A NEW METHOD FOR MAXIMIZING THE USE OF SPERM CELLS

A NEW METHOD FOR MAXIMIZING THE USE OF SPERM CELLS FROM
GONADS - A MULTI-SPECIES APPROACH
Maureen Ritter
Director of Aquaculture and Conservation North America
Background
Using sperm cells directly from gonads of mature fish has been a
technique used since the 1970s. Cryogenetics has further optimized
this technique and developed a new protocol for use in commercial
egg production.
In the 2015/2016 season in Norway, 330 million out of 550 million
Atlantic Salmon eggs (about 60 %) were produced exclusively using
gonad-extracted sperm according to our methods with very good
fertilization results (between 80-95%).
Measuring sperm concentration
•
The SDM6 photometer codeveloped by Minitube GmbH
and Cryogenetics is used to
measure sperm concentration
•
Method is quick and can be
implemented in the daily
workflow
•
Calibrated for multiple species
•
Measuring sperm concentration
Atlantic Salmon (stripped)
Sperm concentration (n=459)
16
Billion sperm per ml
14
12
10
8
6
4
2
0
0
50
100
150
200
250
Male #
300
350
400
450
500
Milt quality can be a gamble
• Even excellent egg quality does
not help if males have
– Low sperm concentration
– Small milt volume
– Late maturation
New technology
• Fish breeding programs have changed radically
(QTLs, genomic selection)
• Producer can command premium price for specific
genetic properties (disease resistance etc)
• This leads to a larger portion of income relying on
the performance of a few males (1-10% of
broodstock)
Sperm is suddenly the limiting factor
Harnessing the potential of gonads
CROSS-SECTION
Weight of gonads on Atlantic salmon : 275-400 g
Strip volume Atlantic salmon: 40-100 ml
GONAD
TISSUE:
High sperm
concentration
SPERM DUCT:
Low sperm
concentration
Gonad extraction procedure
Sperm concentration – stripping vs. gonads
Sperm concentration Atlantic Salmon
20
Billion sperm per ml
18
16
14
12
10
8
6
4
2
0
1
2
3
4
5
6
7
8
Extraction
5.68
4.34
4.9
7.97
4.65
6.28
4.25
2.24
Gonad
18.71
16.33
14.74
16.56
17.83
17.27
15.47
17.88
After stripping, gonads were removed and sperm concentration measured in strip
and extract.
Sperm production facts
 An Atlantic Salmon male carries a reservoir of ~1000 billion sperm cells.
 Average strip: sperm conc. 8 bill/ml, volume ~70 ml
 Average gonad extract: sperm conc. 11 bill/ml, volume 700 ml
 Gonad extraction over 10 x more efficient than stripping!!
 If males are stripped 3-4x on average per season, more than 50% of
sperm cells are left in gonad and re-absorbed
 Equivalent values for Arctic charr (Salvelinus alpinus)
 Average strip: sperm conc. 8 bill/ml, volume 8 ml
 Average gonad extract: sperm conc. ??, volume ~70 ml
 Gonad extraction over 7-8x more efficient
 Equivalent values for lumpfish (Cyclopterus lumpus)
 Average strip: sperm conc. 9 bill/ml, volume 2.5 ml
 Average gonad extract: sperm conc. 12 bill/ml, volume 10-15 ml
 Gonad extraction over 6x more efficient
Can season be extended by harvesting gonads early ?
Gonadal development and preparation for spawning starts 2-3 months
prior to season. To sample the viability of these sperm cells during various
stages of final development Cryogenetics conducted a trial in cooperation
with Huntsman Marine Science Center, NB, Canada.
In a group of male fish normally set to spawn in mid-October, sperm cells
were collected and cryo-preserved in 2 week intervals from the end of
July and forwards.
(Final Results not yet in but initial results are positive )
Results from early season trials (Norway)
• Trials at Atlantic Salmon producer site
• Early October - stripped vs. gonad extraction
• Stripped milt had low concentration, but
seemingly good quality
• Stripped milt was used for fertilization
• Milt was extracted from gonads for comparison
• AquaBoost SpermCoat
Results
• Gonad-extracted milt gave better fertilization than
stripped milt
• 88 % vs 60 %
• Extracted milt from one male fertilized up to 1 mill
eggs!
• After trials, commercial partner switched to doing
all milt extraction from gonads!
• 2015/2016 season
Cryogenetics product development team
R&D team Norway
Inger S. Grevle and Jan Sunde
With support and facilities for large scale testing from
• Marine Harvest Norway
• Lerøy Norway
• Dr. Amber Garber, Huntsman Marine Science Center, Canada