Highly fertile cows establish pregnancy sooner after calving and require fewer inseminations than lower-fertility cows.

Irrespective of geography and husbandry, modern dairy cows experience heat stress (HS) effects leading to fertility declines, but it worsens in tropical climates. The threshold of HS experience among modern dairy cow has lowered, leading to decreased thermal comfort zone. Studies show that this threshold is lower for fertility than for lactation. HS abatement and robustness response to lactation yield lead to negative energy balance, and cow's reproductive requirements remain unfulfilled. The adverse effects of HS commence from developing oocyte throughout later stages and its fertilization competence; the oestrus cycle and oestrus behaviour; the embryo development and implantation; on uterine environment; and even extend towards foetal calf. Even cows can become acyclic under the influence of HS. These harmful effects of HS arise due to hyperthermia, oxidative stress and physiological modifications in the body of dairy cows. Proper assessment of HS and efficient cooling of dairy animals irrespective of their stage of life at farm is the immediate strategy to reduce fertility declines.

There is an antagonistic relationship between fertility and milk yield, and intensive selection for milk yield has severely deteriorated reproductive efficiency.

This can be profoundly explained that the photons emitted by LEDs are absorbed by the chromophores of the skin (e.g., mitochondrial, cytochrome C, melanin, and endogenous protoporphyrins), causing downstream alterations in its bio-physiology, leading to changes in cellular proliferation, migration, differentiation, inflammation, and collagen production

Immunofluorescence staining demonstrated that a considerable number of cells in the labyrinth zone and chorionic plate expressed CD117. Additionally, immunofluorescence staining and flow cytometric analysis revealed a high percentage of CD117+ TSCs also expressed Sca-1 (> 70%), but did not express markers of hematopoietic cells (Figs. 1c and 2a, b) or MSCs (Figs. 1d and 2a, b).

Natale et al. found that undifferentiated trophoblasts, from mid-gestation mouse placentas, expressed the murine cell surface protein Sca1. The Sca1+ subpopulation of TCs demonstrated proliferation and multipotency with differentiation into TC types of both the junctional zone and the labyrinth layer

To avoid serum contamination, some researchers are opting for gamma irradiation. Several common contaminants, including Mycoplasma, are sensitive to even low levels of radiation. But this requires a balancing act: radiation also damages growth proteins and bioactive molecules that help cells thrive.

“Every year since 1980, people have been saying that serum is dead,” he says. “Serum is still very popular because people like the idea that they can grow cells and not have fabulous technique.” Culture is tough on cells: researchers pipette them from dish to dish, freeze and thaw them, add digestive enzymes to detach them from substrates and more. Serum is a balm for such abuses

Hormones, growth factors and other signalling molecules are abundant in serum, but tightly regulated in organs, he says

The most basic step is to ensure cells' genetic identity. Journals and funders now ask researchers to disclose whether they have checked to make sure that, say, cell lines representing corneal or skin tissue are not actually a fast-growing line derived from human cervical cancer. But cells' behaviour can also change with density, proliferation rates, growth media, the presence of contaminants and the time kept in culture2.

Most academic labs culture cells by using fetal bovine serum (FBS), a liquid extracted from clotted cow blood and collected from abattoirs when pregnant cows are slaughtered. What ends up in the serum depends on factors such as diet, geographical location, time of year, whether the animals receive hormones or antibiotics and the gestational age of fetal calves. Substantial amounts of FBS are added as a supplement to the culture media in which cells grow; 5–15% of the volume of growth media is typical. FBS composition can affect how thick an engineered tissue becomes, cause spontaneous artefacts that mimic cell activity and even influence how surface receptors respond to a given compound. “FBS is like a big dark cloud over our heads, not knowing what's real and what's not,” says Khodabukus, now a postdoctoral researcher at Duke University in Durham, North Carolina.

Carnegie stage 7 (Days 15–17) At the second stage of chorionic villi development, i.e. CS7, extra-embryonic mesoderm proliferates and penetrates into the core of the primary villi. This structure, in which extra-embryonic mesoderm is surrounded by CT and ST, is called the ‘secondary villi’ (Figs 2D, 3B). The embryonic body is now about 0.4 mm in size at the diameter. Laterality is established, gastrulation starts and germ layers are formed from the epiblast.

Carnegie stage 6 (Days 13–14) CS6 marks the first stage of chorionic villi development, when the CT grows externally and penetrates into the primitive ST to form cellular columns. The columns are called primary villi and have two cellular layers (Fig. 3A); the outer layer is ST, and the inner layer is CT. The embryonic body at this stage is now about 0.2 mm diameter in size. Furthermore, extra-embryonic cavities coalesce to form the chorionic cavity.

Carnegie stage 5c (Days 11–12) In CS5c, the primitive ST continues to penetrate into the endometrium, maternal capillaries connect with lacunae in the primitive ST, and maternal bloods flow into the lacunae. The ST forms about three quarters of the total trophoblastic shell, and the CT constitutes the remaining one-quarter (O’Rahilly and Müller, 1987).

Carnegie stage 5b (Days 9–10) At CS5b, the trophoblast has two morphologically and functionally distinct layers of cells; the inner layer (i.e. CT) and outer layer (i.e. ST) (Fig. 2C). Lacunae appear in primitive ST, in which small vacuoles fuse with each other, thus leading to CS5b also being called ‘lacunar stage’ or ‘primitive syncytium’ (Fig. 2C) (Hertig et al., 1956; Boyd and Hamilton, 1970; James et al., 2012). Tissue specimens at the time of implantation indicate that CT and ST emerge concurrently (O’Rahilly and Müller, 1987), however, whether TE differentiates into primitive ST through a CT stage is controversial (Boyd and Hamilton, 1970; Knofler and Pollheimer, 2013).

Carnegie stage 5a (Days 7–8) At CS5a, the trophoblast exists as a mass of cells and is called solid trophoblast (Fig. 2B). Two distinct layers of cells (bilaminar germ disc), epiblast and primitive endoderm, appear. The amniotic cavity appears between the epiblast and TE and the yolk sac appears between primitive endoderm and TE.

The colony-forming unit (CFU) assay is one of the most widely used assays for hematopoietic stem and progenitor cells (HSPCs). CFU assays allow measurement of the proliferation and differentiation ability of individual cells within a sample. The potential of these cells is measured by the observation of the colonies (consisting of more differentiated cells) produced by each input progenitor cell.