11 The impact of multiple ovum pickups on reproductive and productive performance of Holstein heifers

The use of high-genetic-merit heifers as donors for in vitro embryo production (IVP) has been an excellent tool to maximise the genetic gain and production of a herd in a short period of time. However, questions arise as to what the impact of this biotechnology is on the future reproductive and productive life of the young donors. The aim of this study was to evaluate the effect of multiple ovum pickups (OPU) on IVP results, number of services, age at conception, pregnancy failure, and milk production of Holstein heifer donors. Data from 199 Holstein heifers from 8 to 21 months, open or until 90 days of pregnancy, aspirated between June 2017 to March 2021 at RuAnn Dairy, Riverdale, CA, were analysed. All donors were synchronised and stimulated with FSH before OPU (intervals between procedures varied, but never fewer than 14 days). In vitro maturation, fertilisation (IVF), and culture (IVC) were performed as described by Demetrio et al. (2020). The number of viable Day 7 embryos (morula to hatched blastocyst) divided by the number of oocytes in IVC after IVF was defined as embryo development rate. A total of 1,073 OPUs were performed with an average of 5.4 ± 2.9 OPUs per heifer and 11.2 ± 5.4 oocytes per OPU. All OPUs were carried out by a practitioner with more than 15 years of experience. All heifers from the RuAnn herd were released to be bred for the first time at 15 months. The first service was performed with sexed semen and the remaining services with conventional semen. The average age of the donor heifers at the first service was 15.8 months. A total of 82% (164/199) became pregnant in the first (47% [93/199]) or second service (35% [71/199]). Two heifers did not get pregnant, and their embryo production data were not included. IVP results, number of services, and age at conception are shown in Table 1. Of the 199 animals evaluated, 4 of 151 heifers (2.6%) who were only aspirated before getting pregnant aborted and 1 out of 46 (2.2%) who were aspirated while pregnant aborted. The abortion incidence was low, suggesting no relationship to OPU. These donors had a 305-day mature equivalent milk production of 14,482 kg, while the other cows of the herd had 13,902 kg. Based on the data collected, there were no negative effects of repetitive OPU procedures on reproductive life, embryo production, or milking performance of donor heifers, but it is worth mentioning that OPU must be performed by an experienced professional so that it does not harm the health of the animal. The advantage of using heifers as donors is that their superior genetics can be multiplied early without harming their future as a lactating cow.

Table 1. Number of ovum pickups (OPUs) and their effect on in vitro embryo production and reproductive indexes of Holstein heifers

This research was supported by RuAnn Genetics.