Optimizing the Use of Sexed Semen

Semen should then be thawed at 95°F for 45 seconds. If this temperature is not accurate, the improper thawing could affect the quality and viability of the semen.
Semen should then be thawed at 95°F for 45 seconds. If this temperature is not accurate, the improper thawing could affect the quality and viability of the semen.
(Taylor Leach)

During the last half of the 20th century (approximately 1955 to 2005), dairy cattle reproduction performance steadily declined. A variety of factors – from increased milk production to more inbreeding to less than optimal nutrition – may have contributed to the decline. 

Reproductive physiologists, geneticists and other dairy industry experts collaborated – with some of it fostered by the Dairy Cattle Reproduction Council (DCRC) – to reverse negative reproduction trends.

During the 2022 DCRC Annual Meeting, Dr. Paul Fricke, University of Wisconsin dairy cattle reproduction professor and Extension specialist, described the “reversal,” which started in 2002, as a reproduction revolution. 

“The dramatic increase in reproduction has occurred during the past decade (or so),” Fricke said.

While improved genetics, nutrition and management protocols helped improve dairy cattle reproduction, adoption of fertility programs, such as timed artificial insemination (TAI) and ovulation resynchronization (resynch) after a nonpregnancy diagnosis, played an important role in increased reproduction performance. Additionally, coupling fertility programs with new technologies for estrous detection, based on activity monitoring systems, effectively helped achieve higher pregnancy rates.

Strategies Leading To Reproductive Progress

During this revolution, sexed semen performance and economics improved. However, sexed semen performance still lags conventional semen performance. The use of sexed semen increases genetic progress in dairy herds through increased dam selection intensity (Khalajzadeh et al., 2012).

Other strategies include genomic testing or pedigrees to identify genetically superior heifers and cows, use of sexed semen to inseminate genetically superior dairy heifers and lactating cows balanced for replacement needs (Weigel et al., 2012), and use of beef semen to inseminate low genetic merit heifers and cows to produce crossbred calves with increased value in the beef market (Ettema et al., 2017).

“This has led to a rapidly evolving trend to use sexed Holstein semen, conventional Holstein semen, and conventional beef semen to inseminate Holstein females in the United States,” Fricke reported. 

Improving Fertility With Sexed Semen
Given sexed semen’s important role in helping dairy producers “right size” their herds and capitalizing on the herd’s best genetics, Fricke focused his presentation on management strategies to improve the fertility of sexed semen in nonlactating heifers and lactating dairy cows.

Fricke explained that heifers do not respond favorably to synchronization protocols based solely on GnRH and PGF2α, such as Ovsynch. The “key” is to include a controlled intravaginal progesterone insert (CIDR) during the protocol. This practice prevents heifers from displaying estrus until CIDR insert removal, which increases synchrony to the protocol.

DCRC recommends the 5-day CIDR-Synch protocol (https://www.dcrcouncil.org/protocols) for dairy heifers. Fricke noted that 27% to 33% of heifers display estrus >24 hours before scheduled TAI with the 5-day CIDR-Synch protocol. “This makes detection of estrus during the 5-day CIDR-Synch protocol a requirement to achieve acceptable conception rates,” he remarked.

Lauber et al. (2021) conducted a field trial to compare reproductive management programs for submission of Holstein heifers for first insemination with sexed semen. The researchers evaluated: 
•    CIDR5 (5-day CIDR-Synch)
•    CIDR6 (6-day CIDR-Synch)
•    EDAI (PGF2α on day 0 was followed by once daily detection of estrous [visual detection of tail-chalk removal and other signs] and AI)

The research team concluded that although delaying CIDR removal by 24 hours in a five-day CIDR-Synch protocol suppressed early expression of estrus before TAI, delaying CIDR removal by 24 hours tended to decrease pregnancy per artificial insemination (P/AI) for heifers inseminated with sexed semen.

Furthermore, submission of heifers to a five-day CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared with EDAI heifers. Fricke explained that the decreased cost per pregnancy was due to decreased days on feed. Further, this decreased cost more than covered the cost of the 5-day CIDR-Synch protocol and resulted in an overall $17 decrease in cost per pregnancy compared with heifers inseminated to estrus after treatment with prostaglandin.

Timing of AI: Sexed vs. Conventional Semen
Is optimal AI timing different for sexed semen compared with conventional semen? It appears that the answer is “yes.”

Bombardelli et al. (2016) evaluated the use of sexed semen in lactating cows with an activity monitoring system in Jersey cows to TAI based on increased activity. Overall, P/AI using sexed semen was greatest for Jersey cows inseminated between 23 and 41 hours after the onset of activity, which is later than the optimal timing for conventional semen of four to 12 hours (radiotelemetric system) after the onset of standing activity (Dransfield et al., 1998) or eight to 16 hours (activity monitoring system) after the onset of activity (Stevenson et al., 2014). 

“Inseminating high-producing cows later using sexed semen may be optimal for cows inseminated to estrus,” Fricke said. This is because ovulation occurs later relative to the onset of estrus in high-producing cows as milk production near the time of estrus increases. 

Fertility program: Optimal AI timing with Sexed Semen
What is the optimal timing of AI using sexed semen when the interval from timing of AI to ovulation is controlled using a fertility program at first service? To address this question, Lauber et al. (2020) submitted primiparous cows to a Double-Ovsynch protocol for first service that included a second PGF2α treatment 24 hours after the first in the breeding-Ovsynch portion of the protocol as described by Brusveen et al. (2009).

The last GnRH treatment (G2) varied between treatments and TAI. To vary the interval between G2 and TAI, cows were randomized to two treatments to receive G2 either 16 (G2-16) or 24 (G2-24) hours before TAI, which was fixed at 48 hours after the second PGF2α treatment of the breeding-Ovsynch portion of the Double-Ovsynch protocol.

The research team found that G2-24 cows had fewer P/AI than G2-16 cows at 34 ± 3 days (44% vs. 50%) and 80 ± 17 days (41% vs. 48%) after TAI. Pregnancy loss and fetal sex ratio did not differ between treatments. Induction of ovulation earlier relative to TAI after a Double-Ovsynch protocol decreased P/AI in primiparous Holstein cows, whereas pregnancy loss and proportion of female fetuses did not differ between treatments.

First Service Insemination Strategy
In a field study, Lauber et al. (2022) enrolled 742 lactating Jersey cows, which were randomized by ear tag number and within parity for submission, to either first service after a Double-Ovsynch (DO) protocol or a protocol for synchronization of estrus with twice-daily detection of estrus (EDAI) using sexed Jersey semen.

The results? Mean days from PGF2α (day 24) to AI was greater for EDAI than DO cows, whereas the proportion of cows inseminated was greater for DO than EDAI cows (100% vs. 75%). “Thus, 75% of cows in the EDAI treatment were detected in estrus and inseminated, whereas 25% of cows were not detected in estrus and were submitted to TAI after an Ovsynch protocol for first service,” Fricke reported. 

Bottom line: This study found that lactating Jersey cows submitted to a DO protocol for TAI at first service had more P/AI for both sexed and beef semen than cows inseminated after estrous synchronization.

 

 

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