The specific role of WNT signaling during preimplantation development remains unclear. Here, we evaluated consequences of activation and inhibition of β-catenin (CTNNB1)-dependent and -independent WNT signaling in the bovine preimplantation embryo. Activation of CTNNB1-mediated WNT signaling by the agonist 2-amino-4-(3,4-(methylenedioxy)benzylamino)-6-(3-methoxyphenyl)pyrimidine (AMBMP) and a glycogen synthase kinase 3 inhibitor reduced development to the blastocyst stage. Moreover, the antagonist of WNT signaling, dickkopf-related protein 1 (DKK1), alleviated the negative effect of AMBMP on development via reduction of CTNNB1. Based on labeling for phospho c-Jun N-terminal kinase, there was no evidence that DKK1 activated the planar cell polarity (PCP) pathway. Inhibition of secretion of endogenous WNTs did not affect development but increased number of cells in the inner cell mass (ICM). In contrast, DKK1 did not affect number of ICM or trophectoderm (TE) cells, suggesting that embryo-derived WNTs regulate ICM proliferation through a mechanism independent of CTNNB1. In addition, DKK1 did not affect the number of cells positive for the transcription factor yes-associated protein 1 (YAP1) involved in TE formation. In fact, DKK1 decreased YAP1. In contrast, exposure of embryos to WNT family member 7A (WNT7A) improved blastocyst development, inhibited the PCP pathway, and did not affect amounts of CTNNB1. Results indicate that embryo-derived WNTs are dispensable for blastocyst formation but participate in regulation of ICM proliferation, likely through a mechanism independent of CTNNB1. The response to AMBMP and WNT7A leads to the hypothesis that maternally derived WNTs can play a positive or negative role in regulation of preimplantation development.

The effects of high thermal stress on serum protein metabolites, milk production of transition dairy cows in semi-arid areas in South Africa were evaluated. Forty, ± 8 months pregnant, Jersey heifers (± 26 months) in zero grazing management were selected during summer from two semi-arid communal areas. Summer thermal-humidity index (THI) of the areas were THI-1 (72–83: extreme caution) and THI-2 (75–87: danger). Blood samples were collected (21 days pre-partum, and 21 and 75 days post-partum) and analysed for serum protein metabolites. Milk yield was recorded daily and samples collected for milk fat, protein, lactose and urea nitrogen analysis. Heifers in THI-2 had lower (P < 0.05) total serum proteins, albumin and blood urea nitrogen than THI-1. Post-calving, cows in THI-1 had higher (P < 0.05) TP (73.4 vs 67.9 g/l) and BUN (4.61 vs 3.77 mmol/l) at 21 DIM, and lower (P creatinine at 21 and 75 DIM than THI-2 group. Milk yield, fat and protein in THI-2 were all lower (P < 0.05) than THI-1 21DIM. The results confirm that heat stress affects utilisation of nutrients in transition dairy cows.

Alterations in maternal environment can sometimes affect embryonic development in a sexually-dimorphic manner. The objective was to determine whether preimplantation bovine embryos respond to three maternally-derived cell signaling molecules in a sex-dependent manner. Actions of three embryokines known to increase competence of bovine embryos to develop to the blastocyst stage, insulin-like growth factor 1 (IGF1), activin A, and WNT member 7A (WNT7A), were evaluated for actions on embryos produced in vitro with X- or Y- sorted semen from the same bull. Each embryokine was tested in embryos produced by in vitro fertilization of groups of oocytes with either pooled sperm from two bulls or with sperm from individual bulls. Embryos were treated with IGF1, activin A, or WNT7A on day 5 of culture. All three embryokines increased the proportion of cleaved zygotes that developed to the blastocyst stage and the effect was similar for female and male embryos. As an additional test of sexual dimorphism, effects of IGF1 on blastocyst expression of a total of 127 genes were determined by RT-qPCR using the Fluidigm Delta Gene assay. Expression of 18 genes was affected by sex, expression of 4 genes was affected by IGF1 and expression of 3 genes was affected by the IGF1 by sex interaction. Sex did not alter how IGF1, activin A or WNT7A altered developmental competence to the blastocyst stage. Thus, sex-dependent differences in regulation of developmental competence of embryos by maternal regulatory signals is not a general phenomenon. The fact that sex altered how IGF1 regulates gene expression is indicative that there could be sexual dimorphism in embryokine regulation of some aspects of embryonic function other than developmental potential to become a blastocyst.