**5. Bull effect on the efficiency of reproductive programs using sex-sorted sperm**

**Interval from TAI to ovulation (h)**

48 Success in Artificial Insemination - Quality of Semen and Diagnostics Employed

sorted sperm.

Schenk et al. (2009)

Sales et al. (2010)

Neves et al. (2010) [62]

**No. cows Pregnant**

"/ 24 87 5.8 (5/87)c 0.24 (0.08-0.70) 0.01

"/ 0 to 12 95 37.9 (36/95)a 2.34 (1.22-4.51) 0.01 After ovulationz 22 36.4 (8/22)ab 1.80 (0.64-5.03) 0.27

**Table 4.** a,b Within a column, proportions without a common superscript differed (P \_ 0.05).x OR, odds ratio; CI, confidence interval.y Reference, reference group for adjusted risk ratio, which is the industry standard for the optimal timing of AI with non-sorted sperm.z Inseminations were performed within 0–12 h after ovulation.Adapted from [8]Risk of pregnancy based on the interval between TAI and ovulation in suckled B. indicus cows inseminated with sex-

Reference Animal category Early AI time Late AI time P *value*

[6] Angus heifers 34 (11/32) 49 (17/35) "/0.10

[63] Jersey heifers 16.2 (17/105) 31.4 (32/102) <0.05

Overall 25.1 (92/366) 37.0 (123/357) <0.01

Importantly to note, the use of in vitro fertilized (IVF) embryos with sexed semen is expect‐ ed to have its use increased throughout the years associated to TET. The overall percentages of oocytes fertilized with sorted and unsorted frozen bovine sperm appear to be similar us‐ ing current IVF methods [20]. While TAI uses one dose of sexed semen by cow, the TET al‐ lows the optimization of the semen use. Just one sexed semen dose is capable to fertilize about 80 oocytes (equivalent to the aspiration of four females; mean of 20 oocytes per aspi‐ rated cow), resulting in the production of approximately 30 viable embryos. Considering that TET provides 40 – 50% of pregnancy rate, transferring the 30 embryos fertilized with just one sexed semen dose, would result theoretically, in 12 – 15 pregnancies. In the case where for TAI is considered the same conception rate of 40 – 50%, each inseminated sexed

**Table 5.** Influence of the AI moment in synchronization of ovulation protocols on the pregnancy rate.

semen dose would result in just 0.4 – 0.5 pregnancies.

Sales et al. (2011) [8]Suckled Nelore cows 42.8 (100/193) 50.8 (99/195) 0.11

"/ 12 to 24 108 19.4 (21/108)b Reference group

**(%) No./No.**

**Pregnancy per AI % (n/n)**

Nelore cows 20.8 (27/130) 30.9 (38/123) <0.05

**Adjusted ORx (95% CI)**

**P**

An important factor to consider in the timing of AI with sex-sorted sperm is the variation in the fertility of individual bulls. Whereas sperm sorting has significantly decreased fertility of certain bulls, sperm sorting does not affect fertility of other bulls [25]. Sales et al. [63] have been evaluated the use of the sexed or conventional semen of 3 different sires to inseminate Jersey heifers after the estrus detection by radio telemetry (Heat Watch®). Wherefore, the conventional semen [64.2% (238/371)] had been a higher conception rate than sexed semen [49.5% (189/382); P = 0.001]. Moreover, there was a bull effect on the conception rate [Bull A = 50.0% (108/216)b; Bull B = 63.4% (211/333)a and Bull C = 53.5% (107/200)b; P = 0.008]. Thus, some bulls can present lower conception rate using sexed or conventional semen for insemi‐ nation (Figure 1). Other studies also have described that conception rates vary in magnitude for individual sires [5, 25, 64].

**Figure 1.** Conception rate of Jersey heifers inseminated artificially with sexed or conventional semen according three different the bull (A, n=216; B, n= 333 e C, n=200). Bull effect (P = 0.008) and semen (P = 0.001).

In another study, Sales et al. [8] synchronized Jersey heifers and used sex-sorted sperm from three different sires to inseminate the females. The conception rate was different among sires used in the experiment, indicating once more the existence of individual discrepancy among bulls producing semen to sex-sorting (Figure 2).

The few number of sorting facilities around the world limits the use of high genetic merit bulls because the distance. The capacity to effectively sex-sort and re-freeze previously fro‐ zen-thawed sperm would allow commercial sorting undertaking to offer sex-sorted sperm from any sire currently in the frozen semen market. This capacity is mainly influenced by variation in the physic-chemical semen properties of the individual bull. A study [65] to ver‐ ify the fertilizing potential of sex-sorted frozen-thawed bull sperm transported cooled or fro‐ zen to the sorting facility, has shown a bull effect on the pregnancy rate after AI [Bull 1: conventional semen (control) 63.0%; previously frozen (FS) 8.6%; previously cooled (CS) 10.0%. Bull 2: control 45.5%, FS 0%, CS 4.8%; P = 0.001].

on Day 4). On Day 6, was given PGF2α analog (Sincrocio®, Ourofino). The ear implant was removed 36 h after the PGF2α analog administration, with the application of LH (Luteotro‐ pin) 48 h after PGF2α analog. The TAI with sex-sorted (4,2x106 cell/AI) or non sex-sorted sperm (40x106 cell/AI) was performed at 12 and 24 h after LH injection. For TAI, it was used semen from same sire. The experimental design used was crossover to avoid individual var‐ iation among donors. The Table 6 summarizes the experiment described, demonstrating a decreasing on fresh and frozen embryos, fresh and frozen embryo rate and an increasing on the unfertilized embryos when using sex-sorted sperm. The accuracy on the use of the sexed semen to produce the desired sex was 90% with pregnancy diagnosis 60 days after TAI. The

> **Sex-sorted sperm (n = 10)**

6.80 ± 0.66 4.20 ± 0.74 0.03 0.88 0.88

The Use Of Sex-Sorted Sperm For Reproductive Programs In cattle

5.9 ± 0.71 3.50 ± 0.65 0.03 0.43 0.99

**Trat Rep Trat vs. Rep**

http://dx.doi.org/10.5772/52180

51

conventional semen produced 52.7% of females.

Transferable embryos (Grade 1,

Frozen embryos (Grade 1 and 2;

2 and 3; n)

or non sex-sorted sperm.

sorted (4.2 x 106

sperm (4.2 x 106

n)

**Non sex-sorted sperm (n = 10)**

Total of structures (n) 9.90 ± 0.78 8.40 ± 1.40 0.28 0.81 0.71

Unfertilized oocyte (n) 1.50 ± 0.48 3.70 ± 0.88 0.01 0.82 0.46 Degenerate (n) 1.60 ± 0.37 0.50 ± 0.16 0.04 0.54 0.78 Transferable embryo rate (%) 68.70 ± 6.30 50.00 ± 5.10 0.01 0.68 0.54 Frozen embryo rate (%) 59.60 ± 5.10 41.70 ± 5.20 0.02 0.32 0.73

**Table 6.** Embryo production of superovulated Nelore cows (*Bos indicus*) and inseminated in fixed time with sex-sorted

In a study by our group research [66], we evaluated different intervals for TAI with sex-sort‐ ed sperm after pLH treatment in *Bos indicus* and *Bos taurus* donors. The hypothesis was that increased embryo production would occur when TAI with sex-sorted sperm was performed closer to the time synchronized ovulations occurred. In the first experiment, hormonal su‐ perstimulation of ovarian follicular development in Nelore donors (n = 71) was performed in randomly allocated animals to one of three treatment groups, and they were inseminated at 12 and 24 h after an ovulatory stimulus with pLH treatment was applied, either with sex-

insemination; NS12/24; n = 18), or they were inseminated at 18 and 30 h using sex-sorted

bryos were found when sex-sorted sperm was used to inseminate the animals at 18 and 30 h compared to insemination at 12 and 24 h. However, a greater embryo production was ob‐

Additionally, Soares et al. [66] used the same insemination times and semen types in lactat‐ ing high-production Holstein cows (n = 12). A crossover design was employed in this trial.

tained with non-sorted sperm (results are summarized on Table 7).

sperm/insemination; S12/24; n = 17) or non-sorted sperm (20 x 106 sperm/

sperm/insemination; S18/30; n = 19). A greater number of transferable em‐

**Figure 2.** Pregnancy rate of Jersey heifers fixed timed artificially inseminated according the bull and type of semen used (conventional or sexed). It was verified a bull effect (P = 0.001) and type of semen (P = 0.001).

Accordingly, the individual difference among bull is an important aspect to consider apply‐ ing the sex-sorted sperm use at livestock level, allowing the sire selection for higher per‐ formance after sexing. Also, it is essential to highlight that this sire effect is one of the most important obstacle to the use of sexed semen in large scale.
