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Experimental infections of lambs with Fasciola hepatica are described. The growth rate of the parasite, time of entry to the bile ducts, and time of patency are recorded and a preferential migration of the parasite in the liver parenchyma noted. The gross and histological lesions produced in the liver from 1 to 40 weeks after infection are described and compared with previous observations in cattle.The parenchymal migration of the parasite is shown to consist of two phases, a free migrating phase up to the 6th week, and a localized phase after the 6th week prior to entry into the bile ducts. Hepatic cell regeneration is observed and hepatic fibrosis is minimal. The localized phase of migration is associated with a unique peripheral palisade of giant cells in the fluke tracts and with the formation of pseudofollicular aggregation of lymphocytes. The presence of flukes in the bile ducts produces fibrosis of the duct walls. The walls, however, remain pliable and expanded to accommodate the parasites and calcification was never observed.

No abstract

There has been an active interest in the toxicology of copper since the middle of the 19th century and a review by Davenport (1953) covers the early work on the hazard to man and animals of both the acute and chronic forms. Review material specific to chronic copper poisoning in farm livestock has also been published by Broughton & Hardy (1934), Eden (1940), Todd (1962) and Bull (1964).The first description of true chronic copper poisoning in farm animals would seem to be that of Mallory (1925) who produced the condition experimentally in sheep. Beijers (1932) described similar symptoms in sheep grazing orchards which had been sprayed with a copper fungicide, and 2 years later Broughton & Hardy (1934) published their detailed experimental investigations showing the dangers of excessive copper intakes to sheep. The similarity between the symptoms described in these reports and those of ‘yellows’ or ‘toxaemic jaundice’ in Australia was recognized (Bull, 1964) and the experiments of Albiston, Bull, Dick & Keast (1940) confirmed that this naturally-occurring condition was of similar origin. The importance of chronic copper poisoning as a nutritional hazard was, therefore, fully established.

S U M M A R YIn an experiment, carried out over 3 years, two groups of dairy cows offered ad libitum access to grass silage received 8 kg/day concentrate differing only in phosphorus content (low P concentrate: 4 0 -4-5 g/kg dry matter (D.M.); high P concentrate: 60-6-5 g/kg D.M.) during the winter feeding period of approximately 6 months. During the summer period all animals were grazed together on perennial ryegrass pastures. There were no consistent significant effects of P content on any of the variables measured. The mean calving indices were 371 (S.E. = 3-71, n = 122) and 379 (S.E. = 4-28, n = 95) days and overall conception rates were 0-70 and 0-68 for the low and high P treatments, respectively. Mean plasma P concentrations during the winter period were significantly reduced (P < 001 or greater) in years 2 and 3 of the study on the low P treatment. In 1 year milk yield was significantly higher (P < 001) on the low P treatment although the fat content was significantly reduced (P < 005) but these effects were not recorded in the other 2 years. e s t ' m a t e s f°r sheep were reduced from 43-5 mg (ARC, 1965) to 140 mg P/kg live weight (LW) per The Technical Review of the nutrient requirements of day. The estimates for cattle were reduced from farm livestock by the Agricultural Research Council between 12 and 28 mg to 12 mg P/kg LW per day. (1965), contained estimates of the requirements of More recent information (Braithwaite, 1984) sugvarious classes of livestock for essential minerals.