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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37023 |
| Date | 23 August 1991 |
| Creators | Polonen, Ilpo Juhani |
| Contributors | Stormshak, Fredrick |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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