A genome linkage scan was carried out using a resource flock of 1029 sheep in six half-sib families. The families were offspring of sires derived by crossing divergent lines of sheep selected for response to challenge with the intestinal parasitic nematode Trichostrongylus colubriformis. All animals in the resource flock were phenotypically assessed for worm resistance soon after weaning using a vaccination/challenge regime. After correcting for fixed effects using a least squares linear model the faecal egg count data obtained following the first challenge and the faecal egg count data obtained after the second challenge were designated Trait 1 and Trait 2, respectively. A total of 472 lambs drawn from the phenotypic extremes of the Trait 2 faecal egg count distribution were genotyped with a panel of 133 microsatellite markers covering all 26 sheep autosomes. Detection of quantitative trait loci (QTL) for each of the faecal egg count traits was determined using interval analysis with the Animap program with recombination rates between markers derived from an existing marker map. No chromosomal regions attained genome-wide significance for QTL influencing either of the traits. However, one region attained chromosome-wide significance and five other regions attained point-wise significance for the presence of QTL affecting parasite resistance.

Two groups of three Merino wethers were infused intravenously with either 0.12 mg mouse epidermal growth factor (mEGF)/kg fleece-free body weight or 0.9% (w/v) NaCl over 24 h. Sheep treated with mEGF rejected food during treatment but feed intake was kept equal for both groups. Wool growth and plasma concentrations of mEGF were measured during the experiment. Pieces of skin taken from the wool-growing regions of the body were incubated with radioactive thymidine in order to measure its rate of incorporation into DNA. The skin was then divided at about the level of the sebaceous glands into sections that contained the upper dermis and epidermis (E sections) and those containing the generative wool-follicle bulbs (D sections). No mEGF was detected in the controls whereas mean levels of about 35 micrograms mEGF/1 plasma were detected during the last 4 h of infusion in the protein-treated group. After infusion, wool growth was reduced by about 20% of the mean pretreatment level in the controls and no shedding of wool fibre was evident. In the mEGF-treated sheep, on the other hand, wool growth was depressed by 75-95% of the mean pretreatment level and the fleeces were almost completely cast in all three of the animals, leaving them nude on the wool-growing regions of the body. Wool growth was restored to its pretreatment level in this group about 1 month after infusion. The D sections of skin contributed 50-60% of skin wet weight in controls throughout the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

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Aust. J. Bioi. Sci., 1978, 31, 373-83 The metabolism of [1,2(n)-3Hldexamethasone intravenously infused for periods of 4 and S days was examined in four Merino wethers.On average 85·6±2·8 (s.e.m.) % of the total dose was recovered, 56·2±5·1 and 29·4±3·3% being excreted in urine and faeces respectively. In total 12·4 % of the dose was associated with the unconjugated steroid fraction which represented 22% of the total urinary radioactivity.Thin layer chromatography of the urinary unconjugated fractlon revealed, apart from dexamethasone, five major and three minor radioactive components designated as I, III, IV, V, VIII and II, VII, IX respectively. Approximately 83 % of the radioactivity associated with the unconjugated fractions was found in constituents more polar than dexamethasone with the radioactivity mainly confined to the principal metabolite IV, Rc = 0·24 (dexamethasone, Rc = 0·45;'cbloroform: formarnide 50:1). The urinary constituent VI, Rc = 0·37, was detected only -during-the second half of the 8-day infusion with the peak of excretion on day 6.During the first 30 h of [3Hldexamethasone administration the plasma radioactivity reached the level which remained relatively constant throughout the infusions. The initial high level of radioactivity detected in the plasma unconjugated fraction as well as dexamethasone during the first 24 h infusion declined over the next 2 days; this was followed by a small increase during the final period of infusions.The radioactivity of the plasma unconjugated fraction was distributed, apart from dexamethasone, into six constituents (I, III, IV, V, VIII and IX) which when analysed by thin layer chromatography appeared to be qualitatively similar to those found in urine.These results led to the conclusion that one or more products of dexamethasone metabolism might be biologically active and thus potentially important in inhibiting wool fibre growth in sheep.