No abstract

Dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs) are hazardous toxic, ubiquitous and persistent chemical compounds, which can enter the food chain and accumulate up to higher trophic levels. Their determination requires sophisticated methods, expensive facilities and instruments, well-trained personnel and expensive chemical reagents. Ideally, real-time monitoring using rapid detection methods should be applied to detect possible contamination along the food chain in order to prevent human exposure. Sensor technology may be promising in this respect. This review gives the state of the art for detecting possible contamination with dioxins and DL-PCBs along the food chain of animal-source foods. The main detection methods applied (i.e., high resolution gas-chromatography combined with high resolution mass-spectrometry (HRGC/HRMS) and the chemical activated luciferase gene expression method (CALUX bioassay)), each have their limitations. Biosensors for detecting dioxins and related compounds, although still under development, show potential to overcome these limitations. Immunosensors and biomimetic-based biosensors potentially offer increased selectivity and sensitivity for dioxin and DL-PCB detection, while whole cell-based biosensors present interpretable biological results. The main shortcoming of current biosensors, however, is their detection level: this may be insufficient as limits for dioxins and DL-PCBs for food and feedstuffs are in pg per gram level. In addition, these contaminants are normally present in fat, a difficult matrix for biosensor detection. Therefore, simple and efficient extraction and clean-up procedures are required which may enable biosensors to detect dioxins and DL-PCBs contamination along the food chain.

No abstract

No abstract

This review focuses on the introduction and investigation of pangola grass as a tropical forage species especially in Thailand. Pangola grass (Digitaria eriantha Steud., synonym D. decumbens) is one of recent examples of grasses that have been successfully introduced to Southeast Asia and is often considered as one of the highest quality tropical grasses popularly grown as pasture. Pangola grass is utilized extensively as grass for animal grazing, hay and silage making. Its crude protein content is commonly in the order of 5 to 14% of dry matter and may exceed 15% of dry matter with young regrowth under high fertilization. It has been documented that the type and number of ruminants receiving pangola grass can determine the success of its use. Results obtained when pangola grass in fresh, hay or silage form was fed to ruminant animals as supplements showed better performances in body weight gain, feed conversion ratio, carcass yield, meat quality, and milk yield and composition. In conclusion, pangola grass is a promising forage and a source of high quality feed for ruminant animals in tropical countries.

Goats fed Leucaena leucocephala (leucaena) at an experimental site in Thailand were shown to be excreting DHP in their urine. This was unexpected as earlier results from another site had shown that goats and cattle fed leucaena did not excrete DHP and so possessed DHP-degrading bacteria. Goats sampled near the earlier sample site excreted no DHP in their urine. Rumen fluid taken from these goats was successfully used to transfer DHP--degrading ability to the goats at the Experimental site some 350 km away that did not show the presence of DHP-degrading bacteria. Degradation of mimosine in-vitro and excretion of DHP in the urine ceased 72 hr after addition of rumen fluid and infusion with rumen fluid from protected goats, respectively. The situation in Thailand may not be unique. Countries where leucaena is fed should check that animals are protected. Fortunately, the ferric chloride urine test is simple to use and effective in detecting the problem and also the recovery after transfer of rumen fluid from protected animals.

Summary Farm intensification options in pasture‐based dairy systems are generally associated with increased stocking rates coupled with the increased use of off‐farm inputs to support the additional feed demand of animals. However, as well as increasing milk production per hectare, intensification can also exacerbate adverse impacts on the environment. The objective of the present study was to investigate environmental trade‐offs associated with potential intensification methods for pasture‐based dairy farming systems in the Waikato region, New Zealand. The intensification scenarios selected were (1) increased pasture utilization efficiency (PUE scenario), (2) increased use of nitrogen (N) fertilizer to boost on‐farm pasture production (N fertilizer scenario), and (3) increased use of brought‐in feed as maize silage (MS) (MS scenario). Twelve impact categories were assessed. The PUE scenario was the environmentally preferred intensification method, and the preferred choice between the N fertilizer and MS scenarios depended upon trade‐offs between different environmental impacts. Sensitivity analysis was carried out to test the effects of choice associated with: (1) the approaches used to account for indirect land‐use change (ILUC) and (2) the competing product systems (conventional beef systems) used to handle the co‐product dairy meat for the climate change (CC) indicator. Results showed that the magnitude of the CC indicator results was influenced by the ILUC accounting approaches and the choice associated with a global marginal beef mix, but the relative CC indicator results for the three intensification scenarios remained unchanged.

The study assessed the value of Leucaena leucocephala bark in leucaena-grass hay diets fed to Thai goats. Thai goats in metabolism pens were fed diets containing leucaena leaf (55%) + pangola grass hay (hay, 45%); leucaena leaf (48%) + leucaena bark (9%) + hay (43%); leucaena bark (57%) + hay (43%); and hay only. Feed percentages are expressed on a dry weight basis. The digestibilities of dry matter (DM) and crude protein (CP) were measured for the four diets. Leucaena bark had lower CP concentration than the leaf (11.7 vs. 25.9), and the leucaena bark + hay diet had lower DM and CP digestibility than the other diets. The calculated bark digestibilities of DM and CP of 44.1% and 38.2%, respectively, were much lower than the values for the leucaena leaf of 62.9% and 89.1%, respectively. The lower than expected CP digestibility was attributed to higher tannin levels in the bark compared to the leaves. Despite this, the bark was well accepted by the goats and was often preferred to the hay. Stripping of the bark by goats also results in stems that dry quicker and have higher calorific value as fuel. However, if leucaena branches are fed as a sole diet, the goats may consume up to 30% of bark on a DM basis and this would reduce nutritive value and animal productivity.