Effect of widespread and limited use of sexed semen on genetic progress and reproductive performance of dairy cows

Abstract

Stochastic simulation was used for studying the impacts of sexed semen on genetic progress and reproductive performance of dairy cows. Three strategies were compared: WSS (use unsexed semen in cows and heifers), SSH (use sexed semen in heifers and unsexed semen in cows) and SSCH (use sexed semen in both cows and heifers). Conception rate (CR) of unsexed semen was considered to be 35% and 65% in cows and heifers, respectively. CR of sexed semen was considered to be 15 (20% in cows and 50% in heifers), 10, 5 and 0 percentage points lower than unsexed semen. Thus, four subschemes were compared under SSCH (SSCH15, SSCH10, SSCH5, SSCH0) and SSH (SSH15, SSH10, SSH5, SSH0). Moreover, the effect was studied in four distinct paths of selection: active sires (AS), young bulls (YB), bull dams (BD) and milking cows (CW). The average genetic superiority of CW was 12% and 9.5% in SSCH15 and SSH15 strategies relative to a base scheme, respectively. The average genetic superiority of CW was 19% and 10.5% in SSCH0 and SSH0, respectively. Regression analysis showed that genetic superiority of CW increased significantly, that is, 0.5% and 0.1% per every 1% increase in CR in SSCH and SSH, respectively. The result showed that there is a significant difference between genetic superiority of cows in SSCH and SSH schemes. Widespread and limited use of sexed semen in commercial dairy herds resulted in a large genetic advantage in CW. The genetic advantage of gender control was minimal in the selection paths of AS, YB and BD. Open days and services per conception reached to 153 v. 125 days and 5 v. 2.86 under SSCH15 compared with WSS. The age at first calving increased from 774 to 790 days in SSH15 and SSCH15 strategies. Mean of parities decreased to 2.26 v. 2.42 by using sexed semen. The widespread use of sexed semen increased the age average of cows in all parities. Sexed semen increased selection intensity in the CW path, and this contributed to the genetic merit of future cows. On the other hand, sexed semen had a negative effect on the reproductive performance of dairy cows. Generally, although the effect of widespread use of sexed semen (SSCH) on genetic progress is significantly more than limited use of sexed semen (SSH), SSCH decreased reproductive performance of dairy herds dramatically, and this suggests that SSH scenarios might be more appropriate in animal breeding programs. Finally, to make a decision of which schemes are more convenient, it is necessary to compare the economic aspects of schemes.Keywords: sexed semen, selection, progeny test, open days, dairy cow Implications Sexed semen might increase the genetic progress of dairy cows by enhancing selection intensity. Sexed semen decreases the reproductive performance of dairy herds owing to low fertility. Reduction in reproductive performance has a negative effect on genetic progress by increasing generation interval and reducing newborn calves. Previous researchers have not considered these positive and negative effects of sexed semen simultaneously in a stochastic simu...

Applications and cost benefits of sexed semen in pasture-based dairy production systems

“…Increased rate of genetic gain A number of authors (Hohenboken, 1999;Weigel, 2004;Khalajzadeh et al, 2012) have hypothesised that sexed semen may be used to accelerate the rate of genetic gain in dairy herds, by selecting only the highest ranking cows to breed replacements from with sexed semen. This may be further emphasised if replacements are bred only from virgin heifers, as these should be the animals with the highest genetic merit in the herd.…”

Fertility of Commercial Sexed Semen and the Economic Analyses of its Application in Holstein Heifers

“…Additionally, application of sexed semen could be an effective tool to improve the annual genetic gain (Sørensen et al, 2011;Khalajzadeh et al, 2012) through production of replacement heifers only from the superior genetics cows or higher chance to select the best genetic potential as replacement heifers (Sørensen et al, 2011;Khalajzadeh et al, 2012).…”

Effect of insemination site and diameter of the pre‐ovulatory follicle on the odds of pregnancy in heifers using sexed or non‐sexed semen

“…5 First-lactation cows that give birth to a heifer calf produce 1.3-1.6% more milk over the 305-day lactation than those that give birth to a bull calf, with a production advantage persisting into the second lactation. 3,8,15 Sexed semen is more commonly used in heifers (rather than lactating cows) because a lower pregnancy per AI in heifers will not lead to an increase in the average days in milk of the lactating herd, although the average interval from birth to parturition in the heifers will increase. Sexed semen is less fertile than nonsexed semen because of chemical and physical effects that occur during flow cytometry and a lower number of sperm per dose.…”

“…A greater number of heifers born can help to reduce the incidence of dystocia, facilitate herd expansion, improve herd biosecurity (by reducing the need to purchase replacements) and accelerate genetic selection within dairy herds. 1,2,[4][5][6][7][8] Sexed semen may also give dairy farmers the opportunity to sell surplus replacement heifers or breed a proportion of cows to beef semen, thus producing more cross-bred beef calves instead of low-value dairy bull calves. 5 First-lactation cows that give birth to a heifer calf produce 1.3-1.6% more milk over the 305-day lactation than those that give birth to a bull calf, with a production advantage persisting into the second lactation.…”

“…10 The pregnancy per artificial insemination (AI) of sexed semen is typically reported to be 70-80% of the pregnancy per AI of non-sexed semen, [11][12][13][14] although this varies, with higher and lower relative pregnancy per AIs also reported. 3,8,15 Sexed semen is more commonly used in heifers (rather than lactating cows) because a lower pregnancy per AI in heifers will not lead to an increase in the average days in milk of the lactating herd, although the average interval from birth to parturition in the heifers will increase. 11 The lower the relative pregnancy per AI of sexed semen, the higher the reproductive cost.…”