Accumulation and depletion of liver copper stores in dairy cows challenged with a Cu-deficient diet and oral and injectable forms of Cu supplementation

Transcriptomics and metabolomics analysis reveal the dietary copper deficiency and supplementation effects of liver gene expression and metabolite change in grazing sheep

BACKGROUND

The appropriate mineral nutrients are essential for sheep growth and reproduction. However, traditional grazing sheep often experience mineral nutrient deficiencies, especially copper (Cu), due to inadequate mineral nutrients from natural pastures.

RESULTS

The results indicated that dietary Cu deficiency and supplementation significantly reduced and elevated liver concentration of Cu, respectively (p < 0.05). FOXO3, PLIN1, ACTN2, and GHRHR were identified as critical genes using the weighted gene co-expression network analysis (WGCNA), quantitative real-time polymerase chain reaction (qRT-PCR), and receiver operating characteristic curve (ROC) validation as potential biomarkers for evaluating Cu status in grazing sheep. Combining these critical genes with gene functional enrichment analysis, it was observed that dietary Cu deficiency may impair liver regeneration and compromise ribosomal function. Conversely, dietary Cu supplementation may enhance ribosomal function, promote lipid accumulation, and stimulate growth and metabolism in grazing sheep. Metabolomics analysis indicated that dietary Cu deficiency significantly decreased the abundance of metabolites such as cholic acid (p < 0.05). On the other hand, dietary Cu supplementation significantly increased the abundance of metabolites such as palmitic acid (p < 0.05). Integrative analysis of the transcriptome and metabolome revealed that dietary Cu deficiency may reduce liver lipid metabolism while Cu supplementation may elevate it in grazing sheep.

CONCLUSIONS

The Cu content in diets may have an impact on hepatic lipid metabolism in grazing sheep. These findings provide new insights into the consequences of dietary Cu deficiency and supplementation on sheep liver and can provide valuable guidance for herders to rationalize the use of mineral supplements.

Selenium, copper and iron in veterinary medicine-From clinical implications to scientific models

Diseases related to copper, selenium or iron overload or deficiency are common and well-described in large animal veterinary medicine. Some of them certainly have the potential to serve as useful animal models for ongoing research in the field of trace elements. Obvious advantages of large animal models compared to laboratory animal models like rats and mice are the option of long-term, consecutive examinations of progressive deficient or toxic stages and the opportunity to collect various, high volume samples for repeated measurements. Nevertheless, close cooperation between scientific disciplines is necessary as scientists using high sophisticated analytical methods and equipment are not regularly in touch with scientists working with large animal diseases. This review will give an introduction into some typical animal diseases related to trace elements and will present approaches where the animal diseases were used already as a model for interdisciplinary research.

Effects of subcutaneously injected Ca Cu EDTA on concentrations of Cu in liver, milk production and reproductive performance in New Zealand dairy cows

AIMS

To determine the effect of dose and frequency of injection of Cu as Ca Cu EDTA on concentrations of Cu in liver, and the effect of a single 200 mg treatment on milk production and reproductive performance in New Zealand dairy cows.

METHODS

Four groups of dairy cows (n=18 per group) on three farms were injected with 100 or 200 mg Cu S/C once, or three times at 6-weekly intervals, commencing 6-8 weeks into lactation. Concentrations of Cu in liver were determined to 119 days after treatment. Cows at peak lactation on one farm were treated with 200 mg of Cu S/C, or received no treatment (n=92 per group). Milk production was determined 11 days before and 24 hours following treatment. In seven dairy herds from throughout New Zealand cows were injected S/C with 200 mg Cu 10 days prior to mating start date (MSD) or received no treatment. Oestrus detection and artificial inseminations were carried out for ≥ 2 - 4 days from MSD. Pregnancy diagnosis was performed at 12 weeks following MSD. The percentage of cows inseminated in the 21 days after MSD (21-day submission rate; n=2,022) and cows pregnant after 21 or 28 days (21- and 28-day pregnancy rates; n=2520) was determined.

RESULTS

Injecting with 200 mg Cu once or 6-weekly increased concentrations of Cu in liver compared with 100 mg (p<0.05). Injection of 200 mg Cu decreased total milk yield (p=0.006) and protein production (p<0.001) in the 24-36 hours after treatment. Compared with Control cows, 200 mg Cu 10 days before MSD reduced 21-day submission (78 vs. 75%; p=0.04) and 21-day pregnancy rates (47 vs. 43%; p=0.03). For 28-day pregnancy rates there was a farm by treatment interaction (p=0.02), with a negative effect observed on some, but not other, farms.

CONCLUSIONS

Injection of 200 mg Cu raised concentrations of Cu in liver for >42 days. A negative impact on milk yield and composition occurred immediately following injection. Injection 10 days prior to mating had a negative effect on submission and pregnancy rates. Further study is required to determine a safe treatment to mating interval and the mechanism by which adverse impacts occur.

CLINICAL REVELENCE

Although 200 mg of Cu as Ca Cu EDTA is an effective supplement and generally well tolerated, determining the necessity for, and giving specific thought to the timing of, parenteral Cu supplementation is imperative to avoid negative impacts on herd production and reproductive performance.

A recent assessment of the elemental composition of New Zealand pastures in relation to meeting the dietary requirements of grazing livestock

An understanding of the benefits and limitations of pasture feeding underpins sustainable grazing systems that produce milk and meat from ruminant livestock. We evaluated the mineral composition of 1,106 pasture samples collected independently from locations across New Zealand from 2001 to 2006. About half were submitted during 2002 and 2003, and 87% came from the North Island. Most herbage was from ryegrass and clover-dominated swards. The concentrations of Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, S, Se, or Zn were measured by nitric acid digestion followed by inductively coupled plasma optical emission spectroscopy or atomic absorption spectroscopy. Median concentrations for the macro elements were Ca 5.5, K 33, Mg 2.2, Na 2.0, P 4.0, and S 3.6 g/kg DM and for the trace elements were Co 0.10, Cu 8.4, Fe 131, Mn 74, Mo 0.66, Se 0.050, and Zn 43 mg/kg DM. Frequency histograms of concentrations revealed distributions ranging from near-normal to bottom-heavy skew with a long tail of high values. The minerals required for good plant growth were found at adequate concentrations in the majority of pastures. The exception was P; only 74% of pastures contained the recommended 3.5 mg P/kg DM. Results of the pasture survey were compared to the dietary intake requirements of cattle and sheep. For 7 elements, >95% of the pastures contained sufficiently high concentrations to meet the needs of unsupplemented animals. Exceptions were the Se dietary requirement, which was met by only 76% of pastures, the Co requirement of sheep met by only 54% of pastures, and the Cu, Na, and P requirements of cattle met by 25, 78, and 87% of pastures, respectively. Pasture analysis is an essential tool for identifying dietary insufficiency as well as unfavorable mineral balances where interactions could induce a deficiency, such as Cu × Mo and Mg × K. Monitoring of animals' nutritional status is also required to manage complex metabolic disorders related to peripartum flux of Ca and Mg. This study is the only large scale assessment of the mineral composition of New Zealand pastures to be published in 30 yr and the first to include a full range of trace elements. Knowing the proportion of pastures that are unlikely to meet nutritional requirements for some elements helps to define the risk areas for grazing livestock systems and provides an estimate of how prevalent mineral deficiencies might be if current practices of supplementation were not in place.

Rates of change in liver copper concentration in cattle given a copper-deficient diet, with or without pre-treatment with tetrathiomolybdate, for evaluation of two parenteral copper supplements

AIM

To minimise the impact of initial variation in liver copper (Cu) on assessments of Cu supplements for cattle in depletion/repletion experiments.

METHODS

Efficacy of two Cu injections was assessed with 18 calves, weighing 200-250 kg, given a Cu-deficient barley diet, containing 4.1 mg Cu/kg dry matter (DM) and added molybdenum (3 mg/kg) and sulphur (3 g/kg). Initial liver biopsy Cu ranged from 3.15-14.17 mmol/kg DM and nine calves with the highest values were given three subcutaneous injections of 235 mg tetrathiomolybdate (TTM) after 42-46 days depletion to lower liver Cu. Untreated (L) and TTM-treated (H) calves were ranked separately for liver Cu after 50 days depletion and allocated to one of three treatments: 100 mg Cu given subcutaneously as CuCaEDTA in either a paraffin (CuP) or aqueous base (CuA) after 56 days depletion (Day 0) or no injection (O). Thereafter, plasma and liver biopsy Cu were measured every 2-4 weeks for 16 weeks. Responses in liver Cu to Cu injections were compared with and without loge transformation and by linear regression.

RESULTS

Prior to Cu injection, the fractional decline in liver Cu concentration (FDLCu) after 50 days depletion was 0.64 (SE 0.066) and 0.80 (SE 0.090) in H and L calves, respectively (p=0.09) and mean liver Cu did not differ on Day -6 (6.65 (SE 0.516) and 4.91 (SE 0.681) mmol/kg DM, respectively). Mean plasma Cu was higher in H than L calves on Day 0 (16.6 (SE 0.52) and 13.3 (SE 0.49) μmol/L, respectively (p<0.001)). Rates of decline in loge liver Cu between Days 0-84 in treatments L and H were: 0.0138 and 0.0071 for Groups O; 0.0033 and 0.0016 for Groups CuP; 0.0073 and 0.0049 for Groups CuA (pooled SE 0.0014) mmol/kg DM/day, respectively. Between Days 84-114, FDLCu was uniformly high across experiments and groups (0.59 (SE 0.042)). Cu injections did not affect plasma Cu, which remained 3.1 (SE 0.41) umol/L higher in Experiment H than in L (p=0.017).

CONCLUSIONS

The use of rates of change in liver copper concentrations improved the assessment of efficacy for two parental copper supplements and that of pre-treatment with tetrathiomolybdate, which, contrary to expectation, slowed Cu turnover by mechanisms that remain unclear.

The impact of highly concentrated Mo and Cu dietary supplements, fed as a bolus, on the efficacy of chelated versus inorganic Cu in cattle on a low-Cu diet

AIM

To compare the efficacy of chelated versus inorganic forms of dietary Cu supplements, fed as a bolus, when challenged by a daily bolus of dietary Mo in cattle on a low-Cu diet.

METHODS

Forty non-lactating, Friesian dairy cows of adequate Cu status were assigned to four groups and fed a basal diet of baled silage containing 5.3 mg Cu and 0.4 mg Mo/kg DM. The experimental design was a factorial of two chemical forms of supplemental Cu and two levels of Mo intake, provided as pelleted grain supplements made from crushed barley/molasses plus Cu and Mo. The supplements contained 140 mg Cu/kg as Cu sulphate pentahydrate (CS), 140 mg Cu/kg as Cu glycinate (CG), CS plus 38 mg Mo/kg as sodium molybdate (CS+Mo), or CG plus 38 mg Mo/kg (CG+Mo). Commencing on Day 0, supplements were fed once daily (offered 1-1.2 kg/cow) and were completely consumed within 5-10 minutes, which constitutes a bolus type of administration. Liver samples were collected by biopsy at Days -24, 13, 41 or 47, and 69 for Cu determinations.

RESULTS

The diets fed to the Cu+Mo groups were roughly equivalent to 25 mg Cu and 5.7 mg Mo/kg DM. Mean initial concentration of Cu in liver for all groups was 516 (SE 54) μmol Cu/kg fresh tissue. In cows supplemented with CS and CG, the final (Day 69) concentrations increased (p<0.01) to 939 (SE 166) and 853 (SE 163) μmol Cu/kg, respectively. These values were not different (p=0.72). For groups CS+Mo and CG+Mo, the final concentrations of 535 (SE 122) and 453 (SE 102) μmol Cu/kg were not different from initial values or from each other (p>0.25). The rate of accumulation of Cu in liver following bolus Cu and Mo intake was highly variable but was not affected by initial concentration of Cu in liver (p>0.9) or by the form of Cu (p>0.6). Mean rates of accumulation of Cu in liver were 4.0 (SD 3.8) and 0.65 (SD 2.0) μmol Cu/kg fresh tissue/day for the Cu-only treatments and the Cu+Mo treatments, respectively.

CONCLUSIONS

When fed together as a bolus, high Mo intake negated the effect of supplemental Cu but it did not reduce liver Cu stores. There was no difference in the reaction of dietary Mo with chelated Cu (as glycinate) versus inorganic Cu (as sulphate) dietary supplements.

Trace element supplementation of livestock in new zealand: meeting the challenges of free-range grazing systems

Managing the mineral nutrition of free-range grazing livestock can be challenging. On farms where grazing animals are infrequently yarded, there are limited opportunities to administer trace element supplements via feeds and concentrates. In New Zealand, where the majority of sheep, cattle, and deer graze pasture year round, inadequate intake of cobalt, copper, iodine and selenium is prevalent. Scientists and farmers have developed efficient strategies to monitor and treat these dietary deficiencies. Supplementation methods suited to grazing livestock include long-acting injections, slow-release intraruminal boluses, trace element-amended fertilisers, and reticulated water supplies on dairy farms.

The role of liver Cu kinetics in the depletion of reserves of Cu in dairy cows fed a Cu-deficient diet

AIM

To determine how the concentration of Cu in liver affects the rate of depletion of that Cu when cows are fed a Cu-deficient diet under experimental conditions, and to mathematically model the rate of depletion of Cu over time.

METHODS

In June 2010, 25 non-lactating Friesian cows were assigned to three groups such that initial mean concentrations of Cu in liver were 265, 534 and 1,486 μmol Cu/kg fresh tissue (Day 0). All cows were managed as a single group and fed a Cu-deficient diet of primarily baled silage. No mineral Cu supplements were given. Liver biopsies were collected from cows on Days 0, 53, 98 and 161 to determine concentrations of Cu. At about the same time, samples of silage and pasture herbage were collected to determine Cu, Mo and S concentrations.

RESULTS

Median concentration of Cu in silage was 6.5 (min 6, max 9) mg/kg DM. Concentration of Cu in liver decreased in all groups (p<0.001), over the duration of the study. The amount of Cu depleted from liver was greater in groups that started the study with higher initial concentrations of Cu in liver. The rate of decline followed exponential first-order kinetics with an elimination rate constant k of 0.0057 (CI 95%=0.0039-0.0074), meaning that about 0.57% of liver Cu reserves were depleted each day. For individual cows this loss amounted to 0.1-14 μmol Cu/kg liver/day.

CONCLUSIONS AND CLINICAL RELEVANCE

Depletion of Cu from liver was dependent on initial concentration of Cu. These results can be used to predict how long an unsupplemented herd will remain in adequate Cu status, which adds confidence to decisions about when Cu supplementation should be withdrawn or reinstated. Cows with high concentrations of Cu in liver can maintain adequate Cu status for months without supplements. Intake of less Cu and more Mo would increase the rate of depletion, and seasonal factors would also have some influence.

High and variable copper status identified among dairy herds in the Waikato region by concentrations of Cu in liver sourced from biopsies and cull cows

AIMS

To document the Cu supplementation practices on dairy farms in the Waikato region, determine the Cu status of those herds, and compare the suitability of liver samples sourced from biopsies and cull cows for assessing Cu status.

METHODS

During spring 2008, concentrations of Cu, Mo and S were determined from pasture samples from 24 dairy farms. Feeding regimens, herd size, milksolids production, soil type, fertiliser policy and Cu supplementation practices were recorded for each property. Based on these data, 10 monitor farms were selected to represent a range of Cu intakes for herds, from 5 to 12 mg Cu/kg dry matter (DM). On each monitor farm 12 healthy lactating cows were selected for liver biopsy and collection of blood samples during the following autumn. Around the same time, livers were collected from 12 cull cows per farm when they were slaughtered, and samples of pasture were again collected from each farm. Concentrations of Cu were measured in all tissue samples.

RESULTS

Concentrations of Cu in pasture tended to be higher (mean 10.4 vs 8.2 mg/kg DM) in the autumn than spring, while concentrations of Mo were lower in the autumn (mean 0.35 vs 1.07 mg/kg DM). Most of the 24 farms used Cu supplementation in some form. Mean concentrations of Cu in liver for herds ranged from 640 (SD 544) to 2,560 (SD 474) micromol/kg fresh tissue in biopsies, and 520 (SD 235) to 2,610 (SD 945) micromol/kg in liver from cull cows. Mean concentrations of Cu in serum ranged from 7.9 to 13.4 micromol/L. The variability in concentrations of Cu for each farm was greater for liver (CV 50%) than serum (CV 21%). For individual cows, concentrations of Cu in liver, obtained by biopsy, and serum were not correlated.

CONCLUSIONS

The concentration of Cu in liver of dairy cows reflected widely differing dietary intakes of Cu between herds, although levels indicated an adequate Cu status on all farms in this study. Use of either biopsy samples or livers from cull cows were indicative of the Cu status of the herd. Wide variation in observed concentrations of Cu in liver indicated that at least 12 cows per herd should be sampled. On farms with intensive, long-term Cu supplementation programmes there is a risk of chronic Cu toxicity in some animals. Thus, the Cu status of dairy herds should be determined, and monitored, before making any recommendations regarding supplementation.