Economic benefits of herd genotyping and using sexed semen for pure and beef-on-dairy breeding in dairy herds

The cost benefits of herd genotyping and the benefits of using sexed semen have been affected by recent improvements in sexing technologies, incorporation of direct health traits in the German total merit index for Holstein cattle, deteriorating prices for purebred heifer calves and bull calves, and introduction of herd genotyping programs. Inseminating genetically superior dams with female-sexed Holstein semen increases the mean breeding value of heifer calves and can produce more Holstein heifer calves than are needed for replacement. This provides an opportunity to increase the selection response in health and production traits at the farm level. A deterministic model is introduced that predicts the increase or decrease in net profit when a farmer takes part in a herd genotyping program and follows a certain insemination strategy. The types of semen allocated to cows and heifers may be sexed or unsexed and Holstein or beef breed. Genetically superior heifers and cows are inseminated with female-sexed Holstein semen, intermediate dams with unsexed Holstein semen, and genetically inferior dams with unsexed or male-sexed beef breed semen. In general, participating in a herd genotyping program is beneficial for German Holstein breeders. The optimum proportions of cows and heifers that should be inseminated with a certain type of semen are sensitive to farm-specific peculiarities. A small price difference between crossbred bull calves and crossbred heifer calves often makes the use of male-sexed beef breed semen uneconomic. Under the conditions considered, it was found to be advantageous to inseminate approximately 50% of heifers and 10% of cows with the highest genetic merit with female-sexed Holstein semen. The optimum proportion of cows that should be inseminated with unsexed beef breed semen was found to be approximately 40%. In a herd with a low replacement rate, the selected heifers can exhibit their genetic superiority over a longer period of time, and a larger proportion of cows can be inseminated with beef breed semen. Participation in a herd genotyping program is, therefore, particularly beneficial for herds with low replacement rates.

Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation

Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM). Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd versus even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol (DO; n = 707) or a protocol to synchronize estrus (ED; n = 565). All ED cows detected in estrus were inseminated (EDAI; n = 424), with undetected cows receiving TAI after an Ovsynch protocol (EDTAI; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5% ± 0.04% vs. 77.1% ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2% ± 0.03% vs. 43.6% ± 0.03%; beef, 64.2% ± 0.04% vs. 56.3% ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1% ± 0.03% vs. 40.6% ± 0.03%; beef, 65.5% ± 0.04% vs. 56.2% ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0% and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1% ± 0.01% vs. 79.2% ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0% ± 0.02% vs. 49.2% ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8% ± 0.04% vs. 51.0% ± 0.05%, respectively) or maintained or gained (55.6% ± 0.04% vs. 50.8% ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1% ± 0.04% vs. 36.1% ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.

Evaluation of sexed semen-based artificial insemination in Tharparkar cattle under organized farm condition

Sexed semen facilitates additional female calf production for the expansion of a herd at a faster rate and also curtails the surplus production of unwanted male calves. A study was conducted to evaluate the performance of sexed semen in indigenous Tharparkar cows based on 114 artificial inseminations (AI) performed at natural oestrus using two protocols i.e., single AI (n = 48) and double AI (n = 66). Overall, the first service conception rate (CR) was significantly higher in double (53.0%) than single (33.3%) AI protocol. The odds ratio of conception rate in double AI was 2.26 (χ2  = 4.4, df = 1, p = .04) with respect to single AI. The time that elapsed since the detection of oestrus to insemination was also analysed. In a single AI protocol, the CR was higher (p < .05) at 16 h (54.6%) than insemination at 8 h (27.0%) following the onset of oestrus. Yet, the CR using double AI protocol did not differ (p = .73) significantly when AIs were performed either at 8 h and 24 h (51.9%) or 16 h and 24 h (57.1%) post onset of oestrus. Besides, like the single AI protocol, the parity of the animals also influenced the CR, being higher in heifers (n = 22) than those of parous (n = 92) cows (72.73 vs. 40.43%, χ2  = 7.48, df = 1, p = .006) in the present study. The odds ratio of conception in heifers was 3.93 with respect to parous cows. Overall, the birth of female calf was 91.7%. In conclusion, the present study indicates a future promise of the sexed semen for the production of more female offspring from Tharparkar cattle.

Characterization of semen type prevalence and allocation in Holstein and Jersey females in the United States

Our objective was to characterize semen type prevalence and allocation to inseminate US Holstein and Jersey females by year, parity, service number, and herd size. A secondary objective was to identify the prevalence of beef breed sires selected to create beef × Holstein and beef × Jersey crossbred calves. The final data set included 8,244,653 total inseminations of 4,880,752 Holstein females across 9,155 herds, and 435,267 total inseminations of 266,058 Jersey females across 2,759 herds from October 2019 to July 2021. This data set represents approximately 42 and 27% of the total dairy cows and heifers, respectively, across approximately 40% of the total licensed dairy herds in the continental United States. Holstein and Jersey females were inseminated with 1 of 4 semen types: (1) beef, (2) conventional, (3) sexed, or (4) other dairy. The top 4 beef breeds used to produce beef × Holstein and beef × Jersey crossbred calves, respectively, were Angus (55.1 and 39.1%), Limousin (13.9, and 23.5%), Simmental (11.7 and 20.5%), and Crossbreed Beef (11.3 and 4.8%). From 2019 to 2021, the use of sexed semen to inseminate Holstein and Jersey females increased from 11.0 and 24.5% to 17.7 and 32.1%, respectively, and the use of beef semen to inseminate Holstein and Jersey females increased from 18.2 and 11.4% to 26.1 and 21.2%, respectively. The use of beef semen to inseminate Holstein and Jersey females increased with increasing parity and service number, whereas the use of sexed semen decreased with increasing parity and service number supporting that farmers used sexed semen more aggressively in higher fertility and younger females with greater genetic merit. Overall, the increase in sexed and beef semen inseminations was driven primarily by larger herds. In conclusion, sexed and beef semen inseminations in US Holstein and Jersey females increased from 2019 to 2021 and was allocated differentially based on parity and service number. This increase was driven primarily by larger dairy herds possibly due to differences in reproductive performance and economies of scale.

Influence of Ovarian Status and Steroid Hormone Concentration on Day of Timed Artificial Insemination (TAI) on the Reproductive Performance of Dairy Cows Inseminated with Sexed Semen

This study aimed to evaluate the effect of the ovarian status and steroid hormone concentration on the day of TAI on the reproductive performance of dairy cows subjected to estrus synchronization treatment and timed artificial insemination with sexed semen. Seventy-eight cyclic Holstein cows pre-treated with PGF2α-GnRH were divided in two groups-I (Preselect-OvSynch, n = 38) and II (OvSynch+PRID-7-day+eCG, n = 40)-and inseminated with sexed semen. The presence of preovulatory follicle (PF) with or without corpus luteum (CL), the PF diameter, the estradiol (E₂) and progesterone (P₄) concentrations on the day of TAI, the pregnancy rate (PR) and embryo loss were determined. On the day of TAI, 78.4% of all the pregnant cows presented a PF (mean size 1.80 ± 0.12 cm) without CL, low P₄ (0.59 ± 0.28 ng/mL) and high E₂ (12.35 ± 2.62 pg/mg) concentrations. The positive correlation between the size of the PF and the level of E₂ in the pregnant cows from group II was stronger than that of group I (R = 0.82 vs. R = 0.52, p < 0.05). The pregnancy rate on day 30 (57.5% vs. 36.8%) and day 60 (50% vs. 26.3%; p < 0.05) and the embryo losses (13% vs. 28.5%) showed better effects of treatment in group II. In conclusion, the ovarian status and the steroid hormone concentration on the day of TAI influence the pregnancy rates of dairy cows subjected to estrus synchronization and timed artificial insemination with sexed semen.

Effect of oestrous expression prior to timed artificial insemination with sexed semen on pregnancy rate in dairy cows

The objectives of the study were to determine (1) oestrous expression rate and (2) the effect of oestrous expression prior to progesterone-based Ovsynch protocol on pregnancy rate in Holstein cows. All cows (n = 917) were subjected to 7-day progesterone-based Ovsynch protocol. In this protocol, cows that expressed oestrus before (HEAT1) the scheduled second GnRH were inseminated 20 h later after the onset of oestrus without GnRH administration. Cows that expressed oestrus after the second GnRH administration (HEAT2) or did not express oestrus (NOHEAT) received fixed-timed AI. Oestrous expression was determined by using activity-rumination monitoring system and all cows were inseminated with sexed semen. Oestrous expression rate prior to FTAI was 40.5% and the majority (p < .01) of oestrous expression were in HEAT2 compared with HEAT1 in both primiparous (71.8 vs. 28.1%) and multiparous cows (69.5 vs. 30.5%). The mean interval from intravaginal device removal to the onset of oestrus was 47.4 ± 0.9 h and 62.9 ± 0.5 in HEAT1 and HEAT2, respectively. Primiparous cows (47.7%) had a higher (p < .01) expression rate compared with multiparous cows (37.2%). Overall pregnancy rate was 37.4% and there was two-way significant interaction between parity and oestrous expression on pregnancy rate (p < .01). Both primiparous (48.1 vs. 35.8%) and multiparous cows (47.4 vs. 28.4%) that expressed oestrus had greater (p < .01) pregnancy rate compared with cows that did not express oestrus. There was no difference in pregnancy rates of HEAT1 and HEAT2 in both primiparous (44.7 vs. 49.5%) and multiparous cows (47.2 vs. 47.6%). Pregnancy rate was not influenced (p = .21) by milk production (high or low) in both primiparous (47.6 vs. 48.6%) and multiparous (54.9 vs. 42.1%) cows that expressed oestrus, respectively. In conclusion, cows showing oestrus before or after second GnRH of the Ovsynch protocol had greater pregnancy rate than cows not showing oestrus.

Application of gender-ablated semen during timed artificial insemination following oestrous synchronization in dairy and beef cows

The objectives of this study were to compare oestrous synchronization expression and conception rate following timed artificial insemination (TAI) with frozen-thawed X-sexed or unsexed semen in dairy and beef cows. For this study, 227 cows (dairy, n = 130 and beef, n = 97) were assigned to a 9-day Ovsynch + controlled intravaginal drug release (CIDR) protocol. All cows were TAI using X-sexed or unsexed semen from 8 sires. Each semen type was obtained from 4 sires [2 dairy (Holstein Friesian) and 2 beef (Angus)]. Pregnancy detection was performed on Days 35, 65 and 95 following TAI by transrectal ultrasonography and hand palpation. The proportion of oestrus expression was higher in dairy (85.3%) cows compared with beef (65.0%) cows (p < .05). Overall, dairy (X-sexed, 61.9% and unsexed, 62.0%) cows had greater conception rates on Day 35 compared to beef (X-sexed, 56.0% and unsexed, 52.2%) cows (p < .05). Concurrently, on Day 95, overall conception rates in dairy (X-sexed, 41.4% and unsexed, 48.5%) cows were greater than beef (X-sexed, 38.0% and unsexed, 37.0%) cows (p < .05). Pregnancy/embryo losses between Days 35 and 65 in dairy (X-sexed, 33.3% and unsexed, 18.2%) cows and beef (X-sexed, 28.6% and unsexed, 29.2%) cows were recorded (p < .05). Dairy (X-sexed, 7.7% and unsexed, 8.3%) cows had higher incidence of pregnancy losses between Days 66 and 95 when compared to beef (X-sexed, 5.0% and unsexed, 0.0%) cows (p < .05). Oestrous expression and conception rates in dairy and beef cows were satisfactory. Advanced reproductive biotechnologies can successfully utilize gender-ablated semen in organized emerging cattle farming systems.

Sorted Bulls' X-Chromosome-Bearing Spermatozoa Show Increased GAPDHS Activity Correlating with Motility

Sperm sexing is a technique for spermatozoa sorting into populations enriched with X- or Y-chromosome-bearing cells and is widely used in the dairy industry. Investigation of the characteristics of sorted semen is of practical interest, because it could contribute to the enhancement of sexed semen fertility characteristics, which are currently lower than those of conventional semen. Comparison of a spermatozoa population enriched with X-chromosome-bearing cells to a mixed population is also intriguing in the context of potential differences that drive the mechanisms of primary sex-ratio determination. In this work, sexed (X spermatozoa) and conventional spermatozoa of Holstein bulls were analyzed for the content and enzymatic activity of GAPDHS, a sperm-specific isoform of glyceraldehyde-3-phosphate dehydrogenase that plays a significant role in the regulation of flagellar activity. No difference in the amount of this glycolysis enzyme per cell was revealed, but, notably, GAPDHS enzymatic activity in the sexed samples was significantly higher. Enzymatic activity among the group of sexed but not conventional sperm samples positively correlated with spermatozoa motility, which indicates the significant role of this enzyme for the sorted cells population.

Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system

This study used a stochastic simulation model to estimate the potential economic benefit of using timed artificial insemination (TAI) in combination with conventional unsorted (TCONV) and sexed (TSEX) semen in heifers only (TCONV-H, TSEX-H) and in both heifers and lactating cows (TCONV-HC, TSEX-HC) in a high-producing, pasture-based production system. The scenarios were compared with a conventional reproductive policy (CONV) in which heifers and cows were inseminated with conventional unsorted semen after estrus detection. Sensitivity analysis was also used to estimate the effect of hormone costs from TAI use on the profitability of each program relative to CONV. The mean annual (± standard deviation) profit advantage (ΔPROF) over CONV for TCONV-H, TCONV-HC, TSEX-H, and TSEX-HC scenarios were €3.90/cow ± 4.65, €34.11/cow ± 25.69, €13.96/cow ± 6.83, and €41.52/cow ± 42.86, respectively. Combined application of both technologies was shown to return a greater annual ΔPROF on average compared with that achievable from TAI alone. However, the risk of not returning a positive annual ΔPROF varied across the scenarios with higher risk in TCONV-H and TSEX-HC. Specifically, TCONV-H and TSEX-HC had a 24 and 18% chance, respectively, of not returning a positive annual ΔPROF. Sensitivity analysis showed that when hormone costs increased by €10/cow TCONV-H and TSEX-HC had a 38 and 23% chance, respectively, of not returning a positive annual ΔPROF. The range in ΔPROF for TCONV policies was most sensitive to the TAI pregnancy rate and TSEX policies were most sensitive to the relative fertility achieved with sexed compared with unsorted semen. This study has shown TAI and sexed semen are complementary technologies that can increase genetic gain and profitability in a pasture-based, dairy production system.

Comparison of reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen based on expression of estrus, pregnancy outcomes, and cost per pregnancy

Our objective was to evaluate reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen. In experiment 1, nulliparous Holstein heifers (n = 462) were submitted to a 5-d progesterone-releasing intravaginal device (PRID)-Synch protocol [d 0, GnRH + PRID; d 5, PGF_2α - PRID; d 6, PGF_2α; d 8, GnRH + TAI] and were randomly assigned for PRID removal on d 5 or 6 of the protocol followed by timed artificial insemination (TAI) with conventional semen. Delaying PRID removal decreased early expression of estrus before scheduled TAI (0.9 vs. 12.2%), and pregnancies per AI (P/AI) did not differ between treatments. In experiment 2, nulliparous Holstein heifers (n = 736) from 3 commercial farms were randomized within farm to 1 of 3 treatments for first AI with sexed semen: (1) CIDR5 [d -6, GnRH + controlled internal drug release (CIDR); d -1, PGF_2α - CIDR; d 0, PGF_2α; d 2, GnRH + TAI]; (2) CIDR6 (d -6, GnRH + CIDR; d -1, PGF_2α; d 0, PGF_2α - CIDR; d 2, GnRH + TAI); and (3) EDAI (PGF_2α on d 0 followed by once-daily estrous detection and AI). Delaying CIDR removal decreased early expression of estrus before scheduled TAI (0.004 vs. 27.8%); however, CIDR5 heifers tended to have more P/AI at 35 (53 vs. 45 vs. 46%) and 64 (52 vs. 45 vs. 45%) days after AI than CIDR6 and EDAI heifers, respectively. Overall, CIDR5 and CIDR6 heifers had fewer days to first AI and pregnancy than EDAI heifers which resulted in less feed costs than EDAI heifers due to fewer days on feed until pregnancy. Despite greater hormonal treatment costs for CIDR5 heifers, costs per pregnancy were $16.66 less for CIDR5 than for EDAI heifers. In conclusion, delaying PRID removal by 24 h within a 5-d PRID-Synch protocol in experiment 1 suppressed early expression of estrus before TAI, and P/AI for heifers inseminated with conventional semen did not differ between treatments. By contrast, although delaying CIDR removal by 24 h within a 5-CIDR-Synch protocol in experiment 2 suppressed early expression of estrus before TAI, delaying CIDR removal by 24 h tended to decrease P/AI for heifers inseminated with sexed semen. Further, submission of heifers to a 5-d CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared with EDAI heifers.

Bovine semen sexing: Sperm membrane proteomics as candidates for immunological selection of X- and Y-chromosome-bearing sperm

The use of sexed semen in dairy and beef farms ensures the production of animals of the desired sex, resulting in a reduction of costs and an improvement of environmental sustainability. Several methods have been developed over the years, but most of them were abandoned due to their limited efficacy. Currently, the only commercially available method for the separation of X- and Y-chromosome-bearing sperm is fluorescence-activated cell sorting. However, this technique is expensive and has limited usefulness for the industry, considering that it cannot produce doses of sexed semen with the desired number of sperm for artificial insemination. Immunological methods have emerged as an attractive alternative to flow cytometry and proteomic knowledge of X- and Y-sperm could be useful to the development of a new method. In this review, we identify the main applications of sexed semen, describe the existing methods and highlight future research opportunities in the field. We consider that immunological methods, based on sperm cell's surface proteins differentially expressed between X- and Y-sperm, could be an interesting and promising approach to semen sexing.

Genetic consequences of terminal crossbreeding, genomic test, sexed semen, and beef semen in dairy herds

The development of breeding tools, such as genomic selection and sexed semen, has progressed rapidly in dairy cattle breeding during the past decades. In combination with beef semen, these tools are adopted increasingly at herd level. Dairy crossbreeding is emerging, but the economic and genetic consequences of combining it with the other breeding tools are relatively unknown. We investigated 5 different sexed semen schemes where 0, 50, and 90% of the heifers; 50% of the heifers + 25% of the first-parity cows; and 90% of the heifers + 45% of the first-parity cows were bred to sexed semen. The 5 schemes were combined in scenarios managing pure-breeding or terminal crossbreeding, including genomic testing of all newborn heifers or no testing, and keeping Swedish Red or Swedish Holstein as an initial breed. Thus, 40 scenarios were simulated, combining 2 stochastic simulation models: SimHerd Crossbred (operational returns) and ADAM (genetic returns). The sum of operational and genetic returns equaled the total economic return. Beef semen was used in all scenarios to limit the surplus of replacement heifers. Terminal crossbreeding implied having a nucleus of purebred females, where some were inseminated with semen of the opposite breed. The F₁ crossbred females were inseminated with beef semen. The reproductive performance played a role in improving the benefit of any of the tools. The most considerable total economic returns were achieved when all 4 breeding tools were combined. For Swedish Holstein, the highest total economic return compared with a pure-breeding scenario, without sexed semen and genomic test, was achieved when 90% sexed semen was used in heifers and 45% sexed semen was used for first-parity cows combined with genomic test and crossbreeding (+€58, 33% crossbreds in the herd). The highest total economic return for Swedish Red compared with a pure-breeding scenario, without sexed semen and genomic test, was achieved when 90% sexed semen was used in heifers combined with genomic test and crossbreeding (+€94, 46% crossbreds in the herd). Terminal crossbreeding resulted in lower genetic returns across the herd compared with the corresponding pure-breeding scenarios but was compensated by a higher operational return.

A Perspective on the Use of Sexed Semen to Reduce the Number of Surplus Male Dairy Calves in Ireland: A Pilot Study

The production of surplus male offspring illustrates a socioethical concern in the dairy industry. In this article, we highlight the animal health and welfare implications of production outputs for surplus dairy calves, namely veal production, dairy calf to beef production, and euthanasia. Moreover, we present a pilot study focus on exploring the perception of key industry actors within the dairy industry in Ireland regarding the use of sexed semen as a mitigation strategy to reduce the production of surplus male dairy calves. A pilot survey was completed by farmers (n = 6), veterinarians (n = 17), and dairy farm advisors (n = 11). All the veterinarians, 80% of the farmers, and 62% of the advisors believed that the use of sexed semen had a positive influence on herd welfare. All participants identified the same barriers to the implementation of sexed semen: lower conception rate, lower availability, and higher cost. The reviewed literature highlights the importance of tailored communication to support knowledge exchange between stakeholders and key industry actors such as dairy farmers, their veterinarians, and advisors. Research to understand stakeholders' perception is pivotal to address socioethical concerns such as the surplus male dairy calves.

Effects of herd fertility on the economics of sexed semen in a high-producing, pasture-based dairy production system

This study used a stochastic simulation model to estimate the potential economic benefit of using sexed semen in heifers only and in heifers and lactating cows in a high-producing, pasture-based system under 3 fertility scenarios. Three breeding strategies were modeled: (1) only heifers inseminated with sexed semen and cows inseminated with conventional unsexed semen (SSH); (2) both heifers and cows inseminated with sexed semen (SSHC); and (3) a reference scenario in which all females were inseminated with conventional, unsexed semen (CONV). Each scenario was evaluated under 3 herd fertility states: high (HF), medium (MF), and low (LF), which, under the reference scenario, corresponded to herd replacement rates of 21, 25, and 31%, respectively. The model estimated the economic profit, including the net present value of the genetic gain from selection intensity. The economic return from adoption of sexed semen strategies declined, with reduced levels of baseline herd fertility turning negative in the LF state. The mean (±SD) sexed semen advantage (SSA) per cow for HF-SSH, MF-SSH, and LF-SSH scenarios were €30.61 ± 8.98, €27.45 ± 7.19, and €14.69 ± 11.06, respectively. However, the SSA per cow for HF-SSHC, MF-SSHC, and LF-SSHC scenarios were €49.14 ± 15.43, €18.46 ± 30.08, and -€19.30 ± 57.11. The range in economic profit for SSA for SSH was most sensitive to calf prices in HF-SSH and the pregnancy rate of sexed semen as a percentage of conventional unsorted semen in MF-SSH and LF-SSH. The range in economic profit for SSA for SSHC scenarios was most sensitive to the pregnancy rate of sexed semen as a percentage of conventional unsorted semen in HF-SSHC, MF-SSHC, and LF-SSHC. This study highlights the effect of baseline herd fertility state on the financial advantage of adopting sexed semen in a pasture-based dairy production system.

Indian dairy farmers' willingness to pay for sexed semen

Sexed semen is one of the newest reproductive technologies available for dairy farmers and can fulfil their desire to produce a high percentage of female calves. The present study was designed to define the willingness of Indian dairy farmers to pay for sexed semen. Hence, 120 small holder dairy farmers and 90 commercial dairy farmers were randomly selected from Karnal and Yamunanagar districts in North-western Haryana, where there is a high proportion of crossbred dairy cattle. Willingness to pay for sexed semen was evaluated by a contingent valuation method and its determinants by an interval regression model. The majority of the small holder dairy farmers (81.67%) were willing to pay for sexed semen and they were ready to pay around INR 340 per sexed semen straw. Almost all (99%) of the commercial dairy farmers were willing to pay around INR 770 per sexed semen straw, i.e. more than double the value identified by small holder dairy farmers. Among all the predictors fitted in the interval regression model to explain the willingness to pay for sexed semen by the commercial dairy farmers, namely education level, herd size and attitude towards public extension systems, were positive and significant contributors. Our findings may help to identify what subsidy is required to promote sexed semen among dairy farmers, and as a consequence further improve breeding policies by introducing this new livestock production technology with the active participation of the dairy farmers.

Short communication: Effect of timing of induction of ovulation relative to timed artificial insemination using sexed semen on pregnancy outcomes in primiparous Holstein cows

Our objective was to determine the effect of increasing the interval from induction of ovulation to timed artificial insemination (TAI) on fertility by decreasing the interval from TAI to ovulation using sexed semen within a synchronized breeding program. Our hypothesis was that induction of ovulation earlier relative to TAI would increase pregnancies per artificial insemination (P/AI). Primiparous Holstein cows from 3 commercial dairy farms in the United States were submitted to a Double-Ovsynch protocol for first service as follows: Pre-Ovsynch (GnRH; 7 d, PGF_2α; 3 d, GnRH), followed 7 d later by Breeding-Ovsynch [GnRH (G1); 7 d, PGF_2α; 24 h, PGF_2α], followed by the last GnRH treatment (G2), which varied between treatments, and TAI. To vary the interval between G2 and TAI, cows were randomized to 2 treatments to receive G2 either 16 (G2-16; n = 373) or 24 (G2-24; n = 357) h before TAI, which was fixed at 48 h after the second PGF_2α treatment of the Breeding-Ovsynch portion of the protocol. All cows were inseminated with sexed semen, and each herd used sires of their choosing, which were randomly allocated between treatments. Pregnancy diagnosis was conducted by herd veterinarians using transrectal ultrasonography. In disagreement with our hypothesis, G2-24 cows had fewer P/AI than G2-16 cows at 34 ± 3 d (44 vs. 50%) and 80 ± 17 d (41 vs. 48%) after TAI. Pregnancy loss (5 vs. 6%) and fetal sex ratio (92:8 vs. 90:10, female:male) did not differ between treatments for G2-16 and G2-24 cows, respectively. Thus, we reject our hypothesis and conclude that induction of ovulation earlier relative to TAI with sexed semen for first service after a Double-Ovsynch protocol decreased P/AI in primiparous Holstein cows.

Economic opportunities of using crossbreeding and sexing in Holstein dairy herds

With the increasing availability of sexed semen, farms have the opportunity to select genetically superior dams to produce their replacement animals and to produce crossbred calves for beef production of higher economic value than the remainder of the herd. However, higher costs and reduced fertility of sexed semen complicate the decision of when and to what extent sexed semen should be applied in a herd. The objective of this study was to explore the economically optimal utilization of sexed semen and crossbreeding among North Rhine-Westphalian dairy farms in a holistic single-farm model. For the analysis, we derived a representative sample of farms from Latin Hypercube sampling based on the observed distribution of farm characteristics from official North Rhine-Westphalian Farm Structure Survey data. Market- and technology-related input parameters such as output prices and sexed semen accuracy and fertility were included in the sampling procedure. Modeling results of the systematic sensitivity analysis were evaluated in a statistical meta-model. We found that the profit-maximizing utilization of sexed semen and crossbreeding was highly heterogeneous among the farms. Farms with lower stocking densities, <2 livestock units (LU)/ha, were generally found to produce excess heifers for sale, whereas farms with stocking densities >2 LU/ha were producing crossbred calves and using sexed semen only to produce replacement animals. On average, female-sexed dairy semen was used on 25.3% of all inseminations. Beef semen (both sexed and conventional) for producing crossbred calves was used in an average of 21.5% of the inseminations. The combination of sexed semen and crossbreeding increased profits from €0 to €568 per cow per year, with an average of €79.42 per cow per year. Farms characterized by low stocking densities (<2 LU/ha) and above-average replacement rates (>40%) were found to have higher profit increases as a result of selling more heifers from the use of sexed semen. Overall, sexed semen and crossbreeding adoption were most sensitive to stocking density and average cow longevity, as well as to additional costs for sexed semen and sexed semen accuracy. Our results show the potential of modern breeding technologies to improve dairy farm profits and the need to judge their profitability in the light of farm-specific production settings.

Characteristics of offspring derived from conventional and X-sorted bovine sperm

The objective of this retrospective study was to compare survival during the first year of life and adult performance of offspring derived from artificial insemination (AI) with X-sorted or conventional sperm processed from the same ejaculates. We analyzed a data set that included AI of dairy heifers and lactating cows with fresh conventional sperm (3 × 10⁶ sperm per straw), fresh X-sorted sperm (1 or 2 × 10⁶ sperm per straw), or frozen X-sorted sperm (2 × 10⁶ sperm per straw). The data set contained records of 5,179 offspring born on 396 farms. Offspring were classified as born from conventional sperm (CONV) if they were the product of an insemination with fresh conventional sperm, or born from X-sorted sperm (SS) if they were product of any of the 3 X-sorted sperm treatments. Generalized linear mixed models were used to evaluate the effect of sperm treatment on (1) survival during the first year of life; (2) reproductive performance, lactation performance, and survival of female offspring; and (3) slaughter characteristics of male offspring. Stillbirth rates and mortality rates during the first 2 mo of life were greater for male calves (2.8 and 5.0%, respectively) than for female calves (1.6 and 2.0%, respectively). No differences between offspring derived from SS and CONV were detected for incidences of stillbirth or mortality during the first 12 mo of life within sex of calf. Reproductive performance, milk volume, milk fat, milk protein yields during first; second; and third lactations, and survival to third lactation did not differ between female offspring derived from CONV and SS. Across all age groups, CONV steers had heavier carcasses than SS steers (325.3 vs. 318.3 kg), but there were no differences in weight between CONV and SS steers within any of the age groups (≤24, 25-27, 28-30, and >30 mo of age). The distribution of slaughter age did not differ between CONV and SS steers when the analysis was restricted to herds that reared steers derived from both types of sperm. Carcass conformation and fat scores of steers were not affected by sperm treatment. There was no difference in carcass weight between young bulls (≤2 yr) derived from CONV or SS. In conclusion, the results provide no evidence of differences in survival during the first year of life between offspring derived from CONV or SS, or for any of the reproductive and lactation performance characteristics studied between female offspring derived from CONV or SS. Modest differences in carcass weight between CONV and SS steers were detected, but this may reflect differences in management and husbandry in the rearing herds rather than the sex-sorting process. A controlled study using steers derived from conventional or X-sorted sperm from split ejaculates and reared under the same husbandry conditions is needed to clarify whether there is a true difference in body weight gain due to the sex-sorting process.

Technical note: Droplet digital PCR precisely and accurately quantifies sex skew in bovine semen

Quantifying the relative population of sperm cells bearing the X or Y chromosome in a sexed-semen sample has historically been limited to methods that are either low throughput and sensitive to user subjectivity (e.g., fluorescence in situ hybridization), conterminous (using the same technology to generate and confirm the sex skew), or relatively insensitive (including quantitative PCR with a change detection threshold of 2×). Customers pay a premium for sexed semen and should have access to reliable sex skew data, generated by an accurate, precise test that is orthogonal to the method used to generate sexed semen. Droplet digital PCR (ddPCR) has the capacity to provide an accurate and precise sex skew quantitation by subdividing a pool of template DNA into nanoliter-scale droplets containing either 1 or 0 copies of template DNA. Then PCR amplification is conducted in the droplets, and the number of copies of the amplicon of interest can be counted as the number of fluorescence-positive droplets based on classic quantitative PCR fluorescent reporters. We have optimized and validated a multiplexed ddPCR assay that uses this copy counting method to quantify the sex skew (ratio of X or Y chromosomes) in frozen-thawed bovine sexed semen. The assay interrogates at least 1,000 cells per sample well, quantifying X and Y chromosome copy numbers along with an autosomal gene, GAPDH, used as an internal assay control to confirm total cells counted. The ddPCR sex skew assay achieved a 0.5-percentage-point variance for %X or %Y with a broad linear detection range, from 10 to 95% X, and provided reproducible skew values across a range of 9 to 27 ng of genomic DNA input. This approach overcomes some limitations of other sex skew assays by quantifying absolute X and Y chromosome copy numbers, thus providing a rigorous, independent assessment of sex-skewed semen.

Review: Recent advances in bovine in vitro embryo production: reproductive biotechnology history and methods

In vitro production (IVP) of embryos and associated technologies in cattle have shown significant progress in recent years, in part driven by a better understanding of the full potential of these tools by end users. The combination of IVP with sexed semen (SS) and genomic selection (GS) is being successfully and widely used in North America, South America and Europe. The main advantages offered by these technologies include a higher number of embryos and pregnancies per unit of time, and a wider range of potential female donors from which to retrieve oocytes (including open cyclic females and ones up to 3 months pregnant), including high index genomic calves, a reduced number of sperm required to produce embryos and increased chances of obtaining the desired sex of offspring. However, there are still unresolved aspects of IVP of embryos that limit a wider implementation of the technology, including potentially reduced fertility from the use of SS, reduced oocyte quality after in vitro oocyte maturation and lower embryo cryotolerance, resulting in reduced pregnancy rates compared to in vivo-produced embryos. Nevertheless, promising research results have been reported, and work is in progress to address current deficiencies. The combination of GS, IVP and SS has proven successful in the commercial field in several countries assisting practitioners and cattle producers to improve reproductive performance, efficiency and genetic gain.

Fertility of fresh and frozen sex-sorted semen in dairy cows and heifers in seasonal-calving pasture-based herds

Our objective in this study was to evaluate the reproductive performance of dairy heifers and cows inseminated with fresh or frozen sex-sorted semen (SS) in seasonal-calving pasture-based dairy herds. Ejaculates of 10 Holstein-Friesian bulls were split and processed to provide (1) fresh conventional semen at 3 × 10⁶ sperm per straw (CONV); (2) fresh SS at 1 × 10⁶ sperm per straw (SS-1M); (3) fresh SS semen at 2 × 10⁶ sperm per straw (SS-2M); and (4) frozen SS at 2 × 10⁶ sperm per straw (SS-FRZ). Generalized linear mixed models were used to evaluate the effect of semen treatment and other explanatory variables on pregnancy per artificial insemination (P/AI) in heifers (n = 3,214) and lactating cows (n = 5,457). In heifers, P/AI was greater for inseminations with CONV (60.9%) than with SS-FRZ (52.8%) but did not differ from SS-1M (54.2%) or SS-2M (53.5%). Cows inseminated with CONV had greater P/AI (48.0%) than cows inseminated with SS, irrespective of treatment (SS-1M, SS-2M, and S-FROZEN; 37.6, 38.9, and 40.6%, respectively). None of the SS treatments differed from each other with regard to P/AI in either heifers or cows. The relative performance of SS compared with CONV was also examined [i.e., relative P/AI = (SS P/AI)/(CONV P/AI) × 100]. Frozen SS achieved relative P/AI >84%. Bull affected P/AI in both heifers and cows, but no bull by semen treatment interaction was observed. In heifers, P/AI increased with increasing predicted transmitting ability for milk protein percentage. In cows, P/AI increased with increasing Economic Breeding Index (EBI) and with days in milk (DIM) at AI but decreased with increasing EBI milk subindex, parity and with DIM². Cows in parity ≥5 had the lowest P/AI and differed from cows in parities 1, 2, or 3. Dispatch-to-AI interval of fresh semen did not affect P/AI in lactating cows, but a dispatch-to-AI interval by bull interaction was detected whereby P/AI was constant for most bulls but increased with greater dispatch-to-AI intervals for 2 bulls. In conclusion, frozen SS achieved greater P/AI relative to conventional semen than was previously reported in lactating cows. Fresh SS did not achieve greater P/AI than frozen SS, regardless of whether the sperm dose per straw was 1 × 10⁶ or 2 × 10⁶. A bull effect for all semen treatments, as well as a dispatch-to-AI interval by bull interaction for fresh semen, highlights the importance of using a large team of bulls for breeding management.

Genomic Selection and Use of Molecular Tools in Breeding Programs for Indigenous and Crossbred Cattle in Developing Countries: Current Status and Future Prospects

Genomic selection (GS) has resulted in rapid rates of genetic gains especially in dairy cattle in developed countries resulting in a higher proportion of genomically proven young bulls being used in breeding. This success has been undergirded by well-established conventional genetic evaluation systems. Here, the status of GS in terms of the structure of the reference and validation populations, response variables, genomic prediction models, validation methods, and imputation efficiency in breeding programs of developing countries, where smallholder systems predominate and the basic components for conventional breeding are mostly lacking is examined. Also, the application of genomic tools and identification of genome-wide signatures of selection is reviewed. The studies on genomic prediction in developing countries are mostly in dairy and beef cattle usually with small reference populations (500-3,000 animals) and are mostly cows. The input variables tended to be pre-corrected phenotypic records and the small reference populations has made implementation of various Bayesian methods feasible in addition to GBLUP. Multi-trait single-step has been used to incorporate genomic information from foreign bulls, thus GS in developing countries would benefit from collaborations with developed countries, as many dairy sires used are from developed countries where they may have been genotyped and phenotyped. Cross validation approaches have been implemented in most studies resulting in accuracies of 0.20-0.60. Genotyping animals with a mixture of HD and LD chips, followed by imputation to the HD have been implemented with imputation accuracies of 0.74-0.99 reported. This increases the prospects of reducing genotyping costs and hence the cost-effectiveness of GS. Next-generation sequencing and associated technologies have allowed the determination of breed composition, parent verification, genome diversity, and genome-wide selection sweeps. This information can be incorporated into breeding programs aiming to utilize GS. Cost-effective GS in beef cattle in developing countries may involve usage of reproductive technologies (AI and in-vitro fertilization) to efficiently propagate superior genetics from the genomics pipeline. For dairy cattle, sexed semen of genomically proven young bulls could substantially improve profitability thus increase prospects of small holder farmers buying-in into genomic breeding programs.

Bovine sperm sex-selection technology in Japan

BACKGROUND

In Japan, Livestock Improvement Association of Japan started commercially producing sexed bovine semen 10 years ago, and sexed bovine semen is currently used for the artificial insemination (AI) in the farms. In this review, the authors introduce the technology for sperm sexing by flow cytometry, the efforts at commercializing sexed semen in Japan, and recent field data on artificial insemination of the cattle with sexed semen.

METHODS

In the procedures of the flow cytometric method, X-chromosome-bearing sperm and Y-chromosome-bearing sperm were fluorescently stained, separated from each other by analyzing the difference in the DNA content, and cryopreserved. The authors surveyed the conception rates after AI with these sperm and sex ratios of the offspring with the cooperation from livestock associations, AI technicians, and farmers.

MAIN FINDINGS RESULTS

Although AI with sexed semen was associated with lower conception rates in comparison with AI with conventional semen, the accuracy of sex selection using AI with sexed semen was beyond >90%.

CONCLUSION

Sexed semen produced by flow cytometry has the potential to produce offspring of the preferred sex with high accuracy and reliability. Thus, it is expected that sexed semen is used for AI more frequently in the farms.

522 Developing innovative digital technology and genomic approaches to livestock genetic improvement in developing countries

Genomic selection has resulted in rapid rates of genetic gains especially in dairy cattle in developed countries and well established conventional genetic evaluations systems have provided the strong foundation. The basic building blocks for data recording and genetic evaluation are lacking in most developing countries. The application of digital technologies such as mobile phones opens pathways to overcome some of the barriers for data collection. Digital systems have been used in projects such as the African Dairy Genetic Gains in Eastern Africa to capture data thus overcoming huge organizational infrastructure and costs. Genotypic data in smallholder systems offer quick wins in terms of parent verification, breed composition determination and genetic evaluation using G . LD SNP panels have been used for determination of breed composition and parent verification for crossbreds in Eastern Africa, beef breeds and small ruminants in South Africa. The few studies on genomic prediction in developing countries are mostly in dairy and beef cattle and are characterized by small reference populations (≈1000 to 2000 animals). The gains in accuracy range from 0.33 to 0.45 in Eastern Africa crossbred cattle but much higher at 0.5 to 0.6 for milk, fat and protein in yields for Gyr and Guzera in Brazil. The use of LD chips accompanied by imputation has been applied in several studies and loss in accuracy has been minimal. Specialized LD chips such as the INDUSCHIP consisting of 45700 SNPs sampled from HD genotypes of mostly four indicus breeds and their taurine crosses in India have been developed and used for genomic prediction. The use of sexed semen of genomically proven young bulls could substantially improve profitability of small holder farmers and therefore offers prospect for farmers buying-in into genomic breeding programs.

A 100-Year Review: Reproductive technologies in dairy science

Reproductive technology revolutionized dairy production during the past century. Artificial insemination was first successfully applied to cattle in the early 1900s. The next major developments involved semen extenders, invention of the electroejaculator, progeny testing, addition of antibiotics to semen during the 1930s and 1940s, and the major discovery of sperm cryopreservation with glycerol in 1949. The 1950s and 1960s were particularly productive with the development of protocols for the superovulation of cattle with both pregnant mare serum gonadotrophin/equine chorionic gonadotrophin and FSH, the first successful bovine embryo transfer, the discovery of sperm capacitation, the birth of rabbits after in vitro fertilization, and the development of insulated liquid nitrogen tanks. Improved semen extenders and the replacement of glass ampules with plastic semen straws followed. Some of the most noteworthy developments in the 1970s included the initial successes with in vitro culture of embryos, calves born after chromosomal sexing as embryos, embryo splitting resulting in the birth of twins, and development of computer-assisted semen analysis. The 1980s brought flow cytometric separation of X- and Y-bearing sperm, in vitro fertilization leading to the birth of live calves, clones produced by nuclear transfer from embryonic cells, and ovum pick-up via ultrasound-guided follicular aspiration. The 20th century ended with the birth of calves produced from AI with sexed semen, sheep and cattle clones produced by nuclear transfer from adult somatic cell nuclei, and the birth of transgenic cloned calves. The 21st century has seen the introduction of perhaps the most powerful biotechnology since the development of artificial insemination and cryopreservation. Quick, inexpensive genomic analysis via the use of single nucleotide polymorphism genotyping chips is revolutionizing the cattle breeding industry. Now, with the introduction of genome editing technology, the changes are becoming almost too rapid to fully digest.

Economic evaluation of sexed semen use in Iranian dairy farms according to field data

In this study, at first, the reproductive consequences of sexed semen use were quantified and then the cost-benefit of sexed semen use on Iranian commercial dairy farms was evaluated. Retrospective data collected during 2006 to 2013 from four large dairy farms in the Isfahan province of Iran were used for this study. These data included of 13,003 heifers records, from which 11.2% used sexed semen from 33 different bulls. All data were analysed using a multivariable logistical regression model, GENMOD procedure from SAS software. The analyses included economic values (EVs) when sexed semen was used in 1, 2 and 3 consecutive services compared with conventional semen use for all insemination. Results showed that rates of female born from sexed semen (86.3%) were 1.8 times higher than those from conventional semen (48.5%). Conception rates were 43.8% for sexed and 59.2% for conventional semen (p < 0.0001). Abortion (4.4% vs. 5.4%) and stillbirth (8.4% vs. 7.2%) rates were not significantly different between sexed and conventional semen (p = 0.09). Dystocia rates were 15.5% for sexed and 19.6% for conventional semen (p = 0.002). Sexed semen use showed negative EVs through all investigated scenarios. The EVs from the implementation of 1, 2 and 3 sexed semen breedings were estimated to be $-6.69, $-14.01 and $-19.08, respectively. Total insemination cost and increased cost of age at first calving were the most important components associated with negative EV for sexed semen. Sensitivity analysis showed that proportion of conception rates of sexed semen to conventional semen and female calf value were the most important biological and economic factors influencing on the EV of sexed semen, respectively. Breakeven would be obtained with 77.4%-79.3% conception rates or female calf value of $719.5-$754.7 through investigated breeding scenarios when all other factors remained the same.

The cost-benefit of genomic testing of heifers and using sexed semen in pasture-based dairy herds

Recent improvements in dairy cow fertility and female reproductive technologies offer an opportunity to apply greater selection pressure to females. This means there may be greater incentive to obtain genomic breeding values for females. We modeled the impact of changes to key parameters on the net benefit from genomic testing of heifer calves with and without usage of sexed semen. This paper builds on earlier cost-benefit studies but uses parameters relevant to pasture-based systems. A deterministic model was used to evaluate the effect on net benefit due to changes in (1) reproduction rate, (2) genomic test costs, (3) availability of parent-derived breeding values (EBV_PA), and (4) replacement rate. When the use of sexed semen was included, we also considered (1) the proportion of heifers and cows mated to sexed semen, (2) decreases in conception rate in inseminations with sexed semen, and (3) the marginal return for surplus heifers. Scenarios with lower replacement rates and no availability of EBV_PA had the largest net benefits. Under current Australian parameters, the net benefit of genomic testing realized over the lifetime of genotyped heifers is expected to range from A$204 to A$1,124 per 100 cows for a herd with median reproductive performance. The cost of a genomic test, a perceived barrier to many farmers, had only a small effect on net benefit. Genomic testing alone was always more profitable than using sexed semen and genomic testing together if the only benefit considered was increased genetic gain in heifer replacements. When other benefits (i.e., the higher sale price of a surplus heifer compared with a male calf) were considered, there were combinations of parameters where net benefit from using sexed semen and genomic testing was higher than the equivalent scenario with genomic testing only. Using sexed semen alongside genomic testing is most likely to be profitable when (1) used in heifers, (2) the marginal return for selling surplus heifers (sale price minus rearing costs) is greater than A$400, and (3) conception rates of no more than 10 percentage points lower than those achieved using conventional semen can be realized. Net benefit was highly dependent on the marginal return. Demonstrating that the initial investment in genomic testing can be recouped within the lifetime of the heifers tested may assist in the development of extension messages to explain the value of genomic testing females at the herd level.

Bioeconomics of sexed semen utilization in a high-producing Holstein-Friesian dairy herd

A bioeconomic, stochastic spreadsheet model, that included calculation of the net present value of the additional value of all future descendants resulting from increased selection intensity, was developed to study the profitability of using sexed semen in a high input-high output dairy herd. Three management strategies were modeled: (1) only heifers inseminated with sex-sorted semen and cows inseminated with unsorted semen; (2) both heifers and cows inseminated with sex-sorted semen; and (3) a reference scenario, in which all breeding females were inseminated with unsorted semen. A Monte Carlo simulation (@risk software, Palisade Corp., Ithaca, NY) was run to study the sensitivity of net profit and sexed semen advantage to key input parameters. Most input parameters were given truncated normal distributions, whereas the maximum numbers of inseminations in heifers and cows were given discrete distribution functions. The calculated intensity of selection accounted for the different numbers of dairy females born for each of the 100,000 iterations. Using sexed semen (X-sorted, female) was shown to be profitable, with insemination of both heifers and cows being most profitable. The returns on assets were higher when only heifers were inseminated with sexed semen (8.54% ± 2.94; ±SD) or all females were inseminated with sexed semen (8.85% ± 2.93) than when all females were inseminated with unsexed semen (8.38% ± 2.95). The range in net profit was most sensitive to the assumed distributions of milk protein price (€/kg), milk fat price (€/kg), cow pregnancy rate, fertilizer price (€/t), and concentrate price (€/t) when unsorted semen was used. When only heifers or both heifers and cows were inseminated with sex-sorted semen, the range in net profit was most sensitive to the same distributions, with fertilizer price and cow pregnancy rate in reverse order of sensitivity. However, the range in sex-sorted semen advantage (in net profit) when only heifers were inseminated with sex-sorted semen was most sensitive to the assumed distributions of cow pregnancy rate, sex-sorted semen pregnancy rate as a percent of unsorted semen rates, standard deviation of index, additional cost of sex-sorted semen (€/dose), dairy bull calf price (€/head), and dairy heifer calf price (€/head). When both heifers and cows were inseminated, the order of importance of the last 2 inputs was reversed. This study highlights the relatively high effect of pregnancy rate and the genetic value of dairy bulls in determining the level of financial advantage from using sex-sorted semen in a dairy herd.

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

OBJECTIVE

To determine if insemination site or pre-ovulatory follicle diameter at fixed-time artificial insemination (FTAI) affects the odds of pregnancy when heifers are inseminated with sexed semen.

METHODS

The study was conducted in 422 Holstein heifers enrolled into 531 inseminations. Inseminations were randomly allocated to 1 of 16 treatment combinations involving three variables: semen type (sexed vs non-sexed), insemination site (uterine horn vs uterine body) and one of four sires. Ovaries were examined by transrectal ultrasound prior to FTAI to determine the follicle diameter and location. AI technician, times bred, age, weight and temperature-humidity index were also recorded. Pregnancy diagnosis was conducted 29 days post-insemination. Follicle diameter and body weight were categorised according to arbitrary cut-points. Each variable was analysed by logistic regression to determine the effect on pregnancy per AI and compare between sexed and non-sexed inseminations.

RESULTS

Insemination site did not affect pregnancy per AI for either sexed (P = 0.528) or non-sexed (P = 0.886) inseminations. Heifers with an 18-22 mm follicle had better odds of pregnancy than heifers that did not (odds ratio (OR) 1.45, 95% confidence interval (CI) 1.004-2.09), although no effect was detected for only sexed or only non-sexed inseminations. Heifers weighing 310-370 kg had a higher pregnancy per AI than heifers weighing > 370 kg for non-sexed inseminations (P = 0.004) and sexed semen from sire 4 caused lower odds of pregnancy than semen from sire 1 (OR 0.40, 95% CI 0.18-0.89).

CONCLUSION

Insemination site did not affect pregnancy per AI, but heifers with an 18-22 mm pre-ovulatory follicle at insemination had better odds of pregnancy for both sexed and non-sexed inseminations.

Economic opportunities for using sexed semen and semen of beef bulls in dairy herds

Dairy farmers can increase the number of dairy heifer calves born in their herd by using sexed semen. They can reduce the number of both dairy bull and heifer calves by using beef semen. Long before sexed semen became commercially available, it was believed that it would provide opportunities for increasing genetic level in both herds and populations. In this study, we studied the potential for increasing the genetic level of a herd by using beef semen in combination with sexed semen. We tested the hypothesis that the potential of increasing the genetic level and the overall net return would depend on herd management. To test this hypothesis, we simulated 7 scenarios using beef semen and sexed semen in 5 herds at different management levels. We combined the results of 2 stochastic simulation models, SimHerd and ADAM. SimHerd simulated the effects of the scenarios and management levels on economic outcomes (i.e., operational return) and on technical outcomes such as the parity distribution of the dams of heifer calves, but it disregarded genetic progress. The ADAM model quantified genetic level by using the dams' parity distributions and the frequency of sexed and beef semen to estimate genetic return per year. We calculated the annual net return per slot as the sum of the operational return and the genetic return, divided by the total number of slots. Net return increased up to €18 per slot when using sexed semen in 75% genetically superior heifers and beef semen in 70% genetically inferior, multiparous cows. The assumed reliability of selection was 0.84. These findings were for a herd with overall high management for reproductive performance, longevity, and calf survival. The same breeding strategy reduced net return by €55 per slot when management levels were average. The main reason for the large reduction in net return was the heifer shortage that arose in this scenario. Our hypothesis that the potential for beef semen to increase genetic level would be herd-specific was supported. None of the scenarios were profitable under Danish circumstances when the value of the increased genetic level was not included. A comparable improvement in genetic level could be realized by selectively selling dairy heifer calves rather than using beef semen.

Expanding the dairy herd in pasture-based systems: The role of sexed semen within alternative breeding strategies

A simulation model was developed to determine the effects of sexed semen use in heifers and lactating cows on replacement heifer numbers and rate of herd expansion in a seasonal dairy production system. Five separate artificial insemination (AI) protocols were established according to the type of semen used: (1) conventional frozen-thawed semen (CONV); (2) sexed semen in heifers and conventional semen used in cows (SS-HEIFER); (3) sexed semen in heifers and a targeted group of cows (body condition score ≥3 and calved ≥63 d), with conventional semen used in the remainder of cows (SS-CONV); (4) sexed semen in heifers and a targeted group of cows, with conventional semen in the remainder of cows for the first AI and conventional beef semen used for the second AI (SS-BEEF); or (5) sexed semen in heifers and a targeted group of cows, with conventional semen in the remainder of cows for the first AI and short gestation length semen used for the second AI (SS-SGL). Each AI protocol was assessed under 3 scenarios of sexed semen conception rate (SS-CR): 100, 94, and 87% relative to that of conventional semen. Artificial insemination was used on heifers for the first 3 wk and on cows for the first 6 wk of the 12-wk breeding season. The initial herd size was 100 cows, and all available replacement heifers were retained to facilitate herd expansion, up to a maximum herd size of 300 cows. Once maximum herd size was reached, all excess heifer calves were sold at 1 mo old. All capital expenditure associated with expansion was financed with a 15-yr loan. Each AI protocol was evaluated in terms of annual farm profit, annual cash flow, and total discounted net profit. The SS-CONV protocol generated more replacement heifers than all other AI protocols, facilitating faster expansion, and reached maximum herd size in yr 9, 9, and 10 for 100, 94, and 87% SS-CR, respectively. All AI protocols, except SS-BEEF and SS-SGL at 87% SS-CR, reached maximum herd size within the 15-yr period. Negative profit margins were experienced for SS-CONV in the first 5, 4, and 3 yr of expansion for 100, 94, and 87% SS-CR, respectively. Total discounted net profit was greater in all sexed semen AI protocols compared with CONV. This study demonstrated that, for each SS-CR, the greatest rate of expansion is achieved when using sexed and conventional semen (SS-CONV). The combined use of sexed semen and beef (SS-BEEF) or SGL (SS-SGL) semen resulted in greater discounted net profit at 100, 94, and 87% SS-CR compared with CONV, but a similar net worth change at 87% SS-CR due to a lower inventory change because SS-BEEF and SS-SGL reached maximum herd size within 15 yr.

Short communication: economics of sex-biased milk production

In a recent data study using 2.4 million lactations of 1.5 million cows, it was reported that gestation of a female calf in the first parity increases cumulative milk production by approximately 445kg over the first 2 lactations. The reported effect in this study is large and remarkable because it has not been found before. To our knowledge, the economic implications of this or any other sex bias have not been studied. The objective of the current study was to quantify the reported influence of fetal sex across lactations by using a simulation model of a dairy herd including youngstock. Two scenarios were evaluated and compared with a scenario in which cows and heifers were exclusively bred with conventional (nonsexed) semen. In the first scenario, sexed semen was used moderately-on 30% of all heifers and 30% of the first parity cows. A second scenario was studied in which sexed semen was used intensively-on all heifers and 50% of the first-parity cows. The simulated proportion of cows giving birth to 2 consecutive heifers increased from 23% when using exclusively conventional semen up to 31 and 48% when using sexed semen moderately and intensively, respectively. The proportion of cows having 2 consecutive bulls decreased from 27% (conventional semen only) to 20 and 8% when using sexed semen moderately and intensively, respectively. When incorporating the sex bias in the simulation model, the simulated milk yield in the scenario in which sexed semen was used moderately increased by 48kg of energy-corrected milk (ECM) per cow/yr, compared with only 36kg of ECM when not incorporating the sex bias in the model. For the scenario in which sexed semen was used intensively, milk yield increased by 66 and 99kg of ECM when excluding and including the sex bias, respectively. The economic implications of the assumed sex bias were €4.0 and €9.9 per cow/yr, in the scenarios in which sexed semen was used moderately and intensively, respectively.

Factors affecting economics of using sexed semen in dairy cattle

The use of sexed semen in the dairy industry has grown rapidly. However, high costs and low fertility have limited the use of this potentially valuable tool. This study used simulation to evaluate 160,000 combinations of key variables in 3 spheres of influence related to profit feasibility: (1) market (e.g., milk and calf prices), (2) dairy farm management (e.g., conception rates), and (3) technology (e.g., accuracy of sexing). These influential variables were used to determine the most favorable circumstances in which managers or technicians can effect change. Three distinct scenarios were created to model 3 initiatives that a producer might take with sexed semen: (1) using sexed semen on heifers, (2) using sexed semen on heifers and a fraction of the genetically superior cows, and (3) using sexed semen on heifers and a fraction of the genetically superior cows, and breeding all other cows with beef semen. Due to the large number of management, market, and technology combinations, a response surface and interpretive graphs were created to map the scope of influence for the key variables. Technology variables such as the added cost of sexed semen had relatively little effect on profitability, defined as net present value gain per cow, whereas management variables such as conception rate had a significant effect. Milk price had relatively little effect within each scenario, but was important across scenarios. Profitability was very sensitive to the price of dairy heifer calves, relative to beef and dairy bull calves. Scenarios 1 and 2 added about $50 to $75 per cow in net present value, which ranged from $0 to $200 and from $100 to $300, respectively. Scenario 3 usually was not profitable, primarily because fewer excess dairy replacement heifers were available for sale. Dairy heifer price proved to be the most influential variable, regardless of scenario.