Insemination management for a one-injection prostaglandin F2α synchronization system. II. One versus two inseminations following detection of estrus

Effect of treatment with human chorionic gonadotropin 7 days after artificial insemination or at the time of embryo transfer on reproductive outcomes in nulliparous Holstein heifers

Our objective was to assess the effect of treatment with human chorionic gonadotropin (hCG) 7 d after artificial insemination (AI) or at the time of in vitro-fertilized (IVF) embryo transfer on reproductive outcomes, including progesterone (P4), interferon-tau stimulated gene 15 (ISG15), pregnancy-specific protein B (PSPB), and pregnancies per AI (P/AI) or pregnancies per embryo transfer (P/ET), in nulliparous Holstein heifers. Heifers in experiment 1 were randomly assigned to receive no treatment (control; n = 129) or 2,000 IU of hCG 7 d after AI to a detected estrus (estrus = experimental d 0; hCG; n = 132). Heifers in experiment 2 were randomly assigned to receive no treatment (control; n = 143) or 2,000 IU of hCG (hCG; n = 148) at transfer of an IVF embryo 7 d after the last GnRH treatment of a 5-d controlled internal drug release-synch protocol (last GnRH = experimental d 0). Blood samples were collected from a subgroup of heifers (experiment 1, n = 82; experiment 2, n = 104) at d 7, 11, 18, 20, 25, 28, and 32, and blood samples from heifers diagnosed pregnant were collected on d 35, 39, 46, 53, 60, and 67. Blood samples were assayed for P4 by RIA and for PSPB by ELISA, and expression of ISG15 was assessed in mRNA isolated from blood leukocytes on d 18 and 20. Data were analyzed by ANOVA and logistic regression using the MIXED and GLIMMIX procedures. In both experiments, treatment with hCG increased P4 concentrations from d 11 to 32; however, treatment did not affect P/AI or P/ET at d 32 or 67, PSPB concentrations from d 11 to 67 of pregnancy, or relative ISG15 mRNA concentrations on d 18 or 20. Heifers diagnosed not pregnant at d 32 in experiment 2 with an extended luteal phase (>20 d) and treated with hCG had greater relative ISG15 mRNA concentrations on d 20 than control heifers. Treatment with hCG did not affect pregnancy loss in experiment 1, whereas heifers treated with hCG at the time of IVF embryo transfer had fewer pregnancy losses from d 32 to 67 than control heifers. We concluded that treatment with 2,000 IU of hCG 7 d after AI or at the time of embryo transfer increased P4 concentrations without affecting P/AI or P/ET in nulliparous Holstein heifers.

Effect of time of artificial insemination on pregnancy rates, calving rates, pregnancy loss, and gender ratio after synchronization of ovulation in lactating dairy cows

In order to assess the optimal time of artificial insemination (AI) in relation to ovulation, lactating dairy cows (n = 732) from herds with rolling herd averages of 9980 to 11,800 kg from three milkings per day were randomly assigned to five groups by stage of lactation and parity. Ovulation was synchronized by administration of GnRH followed 7 d later with PGF2 alpha followed 2 d later with a second treatment with GnRH. Cows were inseminated at 0, 8, 16, 24, or 32 h after the second injection of GnRH (ovulation occurs between 24 and 32 h after GnRH). Pregnancy diagnoses were performed by ultrasound at 25 to 35 d post-AI. Pregnancy rates per AI were similar for the groups inseminated at 0, 8, 16, and 24 h and lower for the group inseminated at 32 h. A significant quadratic effect of treatment suggests that the middle time periods (8, 16, and 24 h) may produce the greatest pregnancy rate per AI. However, the group inseminated at 0 h had lowest pregnancy loss, and the group inseminated at 32 h tended to have the greatest pregnancy loss compared with that of the other groups. The calving rate was similar between the groups inseminated at 0, 8, 16, and 24 h and lower in the group inseminated at 32 h. The time of AI also appeared to affect gender of calf: cows bred at 0 and 32 h having a higher percentage of female offspring. In conclusion, there appears to be substantial flexibility in the time of AI after the second injection of GnRH, and lower reproductive rates were observed only when AI was after the time of ovulation.

The relationship of rheological behavior of the vaginal fluid at the time of insemination to the pregnancy rate in dairy cows

The objective of this study was to determine whether rheological properties of the vaginal fluid at the time of insemination could be used as an indicator of potential fertility in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal samples were collected from 347 cows at the time of insemination, within a 12- to 24-h interval after the onset of a natural estrus. Logistic regression analysis showed no significant effects of thixotropy measurements on the pregnancy rate, while flow behavior and the index of consistency (K) had a significant effect. The decrease in the consistency index (K) was related to the increase in the pregnancy rate (odds ratio = 0.99; P = 0.014), and the risk of nonpregnancy was higher (odds ratio = 0.46; P = 0.024) in cows in which vaginal fluid had a Newtonian behavior. Non-Newtonian behavior was recorded in 294 samples (85%) while 53 behaved as Newtonian fluids. For samples from all cows, the mean value of the consistency index was 310 +/- 28.2 milliPascals.second(n) (x +/- SEM) and ranged from 0 to 3881 milliPascals.second(n). In Newtonian samples, the consistency index mean was 2.6 +/- 0.6 milliPascals.second(n) and 367.6 +/- 30.4 milliPascals.second(n) for non-Newtonian samples. Of the 347 cows, 131 (38%) became pregnant. For flow behavior classification, 15 (28.3%) cows in which samples had Newtonian behavior and 116 (39.5%) cows with non-Newtonian samples became pregnant. Therefore, the highest probability of pregnancy was shown by cows in which samples had non-Newtonian behavior and the lowest consistency index values. Our data suggest that flow behavior measurements of the vaginal fluid at the time of insemination may be an indicator of potential fertility in cattle.

Timing of artificial insemination of dairy cows: fixed time once daily versus morning and afternoon

Nonreturn rates to professional technician service of 7240 first AI Holstein cows were calculated to evaluate differences between once daily and a.m.-p.m. AI. To determine whether management practices affected nonreturn rates, participating herd owners were surveyed for methods used for detection of estrus. Nonreturn rates for once daily and a.m.-p.m. AI were 64.6 and 65.6% for 60-d, 60.1 and 60.6% for 75-d, and 58.4 and 57.8% for 90-d nonreturn periods. Signs of estrus for AI and interval from detection of estrus to AI were related to nonreturn rates. Nonreturn rate was highest, 63.4%, when cows were in standing estrus. Nonreturn rates were lowest, 36%, when cows were bred after treatment with PGF2 alpha without being detected in estrus or bred strictly on veterinary advice based on palpation. Nonreturn rates were similar for different times of the day when once daily AI was practiced. However, AI in the midmorning may have some advantages. The highest nonreturn rate for a 3-h period was 68.2% for 0800 and 1100 h; the lowest was 54.7% for 1300 to 1600 h. Movement before observation for estrus and an observation period > 15 min improved nonreturn rates for once daily AI. Once daily AI can be used effectively with no difference from the traditional a.m.-p.m. system; results are best when AI is based on standing estrus and performed between 0800 and 1100 h.

Synchronization of estrus after treatment with Luprostiol in beef cows and in beef and dairy heifers

Four trials were conducted to study synchronous estrous response in beef cows and in beef and dairy heifers to Luprostiol (13, thia-PG-F(2)alpha analog) in comparison with other prostaglandin products. In Trial 1, 60 virgin beef heifers were observed for estrus for 5 d and artificially inseminated. Heifers not observed in estrus within 5 d were randomly assigned to receive 15 mg Luprostiol or 25 mg Lutalyse. In Trial 2, 75 multiparous, lactating beef cows were randomly assigned to receive either 15 mg Luprostiol, 25 mg Lutalyse or 500 mcg Estrumate. All cows received a second injection of the respective treatment 11 d later. In Trial 3, 96 multiparous, lactating beef cows were randomly assigned to receive 15 mg Luprostiol or 25 mg Lutalyse. All cows received a second injection of the respective treatment 11 d later. In Trial 4, virgin dairy heifers were palpated per rectum. Seventy-seven heifers with a palpable corpus luteum (CL) were randomly assigned to receive 15 mg Luprostiol or 500 mcg Estrumate. In all trials animals were artificially inseminated 12 h following observed estrus. Estrous response during the 5-d synchronized period was 44% for Luprostiol and 42% for Lutalyse treated heifers in Trial 1. It was 52, 56 and 60%, respectively, for Luprostiol, Lutalyse and Estrumate treated cows in Trial 2; 23% for Luprostiol and 19% for Lutalyse treated cows in Trial 3; and 68% for Luprostiol and 70% for Estrumate treated heifers in Trial 4. Treatment with Luprostiol results in a similar synchronous estrous response as with the other prostaglandin products used in these studies.