240 OVUM-PICK UP IN HOLSTEIN-FRIESIAN COWS AT 9 TO 10 MONTHS OF AGE

Abstract

Rate of genetic gain can be improved by increasing selection intensity, increasing selection accuracy, creating a higher amount of variation, or shortening the generation interval. A reduction in the generation interval can be realised by collecting embryos from animals at a young age. At CRV it is currently routine practice to start embryo collection (by flushing) at 12 to 15 months of age. The aim of this study was to investigate if the collection of embryos at a younger age by means of ovum pickup (OPU) is beneficial for our breeding program. Healthy 9- to 10-month-old Holstein-Friesian animals were selected at young age based on their maturity, (i.e. OPU could be performed by normal standard procedure/equipment). Animals were not stimulated with hormones. Oocytes were collected by OPU once every week during a period of ~8 weeks. Collected oocytes were matured, fertilized, and cultured for 7 days in SOF culture medium according to standard procedures (Merton et al. 2002). Embryo development was scored at Day 7. Results were analysed by Student's t-test. On average 11.7 oocytes were collected from animals as young as 9 months of age. However, embryo development of the oocytes from young animals was only 0.4 embryo per session at Day 7 (3% embryo development). When only the results of the first OPU session were taken into account, 18.2 oocytes and 0.8 embryo could be collected per animal per session. Whether an animal was observed in oestrus before the first OPU session affected results. Animals that had shown clear signs of oestrus before the first OPU session produced significantly more embryos than animals that did not (Table 1). It is concluded that OPU is possible on animals at 9 to 10 months of age but only when animals have been in oestrus before the first OPU session. Best results were obtained for the first OPU session.

Table 1.  Effect of first oestrus before OPU on embryo production