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A Veldman

Publications and source records attributed to A Veldman.

32 records · Page 2Linked to original sources
PubMed1994

Xylanase in broiler diets with differences in characteristics and content of wheat.

1. Experiments were conducted to measure the effect of xylanase supplementation on the performance of broilers fed on wheat-based diets containing high and low extract viscosity wheat (experiment 1), baking and feeding quality wheat (experiment 2) and with variation in wheat content (experiment 3). 2. Xylanase supplementation improved food conversion ratios by 2.2-2.9% and body weight gain by 0.2-2.5%. This was independent of wheat characteristics but slightly dependent on the wheat content of the diet. These effects were related to a lowering of digesta viscosity. 3. Differences in extract viscosity of wheat were not reflected in broiler digesta viscosity. 4. Reduction of digesta viscosity resulted in only a slight improvement of litter score. Reduced intestinal viscosity decreased relative pancreas weight and to a lesser extent relative small intestinal weight. 5. Baking quality wheat Baldus gave better performance than the feed quality wheats Apollo and Slejpner. 6. It was concluded that xylanase supplementation of wheat-based diets invariably had a positive effect on broiler performance.

Analysis of Variance↗
PubMed1992

[Probiotics].

Probiotics, living cultures of micro-organisms, are currently of great interest as counterparts to antibiotics. The idea behind the use of probiotics is that the development and stability of intestinal microflora can be enhanced. The protection against infections is increased, resulting in fewer health problems and increased productivity. The mechanism of action of probiotics is not yet known, although there are several hypotheses. There is increasing evidence to suggest that probiotics act by stimulating the host's immune systems. The only accepted example of effective protection against infections provided by living micro-organism is the 'Nurmi concept', whereby one-day-old chicks acquire an enhanced protection against Salmonella infections when they are administered the complex intestinal flora of older chicks. The effects of probiotics on the growth, feed conversion or production of farm animals are, even in specific situations, not consistent enough to consider their use out of economic considerations. Probiotics are used to (re)establish the intestinal flora of patients or persons with lactose intolerance. The claims that probiotics have cholesterol-lowering and anti-tumour actions are based on animal experiments and require further investigations.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Fluorescence probe measurement of the pH of the transferrin microenvironment during iron uptake by rat bone marrow erythroid cells.

Fluorescence probe measurements of the transferrin micro-environment during iron uptake by rat erythroid cells revealed that part of the transferrin is taken up in an acidic environment. The pH of this intracellular transferrin environment is 5.7. When rat erythroid cell precursors are incubated with diferric transferrin then in the incubation medium monoferric transferrins TfNFe and TfFeC appear. In view of the known instability of TfNFe at acidic pH, TfNFe cannot arise after endocytosis of Tf2Fe in acid vesicles at pH below 6.0. The results support the existence of a mechanism other than endocytosis in the iron uptake process in rat erythroid cells.

Animals↗
PubMed1984

Are lysosomes directly involved in the iron uptake by reticulocytes?

The mechanism by which iron is transferred from the plasma protein transferrin into erythroid precursors for incorporation in heme is not completely understood. To show a direct functional role of lysosomes in the process of iron uptake we tried to isolate lysosomes from reticulocytes, which have been incubated with 125ITf59Fe. However, with various cell fractionating techniques described for liver cells no pure lysosomes from reticulocytes could be obtained. Fluorescence and electron microscopy showed that reticulocytes hardly contain well-defined lysosomes. There are several indications that in reticulocytes acid vacuoles instead of lysosomes are involved in the removal of iron from endocytosed transferrin. The presence of apoTf, monoferric TfFe(A), monoferric TfFe(B) in the medium after incubation of reticulocytes with diferric transferrin, together with the fact that both iron binding sites of transferrin release their iron at pH present in acid vacuoles, suggests a second mechanism of iron uptake by reticulocytes, in which acid vacuoles are not involved.

Animals↗
PubMed1984

Two mechanisms are involved in the process of iron-uptake by rat reticulocytes.

The iron uptake by red cell precursors has been studied in the presence of the carboxylic ionophore monensin, which achieves a concentration dependent inhibition of iron uptake, without influencing the transferrin uptake. It seems that two mechanisms are involved: Iron is released from endocytosed transferrin by acid vesicles. Iron is released from surface-receptor-bound transferrin at the plasma membrane, without internalization of the transferrin receptor complex.

Animals↗
PubMedDate not supplied

[Lavage with exogenous surfactant in neonatal meconium aspiration syndrome].

BACKGROUND: Meconium aspiration syndrome is a disease in near term infants which requires invasive techniques to decrease mortality. Lavage of the tracheobronchial tree with exogenous surfactant has been shown to be effective in animal studies. We studied the effectiveness of this technique in newborn infants and compared them with a historical control group. PATIENTS AND METHODS: From 1987 to 1998, we treated 18 neonates with meconium aspiration syndrome. In 11 babies a lavage with bovine derived diluted surfactant was carried out immediately after admission. In 7 infants of the control group only the meconium was suctioned or a lavage with saline performed. There were no differences between both groups concerning other therapeutic interventions like high frequency ventilation or inhalative NO. The control group contained significantly more outborn patients compared with the lavage group. Criteria of effectiveness were change in oxygenation index (OI), duration of mechanical ventilation and oxygen supplementation greater than 30 %. In addition, the two groups were compared for incidence of death, need for ECMO, and air leaks. RESULTS: One infant of the lavage group died, one had to be transferred to ECMO (no significant difference). There was a significant decrease in OI after surfactant lavage from 22 at admission to 5.1 one day later (p=0.007), whereas in the control group, OI did not change significantly over time (15.8 to 11.4). There were no differences in the duration of mechanical ventilation or oxygen supplementation. CONCLUSIONS: In our study, lavage with exogenous surfactant had only a short-term effect in decreasing OI in neonates with meconium aspiration. Larger numbers of patients need to be investigated to demonstrate an improvement in long-term outcome.

Bronchoalveolar Lavage↗
PubMedDate not supplied

Occurrence of the mycotoxins ochratoxin A, zearalenone and deoxynivalenol in feed components.

The mycotoxin contamination of feed components used by the Dutch cooperative feed industry was surveyed to estimate the risk for animal production losses. Of 89 randomly and 6 selectively taken samples of raw materials harvested in 1988 and 1989 27% were contaminated with ochratoxin A (OCHRA), 31% with zearalenone (ZEA) and 20% with deoxynivalenol (DON). The mean content (microgram/kg) of all positive randomly taken samples was 18 (OCHRA), 62 (ZEA) and 630 (DON). The highest level (microgram/kg) for all samples was 120 (OCHRA) in barley, 3100 (ZEA) in corn cob mix and 1900 (DON) in maizegluten feed. The results of this survey show that feed components are often contaminated with mycotoxins. However, the contamination level could only sporadically cause production losses in animal husbandry.

Animal Feed↗