Kirsti Rouvinen

Influence of Dietary Fat Source on the Body Fat Composition of Mink (Mustela vison) and Blue Fox (Alopex lagopus)

Abstract The influence of dietary fat source on the fatty acid composition of mink and blue fox fat in different parts of the body was studied. In addition, seasonal changes in the fatty acid composition of the skin and subcutaneous fat were determined. The dietary fat sources used in the experiments were beef tallow, mink fat, capelin oil, soybean oil and rapeseed oil. The fat level supplied by the diets was 20% in the dry matter of feed. Skin and subcutaneous fat samples were taken in August and November. Body fat samples were collected from the groin, around the kidneys and from the liver in November. Raw skin samples were taken after skin grading in January. The fatty acid compositions of the fat samples studied all markedly reflected the fatty acid profile of the respective dietary fat source. Blue fox fat was found to be more saturated than the fat of minks fed the same diet. The amount of unsaturated fatty acids in the skin and subcutaneous fat increased towards winter. This increase was more notab...

Digestibility of Different Fats and Fatty Acids in the Mink (Mustela vison)

Abstract This paper reports the influence of level and type of fat on the digestibilities of fat and different fatty acids in the mink (experiment A). In addition the synergistic effect of saturated and polyunsaturated fatty acids is clarified (experiment B). The fats used in experiment A were beef tallow, capelin oil and rapeseed oil and the supplemental fat levels were 15 and 25% in the dry matter of feed. In experiment B the fats employed were beef tallow, soybean oil and their mixture (50:50), and the fat level was 20%. The experiments were carried out with adult standard male minks and the digestibilities were determined by the total collection method. The number of animals was 4–6 per experimental group. The apparent digestibilities of beef tallow, capelin oil and rapeseed oil on the 15% level of supplemental fat were 74, 94 and 95, and on the 25% level 71, 96 and 96, respectively. The respective digestibilities of beef tallow, soybean oil and their mixture were 71, 93 and 86. In experiment A the di...

Dietary Effects of Omega-3 Polyunsaturated Fatty Acids on Body Fat Composition and Health Status of Farm-raised Blue and Silver Foxes

Abstract Farm-raised blue and silver foxes were fed diets based on slaughterhouse offal (SH) and fish mixture supplemented with fish oil (FM) from weaning to pelting in order to clarify the effects of accumulation of omega-3 fatty acids in the tissues and organs. Some blue foxes were also fed an antioxidant (Rexoquin®, 200–1000 ppm) supplemented diet. The dietary background of the animals significantly influenced the fatty acid composition of all body fat depots in both fox species. The animals of the FM group had considerably more eicosapentaenoic (EPA), docosahexaenoic (DHA) and cetoleic acids in their tissues than the animals of the SH group. In silver fox livers, the amount of DHA was even higher than in blue foxes. Fat accumulation pattern of the blue and silver fox livers also differed considerably between the diets. In the SH diets fat accumulated in the liver in large droplets, while in the FM diets it was present in small droplets. Furthermore, degenerative changes were more numerous and severe i...

The use of resting platforms by young silver foxes (Vulpes vulpes)

Abstract According to the current European recommendation for animal protection regulations for fur animals, farmed foxes should have a resting platform in their cages. Therefore, the total time of use and factors affecting the use of resting platforms by 20 young silver foxes were studied on an experimental fur farm in western Finland. Silver foxes used the platforms on average 70 min day −1 (median 24 min day −1 ). The use declined over time from September/October (146 min day −1 ) to January (9 min day −1 ). Interindividual differences in platform use were marked especially in September/October. Platforms with a more unobstructed view of the surroundings were preferred to platforms with a more restricted view. Platforms were used most during the working week, but outside the working hours. Neither daily temperature nor wind velocity had an effect on platform use. It can be concluded that platforms function neither as protection against cold and draught nor as a hiding place. The role of the platforms as a resting place is not supported by the short and decreasing duration of their use as a function of time. They may have a role as a place for making observations, or simply as an environmental enrichment.

High Dietary Ash Content Decreases Fat Digestibility in the Mink

Abstract This study clarifies the effect of high dietary ash and calcium on fat and fatty acid digestibilities in the mink. Differences between various calcium sources are also evaluated. We performed three digestibility experiments by the total collection method with 30 adult male minks of standard genotype. Each experiment had two dietary fat sources, beef tallow and rapeseed oil, and three different ash levels, 4, 8, and 14% in dry matter (DM) of the diet. Ash level in the diets was increased either with limestone grist (experiment A), fish offal meal (experiment B), or bone meal (experiment C). Fat level in the diets was 20% in DM. In experiment A, the digestibility of beef tallow decreased from 76 to 67% and the digestibility of rapeseed oil from 94 to 85% with increasing ash level. In experiment B, digestibility coefficients for beef tallow and rapeseed oil varied between 67–70 and 94–95, respectively. In experiment C, the digestibility of beef tallow decreased from 87 to 66% and that of rapeseed oi...

Influence of dietary fat source on growth and fur quality of mink and blue fox

Abstract The influence of different dietary fat sources on growth and fur quality of the mink and the blue fox was studied. The fats used in the study were beef tallow, mink fat, capelin oil, soybean oil, rapeseed oil, and beef tallow: rapeseed oil mixture (50:50). The level of dietary fat was 20% in the dry matter of feed. All of the fat sources investigated here were of good quality guaranteeing approximately normal growth performance to the animals. No signs of fat peroxidation or vitamin E deficiency were found, and no adverse effects on feed consumption, feed palatability, growth of the animals and their fur characteristics were observed in the mink or in the blue fox.

Effects of Slaughterhouse Offal and Fish Mixture Based Diets on Production Performance of Blue and Silver Foxes

Abstract A production experiment with blue and silver foxes was performed in order to reveal the long-term effects of feeding a diet abundant in polyunsaturated omega-3 fatty acids during the growth period. The main emphasis was on the growth performance and general fur characteristics of the animals. The experiment consisted of 200 blue foxes and 44 silver foxes and it lasted from July to pelting in 1988. The experimental diets were a SH = slaughterhouse offal based diet and a FM = fish mixture based diet supplemented with fish oil. The fat level of the diets was 20% in dry matter. In both fox species, there were no great differences between diets in the body weight of the animals at pelting. Only blue fox males in the FM dietary group were lighter than those in the SH group. In silver foxes, the dried raw skins were longer in the FM group than in the SH group. Fur characteristics were in general better in both blue and silver foxes on the FM diet than on the SH diet, except for the color purity of the f...

Influence of Fatty Acid Composition in Dried Raw Mink and Blue Fox Skins on Their Storage Aging and Dressing Properties

Abstract The influence of fatty acid composition in dried raw mink and blue fox skins on their storage aging and dressing properties was assessed. The parameters studied were: changes in the fatty acid composition of the skins during one years cold storage (+8°C, 70% RH), swelling, tannin fixation and such mechanical characteristics as tensile strength and tearing strength in fresh and one-year-old raw skins. The animals’ dietary backgrounds significantly influenced the changes in the fatty acid compositions of raw skins during storage. In addition, the duration of storage had a marked effect, with mink and blue fox skins differing significantly in this respect. Tannin fixation, skin thickness and percentage of elongation at break were considerably influenced by aging the furskins. Rancid dietary fat was found to cause collagen damage to mink skins. No other dietary effects were observed. Mink and blue fox skins differed from each other in all of the dressing characteristics measured. Blue fox skins seem...