P.G. van Wikselaar

Effect of a bacterial inoculant on rate of fermentation and chemical composition of high dry matter grass silages

Four experiments were carried out in Lelystad, The Netherlands in 1994, in which perennial ryegrass wilted to 421–568 g dry matter (DM) kg −1 was ensiled with and without an inoculant containing Lactobacillus plantarum and Enterococcus faecium strains in 1-litre capacity laboratory silos. Treated silages showed a markedly increased rate of pH decline. The final pH of treated silages was reached 20–30 days after ensiling, whereas acidification of control silages continued during the full 180-day ensilage period. After 180 days ensilage, treated silages showed significantly ( P <0·001) lower pH, DM loss and ammonia-N concentrations and significantly ( P <0·001) higher lactic acid concentrations than control silages in all experiments. Concentrations of ethanol and acetic acid were significantly (at least P <0·05) lower for the treated silages, except for acetic acid in one experiment and ethanol in another. Butyric acid was not found in any of the silages. One of the control silages (ensiled at 517 g DM kg −1 ) contained ethanol as the major fermentation product indicating that alcoholic fermentation had taken place, probably by yeasts. Treated and untreated grasses used in the first experiment (432 and 442 g DM kg −1 , respectively) were also used to produce silages in two 40-t capacity clamp silos. Similar to the laboratory silos, the treated silage had a higher lactic acid concentration and lower pH and ethanol, acetic acid and ammonia-N concentrations than the untreated silage.

Validation of growth as measurand for bacterial adhesion to food and feed ingredients.

Aims:  A miniaturized adhesion test was designed to study the binding capacity of food and feed ingredients for bacterial cells.

Dietary effects of linseed on fatty acid composition of milk and on liver, adipose and mammary gland metabolism of periparturient dairy cows

During the transition period in dairy cows, drastic adaptations within and between key tissues and cell types occur in a coordinated manner to support late gestation, the synthesis of large quantities of milk and metabolic homoeostasis. The start of lactation coincides with an increase of triacylglycerols in the liver, which has been associated with several economically important diseases in dairy cows (i.e. hepatic lipidiosis, mastitis). The polyunsaturated fatty acids have been used to improve liver metabolism and immune function in the mammary gland. Therefore, the effects of dietary linseed supplementation on milk quality and liver, adipose and mammary gland metabolism of periparturient dairy cows were studied in 14 cows that were randomly assigned to control or linseed supplementation. Animals were treated from 3 weeks antepartum until 6 weeks post-partum. Linseed did not modify dry matter intake, but increased milk yield and lactose yield, and decreased milk fat concentration, which coincided with lower proportion of C16 and higher proportions of stearic acid, conjugated linoleic acid and α-linolenic acid in milk fat. Linseed supplementation did not significantly change the expression of key lipid metabolism genes in liver and adipose tissues, except of glucose transporter 2 (GLUT2) in liver, which was increased in cows supplemented with linseed, suggesting that more glucose was secreted and probably available for lactose synthesis compared with cows fed control diet. Large adaptations of transcription occurred in the mammary gland when dairy cows were supplemented with linseed. The main affected functional modules were related to energy metabolism, cell proliferation and remodelling, as well as the immune system response.

Concentrations of dimethylaniline and other metabolites in milk and tissues of dairy cows treated with lidocaine

Lidocaine is a topical anaesthetic drug used in dairy cows for laparotomy (caesarean section, abomasal displacement). Because there are no registered drugs for this indication, it can be applied under the so-called Cascade rules (off-label use), with the restriction that the off-label withdrawal periods of 7 days for milk and 28 days for meat are taken into account. In animals, lidocaine is rapidly metabolised into various metabolites, one being 2,6-dimethylaniline (DMA) which is reported to possess carcinogenic and mutagenic properties and detected also in milk. To investigate whether the off-label withdrawal periods are long enough to exclude the presence of lidocaine and DMA, and potential other metabolites, in edible products, a study was performed with eight dairy cows treated with lidocaine by injection in the abdominal muscles. At various time points blood samples, milk and urine were collected. Four animals were slaughtered 3.5 h after treatment, the other four after 48.5 h. The injection site, meat, liver and kidney were analysed for levels of lidocaine, DMA, monoethylglycinexylidide (MEGX) and 3-OH-lidocaine. It was shown that DMA is an important metabolite in dairy cows and can be detected in both meat and milk. In addition, also MEGX, 3-OH-lidocaine and three other metabolites were identified and to some extent quantified. These metabolites were 4-OH-lidocaine, lidocaine-N-oxide and 4-hydroxy-DMA. The latter compound was the most important metabolite in urine. However, levels in milk and meat decreased rapidly after the application. Overall, it can be concluded that the off-label withdrawal times of 7 and 28 days for milk and meat, respectively, guarantee the absence of detectable levels of lidocaine and metabolites.