Ž .
SYSTAT, 1991 . The same package was used to derive linear correlation coefficients between parameters.
3. Results
3.1. Experiment 1 Although all experimental treatments tended to be associated with higher mean milt
Ž .
volumes relative to controls Fig. 1 , only volumes from fish treated with GnRHa in
Ž
y1
. Ž
. Fig. 5. Blood plasma 11KT, 17,20bP and 17P ngPml
in Atlantic salmon injected with vehicle control , Ž
. GnRHa, 17P, 17,20bP, GnRHaq17P or GnRHaq17,20bP. Values are meanqs.e. ns 4–5 . Columns with
Ž .
the same superscript are not significantly different P - 0.05 .
Ž .
combination with 17P were significantly different from controls P - 0.05 . Similarly, all experimental treatments tended to be associated with lower blood plasma 11KT
Ž .
levels relative to controls Fig. 2 although, again, the reduction was only significant Ž
. P - 0.05 in those fish which received the combined GnRHa, 17P treatment. Treatment
with 17P or 17,20bP, alone or in combination with GnRHa, resulted in significantly Ž
. Ž
. higher
P - 0.05 blood plasma 17,20bP levels Fig. 2 , and 17P treatments were Ž
. Ž
. associated with significantly higher P - 0.05 blood plasma 17P levels Fig. 2 . There
were no significant treatment-related differences in seminal plasma 11KT or 17P, while Ž
. only the 17P-treated fish displayed significantly
P - 0.05 elevated seminal plasma Ž
. 17,20bP levels Fig. 3 .
Ž
y1
. Ž
. Fig. 6. Seminal plasma 11KT, 17,20bP and 17P ngPml
in Atlantic salmon injected with vehicle control , Ž
. GnRHa, 17P, 17,20bP, GnRHaq17P or GnRHaq17,20bP. Values are meanqs.e. ns 4–5 . Columns with
Ž .
the same superscript are not significantly different P - 0.05 .
Individual milt volumes were negatively correlated with blood plasma 11KT levels Ž
. r s y0.605, P - 0.01 which were in turn, negatively correlated with blood plasma
Ž .
17,20bP levels r s y0.447, P - 0.05 . Blood plasma 17,20bP and 17P levels were Ž
positively correlated with seminal plasma 17,20bP levels r s 0.719 and 0.795, respec- . Ž
. tively, P - 0.01
data not shown . 3.2. Experiment 2
As in experiment 1, although all experimental treatments tended to be associated with Ž
. higher mean milt volumes relative to controls Fig. 4 , only fish treated with GnRHa in
Ž .
combination with 17P had significantly higher P - 0.05 milt volumes compared to
controls. Mean blood plasma 11KT levels displayed a marked decline between days 0 Ž
. Ž
. and 8 Fig. 5 . This decline was significant P - 0.05 in fish receiving both 17P and
17,20bP alone and in combination with GnRHa. Blood plasma 17,20bP increased Ž
. significantly between days 0 and 8 P - 0.05 in fish receiving both 17P and 17,20bP
Ž .
either alone or in combination with GnRHa Fig. 5 . Only 17P treatment resulted in a Ž
. Ž
. significant
P - 0.05 increase in blood plasma 17P Fig. 5 . Progestogen treatment, Ž
. alone and in combination with GnRHa, resulted in significantly lower
P - 0.05 Ž
. seminal plasma 11KT levels and significantly higher P - 0.05 17,20bP levels relative
Ž .
to controls Fig. 6 . As in experiment 1, there were no significant treatment-related differences in seminal plasma 17P levels.
Unlike in experiment 1, individual milt volumes did not correlate strongly with day 8 blood plasma 11KT levels. However, milt volumes did display a negative correlation
Ž
y1
. Ž
. Fig. 7. Milt volume mlPkg body wt.
in Atlantic salmon injected with vehicle control , GnRHa, 17P, or Ž
. GnRHaq17P. Values are meanqs.e.
ns 4-5 . Columns with the same superscript are not significantly Ž
. different P - 0.01 .
Ž .
with seminal plasma 11KT levels r s y0.429, P - 0.05 which were in turn nega- Ž
tively correlated with day 8 blood and seminal plasma 17,20bP levels r s y0.665 and . Ž
. y0.731, respectively, P - 0.01
data not shown 3.3. Experiment 3
GnRHa treatments, alone or in combination with 17P, were associated with signifi- Ž
. Ž
. cantly higher
P - 0.01 mean milt volumes relative to controls Fig. 7 . However,
Ž
y1
. Ž
. Fig. 8. Blood plasma 11KT, 17,20bP and 17P ngPml
in Atlantic salmon injected with vehicle control , Ž
. GnRHa, 17P or GnRHaq17P. Values are meanqs.e. ns 4–5 . Columns with the same superscript are not
Ž .
significantly different P - 0.05 .
unlike previous experiments, treatment with 17P alone had no effect on milt volume Ž
. Fig. 7 . As in experiment 2, mean blood plasma 11KT levels displayed a significant
Ž .
Ž .
decline P - 0.05 between days 0 and 8 Fig. 8 , at which time, the levels displayed by Ž
. both groups of 17P-treated fish were significantly lower
P - 0.05 than those of
Ž .
controls. These treatments also resulted in significant increases P - 0.05 in 17,20bP Ž
. and 17P between days 0 and 8
Fig. 8 . The same treatments also resulted in Ž
. significantly lower
P - 0.05 seminal plasma 11KT levels and significantly higher Ž
. P - 0.05 seminal plasma 17,20bP levels, while seminal plasma 17P levels displayed
Ž .
no significant treatment-related differences Fig. 9 .
Ž
y1
. Ž
. Fig. 9. Seminal plasma 11KT, 17,20bP and 17P ngPml
in Atlantic salmon injected with vehicle control , Ž
. GnRHa, 17P or GnRHaq17P. Values are meanqs.e. ns 4–5 . Columns with the same superscript are not
Ž .
significantly different P - 0.05 .
Neither the day 8 blood or the seminal plasma 11KT levels correlated with individual milt volumes. However, day 8 blood plasma 17,20bP was negatively correlated with
Ž both blood and seminal plasma 11KT r s y0.528 and y0.618, respectively, P - 0.05
. and 0.01, respectively and was positively correlated with seminal plasma 17,20bP
Ž .
r s 0.713, P - 0.01 , which in turn displayed a positive correlation with milt volume Ž
. Ž .
r s 0.585, P - 0.01 data not shown .
3.4. Milt quality There were no significant treatment-related differences in spermatocrit during any of
Ž .
the experiments data not shown . Although other quantitative aspects of milt quality Ž
. e.g. sperm motility, fertilisation success were not examined, where possible, milt
collected during the experiments was used to fertilise routinely spawned ova with no discernible deleterious effects on egg performance. Furthermore, combined GnRHar17P
treatment has been successfully adopted as a routine method for induced spawning of male Atlantic salmon at SALTAS Freshwater Operations, albeit with a simplified
protocol involving only a single 17P injection on day 6.
4. Discussion
