Involvement of the solid phase of rumen digesta in the interaction between copper, molybdenum and sulphur in sheep

Abstract

1. Merino sheep fed on a diet of chopped wheaten hay, chopped lucerne (Medicago saliva) hay and oat grain were the source of rumen contents for the study. The diet contained (mg/kg dry weight) 3.3 copper, 024 molybdenum and 2-8 sulphur. The effects of adding between 5 and 25 mg Mo/kg as ammonium molybdate (AM) or tetrathiomolybdate (TTM) on the distribution and forms of Cu and Mo in rumen contents were investigated in vivo and in vitro. 2.Approximately 88 YO of the Cu and 94% of the Mo in rumen contents were associated with the solid phase.When AM or TTM was added to rumen contents in vivo or in vitro the proportion of these elements in the solid phase was increased at the expense of the fluid phase.3. The addition of AM and TTM to rumen contents also decreased the proportion of Cu that was soluble in trichloroacetic acid (50 g/l ; TCA) and increased the proportion of Cu that was not extractable by sequential treatment with TCA and neutral detergent.4. Column chromatography of neutral-detergent extracts of rumen contents revealed that TTM treatment caused Cu to be strongly bound to proteins of high molecular weight.5. Addition of sulphide to rumen contents did not result in significant changes in the distribution of Cu between the fluid and solid phases, or in the solubility of Cu in TCA.6. It is postulated that constant removal of TTM from the fluid phase via reaction with proteins and other macromolecules in the solid phase results in greater formation of TTM in vivo than would be expected from solution chemistry. The molybdo-proteins so formed are strong chelators of Cu and may be the agents responsible for the decrease in Cu absorption in animals that consume diets containing high concentrations of Mo.When relatively high concentrations of molybdenum and sulphur are simultaneously present in the diet of ruminants the availability of copper to the animal is seriously compromised (Dick, 1956). The production of thiomolybdates in the rumen, and the subsequent decrease in the availability of Cu due to the formation of insoluble Cu thiomolybdates has been suggested as a hypothesis for the interaction (Dick et al. 1975). Confirmation of the hypothesis via spectrophotometric evidence of the presence of these compounds in rumen contents has been hampered by interference from other compounds, and by the low concentrations of Mo normally present. However, at moderately high molybdate concentrations, absorption spectra typical of thiomolybdates have been found in washed suspensions of rumen micro-organisms (Dick et al. 1975;El Gallad et al. 1983), in an artificial rumen apparatus (Bray et al. 1982), and in whole rumen contents (El Gallad et al. 1983), thereby indicating that the potential for thiomolybdate formation does exist .Interest has also centred on the particular species of thiomolybdates that may occur in vivo. Based on observations of solution chemistry, Clarke 8z Laurie (1980) concluded that tetrathiomolybdate (TTM) would not form unless the sulphide : Mo ratio was very high, and that at the lower ratios mor...

Teores séricos e hepáticos de cobre, ferro, molibdênio e zinco em ovinos e caprinos no estado de Pernambuco

“…Já em relação aos teores hepáticos e considerando os dados de grupos controle de diferentes delineamentos experimentais, foi possível encontrar uma amplitude de valores, que variaram de 1,80mg/kg (Allen & Gawthorne 1987, 2,9mg/kg (Van Ryssen & Stielau 1981, 3,62mg/kg (Antonelli 2007), 3,80mg/kg (Jones et al 1984), 5,88mg/kg (Pott et al 1999) e 8,55mg/kg (Gonzáles et al 2000. Tais valores médios da concentração hepática de Mo estão abaixo dos encontrados nos animais deste estudo, porém próximos aos encontrados por Pott et al (1999) e Van Ryssen & Stielau (1980.…”

Rumen microbial fermentation, protozoan abundance and boron availability in yearling rams fed diets with different boron concentrations

“…In the present study, the increased protozoan abundance was observed after the highest dose of boric acid was added into diet, which could result in the reduction of ammonia utilizing bacteria. Since trace minerals form the complexes with protozoa and bacteria (Allen and Gawthornet, 1987), this form could be effective on bioactivity and metabolism by evaluating the degradation. However, further studies are needed to evaluate the effect of boron on the degradation of nutrients, such as fibre and crude protein, in rumen fluid both in vitro and in vivo.…”

“…Some trace minerals such as molybdenum and copper form complexes with solid rumen digesta including bacteria and protozoa (Allen and Gawthornet, 1987;Spears, 2003). Having this in mind, we hypothesized that the boron as a trace mineral might improve rumen microbial fermentation and protozoa abundance.…”

Modest Copper Supplementation Blocks Molybdenosis in Cattle

“…Although forage S was not analyzed as part of this experiment, historical S concentrations on the sites, taken over several years, were only 0.01% to 0.1%. Sulfur is a critical part of the Cu-Mo interaction, 1,9,11,21 and it is possible that if forage S was significantly greater Mo effects would have been seen in Group III.…”

“…2,4,10 Sulfur (S) potentiates most, if not all, of the effects of Mo in ruminants. Sulfide, which is formed in the rumen, displaces the oxygen in molybdate, forming various thiomolybdates that react with Cu at several levels, reducing both the dietary uptake 1 and biological availability of Cu to the cell. 9,19 The ratio of Cu, Mo, and S in the diet is critical to the Cu-Mo-S interaction and thus toxicity.…”