Nd Grace

Fertiliser contaminants in New Zealand grazed pasture with special reference to cadmium and fluorine: a review

Phosphorus (P) fertilisers are an essential input for the economic production of legume-based pastures in New Zealand (NZ) and Australia, but they often contain some unwanted elements that can contaminate the soil, thereby creating potential risks to the health of grazing animal, food quality, and soil quality. Fluorine (F) and cadmium (Cd) are considered to be the elements of most concern. Incidences of F toxicity (from direct ingestion of fertiliser), and accumulation of Cd in offal products above the maximum permissible concentration (MPC) set by the food authorities, have been reported in NZ. Similarly, Cd concentrations in some food grains may exceed the newly proposed MPCs by the Australian and New Zealand Food Authority. Cadmium and F continue to accumulate in the topsoils of NZ and Australian pastures as a result of P fertiliser use. The mobility of both these elements in soils is low and is similar to that of P. Risk of ground water contamination from F and Cd applied to most NZ pastures is low. The plant uptake of these elements, especially F, is also low in most pastoral soils. Cadmium accumulates mainly in liver and kidney of grazing animals mostly through herbage ingestion, whereas F accumulates mainly in the bones of these animals, mostly through soil ingestion. Soil ingestion is highest during the wetter winter months and at high stocking rates. Models have been developed to assess the impact of fertiliser use on the potential risks associated with F and Cd accumulation in soils. Measures to control F and Cd accumulation in soils, plants, and grazing animals are presented and future research needs are identified.

Pasture Soils Contaminated with Fertilizer-Derived Cadmium and Fluorine: Livestock Effects

Fertilizers are indispensable for ensuring sustainability of agricultural production, thereby achieving food and fiber security. Nitrogen, sulfur, and potassium fertilizers are relatively free of impurities, but phosphorus (P) fertilizers, the main fertilizer input for the economic production of legume-based pastures, contain several contaminants, of which F and Cd are considered to be of most concern because they have potentially harmful effects on soil quality, livestock health, and food safety. Incidences of fluorosis in grazing livestock, and accumulation of Cd in the edible offal products of livestock, above the maximum permissible concentration set by food authorities have been reported in many countries. The majority of Cd and F applied to pastures in many countries continues to accumulate in the biologically active topsoil due to strong adsorption to soil constituents. However, the rate of Cd accumulation in the last decade has slowed as a result of selective use of low-Cd fertilizers. Cd and F adsorption in soils increase with increased contents of iron and aluminium oxides, layer silicates and allophane in soils, and increased soil pH. Cadmium adsorption also increases with increased Mn oxides and organic matter in soil. However, some Cd will be released during decomposition of plant and animal remains and organic matter. In most pastoral soils the majority of Cd and F added in fertilizers remains in the topsoil and little moves below 20-30 cm, and therefore these are unlikely to contaminate groundwater. However, F may pose a risk to shallow groundwater in very acidic low-P-fixing soils, and Cd may pose a risk in very acidic soils containing low organic matter and clay contents, or in soils with high chloride concentrations. Research is required both to test whether groundwater beneath farms with long histories of P fertilizer use is contaminated by these elements and also to examine their mechanisms of movement. Cd intake by grazing livestock occurs mostly by ingestion of pasture, and therefore measures to decrease plant availability of Cd in soils (e.g., maintaining high organic matter, reducing soil acidity and salinity, alleviating zinc deficiency, reducing weed) can reduce Cd accumulation in livestock. F intake by grazing livestock is mostly by soil ingestion; therefore, reducing soil ingestion by maintaining good pasture cover especially during winter periods can reduce F accumulation in livestock. In grazing livestock, Cd accumulates in kidney and liver, whereas F accumulates mainly in bones. Very little research has been carried out to study the effects of sustained but low levels of Cd and F additions on soil microbial activity, especially on the economically important N-fixers in symbiosis with pasture legumes and mycorrhizae. This subject also needs to be researched. The impact of F accumulation in bones of animals as influenced by the alternative low and high soil F intake between seasons and the effect of increasing age of animals needs further study to more accurately determine the potential risk of fluorosis and elucidate potential solutions to minimize F accumulation in bones and teeth of aged breeding stock. Computer-based models are required to identify farming systems that present a high risk of Cd concentrations in edible offal exceeding the MPC and livestock at risk of chronic fluorosis. A decision support model of this kind may be useful in developing management strategies capable of reducing Cd and F accumulation in animals. Preliminary empirical models have been developed for Cd (Loganathan et al. 1999) and F (Bretherton et al. 2002) accumulation in sheep grazing New Zealand pastures. Further development of these models is required for their wider applicability.

A review of tissue reference values used to assess the trace element status of farmed red deer (Cervus elaphus)

Abstract AIMS: This paper reviews the principles for the establishment of biochemical reference criteria for assessing the trace element status of farmed livestock and summarises data for copper, selenium, vitamin B12 and iodine for farmed red deer. COPPER: Enzootic ataxia and osteochondrosis occur when liver copper concentrations are below 60 µmol/kg fresh tissue, and serum copper concentrations are below 3–4 µmol/l. Growth responses to copper supplementation have been equivocal when blood copper concentrations were 3–4 µmol/l, but were significant when mean blood copper concentrations were 0.9–4.0 µmol/l. No antler growth or bodyweight response to copper supplementation was observed when blood ferroxidase levels averaged 10–23 IU/l (equivalent to serum copper concentrations of 6–13 ώmol/l) and liver copper concentrations averaged 98 µmol/kg fresh tissue. These data suggest that ‘deficient’, ‘marginal’ and ‘adequate’ ranges for serum copper concentrations should be <5, 5–8, and >8 µmol/l, respectively, and those for liver copper concentrations should be <60, 60–100, and >100 µmol/kg, respectively. SELENIUM: White muscle disease has been reported in young deer with blood and liver selenium concentrations of 84–140 nmol/l and 240–500 nmol/kg fresh tissue, respectively. No growth-rate response to selenium supplementation occurred in rising 1-year-old deer when blood selenium concentrations were less than 130 nmol/l, the range in which a growth-rate response would be expected in sheep. VITAMIN B12: Vitamin B12 concentrations in deer are frequently below 185 pmol/l without clinical or subclinical effects. No growth response was observed in young deer with vitamin B12 concentrations as low as 75–83 pmol/l. A growth response to cobalt/vitamin B12 supplementation occurs in lambs with serum vitamin B12 concentrations <336 pmol/l. CONCLUSIONS: Data that can be used to establish reference ranges for assessing trace element status in deer are limited. More robust reference values for farmed red deer need to be established through further studies relating biochemical data to health and performance.

Trace element metabolism, dietary requirements, diagnosis and prevention of deficiencies in deer

Abstract The first deer farms were established in New Zealand about 30 years ago. Extensive studies on trace elements in sheep and cattle have resulted in clarification of the requirements of those species and the development of protocols to diagnose and prevent deficiencies. In contrast, there have been very few studies conducted with deer. This review summarises information available on trace element nutrition of deer and concludes that, in New Zealand, cobalt (Co), vitamin B12, selenium (Se) and iodine (I) deficiencies are of lesser importance than copper (Cu), which can have a significant impact on deer health and performance. However, on individual farms, Se and I deficiency may cause significant production losses if not managed appropriately. There are no reports of production limitations caused by Co deficiency. Copper deficiency manifests itself as clinical disease, namely enzootic ataxia and osteochondrosis. Growth responses to Cu supplementation have only been reported in 2/11 trials and were not predicted from low serum and/or liver Cu concentrations. On the basis of clinical signs of Cu deficiency, the proposed reference ranges used to predict Cu status from serum Cu concentrations (𝛍mol/l) are: <5, deficient; 5-8, marginal and; >8, adequate; and for liver Cu concentrations (𝛍mol/kg fresh tissue) are: <60, deficient; 60-100, marginal and; >100, adequate. Copper supplementation strategies based on Cu-EDTA injections, Cu-oxide needles or the application of Cu to pasture are effective at increasing Cu status for varying periods. More recent research suggests that alternative forage species that have a high Cu content (>10 mg/kg dry matter (DM), may play a role in the prevention of Cu deficiency.

Articular / epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: influences of growth of the foal and prenatal copper supplementation of the dam.

Abstract AIMS: To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dams age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. METHODS: Thirty-three Thoroughbred foals, born in two consecutive years, were weighed every 2 weeks from birth. The dams had been supplemented with parenteral Cu or saline during late gestation, and the supplementation regimens were different in each year. Foals had liver biopsies harvested at birth for determination of Cu concentration. Pasture samples were collected every 4–8 weeks for analysis of concentration of Cu and zinc (Zn). At 160 days of age, articular cartilage of long bones was examined. Gross lesions were counted and scored, then sawn and radiographed, and processed for histopathology. Lesions were given radiographic scores and histopathological scores. Maximum scores for each lesion were combined to give a total OC score for each joint and each foal. The fatness of 20 foals (10 each from Years 1 and 2) at 160 days of age was determined chemically. RESULTS: Supplementation of dams with Cu had no significant effect on the concentration of Cu in the liver of foals at birth, or on the frequency or severity of lesions in articular cartilage at 160 days of age. The Cu and Zn concentrations of pasture were similar in Years 1 and 2, and were lower than current recommendations. All foals in Year 2, and 9/10 foals in Year 1 had irregularities in cartilage that was confirmed histologically to be indicative of OC. The average number of lesions per foal was 4.7 (SD 1.1) and 5.7 (SD 1.1) in Years 1 and 2, respectively. However, the severity of the lesions was considered mild, and no foals showed any clinical evidence of OC while alive. The number of lesions in the tarsocrural (TC) joint and the TC OC score at 160 days were positively associated with average daily weight gain (ADG) in the previous 4 weeks (p=0.005 and p=0.001, respectively). There was no significant effect of sex, fatness, birth-weight, weight at 160 days of age, or year of birth of the foal on the frequency and severity of OC lesions. CONCLUSIONS: Many of the lesions classified as OC, using classification systems described by other authors, were likely to be normal variations of the process of endochondral ossification. Despite the high frequency of such lesions, they were considered to be of minor significance and none were clinically evident. The distribution of lesions was not typical, and most probably reflected the subtlety of the lesions. These results support the hypothesis that Cu is an over-emphasised factor in the aetiopathogenesis of OC. The relationship between subtle macroscopic lesions and lesions resulting in clinical signs of disease requires further investigation.

Relationship between blood selenium concentration or glutathione peroxidase activity, and milk selenium concentrations in New Zealand dairy cows

Abstract Aim: To determine the relationships between blood selenium (Se) concentrations or glutathione peroxidase activity (GSH-Px), and milk Se concentrations in dairy cows. Methods: Seventy-two Friesian dairy cows were either untreated or injected with 0.5, 1.0 or 2.0 mg Se/kg liveweight as barium selenate (BaSeO4) formulations, resulting in 6 groups of animals with mean blood Se concentrations that varied from 212 to 2272 nmol/l. Milk samples were collected on Days 104 and 188, and blood samples were collected prior to treatment and on Days 41, 76, 104, 188, 244, and 292 after Se injection. Results: Significant quadratic relationships between blood Se and milk Se concentrations, as well as blood GSH-Px activity and milk Se concentrations, were evident at Days 104 and 188. Using combined data, these were represented by the equations: milk Se = 27.3 + 0.073 blood Se -0.00001 (blood Se)2; R2=0.79, p<0.005, and; milk Se = 34.8 + 4.99 GSH-Px -0.068 (GSHPx)2; R2=0.79, p<0.005. Conclusions: The Se status of dairy cows can be assessed from milk Se concentrations. Clinical significance: Bulk-tank milk Se concentrations could be evaluated as a method to assess the Se status of dairy herds.

Influence of high zinc intakes, season, and staple site on the elemental composition of wool and fleece quality in grazing sheep

Abstract The effect of high zinc (Zn) intakes on calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), sulphur (S), and Zn content of wool was studied in Romney wethers given no ZnO, 12 g Znf) weekly, or 12 g ZnO fortnightly for 12-months. The wool was sampled as a 12-month fleece or monthly from the midside. Dosing with 12 g ZnO weekly caused an immediate increase in the plasma Zn concentration from 0.5 to 2.6 μg/mlfollowed by a slow decrease to about 0.75 μg/ml after 7 days. The untreated sheep plasma remained at about 0.6 μg/ml.The concentrations of other plasma elements measured were not influenced by Zn intake. The Zn treatment increased the Zn concentration in the liquid phase (30000 g supernatant) of the digessta particularly in the abomasum and small mtestine. Most of the Zn dose was associated with the solid phase (30000 g pellet). The high Zn intakes caused a small, but non-significant, increase m the Zn content of the 12-month fleece e...

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

Abstract AIM: To quantify the capacity of the liver to respond to a Cudeficient diet and various forms of Cu supplementation in dairy cows with high Cu status. METHODS: Sixty non-pregnant, non lactating mixed-age Freisian dairy cows were fed baled silage for 116 days, containing 5.8 mg Cu/kg dry matter (DM), that provided an inadequate Cu intake. They were either unsupplemented (Control); or treated thrice weekly orally with solutions containing the equivalent of 150 mg Cu/day as copper sulphate pentahydrate (CS), copper amino chelate (CAC), or copper glycinate (CG); 16 g Cu as Cu0 wire particles, administered in an intra-ruminal bolus on Day 0; or 100 mg Cu as calcium copper edetate, administered by S/C injection on Days 0 and 58. On Days -5, 14, 28, 58, 86 and 116, liver biopsies and blood samples were obtained for determination of Cu. RESULTS: Mean initial concentrations of Cu in liver for all groups was 827 (SE 42) µmol/kg fresh tissue. In control cows, this decreased to 552 µmol/kg on Day 116, and averaged 670 µmol/kg over the length of the trial. Oral forms of Cu supplementation increased overall mean concentrations in liver to 960 (SE 79), 1,050 (SE 81) and 1,100 (SE 84) µmol/kg for CS, CAC and CG, respectively, but there was no difference between form of supplement. Mean concentrations were significantly increased by bolus treatment, but not by injection. Concentrations of Cu in serum in all groups decreased from 12.1 (SE 0.3) to 10.4 (SE 0.6) µmol/L by Day 116, with no differences due to treatments. The initial concentration of Cu in liver significantly affected the rate of accumulation of Cu among cows supplemented orally. In cows with an initial concentration <1,100 µmol/kg, the average increase was 4.1 µmol/kg fresh tissue/day, whereas rates were variable, even negative, when initial concentrations were >1,100 µmol/kg. Release of Cu over 116 days in cows given the bolus was calculated to be equivalent to an oral intake of CS of 106 mg Cu/day. CONCLUSIONS: In dairy cows with a high Cu status fed a Cu-deficient diet, responses to supplementation with two chelated forms of Cu administrated orally were similar to those due to CS. Copper as CuO was about 77% as effective as oral supplementation with chemically similar inorganic Cu. Initial concentrations of Cu in liver influenced the rate of accumulation following oral supplementation. CLINICAL RELEVANCE: Changes in concentrations of Cu in liver were readily observed following oral supplementation over a wide range of initial concentrations, whereas these changes could not be detected in serum. The liver is thus a good index of the Cu status of dairy cows.

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

Abstract 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) µmol/kg fresh tissue in biopsies, and 520 (SD 235) to 2,610 (SD 945) µmol/kg in liver from cull cows. Mean concentrations of Cu in serum ranged from 7.9 to 13.4 µmol/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.

Influence of Se status on milk Se concentrations in dairy cows

Abstract Changes in blood and milk selenium (Se) concentrations were measured in dairy cattle grazing Se‐deficient pastures compared with animals grazing the same pasture but given either an intraruminal Se bolus or a barium selenate injection. The Se supplementation significantly increased and maintained the blood Se concentrations (e.g., 342 versus 1113 nmol/1) over 190–265 days during the lactation and also increased milk Se concentrations 2‐fold (e.g., 77.2 versus 132.3 nmol/1).