FACTORS AFFECTING THE OPTIMIZATION OF OVUM PICK-UP FREQUENCY IN BRAHMAN AND FRIESIAN CATTLE DURING IN-VITRO FERTILIZATION; A COMPREHENSIVE REVIEW

Abstract

Reproduction is key area to produce livestock with desirable traits and in this regard, assisted reproductive technology (ARTs) play a major role particularly in-vitro fertilization (IVF) technology. In-vitro embryo production (IVEP) has increased dramatically over the past 10 to 15 years, Initially, oocytes for IVEP were collected from slaughterhouse ovaries, however, with technological advancements oocytes are now being collected from the live animal through the ovum pick-up (OPU) methodology (Sarkar D et al., 2021). To maximize oocyte yield, maintain donor health and improve the efficiency of IVEP programs, it is essential to determine and optimize the appropriate frequency of OPU sessions in different cattle breeds. The optimization of ovum pick-up (OPU) frequency plays a pivotal role in maximizing oocyte recovery, ensuring donor welfare, and improving the cost-effectiveness of in-vitro fertilization (IVF) programs in cattle. This review consolidates current knowledge on biological, hormonal, technical, environmental, and welfare-related factors influencing OPU outcomes, with special emphasis on breed-specific differences between Bos indicus (Brahman) and Bos taurus (Friesian) cattle. Distinct ovarian physiology, including higher antral follicle counts, smaller follicle diameters, and differential follicular wave dynamics in Bos indicus, dictates a more conservative OPU frequency compared with Bos taurus donors. Evidence suggests that weekly or biweekly non-stimulated OPU is optimal for Brahman donors, while Friesian donors can sustain twice-weekly OPU under skilled management and high laboratory capacity. Hormonal priming with FSH or eCG can improve oocyte yield and competence, though repeated super stimulation demands cautious spacing (10 – 14 days) to avoid ovarian fatigue. Environmental factors such as heat stress, nutritional status and oxidative balance further modulate follicular response and oocyte quality. Despite technical advancements, significant gaps persist regarding long-term donor effects, breed-optimized FSH regimens, and frequency adaptation under tropical heat load.