Low oxygen tension during in vitro embryo production improves the yield, quality, and cryotolerance of bovine blastocysts.

Mammalian oocytes undergo maturation and fertilization in the low-oxygen (O) environment of the oviduct. To evaluate the effect of O tension during in vitro maturation and fertilization on embryo yield, quality, cryotolerance, and gene expression, we matured and fertilized bovine cumulus-oocyte complexes under low (5%) or high (20%) O tension. Presumptive zygotes from both groups were cultured at 5% O for 8 days.

Effect of creep feeding with rice bran and temporary weaning on cow-calf performance.

This study was conducted to investigate if calves supplemented with rice bran in a creep feeding (CF) system associated with temporary weaning (TW) affects the performance of the cow-calf pair grazing natural grasslands during summer. Two experiments were performed using 275 cow-calf pairs of British breeds and their crosses of different parities (primiparous [n = 188] in Experiment 1 and multiparous [n = 87] in Experiment 2). In both experiments, the factors evaluated were: (1) supplementation of calves with rice bran using CF: yes (+CF) or no (-CF); (2) TW for 14 days using nose plates: yes (+TW) or no (-TW).

Effect of temporary weaning and creep feeding on calf growth and the reproductive efficiency of their Hereford dams.

Objective: The objective was to test if creep feeding (CF) improves the average daily gain (ADG) and weaning weight of calves submitted to temporary weaning (TW) and if the combination of CF and TW improves conception and pregnancy rates of cows.

Methods: Primiparous (n = 74) and primiparous and multiparous (n = 104) cows grazing native grasslands were used in experiment 1 and 2; respectively. The experimental design was in plots divided into complete random blocks with two replications.

Effect of season on germinal vesicle stage, quality, and subsequent in vitro developmental competence in bovine cumulus-oocyte complexes.

Although the reproductive performance of grazing cattle is lower in summer compared to winter, the effect of season on oocyte developmental competence has not been thoroughly examined. We measured the effect of season on oocyte chromatin compaction, cumulus cell quality, and embryonic development after in vitro fertilization. Cumulus oocytes-complexes (COCs) were collected from abattoir cows' ovaries during the winter and summer months.