Effects of contrasting forage diets on phosphorus utilisation in lactating dairy cows

The effects of different forage mixtures on duodenal flow and faecal output of phosphorus (P) were measured in lactating dairy cows in two experiments. The forages comprised grass silage (GS) alone or mixtures of GS and urea-treated whole crop wheat (WCW). Replacement of GS by high levels of WCW resulted in a significant decrease in total P (TP), water-soluble P (WSP) and acid-soluble P (ASP) intakes, but increased phytate P (PP) and acid-insoluble P (AIP) intakes. Duodenal flows of all P fractions were unaffected by dietary treatments. However, the amounts of all fractions flowing to the intestine were much higher than the amounts consumed-with the exception of AIP, which was unchanged, and PP, which was considerably reduced. Diets did not significantly affect faecal outputs of TP, ASP, PP and AIP; however, faecal outputs of WSP were significantly higher on WCW than GS diets. Inclusion of WCW significantly decreased TP and WSP availabilities in the total tract but did not affect PP and AIP availabilities. A new fraction of P, which was not present in the feeds, was found in significant amounts in the intestines and proved to be soluble in dilute acid but insoluble in water. Estimated annual excretions for a herd of 100 cows ranged from 1550 to 1721 kg for total P of which 337-786 kg was WSP. The results suggest that GS based diets deposit more P in the environment. However, the potential to cause P pollution depends not only on the quantity but also on the nature of faecal P and on soil parameters. © 2004 Elsevier B.V. All rights reserved.

Maintenance of the African easterly jet

The maintenance of the African easterly jet (AEJ) has been examined using a zonally symmetric general circulation model with simple parametrizations. It is shown that the AEJ is maintained in association with two diabatically forced meridional circulations: one associated with surface fluxes and dry convection in the Saharan heat-low region and one associated with deep moist convection in the intertropical convergence zone equatorward of this. the heat-low heating, which reaches the height of the AEJ around 700 mb, is particularly important in maintaining the AEJ and its associated meridional gradients in potential vorticity. It is concluded that the mean observed AEJ results from a combination of the diabatically forced meridional circulations which maintain it and easterly waves which weaken it.

Unique structural properties associated with mouse prion Δ105-125 protein

Murine prion protein deleted for residues 105-125 is intrinsically neurotoxic and mediates a TSE-like phenotype in transgenic mice. Equivalent and overlapping deletions were expressed in E.coli, purified and analyzed. Among mutants spanning the region 95-135, a construct lacking solely residues 105-125 had distinct properties when compared with the full-length prion protein 23-231 or other deletions. This distinction was also apparent followed expression in eukaryotic cells. Unlike the full-length protein, all deletion mutants failed to bind to synthetic membranes in vitro. These data suggest a novel structure for the 105-125 deleted variant that may relate to its biological properties