Opportunities and Challenges with Sexed Semen

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Opportunities and Challenges with Sexed Semen
Joseph C. Dalton, PhD
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Introduction

• Sperm contain an X or a Y chromosome.
• Ova contain only an X chromosome.
• When fertilization occurs
• X-sperm X-ova XX female
• Y-sperm X-ova XY male

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Introduction

• 1980s Technology to separate X and Y sperm via
  flow cytometry was developed.
• 1996 XY, Inc. became the exclusive worldwide
  licensee of sperm separation in non-human
  mammals.

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How are sperm separated?

• The X chromosome is larger and contains
  approximately 3.8 more DNA than the Y
  chromosome.

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How are sperm separated?
Semen collection
Evaluation, initial extension, staining, and
incubation
Initiation of separation
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How are sperm separated?
(Mo-Flo diagram courtesy of XY Inc.)
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How are sperm separated?

• 35,000 sperm pass the laser per second
• 5,000 X sperm are sorted per second
• X sperm are collected
• Y sperm and unknown and dead sperm are discarded

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Sexed semen processing

• After sorting, the semen is
• Packaged into 1/4 mL straws
• Frozen and stored in liquid nitrogen

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Opportunities with Sexed Semen
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Opportunities

• Flow cytometry is the only reliable sexed semen
  technology available today.
• Breed heifers with X sperm to decrease calving
  difficulty.
• Eliminate biosecurity risks with closed herd
  expansion.
• On average 9 out of 10 calves will be of the
  desired sex.

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Heifers (no.) expected in 100 calvings
conventional semen
(ABS Global)
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Heifers (no.) expected in 100 calvings sexed
semen
(ABS Global)
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Recommendations for use of sexed semen

• Use only in well-managed virgin heifers.
• Inseminate 12 h after heat is observed.
• Thaw using warm water at 95 to 98 degrees F for a
  minimum of 30 seconds.
• Time, temperature, hygiene, and skill.

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Goals for Holstein heifers
Average daily gain 1.8 lb/d
Weight at first service 800 lb
Age at first calving 22 to 24 mo
Weight at first calving 1350 to 1400 lb
Weight after first calving 1250 lb
BCS at first calving 3.25 to 3.5
(Adapted from Vandehaar, 2001, and Hoffman, 1997)
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First service strategy

• Use sexed semen at first service only.
• Use conventional semen at second and later
  services.
• Results decreased average age at calving for
  heifers inseminated with sexed semen as compared
  with those inseminated with conventional semen.

(Weigel, 2004 DeJarnette et al., 2007)
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What results can you expect?

• Conception rate
• Holstein heifers 41 to 57
• Greater than 70 of herds achieved a heifer CR gt
  70 of first service CR obtained using
  conventional semen

In well-managed virgin heifers, the conception
rate will be 70 to 85 of conventional semen.
(XY, Inc./Weigel, 2004 Cerchiaro et al., 2007
DeJarnette et al., 2007)
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Sexation data
84
49.1
41.4
N 7946
(ABS Global, 2008)
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Conception rate by service number
Service Sexed semen, (n) Conventional semen, (n) Sexed semen relative to conventional,
First 47.0 (26,465) 56.4 (21,864) 83.3
Second 43.1 (6,375) 53.8 (13,389) 80.1
Third 38.1 (2,567) 45.4 (11,772) 83.9
(DeJarnette et al., 2008)
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Challenges with Sexed Semen
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Challenges

• With good management, conception rates will
  average 70 85 of conventional semen.
• The lower concentration of sperm (2.1 million per
  dose) can affect the fertility of the semen.
• Potential damage due to cold shock is greater in
  the 1/4 mL straw.

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Why not increase the number of sperm per dose?

• Processing is slow (3,000 to 6,000 sperm per
  second) 1 hour to produce 1 straw with 20
  million sperm.
• Research has focused on maximizing fertility of
  low concentration of sperm in heifers.

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Optimum fertility of the population
Bull A
Bull B threshold value for optimal results
Fertility ()
Bull B
Bull C
0
5
10
15
20
Total number of sperm (millions)
(Salisbury and VanDemark, 1961)
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Why not increase the concentration of sperm per
dose?
Concepcion rate, ()
Concentration of sperm per dose, (millions)
(DeJarnette et al., 2008)
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Why not increase the number of sperm per dose?

• Overall, there was no effect of sperm dosage on
  conception rates in heifers.
• Bull A Increase in sperm dosage resulted in an
  increased conception rate.
• Conception rates averaged 47 (range 33-68).

(DeJarnette et al., 2008)
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Why isnt sexed semen availablefrom all bulls?

• Not all bulls are suitable for sorting
• Demand
• Genetics
• Semen quality
• Poor motility
• Poor morphology
• Inadequate concentration

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Why isnt sexed semen availablefrom all bulls?

• Reduction in total sperm available for freezing
  and distribution
• 20 of total sperm are able to be used
• 80 of sperm are discarded
• Y-chromosome bearing sperm
• Abnormal or dead cells
• Sperm cells not recognized by the laser

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What results can you expect with sexed semen in
cows?

• Conception rate
• Holstein cows 15 to 41
• Possible effect of
• Parity
• Days in milk
• Insemination at heat vs. timed AI

In cows, conception rates are 45 to 66 of
conventional semen.
(Andersson et al., 2006 Schenk and Everett,
2007 DeJarnette et al., 2008)
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The key to the value of sexed semenlies in the
opportunity to have better heifers.
(Fetrow et al., 2007)
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Economics including the value of increased
genetics

• Heifer value US1,800
• Inseminate the top 30 of heifers with sexed
  semen.
• Inseminate the remaining 70 of heifers with
  conventional semen.
• Results
• 22 profit per animal for all animals in the
  breeding pool

(Fetrow et al., 2007)
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Which economic factors should be considered?

• Value of heifers relative to bulls
• Cost of sexed semen relative to conventional
  semen
• Genetic merit of the heifer to be inseminated
• Value of a heifer relative to the cost to raise a
  heifer

(Fetrow et al., 2007)
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NAAB scoring system for calving ease
Degree of difficulty Calving ease score
No problem 1
Slight problem 2
Needed assistance 3
Considerable force 4
Extreme difficulty 5
(Scores recorded by producers, then submitted to
DHIA or AI Stud Adapted from K. Weigel)
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Frequency of difficult calvings
Calving ease score Lactation 1,
1 71
2 10
3 9
4 3
5 7
(Meyer, 2001 Adapted from K. Weigel)
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Economics of decreased dystocia

• Herd-level benefit of decreased dystocia will
  likely be low the value of this decrease is
  1.00/calving.

Therefore, decreased dystocia will probably not
be the principle driver of sexed semen use.
(Fetrow et al., 2007 Photo courtesy of M. Drost)
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Stillbirths

• Definition Calves born dead or that die within
  48 h of birth (The majority are usually born
  dead).

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What is the incidence of stillbirths following
use of conventional semen?
Meyer et al. 2000 Lombard et al. 2007
Lactation 1 11.1 12
Lactation 2 5.7 6.2
Overall 7.1 8.2
(666,341 calvings over 12 years 7,380 calvings
on 3 dairies over 13 mo., 24-h)
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What is the incidence of stillbirths following
use of sexed semen?
Calf sex Calf sex Calf sex Calf sex
Female Female Male Male Total Total
Semen type Live Dead Live Dead Live Dead
Sexed, 80.8 8.2 8.8 2.2 89.6 10.4
Conventional, 44.7 5.3 43.6 6.5 88.3 11.8
Total incidence of stillbirths is not influenced
by sexed semen
Average incidence 20, nevertheless, males
represent only 10 of total births
(DeJarnette et al., 2008)
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Further research is neededto improve sexed semen

• Increase sorting efficiency
• 400,000/sorter
• Increase market share
• TAI protocol in heifers?
• Targeted use in lactating cows?
• Is the male stillbirth data real?

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Final thoughts

• Use only in well-managed virgin heifers.
• Consider genetic merit of heifers.
• Inseminate 12 h after heat is observed. Do not
  use timed AI.
• Recognize the inevitable decrease in conception
  rate.

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Final thoughts

• What is the conception rate in your heifers with
  conventional semen?
• What management factors contribute to high or low
  conception rates (with conventional semen or
  sexed semen?)

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Acknowledgements

• Neil Michael
• Kylene Anderson
• John Schenk
• ABS Global Technical Services Team

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Thank you. Gracias. Obrigado.
Questions?