Influence of practitioner expertise during early pregnancy diagnosis on pregnancy loss rate: A controlled, blinded trial.

A controlled field trial was conducted to assess the potential influence of practitioner inexperience during early pregnancy diagnosis with ultrasound (PD-US) on the risk of pregnancy loss. A veterinarian with more than 10 years' experience in PD-US (Vet-A) and a veterinarian with fewer than 12 months' experience at the start of the study (Vet-B) visited the same dairy farm once a week for 33 and 26 weeks, respectively. The two veterinarians did not interact with each other at any time during the study, nor did they know that their data would later be used in this study. Using the same farm scanner, they performed PD-US at 28-34 day after breeding, together diagnosing 915 pregnancies. All cows were re-checked at 49-56 day after artificial insemination, and cows no longer pregnant were recorded as having suffered pregnancy loss. Although Vet-A and Vet-B diagnosed a similar proportion of pregnancies (58.44 ± 16% vs 56.96 ± 18%, p > .05), the rate of pregnancy loss was significantly higher among cows diagnosed by Vet-B (10.41 ± 11.2% vs 4.87 ± 9.0, p = .029). In addition, among cows diagnosed by Vet-B, the rate of pregnancy loss was significantly higher among cows diagnosed, while he had fewer than 12 months' PD-US experience (11.17 ± 12.14%) than among cows that he diagnosed later (7.14 ± 11.01%, p = .038); in fact, this latter loss rate was comparable to that among cows diagnosed by Vet-A during the same period (3.51 ± 9.83%, p = .620). These results suggest that inexperience with PD-US during the late embryonic period can increase risk of early pregnancy loss, supporting the need for proper training.

Early postpartum administration of equine chorionic gonadotropin to dairy cows calved during the hot season: Effects on fertility after first artificial insemination.

Heat stress reduces fertility of high-producing dairy cows, and early administration of equine chorionic gonadotropin (eCG) may improve it. Here, 401 heat-stressed, high-producing dairy cows on a single commercial farm were given eCG (500 UI, n = 214) or saline (n = 187) on days 11-17 after calving, and the effects on fertility after the first artificial insemination (AI) were assessed. On post-partum day 96.34 ± 9.88, all cows were inseminated after a "double short Cosynch" synchronization protocol. Ovarian activity and uterine status were checked by ultrasound on the day of eCG administration and every 7 days thereafter for a total of 3 weeks; checks were also performed during synchronization, and 7 days after AI. On post-partum day 30, cytobrush uterine cytology was performed to check for subclinical endometritis. Pregnancy status was checked on days 30 and 60 after AI. The eCG and control groups did not differ significantly in terms of average lactations per cow (2.33 ± 1.34), days in milk at first AI (96.33 ± 9.88), average milk yield at AI (41.38 ± 7.74 L), or the particular inseminator or bull used for AI. The eCG and control groups showed increasing ovarian activity with time, with approximately 75% of cows in both groups showing a corpus luteum at the beginning of the synchronization protocol. On post-partum day 30, 17.4% of eCG cows and 22.9% of control cows showed subclinical endometritis. Cows treated with eCG showed a tendency toward lower hyperecogenic intraluminal content (16.8 vs. 21.4%, P = 0.15), but ovarian activity during the synchronization protocol was similar between eCG and control groups, with 91% of animals in both groups showing luteolysis after prostaglandin application and 88% showing ovulation after the last administration of gonadotropin-releasing hormone. Fertility was similar between the two groups at both time points after AI (30 days, 34.9 vs. 31.8%; 60 days, 30.6 vs. 28.5%; P > 0.2). These results suggest that early postpartum eCG administration does not improve fertility of heat-stressed dairy cows as long as 60 days after AI. Other strategies may be more effective at mitigating the ability of post-partum heat stress to reduce fertility of high-producing dairy cows.

Maternal aging affects life performance of progeny in a Holstein dairy cow model.

The development and life performance of 404 high-producing Holstein dairy cows was studied from birth onwards and during two lactations. The management, environment and parental genetics of the cows were known in detail. Cluster analysis identified four performance 'types': high-yielding (HY) cows and persistently high-yielding (PHY) cows, which accounted for 33% of the animals; medium-yielding (MY) cows, 41%; and low-yielding (LY) cows, 26%. Prenatal determinants of the life performance of the progeny were analyzed. Developmental and environmental factors were excluded as determinants of performance (including birth weight, level of passive immunity transfer, growth rate, age at first parturition and reproductive efficiency). Life performance did show minor seasonal effects, with more HY cows but less PHY being born during the cold season (90.1% in HY; 58.3% in PHY v. 81.5%). Instead, the single most important factor influencing life performance of daughters was maternal age. HY cows were born from the youngest mothers (1.89±1.14 parturitions, 3.12±1.42-year old), whereas LY cows were born from the oldest (2.72±1.80 parturitions, 3.97±2.01-year old; P<0.001). Life performance of the dams did not differ among clusters. In addition, metabolic parameters (fat and protein yield) were found to correlate significantly with yields between the first and second lactations (milk yield: r=0.357; fat yield: r=0.211; protein yield: r=0.277; P<0.0001), suggesting the influence of the individual. These results suggest that under optimal health, nutritional and environmental conditions, maternal aging is an important determinant of the life performance of progeny and argue for the need to identify conditions that contribute to health and disease in progeny according to the Developmental Origin of Health and Disease or DOHaD concept. Our findings may help the development of novel management guidelines for dairy farms.

Pregnancy per AI differences between primiparous and multiparous high-yield dairy cows after using Double Ovsynch or G6G synchronization protocols.

The objective of the present work was to determine the optimal protocol for timed AI on high-yield dairy cows. The pregnancy per AI (pregnancy/AI) arising from 7805 first timed artificial inseminations on 27 dairy farms in eastern Spain was examined after use of the Double Ovsynch (DOv; N = 6783) or G6G (N = 1022) synchronization protocols. Parity number, farm, prostaglandin analogue, and season (hot or cool) were examined for their possible association with postsynchronization fertility (in terms of pregnancy/AI). Mean pregnancy/AI overall was 36.1 ± 8.4%, with no significant differences between the DOv or G6G protocols (36.3 ± 8.3% vs. 34.8 ± 9.1%). However, parity and synchronization treatment resulted in a significant interaction (P = 0.03). When DOv AIs (N = 6783) and G6G AIs (N = 1022) were analyzed separately it was observed that pregnancy/AI was significantly better in primiparous than in multiparous cows after DOv (44.3 ± 11.4% vs. 31.4 ± 8.2%; P < 0.0001), and pregnancy/AI was similar after G6G in primiparous and in multiparous cows (34.7 ± 9.2% vs. 34.8 ± 9.9%). Hot season significantly reduced pregnancy/AI to a similar extent for primiparous and multiparous cows and showed a significant interaction of protocol and season (P = 0.001). These results were similar across all farms, regardless that their overall pregnancy/AI was similar or significantly different from the average. These results indicate that G6G tended to be associated with a higher pregnancy/AI than DOv in multiparous cows, and the opposite was observed in primiparous cows.