1. Extent of sexed-semen usage
INTRODUCTION
There has been increasing use of sex-sorted semen since 2006 because producers can obtain more animals of the gender they prefer (usually heifers). The sexing process compromises conception rate (CR), and is the basis for recommending its use primarily on heifers because they have better fertility than older animals.
OBJECTIVE
To document CR obtained in different situations so producers know more precisely what kind of fertility to expect with various types of breedings.
DATA & METHODS
Breeding reports were provided to AIPL by the dairy records processing centers using AIPL Format 5
Data included Holstein breedings from January 2006 through December 2008
1,250,132 heifer breedings (116,846 with sexed-semen)
10,592,318 cow breedings (24,239 with sexed-semen)
The outcome for each breeding was coded as a failure (0) or a success (1), and was the basis for deriving CR
CR was derived separately for:
Virgin heifers (first through seventh services)
Cows (first through seventh services for each parity 1 through 5
Correlation between sire conception rate (SCR) for traditional vs. sexed-semen was calculated
RESULTS
Extent of sexed-semen usage
Cow breedings
% Sexed-semen breedings
Service number
Lactation number 1 2 3 4 5 42 14 7 11
>4
Conception rate (%)
Service number
Lactation number
All lactations 1 2 3 4 5
Conventional semen 35 31 30 28 26 32 34 29
>4 27 25
All services 33
Sexed-semen 22 23 24 15 20 17 19 21
Year of breeding
Conventional semen
Sexed-semen
Number %
Heifer breedings
2006
396,926
98.6
5,545
1.4
2007
394,660
90.6
41,186
9.4
2008
341,700
83.0
70,115
17.0
Cow breedings
2,490,850
99.9
2,003
0.1
4,105,396
99.8
7,951
0.2
3,971,833
99.6
14,285
0.4
53% of sexed-semen breedings occurred in first 2 services in first lactation; 72% occurred within first 2 lactations and first 2 services
Mean CR achieved with sexed-semen was 27% for cows (31% for conventional semen)
Trend toward increasing usage of sex-sorted semen from 2006 through 2008, nearly doubling in heifer usage in 2008 compared to 2007
82% of sexed-semen inseminations were on heifers
9.3% heifers bred using sexed-semen; 0.23% cows bred using sexed-semen across all years
In most cases, CR decreased 5 to 8 percentage points (16 to 28% reduction) when using sexed-semen compared to conventional semen
Correlation of SCR from conventional vs. sexed-semen was 0.49 for bulls with >300 breedings (51 bulls); for bulls with >800 breedings (15 bulls)
Heifer breedings
CONCLUSIONS
Trends show increasing usage of sexed-semen, especially in heifers from 2006 through 2008
93% of all sexed-semen inseminations were to either heifers or first lactation cows, where CR are typically higher
Mean CR with sexed-semen averaged 43% for heifers (~75% of that achieved with conventional semen) and 27% for cows (~87% of that achieved with conventional semen)
Based on mean CR, it takes 2.3 sexed services/pregnancy for heifers (1.8 using conventional) and 3.7 sexed services/pregnancy for cows (3.2 using conventional); a 0.5 increase in both heifers and cows
Correlations with SCR indicate that success with conventional semen may not always be predictive of success with sexed-semen
Service number
% of total breedings
% Sexed-semen breedings
Conception rate (%)
Conventional
Sexed 1 56 8 82 60 45 2 21 14 38 3 51 35
>4 6 44 30
All services 57 43
9% of heifer breedings were to sexed-semen (82% in first service); 96% of sexed-semen breedings occurred within first 2 services
Mean CR achieved with sexed-semen was 43% for heifers (57% for conventional semen)
CR decreased 14 to 18 percentage points (25 to 32% reduction) during first 7 services when using sexed-semen compared to conventional semen
Correlation of SCR from conventional vs. sexed-semen was 0.19 for bulls with >300 breedings (67 bulls); 0.32 for bulls with >800 breedings (31 bulls)