The purpose of this study was to evaluate the impact of repeated follicular puncture used in the ovum pick-up technique on the welfare of cows. The evaluation relies on the physiological measurement of stress, milk production criteria, immune status, and the histological examination of ovaries. Two groups of five Holstein cows were submitted to epidural anaesthesia and genital palpation with insertion of an intravaginal ultrasound probe for transvaginal puncture (the puncture was not performed in the control group). Animals were manipulated twice a week for 8 weeks (16 manipulation sessions). The blood cortisol concentrations increased after each session; however, the concentrations were the same in both the control and the punctured groups. Two adrenocorticotrophic hormone challenge tests, performed before the first session and after the last session, showed an unchanged adrenal sensitivity through repeated puncture sessions. The transvaginal puncture did not affect milk production, or blood and milk somatic cell counts. Ovariectomies were performed on another group of four Holstein cows at various intervals (0 to 30 days) after five similar puncture sessions. Histological examination of the ovaries 4 days after puncture revealed blood-filled follicles and haemorrhagic foci in ovarian stroma, but the examination 30 days after the last puncture session demonstrated very limited, if any, fibrosis. On the basis of the criteria chosen for this study, repeated transvaginal follicular puncture on its own does not impact adversely on the welfare of cows.

The reduction of the generation gap has become of main interest in the race for the genetic improvement of cattle and in reducing the environmental impact of dairy farms. Sexual precocity of high genetic merit heifers is therefore essential, as it allows the development of their potential as soon as possible thanks to embryo collection. Many factors influence the sexual precocity and embryos production of bovine females. A major effect of the calves’ growth rate has often been observed on puberty precocity in experimental trials. This study was carried out on data recorded from January 2010 to May 2015 on 617 Holstein heifers housed in 2 centers of embryos production with similar breeding conditions in France. The purpose was to find optimal breeding values of Holstein heifers for embryo production in these centers. The heifers entered at the centers between 4 to 15 months old (after a quarantine of 30 days) to produce in vivo embryos during 2 to 4 collections before to come back pregnant to their breeder owner. The first treatment of superovulation was programmed when a first heat was observed visually or via an activity sensor (Heatime R) or when a corpus luteum had been detected (ultrasound scans). The studied variables were the date of the first flushing as a precocity indicator and the collection results for the production of embryos (numbers of total and viable embryos). In this population, the average age at entry was 8.5 ± 2.3 months old (minimum = 3.4; maximum = 15.0), the average age at the first collection 14.3 ± 1.2 months (minimum = 11.0; maximum = 19.0), the average daily gain (ADG) between 0 and 12 months was 792 ± 86 g day–1 (minimum = 492; maximum = 1027), the average number of total structures by collection 9.3 ± 6.1, the mean number of viable embryos 5.5 ± 3.8. Data analysis by multivariate ANOVA test showed an effect on age at first collection for the center (P = 0.009), age at entry (P < 0.001), and ADG between 0 and 12 months (P < 0.001). Heifers with ADG between 0 and 12 months of <650 g day–1 had a delay of 70 days for the first collection compared to those with an ADG of >900 g day–1. The ADG between 0 and 12 months had also the strongest negative correlation found with the age at first collection (r = 0.52). Similarly, ADG between 0 and 6 months of the 40 heifers entered in the centers before the age of 6 months was significant for age at the first collection (P = 0.0001), whereas ADG between 6 and 12 months was not. Regarding the production of embryos, only the weight at the first collection tended (P = 0.07) to have an effect on the total number of collected structures: 10.1 ± 6.5 for heifers that weighted more than 420 kg v. 7.3 ± 4.0 for those that weighted less than 340 kg. No effect on the percentage of grade 1 or 2 embryos could be observed. In conclusion, this study conducted in production conditions confirmed the observations made in experimental trials and refined the recommendations and practices of the two centers to reduce the age at first embryo flushing.

Insemination of superovulated bovine donors in due time is of central importance for fertilization and embryo viability. A preliminary test focusing on LH surge detection during superovulation (unpublished datas) indicated that one quarter of the donors present LH surges 12 to 24 h before heat observation (which could correspond, in the case of AI after heat observation, to post ovulation AI). Therefore, it was hypothesised that the average number of embryos per flush could be improved by inseminating donors with early LH surge 12 h after the beginning of the LH peak whenever the heat occurs.In a donor herd station, a trial was performed with 54 Holstein heifers, equipped with Heatime® tags (system detecting the peak activity linked to the heat) collected twice or 3 times after the following superovulation protocol: D-6 to D-11 = reference heat; D0 = input of an implant of norgestomet (Crestar®); D2 8:00 = first FSH (Stimufol®) injection (FSH1); D4 8:00 = cloprostenol (Estrumate®) injection; D4 16:00 = implant removal; D5 8:00 = FSH7 and first LH surge detection test (Predi'Bov®); D5 16:00 = FSH8 and 2nd Predi'Bov® test. Two AI's at interval of 8 to 16h were done (AI's were performed either at 9:00, or between 17:00 and 19:00). For the standard protocol (= STA), thefirst AI occurred after heat observation or activity peak detection by Heatime (whatever the Predi'Bov® test results were). For the adjusted protocol (= ADJ), the first AI occurred from 11 to 16 h after the first positive Predi'Bov® test result or like STA protocol if both results were negative. Heifers followed alternately the 2 protocols, 27 beginning with the ADJ protocol, 27 others with the STA one. LH surge precocity was not repeatable among donors. In the case of an early LH surge detection (one positive Predi'Bov® test), the heat activity peak occurred from 2 to 8 h after the FSH8 for 44% of the flushes, from 8 to 24 h after FSH8 for 54% of the flushes and never for 2% of the flushes. When no early LH surge was observed, the heat activity peak occurred more than 8 h after FSH8 for 78% of the flushes. Interval of heat activity peak-FSH8, IA1-heat activity peak and IA1-early LH surge were highly variable but did not effect the mean number of viable embryos. However, we observed a significant effect (P = 0.04) of the precocity of the heat on the average number of total embryos: 13.8 ± 8.4 v. 11.1 ± 8.1 when the interval heat activity peak-FSH8 had been respectively <8 h or ≥8 h, respecively. Among the 148 collections, 74 were done after the STA protocol, 74 after the ADJ protocol and 70 followed an early LH surge. The adjustment of the AI depending on the detection of an early LH surge (ADJ protocol) had a significant positive (P = 0.04) effect on the mean percentage of viable embryos per flush (52% ± 28 in STA group and 62% ± 31 in ADJ group). Nevertheless, regarding the mean number of viable embryos, this effect failed to reach significance (P = 0.23) (respectively 5.7 ± 5.1 in STA group and 6.7 ± 6.7 in ADJ group). A larger study on more animals is necessary to obtain a significant difference in the number of viable embryos.

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