The effect of gastrointestinal parasitism on the metabolism of copper, cobalt and selenium in sheep and goats

Abstract

Three 18 month old sheep and three 12 month old goats with bile duct cannulae were housed indoors in metabolism crates under 24 hour lighting. The animals were fed low Cu diets (10.98 ppm DM) with the exception of one goat which was fed a high Cu diet (43 ppm DM). The initial part of the trial was to determine the effect of different feeding regimes on daily bile flow so that bile flow fluctuations could be minimised. The animals were then inoculated with abomasal and intestinal parasites to monitor the changes in plasma Cu and biliary Cu excretion as a result of parasitism. It was found that there were no changes in the pattern of bile flow when the animals were fed once a day, every four hours, or starved for 24 hours. It was also concluded that an eight hour sampling of bile flow can be used to estimate total daily bile flow and daily bile Cu excretion. Weekly eight hour samplings were used throughout the trial to determine plasma copper, bile flow rate and biliary Cu excretion. The animals were used as their own controls for a period of three weeks before parasite inoculation began. In the third week the animals were inoculated with Ostertagia circumcincta and Trichostrongylus colubriformis and this continued every second day until the animals were drenched eight weeks later. Plasma pepsinogen levels and faecal egg counts were used to monitor the parasite infection. In conclusion, there was found to be no effect of frequency of feeding on daily bile flow. There was a rapid decline in plasma Cu in association with the onset of infection. The fact that plasma Cu levels began to rise before anthelmintic treatment and the lack of independent controls made it difficult to judge its significance. There were no changes in biliary Cu excretion due to parasitism.