Birth To Live Lambs Research Articles

Nuclear transfer procedures in the ovine can induce early embryo fragmentation and compromise cloned embryo development

Cytoplasmic fragmentations are frequently observed in early mammalian embryos, and especially in the human. In our research we have observed subtle clues that the occurrence of fragmentation was most likely a result of somatic cell nuclear transfer (NT) protocols, and in particular, the in vitro culture system. In this study we examined various putative factors that might induce early embryo fragmentation in the ovine. The results indicate that nuclear transfer protocols such as the fusion parameter, activation treatment, and especially the choice of culture medium affected embryo cleavage rates and resulted in a higher incidence of fragmented embryos. Upon using the same fusion parameter, activation parameters that were based upon amino acids containing synthetic oviduct fluids (SOFaa) culture system resulted in significantly lower fragmentation rates than when utilizing a Charles Rosenkrans 1 (CR1aa) culture system. Fragmented embryos typically exhibited irregular numbers of blastomeres with the majority of blastomeres devoid of chromatin. Factors such as fusion DC pulse, activation treatment and culture system led to higher fragmentation and also affected in vitro and in vivo embryo development. The SOFaa based culture system produced a higher number of quality NT embryos resulting in higher pregnancy rates and the birth of live lambs as compared to the CR1aa based system ( P < 0.05). We conclude that early embryo fragmentation in the ovine is caused by suboptimal cloning protocols, and NT embryo development is especially affected by the culture system used.

High levels of congenital transmission of Toxoplasma gondii in a commercial sheep flock

Our current understanding of congenital transmission of Toxoplasma gondii from ewe to lamb dictates that infection frequently results in abortion and the death of the developing foetus, that the birth of live infected lambs occurs rarely and that the cat is the predominant source of infection in ewes. Using direct polymerase chain reaction detection of T. gondii, we report high levels of congenital transmission occurring in a commercially managed sheep flock. We sampled foetal-derived placental tissue and tissues from aborted lambs and showed that congenital transmission was detected in these tissues from 61% of all pregnancies. Where pregnancies resulted in the death of one or more lambs, T. gondii was detected in the lamb tissue for all but one of 18 (94%) pregnancies. Of the successful pregnancies resulting in the birth of live lambs we were able to detect T. gondii in foetal-derived placental tissue from 37 of 70 (42%) pregnancies. These results show that congenital transmission is occurring in a high percentage of lambings including normal healthy lambings, at this farm, suggesting that this route of transmission from generation to generation may be much more significant than that reported previously. These results may have implications for sheep husbandry and future epidemiological studies of T. gondii.

Totipotency or multipotentiality of cultured cells: Applications and progress

The stable introduction of new genetic material into breeding programmes for farm animal species requires germ line modification. One route by which to achieve this is by the combination of embryo manipulation and molecular biological techniques. In the mouse, genetic manipulation of embryonic stem (ES) cells in culture followed by the production of chimeric animals by blastocyst injection has proved a powerful tool for germ line manipulation. In contrast, the absence of proven ES lines in farm animal species has restricted similar progress, the production of transgenic animals being limited to gene addition using the technique of pronuclear injection. An alternative and desirable route to germ line modification in farm animals is to produce offspring by nuclear transfer from a cell line which can be maintained in culture. In sheep this has now been achieved with the birth of live lambs from an embryo derived, epithelial like cell line. The combination of this technology with that developed in ES cells for genetic modification will herald a new era in the germ line modification of farm animal species.

Premature birth of live lambs induced by pulsatile infusion of ACTH

This study was designed to investigate the effects of pulsatile infusion of ACTH into ovine fetuses on the endocrine changes that precede parturition, the timing of birth and the subsequent survival of the lamb. Where appropriate, these parameters were compared with fetuses infused with pulses of saline and uninfused normal term fetuses. Ten fetuses received a 15-min infusion of synthetic ACTH(1-24) (79 ng/min) from day 125 (n = 9) or day 126 (n = 1) of gestation. Seven fetuses were born prematurely within 174 +/- 14 h (mean +/- S.E.M.) after the commencement of the infusion, i.e. at 132 +/- 0.6 days, whilst three died in utero at 130-131 days. When born all lambs could breath, walk and suckle. Of the seven premature lambs, four died 2-10 days after parturition but three survived for at least 12 months after birth. Fetuses infused with pulses of ACTH exhibited intermittent but very large increases in plasma ACTH values, with the first pulse, on day 1, increasing ACTH values from 5.1 +/- 1.1 to 140 +/- 31.3 pmol/l (P less than 0.001). At the next sampling time, ACTH values were not significantly different from preinfusion values. A similar plasma ACTH profile was observed on each subsequent day of ACTH treatment. In contrast, fetuses (n = 4) infused with pulses of saline between 125 and 131 days exhibited fetal plasma concentrations of ACTH which ranged between 2 and 12 pmol/l for the majority of the time.(ABSTRACT TRUNCATED AT 250 WORDS)