Impact of oocyte donor age and breed on embryo production in cattle, and relationship of dairy and beef embryo recipients on pregnancy and the subsequent performance of offspring: A review.

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.

Use of embryo transfer to alleviate infertility caused by heat stress.

Heat stress (HS) has a pronounced deleterious effect on fertility in dairy herds throughout the world, especially in hot and humid summer months in tropical and subtropical areas. Summer HS reduces feed intake and increases negative energy balance, induces changes in ovarian follicular dynamics, reduces estrus detection rates and alters oviductal function leading to fertilization failure and early embryonic death. Furthermore, oocytes harvested from lactating cows during summer HS have a decreased ability to develop to the blastocyst stage after in vitro fertilization when compared with oocytes harvested during winter.

Use of FSH in two different regimens for ovarian superstimulation prior to ovum pick up and in vitro embryo production in Holstein cows.

We aimed with the present study to evaluate the effects of FSH treatment (200 mg) split in four or six administrations on ovarian follicle stimulation and in vitro oocyte competence for embryo production in dairy cows with synchronized follicular wave emergence. On random days of the estrous cycle (Day 0), non-lactating Holstein cows received a progesterone (P4)-releasing intravaginal device and 2 mg estradiol benzoate IM. On Day 3, they received 0.

The Infertility of Repeat-Breeder Cows During Summer Is Associated with Decreased Mitochondrial DNA and Increased Expression of Mitochondrial and Apoptotic Genes in Oocytes.

Oocyte quality is known to be a major cause of infertility in repeat-breeder (RB) and heat-stressed dairy cows. However, the mechanisms by which RB oocytes become less capable of supporting embryo development remain largely unknown. Thus, the aim of this study was to investigate whether the decreased oocyte competence of RB cows (RBs) during summer is associated with an altered gene expression profile and a decrease in mitochondrial DNA (mtDNA) copy number.

Reference gene selection for gene expression analysis of oocytes collected from dairy cattle and buffaloes during winter and summer.

Oocytes from dairy cattle and buffaloes have severely compromised developmental competence during summer. While analysis of gene expression is a powerful technique for understanding the factors affecting developmental hindrance in oocytes, analysis by real-time reverse transcription PCR (RT-PCR) relies on the correct normalization by reference genes showing stable expression. Furthermore, several studies have found that genes commonly used as reference standards do not behave as expected depending on cell type and experimental design.

Bovine embryo transfer recipient synchronisation and management in tropical environments.

Numerous studies have shown that it is possible to manipulate follicular and luteal dynamics, thereby eliminating the need for oestrus detection in embryo transfer (ET) programmes. Fixed-time ET (FTET) protocols are based on the use of gonadotrophin-releasing hormone (GnRH) and prostaglandin (PG) F or progesterone/progestogen (P4)-releasing devices and oestradiol. The FTET protocols increases the proportion of recipients transferred, and therefore pregnancy rates, compared with the use of PGF followed by ET 7 days after oestrus.

Toxoplasma gondii: Evidence for the transmission by semen in dogs.

Ten male dogs were distributed into three experimental groups for infection with Toxoplasma gondii: GI - three dogs inoculated with 2.0x10(5) P strais oocysts, GII - three dogs infected with 1.0x10(6) RH strain tachyzoites, and GIII - four controls dogs.