Impact of oocyte donor age and breed on

Abstract

Genomic selection combined with in vitro embryo production (IVEP) with oocytes from heifer calves provides a powerful technology platform to reduce generation interval and significantly increase the rate of genetic gain in cattle. The ability to obtain oocytes with developmental competence from calves has been recognised for more than 60years. There is renewed interest in the potential of this reproductive technology as the beef and dairy industries seek to identify and multiply animals that satisfy consumer demand for efficient utilisation of natural resources, with minimal environmental impact and high product quality. Heifer calves show a good follicular response to FSH stimulation and oocytes can be recovered by ovum pick-up (OPU). However, the efficiency of OPU/IVEP remains lower for calves compared with peripubertal heifers and cows, in both indicus (Zebu, Bos indicus) and taurus (Bos taurus) breeds. Indicus cattle generally have more follicles, yield a greater number of oocytes, and have a better IVEP outcome, compared with taurus cattle. The treatment of prepubertal heifers with bovine somatotrophin (bST) and propylene glycol before OPU/IVEP has yet to show a major improvement in embryo production. Holstein (taurus) dairy heifers derived from different reproductive technologies (AI, MOET, OPU/IVEP) showed a similar age at puberty and first-lactation milk production. OPU/IVEP Holstein embryos transferred to beef or dairy cows likewise yielded heifers with the same performance. The gains in productivity that can be achieved with strategic use of OPU/IVEP in heifer calves make this a relevant and highly important reproductive technology in cattle breeding. Ongoing optimisation of the technology is needed for the potential of OPU/IVEP in young donors to be fully realised.

Fitness of calves born from in vitro-produced fresh and cryopreserved embryos

“…However, in our experimental herd, there were no BW differences between fresh, F/T, and V/W calves. Beef recipients, like AV, have shorter GL than dairy cattle ( 65 ) and lower milk yield. For this reason, the recipient breed (Holstein, AV, crossbred) was a factor to correct in our study, which affected nasal flux, conjunctival appearance, Na + , and Cl − values at birth.…”

Review: Some challenges and unrealized opportunities toward widespread use of the in vitro-produced embryo in cattle production

“…Space limitations mean that some issues are not included or are discussed in a limited fashion. The reader is directed elsewhere ( Sirard, 2016 ; Ealy et al, 2019 ; Hansen, 2020a and 2020b; Baruselli et al, 2021 ; Valente et al, 2022 ) for treatment of some relevant topics not discussed here, such as recipient management, cryopreservation, and the impact of sire and genetics, as well as for a more detailed analysis of specific topics discussed here.…”

Perspectives of gene editing for cattle farming in tropical and subtropical regions

“…In animal breeding, genetic gain can be accelerated if spermatogonia are collected from high genomic value male calves at a very young age and transplanted into surrogate knockout adult males, enabling the surrogate male to produce normal sperm from the young donor. Semen from the surrogate sire can then be used for in vitro fertilization of oocytes collected from prepubertal heifers or calves ( Baruselli et al, 2021 ; Silva et al, 2022 ) thus dramatically reducing generation interval. This latter application can be particularly interesting for breeds with delayed puberty, as found in some indigenous cattle ( Cooke et al, 2020 ).…”