Copper deficiency in ruminants; recent developments

The aetiology of copper deficiency in grazing ruminants has been clarified by a number of recent discoveries: the low availability of copper in lush grazed pasture compared with conserved forage; the inhibitory effects on absorption of small increases in herbage molybdenum and sulphur and the antagonism from iron ingested in soil; and the wide genetic variation in copper absorption between different breeds of sheep. The economic importance of copper deficiency has been emphasised by the discovery of unsuspected causes of loss: increased susceptibility to infection and growth retardation in lambs and infertility in cattle. The diagnosis of functional copper deficiency has been improved by the addition of erythrocyte superoxide dismutase to the assays of copper status.     

Responsiveness of prehaemolytic copper poisoning in sheep from a specific pathogen-free environment to a relatively high dose of tetrathiomolybdate

Efficacy of ammonium tetrathiomolybdate (3.4 mg/kg LW, TTM(3.4)) was monitored in nine, specific pathogen-free sheep with mild-to-severe, prehaemolytic copper poisoning (pre-HCP). Five sheep were given three subcutaneous injections over seven days and four began a shorter, five-day course four days later. Plasma bile acid (BA) and glutamate dehydrogenase (GDH) had fallen significantly after six days but BA briefly rose again between days 10 to 18. Aspartate aminotransferase (AST), δ-glutamyl transferase (GGT) were later to decline but presented little evidence of hepatotoxicity by day 45. Erythrocyte superoxide dismutase (ESOD) was rapidly inhibited, activities falling by 65 per cent within three days and taking 25 days to recover. Trichloroacetic (TCA)-insoluble copper increased by 6 to 8 μmol/l after three days but had largely disappeared by day 18. Six lambs had become hypercupraemic by day 18 due to a rise in TCA-soluble Cu. ESOD activity fell again by 188±29.5 U/gHb between days 25 and 45 but had largely recovered by day 62. TTM(3.4) gave better control of hepatotoxicity than TTM(1.7) had done in more severely affects cohorts but at the expense of greater inhibition of ESOD. Treatment of pre-HCuP should rely more on reducing copper absorption until more is known of the side effects of TTM on cuproenzymes.     

Total gas pressure and oxygen and nitrogen saturation in warmwater ponds aerated with airlift pumps

Gas bubble disease and improper inflation of swim bladders in larval striped bass Morone saxatilis have been recently related in laboratory studies to very low levels of gas supersaturation. In other species, kills resulting from gas supersaturation have been reported in natural waters as large as Galveston Bay. We monitored warmwater ponds during spring to determine the extent of naturally occurring gas supersaturation and compared these levels with levels of gas saturation in ponds equipped with airlift pumps. Total gas pressure averaged 110% in the morning at the surface of non-aerated ponds and in the afternoon in ponds with airlift pumps. At other times of the day total gas pressure averaged 106–107% at the surface and bottom, morning and afternoon, in both aerated and non-aerated ponds. No evidence of gas bubble disease was found in 15-day-old striped bass fry cultured for 42 days in either aerated or non-aerated ponds.     

The Pink Eye Syndrome Does Not Impair Tuber Fresh Cut Wound-Related Responses

The potato tuber pink eye (PE) syndrome is a costly physiological disorder that results in corruption of the native periderm, susceptibility to infection, water vapor loss and associated shrinkage, roughened and cracked tuber surfaces, and various related blemishes and defects. PE results in aberrant internal suberin deposition without overt induction by a wound, yet little is known of the effect of PE on wound healing. Herein, we determined the effect of the PE syndrome on basic wound-healing processes: reduction of water vapor loss, suberization and induction of the wound-related hormones abscisic acid (ABA) and jasmonic acid (JA). There was no significant difference in reduction of water vapor loss, rate of accumulation of suberin biopolymers or induction of ABA and JA biosynthesis during wound healing in PE vs. control tubers. These results are important because they indicate that the PE syndrome does not induce a systemic effect that adversely impacts these crucial wound-related processes throughout the tuber, including those areas of the tuber that have no detectable PE symptoms.     

Auxin-induced sprout growth inhibition: Role of endogenous ethylene

The role of endogenous ethylene in auxin-mediated tuber sprout growth inhibition was determined in potato (Solanum tuberosum L. cv. Russet Burbank) minitubers. Treatment of tubers with biologically active auxins resulted in a transient, dose-dependent increase in ethylene production and inhibition of sprout growth. Biologically inactive auxin analogs elicited neither response. Continuous exposure to > 0.001 μL L^-1 exogenous ethylene inhibited sprout growth in a dose-dependent manner with complete inhibition occurring at ethylene concentrations ≥1 μL L^-1. In further studies with the active auxin α-naphthalene acetic acid (NAA), the role of ethylene in auxin-induced sprout growth inhibition was determined using ethylene biosynthesis and action inhibitors. The ethylene biosynthesis inhibitor aminoethoxyvinylglycine reduced NAA-induced ethylene biosynthesis by over 80% but had no effect on sprout growth inhibition. The non-competitive ethylene action inhibitor silver thiosulfate had no effect on NAA-induced sprout growth inhibition. Similarly, both the competitive ethylene action inhibitor 2,5-norbornadiene and the irreversible action inhibitor 1-methylcyclopropene were ineffective in reducing NAA-mediated sprout growth inhibition. Collectively, these results do not support the proposal that, in the case of potato tuber sprouts, auxininduced growth inhibition is mediated by endogenous ethylene action.     

Use of erythrocyte copper:zinc superoxide dismutase activity and hair or fleece copper concentrations in the diagnosis of hypocuprosis in ruminants

Changes in the activity of superoxide dismutase, a copper-containing enzyme in erythrocytes (ESOD), and changes in copper in hair or fleece were compared with the changes in plasma copper during copper depletion and repletion in steers, lambs and ewes. During depletion the decline in ESOD began later than the decline in plasma copper: the lag varied from 0 to 80 days in individual steers and it was least evident when young rapidly growing lambs were subjected to severe depletion. ESOD activity eventually declined at only one-third to one-seventh of the rate shown by plasma copper, the difference being particularly marked in severely depleted lambs. Repletion of ESOD began after repletion in plasma copper and continued more slowly particularly in growing animals. Hair and fleece copper also responded relatively slowly to depletion and repletion. Low values of ESOD and hair or fleece copper may have diagnostic significance, indicating a more prolonged or intense deficiency of copper and a higher probability of clinical and production responses to copper therapy than low plasma or liver copper values.