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The in vitro affinity and adsorption capacity of a humic acid, oxihumate, for aflatoxin B1 (AFB1) was evaluated, utilizing Langmuir and Freundlich adsorption isotherms. Oxihumate showed a high in vitro affinity for AFB1. The Freundlich isotherm fitted the data better than the Langmuir isotherm, and binding capacities of 10.3, 7.4, and 11.9 mg of AFB1/g of oxihumate at pH 3, 5, and 7, respectively, were calculated. The in vivo efficacy of oxihumate as an aflatoxin binder in male broiler chickens exposed to aflatoxin-contaminated feed from 7 to 42 d of age was also assessed. The efficacy of oxihumate was compared with a commercially available product with a brewers dried yeast (BDY) and brewers fermentation solubles as main active ingredients. A total of 420 birds were assigned to 28 pens, with 15 birds per pen. The following treatments were applied: 1) 0 mg of AFB1 + 0 additives, 2) 1 mg of AFB1/kg of feed + 0 additives, 3) 1 mg of AFB1/kg of feed + 3.5 g of oxihumate/kg of feed, 4) 1 mg of AFB1/kg of feed + 3.5 g of BDY/kg of feed, 5) 2 mg of AFB1/kg of feed + 0 additives, 6) 2 mg of AFB1/kg of feed + 3.5 g of oxihumate/kg of feed, and 7) 2 mg of AFB1/kg of feed + 3.5 g of BDY/kg of feed. Each treatment consisted of 4 replicates. Oxihumate was effective in diminishing the adverse effects caused by aflatoxin on BW of broilers (P < 0.05). Oxihumate also showed protective effects against liver damage, stomach and heart enlargement, as well as some of the hematological and serum biochemical changes associated with aflatoxin toxicity (P < 0.05). Results indicated that oxihumate, but not BDY, could alleviate some of the toxic effects of aflatoxin in growing broilers. Oxihumate might, therefore, prove to be beneficial in the management of aflatoxin-contaminated feedstuffs for poultry when used in combination with other mycotoxin management practices. Additional studies are warranted to assess its efficacy under a wide variety of circumstances.

Animals may act as bio-indicators for the pollution of soil, air and water. In order to monitor changes over time, a baseline status should be established for a particular species in a particular area. The concentration of minerals in soil is a poor indicator of mineral uptake by plants and thus their availability to animals. The chemical composition of body tissue, particularly the liver, is a better reflection of the dietary status of domestic and wild animals. Normal values for copper, manganese and cobalt in the liver have been established for cattle but not for African buffalo. As part of the bovine tuberculosis (BTB) monitoring programme in the Kruger National Park (KNP) in South Africa, 660 buffalo were culled. Livers (n = 311) were randomly sampled in buffered formalin for mineral analysis. The highest concentrations of copper were measured in the northern and central parts of the KNP, which is downwind of mining and refining activities. Manganese, cobalt and selenium levels in liver samples indicated neither excess nor deficiency; however, there were some significant area, age and gender differences. The results will be useful as a baseline reference when monitoring variations in the level and extent of mineral pollution on natural pastures close to mines and refineries.

The use of broiler litter as an emergency feed during droughts and other periods of feed shortages was evaluated in terms of its effect on the health of sheep. Pure broiler litter (i.e. excreta plus wood shavings), and litter mixed with 7.5 or 15% molasses were fed for 83 days to 2-year-old wethers. The addition of molasses to the litter caused a significant increase (p < 0.01) in feed intake and final body mass. Various parameters such as plasma enzyme activity, plasma metabolite concentrations and urine mineral and purine excretion did not differ among treatments. Histological evaluation revealed no liver or kidney pathology. Mild myocardial pathology was observed in all 3 treatment groups. This seems to be related to the presence of the ionophore-based coccidiostat, narasin, which was present in the litter at a concentration of 10 mg/kg. It is suggested that these histological lesions are of little practical significance and would not affect the health of sheep being fed the broiler litter as a survival feed.

Two trials were conducted to evaluate the effectiveness of different methods of reducing the liver copper (Cu) concentration of sheep whose livers had been loaded with Cu, in order to protect the sheep from Cu toxicity, after dietary Cu had been withdrawn. In the first trial 0, 75, 150 and 300 mg zinc (Zn) kg-1 feed were added to a basic diet low in Cu and fed to hypercuprotic sheep (n = 32) for 88 d. At the end of the trial, liver Cu concentrations (c 800 mg Cu kg-1 DM) in all 4 treatments did not differ significantly from the Cu concentrations of the liver biopsy samples taken at the onset of the trial. From other measurements taken, none of the sheep appeared to be close to the haemolytic phase of chronic Cu toxicity. In the second trial, lasting 79 d, 40 hypercuprotic sheep were allocated to 4 treatments, viz. a control, a group receiving a parenteral treatment of Zn, amounting to approximately 7 mg Zn d-1 and 2 further groups receiving molybdenum (Mo) (15 and 30 mg Mo sheep-1 d-1), added to the basic diet high in sulphur (4,06 g kg-1 DM). The parenteral Zn treatment did not change liver Cu concentrations. The 15 mg and 30 mg Mo treatments reduced the Cu in the livers significantly by 24% and 42% respectively. It is suggested that both oral and parenteral Zn supplementation are ineffective in reducing liver Cu concentration once dietary Cu has been withdrawn from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

The response to selenium supplementation of sheep grazing cultivated pastures was investigated on different farms in the Natal Midlands, Republic of South Africa. Over a period of one year, a significant (P < 0.01) improvement of 18.2% in live mass gain and of 13.7 and 15.8% (P < 0.05) in greasy and clean wool production, respectively, was measured in response to selenium supplementation in young ewes at the Cedara Research Station. In ewes injected with a long-acting barium selenate product, the glutathione peroxidase (GSH-Px) activity in the erythrocytes was maintained at elevated levels, above that of the control group, for almost 2 years. On 6 private farms, mature ewes were dosed approximately 6 weeks before mating, with a long-acting intraruminal selenium pellet. On 2 of the farms, a significant improvement (P < 0.05) in fertility of ewes was observed with no response to supplementation in the birth mass, lamb growth rate, or in lamb mortality. The long-acting pellets maintained elevated erythrocyte GSH-Px activity in the ewes for approximately one year. Although sheep on some farms in the Natal Midlands responded to selenium supplementation, it seems advisable to establish the selenium status of a flock before embarking on a supplementation programme. The risk of an excessive selenium intake, through the inadvertent supplying of selenium in different feed sources, has been demonstrated and should be guarded against.

Blood samples were collected from sheep on 24 farms in the Natal Midlands to ascertain the selenium, copper and zinc status of sheep kept under intensive grazing conditions on cultivated pastures in this region. The mean erythrocyte glutathione peroxidase activity was 34.1 enzyme units (EU: nmol NADPH oxidised min-1 mg-1 haemoglobin). A total of 59.4% of the samples contained less than 30 EU, a level below which a marginal deficiency may exist. The mean selenium concentration in whole blood was 0.57 mumol l-1. Sixty four per cent of the samples contained less than 0.63 mumol l-1, a level below which the animals were considered to be marginally deficient. The mean copper concentration in plasma was 16.1 mumol l-1 and that of zinc 15.0 mumol l-1. On none of the farms was the copper concentration in plasma below the concentrations accepted to represent a marginal deficiency, and ewes on only one farm had relatively low plasma zinc concentrations. It is concluded that many sheep grazing cultivated pastures in the Natal Midlands may be marginally deficient in selenium. However, the selenium status in sheep should be determined on individual farms before supplementation is recommended, as external sources of selenium are often supplied, mostly unintentionally. Seasonal variations in blood selenium concentrations did not follow a specific trend, probably because the sheep were grazing cultivated pastures for most of the year and feeding practices differed from farm to farm. It is therefore suggested that the selenium status of sheep be determined at the pre-mating and pre-lambing stages rather than in a specific season of the year.

Two trials were conducted to determine the effect of monensin in broiler litter on sheep receiving the broiler litter in their diets. Broiler litter from chickens fed monensin as a coccidiostat, and from chickens receiving no coccidiostat, was included at a level of 30% in 2 sheep diets. In a further 2 treatments, monensin (15 mg kg-1) was added to each of the 2 diets to give a 2x2 factorial experimental design. In the first trial, copper (20 mg kg-1 feed) was added to the diets. These lambs were fed individually at a slightly restricted level of intake. No differences between treatments were observed in feed intake, average daily gain or efficiency of feed utilisation or in the concentrations of zinc, iron and manganese in the liver, glutathione peroxidase in erythrocytes and creatine kinase concentrations in the plasma. Hepatic copper content and copper retention in the livers of the sheep receiving the added monensin were significantly higher (P less than 0.05 and less than 0.01 respectively) than in those not receiving added monensin. The aspartate transaminase and alkaline phosphatase concentrations in the plasma of these sheep were also higher (P less than 0.05) than in those not consuming added monensin. In the second trial, the lambs were group-fed according to treatment and received the diets on an ad lib basis. The mean intakes of the groups receiving the diets with the added monensin, were lower than the intakes by the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

1. Distribution of copper and molybdenum was followed in the body tissues of sheep fed on high levels of Cu (82 mg Cu/sheep per d), sulphur (3.77 g S/sheep per d) and different levels of Mo (0.6 20.8, 38.4 and 58.5 mg Mo/sheep per d). 2. Liver Cu content decreased as Mo intake increased from 0.6 to 38.4 mg/d, but increased again at high intakes of Mo. With an Mo intake of 58.5 mg/d, the Cu content of liver, kidney, lung, spleen and muscle tissue was significantly higher than with an intake of 20.8 mg Mo/d. The trend of increased Cu concentrations in kidneys and plasma was already evident at an Mo intake of 38.4 mg/sheep per d. 3. High positive correlations were observed between Cu and Mo in both the kidney cortex and medulla of the sheep at the two highest Mo treatments. 4. At constant S intake, Mo concentrations in the tissues tended to increase in proportion to Mo intakes. No indication of any detrimental effect due to the accumulation of Mo in the tissues was observed. 5. It was suggested that in the presence of an abundance of Mo, Cu and S, compounds containing these minerals in metabolically unavailable forms accumulate in the body, first in the kidneys, but eventually also in the other tissues of the sheep.

Molybdenum at levels of 2, 20, 40, and 60 mg/kg dry matter was added to a sheep ration containing 82 copper and 3, 8 g sulphur per kg dry matter. At the 2 higher levels of molybdenum, a substantial accumulation of copper and molybdenum was observed in the kidney cortices of the South African Mutton Merinos (reported elsewhere). The effect of these treatments on the health of the sheep was investigated. Observations on the 3 molybdenum supplemented treatments were: Serum enzyme levels remained normal throughout the trial. No evidence of kidney damage due to treatment could be obtained from kidney clearance studies. No pronounced liver lesions were evident from histophathological evaluations. A significant increase in Periodic acid Shiff positive stained granules was observed in the cortical tubules of the kidneys at increased molybdenum intakes. However, this was considered to be of minimal physiological significance. It was concluded that molybdenum prevented liver damage due to excess copper and that copper and molybdenum which did accumulate in the kidneys were probably harmless and present in an unavailable form to the body or caused minimal morphological changes. No haemolytic crisis occurred in the sheep receiving no added molybdenum. However, their concentration of serum enzymes Aspartate transaminase and Lactate dehydrogenase increased throughout the 193 day trial. It is suggested that elevated levels of these enzymes may be unreliable indicators of an approaching haemolytic crisis in the Merino.

Retention of 75Se following a single oral dose and stable Co, Cu, Zn, and Mg were determined in tissues of calves fed a diet containing 0, 10, or 40 ppm supplemental Co for 21 d. Concentrations of 75Se in tissue were numerically higher with 10 ppm Co than with the other two diets, but the effect was significant only in small intestine tissues of calves fed 40 ppm Co. Dietary Co did not affect fecal 75Se. Average total fecal 75Se excretion was 53, 48, and 51% of the dose over 6 d in calves fed 0, 10, and 40 ppm added Co. Concentrations of Co in tissues increased with increased supplementation. Dietary Co did not significantly affect growth, feed intake, tissue Zn, tissue Cu, blood hemoglobin, packed cell volume, plasma alkaline phosphatase, or plasma glutamic oxaloacetic transaminase. Magnesium in heart and skeletal muscle was increased in calves fed 40 ppm Co. Although high amounts of added dietary Co had some influence on metabolism of Se, the magnitude and extent of the effects appeared to be too small to be of practical concern.

The total liver mass of live ruminants is frequently required in mineral nutrition studies. In healthy, well-fleshed sheep high correlations were obtained between liver mass and body mass. In 169 sheep older than 15 months the wet liver represented 1,13 +/- 0,129% and the dry liver 0,34 +/- 0,036% of the live body mass respectively, while in 51 young sheep (6--9 months of age) these values were 1,65 +/- 0,135% and 0,48 +/- 0,062% respectively. Some of the factors influencing these values are discussed. The dry matter content of the livers in healthy sheep--irrespective of the breeds used, their age, body mass or the portion of the liver sampled--showed little variation, being 29,5 +/- 1,02%.

The iodine content of fresh milk samples from bulk milk transport vehicles (tankers) and from bulk tanks on individual farms was determined. Approximately 75 percent of all the samples fell within the normal range of 25 to 300 micrograms iodine/l of milk. The mean iodine concentration in the tanker samples was 257 micrograms/l and in the farm tank samples 294 micrograms/l, while the medians of the iodine concentrations in the surveys were 214 and 218 micrograms/l respectively. A total of 1.75 percent of the tanker samples and 5.5 percent of the individual farm samples contained more than 1000 micrograms/iodine/l, a level which is considered to be undesirable for human consumption. Iodine containing teat dips (2000 mg available iodine/l) increased the iodine concentration of the milk of cows treated with these teat dips by between 11 and 60 micrograms/l.