Publications by authors named "H Knijn"

Background: Since the identity of the embryo is of outmost importance during commercial in vitro embryo production, bovine oocytes and embryos have to be cultured strictly per donor. Due to the rather low yield of oocytes collected after ovum pick-up (OPU) per individual cow, oocyte maturation and embryo culture take place in small groups, which is often associated with inferior embryo development. The objective of this study was to improve embryonic development in small donor groups by using the Corral dish.

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Genomic tools are now available for most livestock species and are used routinely for genomic selection (GS) in cattle. One of the most important developments resulting from the introduction of genomic testing for dairy cattle is the application of reasonably priced low-density single nucleotide polymorphism technology in the selection of females. In this context, combining genome testing and reproductive biotechnologies in young heifers enables new strategies to generate replacement and elite females in a given period of time.

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Optimization of ovum pick up (OPU) followed by in vitro embryo production (IVP) is strongly driven by the needs of both beef and dairy cattle breeders to enhance genetic improvement. The rapidly growing use of genomic selection in cattle has increased the interest in using OPU-IVP technology to increase the number of embryos and offspring per donor, thus allowing enhanced selection intensity for the next generation. The aim of this study was to optimize embryo production through supplementation of cysteamine during in vitro maturation (IVM) and in vitro culture (IVC) of both slaughterhouse- and OPU-derived oocytes.

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The objective of this study was to assess the quality of a diagnostic model for the detection of hyperketonemia in early lactation dairy cows at test days. This diagnostic model comprised acetone and β-hydroxybutyrate (BHBA) concentrations in milk, as determined by Fourier transform infrared (FTIR) spectroscopy, in addition to other available test-day information. Plasma BHBA concentration was determined at a regular test day in 1,678 cows between 5 and 60 d in milk, originating from 118 randomly selected farms in the Netherlands.

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The aim of this study was to determine the optimal maturation culture period of ovum pick up (OPU)-derived cumulus oocytes complexes (COCs) in relation to their developmental capacity. Embryo production, embryo cryotolerance, post-transfer embryonic survival and calf characteristics such as gestation length, birthweight and sex ratio were investigated. This retrospective study covers the analyses of ovum pick up -in vitro production and calving results from a commercial programme that took place between March 1994 and September 2004.

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