0.98) and percent body fat (R 2 = 0.89) when using simple regressions. As this depot can be laborious and difficult to remove with consistency, the omental fat mass could be also used as a predictor for total fat mass (R 2 = 0.70) and percent body fat (R 2 = 0.42) in juveniles and the retroperitoneal fat mass in subadults/adults (R 2 = 0.80 and 0.79, respectively). We also evaluated the different fat depots using the part-whole methodology by removing the mass of the fat depot of interest from the dependent variable. According to the part-whole regressions, the masses of the omental (R 2 = 0.66) and mesenteric depots (R 2 = 0.56) were the best predictors for total fat mass in the juveniles and the masses of the retroperitoneal (R 2 = 0.78) and diaphragmatic depots (R 2 = 0.77) in the subadults/adults. Based on both simple and part-whole regressions, omental fat can be suggested as a predictor for total fat mass in juvenile mink and retroperitoneal fat in subadult/adult mink due to their relatively good predictive power and ease of dissection.