Copper (Cu) metabolism in domestic herbivores as guide to criteria for predicting the Cu nutritional status of wild ruminants in southern Africa.

In southern Africa game farming has become an effective way of using underutilised resources and a valuable method of preserving and increasing wildlife numbers. However, little is known about the mineral requirements of wild animal species or the assessment of the mineral nutritional status of these species. To establish criteria for estimating the copper (Cu) nutritional status of wildlife, current knowledge about Cu metabolism and criteria for domestic animals has been used. Since the Cu metabolism of ruminants differs substantially from that of non-ruminants, Cu metabolism in domestic species such as cattle and sheep representing wild ruminants, and pigs and horses as non-ruminant species, has been scrutinised to propose criteria for wild bovids in southern Africa. In the adequate range of dietary Cu intakes, literature suggests that hepatic Cu concentrations in ruminants increase linearly with an increase in Cu intake, allowing a relatively reliable measure of sufficiency. In non-ruminants, hepatic Cu concentrations follow a lag phase during which hepatic Cu concentrations remain relatively constant with increasing dietary Cu intakes of more that 25 times their requirements. A consequence is that non-ruminants can tolerate much higher dietary levels of Cu compared to ruminants. It is proposed that at liver Cu concentrations of < 20 mg/kg dry matter (DM), a wild ruminant could benefit from Cu supplementation; liver Cu concentrations of between 20 and 300 mg Cu/kg DM suggest an adequate Cu intake; concentrations of 300 to 500 mg/kg DM indicate a potentially unhealthy accumulation of Cu, while liver Cu concentrations of > 500 mg/kg DM indicate that the animal probably consumed more Cu than required and might be at risk of developing Cu toxicosis.

Liver moisture content in animals and possible causes of variations in hepatic dry matter content.

The concentration of trace elements in the liver is used as an indicator of the mineral nutritional status of an animal, as a benchmark of environmental mineral exposure, to follow the metabolism of an element in the body and for various other purposes. Concentrations are expressed on a wet (fresh) liver basis or on a dry liver basis. From a literature search and evidence from an analytical laboratory, large variations (varying from < 20% to > 40%) have been recorded on the percentage of moisture in the livers of ruminants. Such variations potentially compromise the interpretation of results on mineral concentrations in livers, and preclude robust comparisons between studies. Among the factors that can affect the moisture content of livers are: inconsistencies in sampling and preparation of liver samples; exposure to toxic substances; ill-health of the animal; fat content of the liver; and age of the animal. It was estimated that the mean dry matter (DM) content of the livers of healthy ungulates containing less than 1% liver fat is between 27.5% and 28.5%, and on a fat-free basis 25-26% DM. For routine analyses of liver samples it is suggested that to limit variations owing to differences in liver moisture content, liver mineral concentrations should be expressed on a DM basis, and for in-depth scientific studies on mineral metabolism on a dry, fat-free basis. However, if mineral concentrations are expressed on a wet basis, it is advisable to supply the liver DM content as well.

In vitro and in vivo assessment of humic acid as an aflatoxin binder in broiler chickens.

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.