Effects of formalin on bacterial growth in mink feed, feed consumption and reproductive performance of adult mink, and growth of mink kits
Li, K.C.; Powell, D.C.; Aulerich, R.J.; Walker, R.D.; Render, J.A.; Maes, R.K.; Bursian, S.J.
Veterinary and Human Toxicology 41(4): 225-232
1999
ISSN/ISBN: 0145-6296 PMID: 10434376 Document Number: 505668
Feed containing 0, 550 or 1100 ppm [mg/kg] formalin was kept refrigerated for up to 7 days and the number of colony forming units of gram-negative and gram-positive bacteria derived from the feed was determined each day. Colony forming units in the formalin-treated feed were significantly fewer than colony forming units in untreated feed. In the second trial, feed containing the same concentrations of formalin was maintained at 30 degrees C for 24 h and cultured bacterial colonies were counted at 0, 12 or 24 h of feed incubation. Both concentrations of formalin were effective in significantly reducing the number of colony forming units. A feed consumption trial determined if mink (Mustela vison) preferred formalin-treated feed to non-treated feed kept refrigerated for up to 7 days. Consumption of feed treated with 1100 ppm formalin was significantly lower than consumption of the non-treated feed on day 1, 2, 4 and 5, but body weight was not affected. A long-term feeding trial determined the effects of formalin on mink reproduction, early growth of offspring and quality of fur. Mink were fed formalin at concentrations of 0, 550 or 1100 ppm for approximately 140 days beginning 1 month prior to mating until kits were weaned at 6 weeks of age. Mating success was not affected by consumption of formalin-treated diets, but kit survival at birth was adversely affected in mink consuming 1100 ppm formalin. Haemoglobin concentration, haematocrit, mean corpuscular volume, and mean corpuscular haemoglobin were significantly decreased in 6-week-old kits, but there were no significant differences in any of these parameters between the kits exposed to 0 and 550 ppm formalin. In a second phase, some kits and their dams were continued on their respective dietary treatments from weaning through pelting (approximately 220 and 320 days, respectively). At pelting, haematocrits and hemoglobin concentrations for the kits fed 1100 ppm formalin were significantly less compared to the control and 550 ppm formalin groups. There were no significant differences in body weights among female kits or adult female mink. The body weights of male kits in the 1100 ppm formalin group became significantly less than the body weights of male kits in the control and 550 ppm formalin groups as the trial progressed. The quality of fur was highest for mink in the control group and lowest for mink in the 1100 ppm formalin group. While dietary 1100 and 550 ppm formalin were effective in suppressing bacterial growth in the feed of mink, deleterious effects of 1100 ppm formalin on kit survival, haematologic parameters, body weight, and quality of fur preclude formalin use at this concentration.