Biomedical subjects
Publications and source records attributed to H Hoogenkamp.
Low temperature preservation of bovine embryos is briefly reviewed. The following subjects are discussed: the desired developmental stage of the embryo, the packaging system during freezing, the cryoprotective agents, the freezing and thawing methods and the results made possible by freezing bovine embryos.
In the first part of the present review paper, not only the current procedures making possible artificial reproduction in cattle are stated, but also the limitations of the methods available for superovulation and sexing, low-temperature preservation and transfer of embryos. In the second part, alternative procedures are reviewed, which may be used to increase the number of embryos per dam to a further extent by methods other than superovulation. Finally, the practical use of these recently acquired methods in breeding and animal products is described.
Superovulation was induced in 129 lactating donor cows for embryo transfer under field conditions. Twenty-nine animals (22.5 per cent) responded with fewer than three corpora lutea. The number of animals flushed was ninety-nine, averaging 8.2 corpora lutea per donor cow. The average proportion of recoveries was 56.4 per cent. The quality of the embryos was satisfactory in 64 per cent of the cases. The average number of embryos and egg cells per donor was 4.6, which resulted in 2.9 good quality embryos per donor. The percentage of pregnant recipients was 56 in good quality embryos and 9 for fair quality embryos.
A good survival rate in culturing mouse blastocysts can be obtained in Ovum Culture Medium, enriched with 20 per cent inactivated Foetal Bovine Serum or Sheep Serum under air. The transfer of fresh blastocysts gives the best results if the recipients are on day 3 of the pseudo-pregnancy, but with 20 hours' cultured blastocysts it is better to use recipients on day 4. Exposure to 1.5 M DMSO has no harmful effect, provided that the DMSO is added at 5 degrees C in 6 steps and is removed, again in 6 steps, at 35 degrees C. The crystallization of the medium containing the embryos at -5 degrees C to -6 degrees C doet not appear te have a harmful influence on culture results of the blastocysts.
Superovulation in mice is most likely to be successful if they are treated at the age of 20-32 days. Both the number of ovulations and the quality of the embryos are significantly better in comparison with superovulated older mice (32-60 days). In this investigation the production of normally developed embryos in young mice of 20-32 days old was 28.7 per superovulated animal and 11.3 or 14.0 in the groups of older mice respectively (32-46 days and 46-60 days).
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A brief introduction is followed by a description of artificial insemination in sheep, based on a review of the literature. A number of experiments are then discussed, which were mainly concerned with the possibilities arising when artificial insemination and synchronisation of oestrus are combined. It is concluded that satisfactory results (70-80 per cent pregnant) may be obtained, provided a large number of live spermatozoa (500 x 10(6)) are inseminated at the right time.