Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals

Arq. Bras. Med. Vet. Zootec., v.62, n.4, p.948-953, 2010 Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals [Digestibilidade dos nutrientes em raposa polar (Vulpes lagopus) alimentada com dietas que continham farinhas de origem animal] A. Gugołek1, W. Zabłocki1, D. Kowalska2, P. Janiszewski1, M. Konstantynowicz1, J. Strychalski1  1 University of Warmia and Mazury in Olsztyn Fur-Bearing Animal Breeding and Game Management Oczapowskiego 5/365, 10-719 - Olsztyn, Poland 2 National Research Institute of Animal Production - Krakowska - Balice, Poland ABSTRACT Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2). Keywords: Vulpes lagopus, feeding, digestibility, animal meal RESUMO Realizaram-se três ensaios de digestibilidade em raposas polares. Os grupos controles receberam dietaspadrão (C1 e C2) compostas por subprodutos de origem animal frescos ou congelados e sementes de cereais em grão. As dietas secas (E1, E2) usadas nos ensaios que continham farinha de origem animal e sementes em grãos extrudadas eram hidratadas antes de administradas. Em ensaio preliminar, avaliouse a digestibilidade da dieta seca E1, submetida a 15 minutos e a 24 horas de hidratação. Verificou-se que o tempo de hidratação não influenciou a digestão. No experimento principal, foram realizados dois ensaios para comparar a digestibilidade das dietas fornecidas às raposas no período de crescimento (C1 vs E1) e no desenvolvimento de pelo (C2 vs E2). Melhor digestibilidade dos nutrientes foi observada para as dietas controle. As maiores diferenças foram relatadas para a proteína total. A desnaturação das proteínas, durante o tratamento térmico, reduz o índice de digestibilidade das dietas. Observou-se alto teor de retenção de hidrogênio em relação ao hidrogênio digerido nas raposas alimentadas com as dietas E1 e E2. Palavras-chave: Vulpes lagopus, alimentação, digestibilidade, farinha de origem animal Recebido em 23 de novembro de 2009 Aceito em 2 de agosto de 2010 E-mail: Nutrient digestibility in Arctic... INTRODUCTION Carnivorous fur-bearing animals are usually fed conventional wet diets composed of raw animal by-products. Complete mixed feeds containing animal meals, in the form of dry pellets, are also becoming increasingly popular, but they are fed primarily to mink (Laplante, 1987; Zou et al., 1997; Kulikov and Bakakiriev, 2004) and only sporadically to foxes. Research results show that the pelts of foxes fed pelleted feed are high in quality, but smaller in size (Weiss, 1987; Lorek et al., 1999, 2002), which is most probably related to body water balance disorders and pellet falling out through the openings in net wire fences. Dry feed in friable form, mixed with water prior to administration to obtain the desired consistency of conventional feed, combines the advantages of wet diets and dry pellets. It is cheaper than pellets, can be formulated and prepared on the farm, and offered from traditional feeders (Sławoń, 1991; Gugołek et al., 2007). Overall feed quality should be evaluated based on both the values of production indicators and the results of digestibility/balance studies. In foxes, the digestion process requires the presence of enzymes (Oleinik, 1995; Szymeczko and Burlikowska, 1996). A comparative analysis of nutrient digestibility in Arctic foxes has been performed, among others, by Ahlstrom and Skrede (1995, 1998), Szymeczko (2001), Ahlstrom et al. (2003), and Vhile et al. (2005a). The objective of the present study was to determine, based on the results of digestibility/balance trials, whether Arctic foxes can be fed dry diets containing animal meals moistened with water. The effect of moistening time on nutrient digestibility was also analyzed. MATERIAL AND METHODS The experimental materials comprised 10 clinically healthy female Arctic blue foxes, averaging four-month-old. The animals were randomly selected from four litters, and were distributed into two equal groups, one individual Arq. Bras. Med. Vet. Zootec., v.62, n.4, p.948-953, 2010 from each litter per group (n=5). All animals had similar average body weights. Foxes were placed in individual metabolism cages equipped for separate quantitative collection of feces and urine, in an experimental unit at the University of Warmia and Mazury in Olsztyn, Poland. The trial was conducted from September to October. A 5-day experimental period proper was preceded by a 10-day adjustment period so that the animals could adapt to different environmental and feeding conditions. The experimental factor was the type of mixed feed offered to foxes. Control group (C) animals were fed standard mixed feed composed of typical ingredients. Dry experimental diets (E) contained animal meals, plant-origin ingredients, fat, vitamin and mineral supplements, and were mixed with water prior to administration (Table 1). The diets had a pulpy consistency and could be offered in traditional feeders. During moistening, diets E1 and E2 absorbed 60% water. Following water addition, 2.2kg moistened feed was obtained from 1kg dry feed. The same vitamin and mineral supplements (1kg/t) and sodium metabisulfite (1kg/t) were added to the diets. Diet composition varied, so as to meet the changing nutrient requirements of foxes. Diets C1 and E1 were offered at the growth stage (July-September) and diets C2 and E2 at the fur development stage (October-November). Table 2 presents the nutritional and energy values of diets C1, E2, C2, and E2, calculated based on their chemical composition, which was comparable in both groups and fulfilled the nutrient requirements of growing foxes (Nutrient..., 1982; Barabasz et al., 1994). At the preliminary stage of experiment 1, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the ex (...truncated)