Physiological status and fur quality of young silver foxes (Vulpes vulpes L.) under use of antiparasitic drug niacid-granules plus and bioactive keratin as a feed additive

Recently, among carnivores, including silver-black foxes, cases of nematode infestation have become more frequent, causing significant economic damage. From helminthic infestations, youngsters suffer the most. Currently, in the veterinary world practice, anthelmintics of the new generation, in particular, avermectin-based products are recognized the most promising. To date, neither in Russia nor abroad, keratin preparations in combination with anthelmintics have been used in fur farming. In the present work, it was experimentally proved for the first time that a new-generation anthelmintic Niacid-granules plus combined with a sulfur-containing feed additive Bioactive keratin improve fur grading indices (size, amount of fur, completeness of fur, damage to fur, damage to skin etc.) in silver-black foxes ( Vulpes vulpes L.). This paper documents physiological effects and fur quality parameters in young silver-black foxes due to the combined use of Bioactive keratin and an avermectin-based anthelmintic. Niacid-granules plus (LLC SPA Ecobiovet, Russia, and Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology, Russia) are brown granules, 300-400 g per pack, with 85 % abamectin B1a and 15 % abamectin B1b contents and the allowed shelf life for at least 21 months. Bioactive keratin (Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology, Russia) is a monoproduct derived from tow of wool and containing 98 % of native protein, a preparative form of homogeneous liquid mass, color from light gray-beige to dark gray-beige, with a specific smell, mass fraction of dry matter 3-10 %, mass fraction of keratin 95-98 %, and a shelf life of not more than 2 years. The preparations Niacid-granules plus and Bioactive keratin belong to the IV class of toxicity. It is shown that the combined use of Niacid-granules plus and Bioactive keratin significantly enhances the effect of each drug used separately. In farm tests (AO Saltykovskii Breeding Farm, Moscow Province, 2017-2018), it was found that deworming young silver-black foxes at the age of 2 months with Niacid-granules plus and the subsequent use of dietary Bioactive keratin as a sulfur-containing feed additive significantly affect body weight gain in foxes. Under the combined use of Niacid-granules plus and Bioactive keratin, the live body weight of pups is 9.1 % higher compared to the control ( t fact. = 7.40 ≥ t tab. = 2.1 at p = 0.05 and t fact. = 0.81 ≤ t tab. = 2.1 at p = 0.05, respectively). Niacid-granules plus together with Bioactive keratin also improved the complete blood counts during the investigation, thereby contributing to a faster normalization of the physiological status of young silver-black foxes. When using both drugs, the weight of young silver-black foxes increased by 30.4 %, the area of the obtained furs by 18.4 %, the hair density by 24.6 % compared to these parameters in intact animals. This confirms the effectiveness of the joint use of the studied preparations. The use of Niacid-granules plus are allowed to animals at the age of 2 months, twice at 10-day interval, and the dietary Bioactive keratin should be added to feed in six cycles (5-day cycles with 10-day intervals).