Linking live animals and products: traceability.

It is rarely possible to successfully contain an outbreak of an infectious animal disease, or to respond effectively to a chemical residue incident, without the use of a system for identifying and tracking animals. The linking of animals at the time they are slaughtered--through the use of identification devices or marks and accompanying movement documentation--with the meat produced from their carcasses, adds further value from the perspective of consumer safety. Over the past decade, animal identification technology has become more sophisticated and affordable. The development of the Internet and mobile communication tools, complemented bythe expanded capacity of computers and associated data management applications, has added a new dimension to the ability of Competent Authorities and industry to track animals and the food they produce for disease control, food safety and commercial purposes.

Effects of the sheep-chewing louse (Damalinia ovis) on the epidermis of the Australian merino.

Frozen longitudinal skin sections taken from the dorsal thoraco-lumbar region of adult Merino sheep that were infested with the sheep-chewing louse were examined by light microscopy. The epidermis of infested sheep exhibited acanthosis due to hyperplasia of the stratum spinosum, and orthokeratosis. The thickness of the uncornified epidermis, the stratum corneum, and the sudanophilic region were significantly greater (P less than 0.005) than equivalent regions in louse-free Merinos and the results suggest that a positive correlation exists between the thickness of each region and the level of louse infestation. The results indicate that the variance in region thickness was greater in lousy than in louse-free sheep (P less than 0.005).

Structure of the epidermis of Australian Merino sheep over a 12-month period.

Light-microscopic examination of frozen sections of skin taken from the dorsal thoraco-lumbar region of Australian Merino sheep in winter revealed that the thickness of the epidermis plus a sudanophilic layer was 24.9 micron in the interfollicular region. The uncornified epidermis (10.9 micron) was separated from the sudanophilic layer (14.0 micron) by a thin stratum corneum. It was concluded that the bulk of the sudanophilic layer was emulsified sebum in which was embedded a disorganized collection of desquamated cornified cells. Although large variances were observed in the thickness of the uncornified epidermis and of the sudanophilic layers between sheep and both within the between blocks of tissue obtained from individual sheep, there were no strong seasonal effects on either epidermal structure or layer thickness over a 12-month period. These results suggest that the Australian Merino differs from Finnish Landrace X Dorset Horn ewes, which are reported to possess, at least in winter, a thicker uncornified epidermis and a thicker stratum corneum that could be divided into two zones and was uniformly permeated by lipid.