Semen from 13 bulls, eight with clinical bovine spongiform encephalopathy (BSE), was used to artificially inseminate (AI) 167 cows with clinical BSE, and their resultant embryos were collected non-surgically seven days after AI. The viable and non-viable embryos with intact zonae pellucidae were washed 10 times (as recommended by the International Embryo Transfer Society) then frozen. Later, 587 of the viable embryos were transferred singly into 347 recipient heifers imported from New Zealand, and 266 live offspring were born of which 54.1 per cent had a BSE-positive sire and a BSE-positive dam. The recipients were monitored for clinical signs of BSE for seven years after the transfer, and the offspring were monitored for seven years after birth. Twenty-seven of the recipients and 20 offspring died while being monitored but none showed signs of BSE. Their brains, and the brains of the recipients and offspring killed after seven years, were examined for BSE by histopathology, PrP immunohistochemistry, and by electron microscopy for scrapie-associated fibrils. They were all negative. In addition, 1020 non-viable embryos were sonicated and injected intracerebrally into susceptible mice (20 embryos per mouse) which were monitored for up to 700 days, after which their brains were examined for spongiform lesions. They were all negative. It is concluded that embryos are unlikely to carry BSE infectivity even if they have been collected at the end-stage of the disease, when the risk of maternal transmission is believed to be highest.
Restriction of feed during the winter store period is an important part of current beef systems to exploit compensatory growth from cheap grazed grass. Previous studies have demonstrated that the composition of finished carcasses can be altered by the type of diet fed during the winter feed restriction period (Baker et al, 1985). The aim of this study is to examine the effects of body composition at the end of the winter store period on the composition of gain during the subsequent grass feeding period
The ability to produce high quality beef carcasses cost-effectively in an 18-month finishing system is partly determined by the feeding regime during winter and the subsequent response to grass during the finishing period. Animals fed on grass silage throughout winter have been shown to develop fatter carcasses (Baker et al., 1985). The aim of this study was to investigate the effects of altered carcass composition at the end of a winter store period on composition at the end of a summer grazing period.
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