The blue fox (Alopex lagopus) is presently the most important species in fur farming in Finland. In recent years selective breeding programmes have focused on producing large and heavy animals. Ten years ago the average weight of blue fox vixens varied between 7 and 10 kg. Nowadays individuals weighing over 20 kg can be found. At present blue foxes are fed ad libitum during the growing furring period, independent of dietary energy concentration. The blue fox exhibits seasonal fluctuations in food intake and accretion of body fat, food intake and body fat retention being very high during autumn and early winter if given free access to food. Ad libitum feeding hence often leads to animals being very fat or even obese at the time of pelting. The accumulation of body fat may have dual purposes, both of crucial importance for animals living in the wild: first to provide insulation of the body and protection from excessive heat losses when ambient temperature is very low and second, to serve as an energy reserve in situations of food scarcity. Studies in other highly seasonal animal species (eg. red deer, Soay sheep, mink) have shown that regulation of food intake, body fat accretion and, indeed, metabolic rate are strongly connected to photo-period (sheep: Forbes, 1982, Lincoln & Richardson, 1998, Lincoln et al, 2001;red deer: Milne et al., 1990;mink: Valtonen et al., 1995;Tauson et al., 1999), the signal monitoring day-length being melatonin (Lincoln, 1983, Arendt, 1998). Energy supply, body condition and reproductive processes are closely connected (Blache et al. 2003). Therefore, the fact that litter size has decreased among Finnish blue foxes during the past few years may indicate that the present rearing routines are harmful for future reproductive performance. Recent data suggest that blue fox vixens being selected for breeding purposes during the summer, and then rearing them on a restricted feeding regimen, has resulted in improved reproductive results when compared to vixens reared on ad libitum feeding (Koskinen et al., 2006). These findings are in good agreement with previous findings in another seasonal animal, the mink: Tauson & Aldén (1984) showed that yearling dams selected for breeding in August/September and then fed restrictedly had a superior reproductive performance compared to dams fed ad libitum until the end of November and then given a period of strong feed restriction in order to reach the same body weight as the restricted group when mating started in early March. Indeed, when analysing the complete material, it was found that the poorest results occurred among dams that had lost most weight from November to March and, on the contrary, that the best results were achieved among those that had increased slightly in weight during this period. Later it was demonstrated that reproductive performance of the mink is highly responsive to nutritional manipulation (Tauson, 1993). Therefore, it can be anticipated that a proper rearing intensity and energy supply prior to conception may be potent tools to improve the reproductive capacity of blue fox vixens. In order to develop feeding strategies that utilise the modern blue foxesâ?? capacity for growth and simultaneously support their reproductive capacity an increased knowledge on the energy requirement of blue foxes during the growth period, and during the reproduction period is necessary. Presently, there are no reliable data available regarding the maintenance energy requirement, the energy requirement for growth (and furring) or the energy requirement for reproductive processes of the blue fox. The relatively few data available are old, and generally based on data from production experiments (see Hansen et al., 1991).
Vastaava tutkija
Koskinen Nita Hankkeen kesto 2007 - 2011
Asiasanat
sinikettu, energia-aineenvaihdunta, perusaineenvaihdunta
Hankkeen vaihe: Päättynyt
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