Effects of presynchronization and postinsemination treatments on pregnancy rates to a timed breeding Ovsynch protocol in dairy cows and heifers

Determination of expression patterns of miR-26a, and preimplantation factor levels for early pregnancy detection in nulliparous and multiparous cows

For maximum productivity in a dairy farm, the earliest and the most accurate detection of pregnancy is essential. The aim of this study was to determine the efficacy of expression patterns of miR-26a, and serum Preimplantation Factor (PIF) levels for pregnancy diagnosis during the early pregnancy in nulliparous and multiparous cows. A total of 60 cows (30 nulliparous and 30 multiparous Holstein cows) were enrolled in the study. Blood samples were collected for miR-26a on days 8 and 16 (D8 and D16), and for the PIF on days 10 and 20 (D10 and D20) following insemination (D0). Pregnancies were determined by ultrasonography on the 28th day after insemination. Expression levels of miR-26a determined by qPCR. PIF levels were assessed by using commercial ELISA kits. All data were analyzed by using the MIXED procedure of SPSS. The expression levels of miR-26a were 6.64 folds higher on D16 in pregnant compared to non-pregnant multiparous cows (p < .05). On D8 and D16, miR-26a expression levels were found higher 13 folds in pregnant compared to non-pregnant nulliparous cows (p < .05). Additionally, miR-26a expressions were higher 5.42 folds (p < .05) on D8, 7.19 folds higher (p < .01) on D16 in pregnant nulliparous and multiparous cows, and were 6.30 folds higher (p < .001) on D8 and D16 according to non-pregnant animals. PIF levels were greater in pregnant animals (p < .05). Analyzing miR-26a on D8 might be considered as sufficient in nulliparous cows. Pregnancy detection in multiparous cows can be made on the 16th day with this method. Furthermore, PIF evaluations may be sufficient on D10 in multiparous cows. Besides, PIF levels and miR-26a expression levels might be used safely in field conditions and clinical applications.

The thermographic monitoring in early pregnancy detection in Holstein cows and heifers

This study aimed to conduct a comprehensive investigation to demonstrate early pregnancy detection using thermography in heifers and cows. A total of 60 heifers (n: 30) and cows (n: 30) were divided into two groups as pregnant (n: 15 heifers, n: 15 cows) and non-pregnant (n: 15 heifers, n: 15 cows) according to the day 28 of gestation. Thermographic images were taken from the vulvar and anal regions on alternate days from D0 to D20. Blood samples were collected to determine estrogen and progesterone concentrations. The mean temperature difference between the anal and vulvar regions (ΔT °C) was used in the statistical analyses. Based on the hormonal profiles, no abnormalities were observed for follicular waves or luteal profiles in heifers and cows. The ΔT °C values between heifers and cows and between days were statistically significant (P < 0.001). In thermographic analyses, the differences observed in other main effects and interactions of the group, sampling time, and pregnancy were not statistically significant (P > 0.05). In receiver operating characteristic (ROC) analyses, it was concluded that the ΔT °C value of ≤ 2.9 °C (100% Se - 61.9% Sp) was highly correlated with pregnancy diagnosis in cows on day six after artificial insemination (AI) (P < 0.001). In conclusion, it was determined that the clinical application of thermography can be used for the detection of pregnancy on day six after AI in cows. However, further studies are needed to determine heifers' thermographic characteristics and profiles.

Extended lactation in high-yielding dairy cows. I. Effects on reproductive measurements

The objective of this prospective field study was to evaluate the effects of extending the lactation period on various reproductive measurements of high-yielding Holstein cows. On 40 d in milk (DIM), cows were gynecologically examined (transrectal palpation, sonography, vaginoscopy). Cows without signs of clinical endometritis were blocked by parity and were randomly allocated to 1 of 3 experimental groups with a voluntary waiting period (VWP) of 40, 120, and 180 d, respectively (G40, n = 135; G120, n = 141; G180, n = 139). Cows of G120 and G180 were reexamined at the end of the VWP. If natural estrus was detected within 46 d after the end of the VWP, an artificial insemination was performed. If no estrus was detected, the respective cows were synchronized by applying the classical Ovsynch protocol. We found no difference in the proportion of cows in which estrus was detected between 40 to 86 DIM or in the days to first estrus between the 3 groups. Estrus detection in this period was lower in cows with body condition score <3 on 90 DIM compared with body condition score ≥3 (61.5 vs. 76.0%) and in cows with high energy-corrected milk production (ECM) on 92 DIM [58.6 vs. 70.1%, for cows with higher and lower than the median (39.9 kg) ECM, respectively]. The proportion of cows that estrus was detected within 46 d after the VWP was greater in G120 (88.9%) and G180 (90.8%) compared with G40 (70.4%). These effects were more apparent in cows with high ECM. The rate of estrus detection and of becoming pregnant in this period was greater for G120 (hazard ratio = 2.2 and 1.6, respectively) and for G180 (hazard ratio = 2.4 and 1.8) compared with G40. Cows in both groups with extended lactation had greater overall first service conception rates (G120 = 48.9%; G180 = 49.6%) and a lower number of services per pregnant cow (G120 = 1.56 ± 0.1; G180 = 1.51 ± 0.1) compared with G40 (36.6%; 1.77 ± 0.1). We observed no difference in pregnancy loss or in the proportion of cows culled up to 305 d of lactation between the 3 groups. The number of Ovsynch protocols per 1,000,000 kg of ECM was reduced by 75% in G180 and by 74% in G120 compared with G40 (5.9 vs. 7.1 vs. 25.1). In conclusion, extending the lactation of dairy cows can improve main reproductive measurements in high-yielding cows.