Graduation date: 1991

Two distinct experiments were conducted. Experiment 1 was conducted to investigate the effects of nutritional conditioning and flushing as a means of improving reproductive performance of female mink. In Exp. 2, vegetable oil and corn syrup were fed during lactation to ascertain whether this nutritional regimen would improve growth of kits and to maintain the female's condition. Ninety-nine Standard Dark kit females in Exp. 1 were assigned to a group (IBC) that was restricted-fed a low energy breeding diet (14.6 MJ/kg DM) beginning in September to keep the animals in lean condition throughout the winter. Concomitantly, a control group (IA, N=51) was full-fed a higher energy diet (16.3 MJ/kg DM) until subjected to short-term conditioning with the breeding diet in January and February. All mink were individually conditioned to average under 900 g weight, which is considered an opti a weight before the meating season. At the beginning of the breeding season one-half of the mink in the experimental group (IBC) were exposed to nutritional flushing (hereafter designated IC) while the other one-half of the mink (IB) were moderately-fed for the entire mating period, as was the control group (IA). Flushing consisted of slight restriction of feed for 2 weeks followed by full feeding from March 1, 3 days before the mating season, until second mating. On April 15, all groups were further divided in half: one-half was fed moderately, while the other one-half was fed to appetite. This experiment failed to improve litter size significantly. Average litter sizes at birth for groups IA, IB and IC were 6.16, 5.74 and 6.48, respectively. However, the relationship between litter size and weight change (%) during flushing was significantly positive and followed a quadratic curve (p = 0.010, R² = 13.8 %). As a consequence, weight increase during flushing (9.32%) was too low and suggests a need for higher energy density during flushing. Conception rate of mink in this experiment was very high (96.7%), apparently as a result of individual conditioning of the mink. Percentage of stillborn kits was higher than normal (highest in the flushing group) but the difference was not significant statistically. Litter sizes at birth based on full (F) and restricted feeding (R) were 5.88 and 6.40, respectively (p=0.07). In relevant field observations on two commercial farms, it was noticed that obesity of females prior to mating lowered reproductive performance. Blue Iris females weighing over 1400-1500 g at mating often did not conceive and had few if any kits at weaning. In Exp. 2, lactating Blue Iris females with kits were fed either lard or vegetable oil as a fat source (40 % of total fat) and cereal (wheat:barley) or corn syrup supplement as a carbohydrate source (40%). Positive effects of vegetable oil on kit weights and of corn syrup on weight loss of dams were revealed. Weight of kits fed lard and vegetable oil were 315 and 332 g (p=0.06) at 6 and 572 and 598 g (0.03) at 8 weeks of age, respectively. Weight losses of dams from parturition to 6 weeks of age averaged 283 and 154 g (p=0.06) for cereal treatment and the corn syrup supplemented treatment, respectively. / Graduation date: 1992

Graduation date: 1996