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Dairy cows are very effective at turning grass into milk. On average, a lactating cow eats around 70kg of grass a day, and produces 18 litres of milk. And that milk, or dairy products derived from it, is a major export earner for New Zealand. But scientists are investigating potential uses for other parts of the animal, particularly things like blood and bone, which are both low-value by-products of the meat industry. Blood meal has potential as a possible feedstock for plastic, while bone may have biomedical value - examples of how science and technology research can add value to a product. 

Much of the research being done in the School of Science & Engineering has actual or potential technological spin-offs. Read about some of them below. 

Bio-resins | Drug deliveryBiomedicals | Pasture probes |



Petroleum-based plastics are very widely used in modern life, but the huge volume produced and discarded has a significant effect on the environment. As a result, there is an on-going search for cost-effective, renewable alternatives to petroleum-based products. Ideally these alternatives will also be recyclable or biodegradable. One possible feedstock is proteins - and a significant source of protein is the bloodmeal produced as a by-product of the meat industry..

Around 18% of the total mass of cows' blood is protein. In New Zealand 80,000 tonnes of blood is collected in abbatoirs each year, and at the moment it is all processed into bloodmeal and sold as low cost animal food and fertiliser. The proteins contained in bloodmeal could make a good basis for plastic production, but the harsh conditions in which bloodmeal is processed make it virtually impossible to be processed like conventional plastics. This is because, at high temperatures, the blood proteins clump together and stable covalent bonds form between each globular protein molecule.

To produce a plastic-type polymer, these covalent bonds must be broken and the protein molecules unfolded. Once that's happened, new covalent bonds can form that link the proteins into sheets rather than clumps, forming a new polymer.

bloodmeal chips and plastic product
Bloodmeal plastic chips and plastic strips

Research by Johan Verbeek and Lisa van den Berg, at the University of Waikato, has led to a method of modifying bloodmeal that allows it to be thermoplastically processed, like polyethylene. This method uses a combination of heat and chemical treatments, and produces a bio-resin that is as strong as polyethylene, but more brittle.  Bio-resins, such as the ones produced here, can be used in the agricultural industry as planting containers, or if the properties are well optimised, as mulch films.

lisa, johan & blood plastic extrusion
Lisa van den Berg & Johan Verbeek with blood plastic extrusion

Related work at the University of Waikato includes research into obtaining proteins from milk (this is a 2089KB poster) - for more information on this topic contact Janis Swan.

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Drug delivery in the rumen
The specialised stomach compartments fround in ruminant animals (e.g. cows, sheep) contain symbiotic microbes that digest the cellulose in the animals' diets. Because conditions in the various parts of the digestive system vary so widely, this may impact on the metabolism of drugs that are given orally, such as drenches for gut parasites. There is a lot of interest in developing ways of placing a reservoir of drugs into the rumen that can be slowly released over a relatively long period of time. But due to the complex chemical environment in the rumen, there are a number of challenges to overcome.

A group of researchers from Waikato University, Dexcel Ltd, InterAg NZ, and the University of Canterbury investigated the use of 'smart' polymers as a tool for the controlled release of drugs into the rumen.  Smart polymers are useful in this context because their molecular structure can change reversibly when environmental conditions alter. The team investigated the use of microcapsules made of a smart polymer that released their contents at low pH but retained them at a neutral pH. This would mean that similar capsules containing drugs could have their release targeted for a particular region of the gut.

You can download a poster (4.14MB) outlining the methods used to prepare the microcapsules.
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Biomedicals from bone

Bone is another readily-available by-product from the meat industry. This has the potential to be used in production of 'biomaterials' - substances that come into contact with living tissues (Mucalo & Worth, 2008). One use is in protheses, to replace damaged joints or missing bone.

Research into biomedical use of bone products is interdisciplinary  - but chemistry plays a major role because of its importance in biomaterials polymer science. Research chemist Michael Mucalo and his team have been investigating the use of biomaterials in replacing bone lost through disease or accident. They are working on the development of xenografts - manmade bone substitutes. While xenografts don't contain any living cells (unlike natural bone, which is a living tissue), they can act as a scaffold supporting the growth of new bone.

michael & students in the lab
Michael Mucalo (left) and research students Dougal Laird & Ashley Easter, working with some of the biomedical materials they have developed from cow bone..

Bone is made up of a matrix of calcium phosphate and the protein collagen that supports the living component: cells and blood vessels. However, it's not a homogenous substance. There's an outer hard layer, called cortical bone, that surrounds the soft, spongy inner cancellous bone. A xenograft replacement for bone must reproduce all this if it's to be successful. In addition it has to be compatible with the body's tissues and also able to be remodelled - reshaped and penetrated by new bone - as the graft heals. Michael's team has focused on developing xenograft materials from cow bone, as this is easy to obtain and - in New Zealand at least - free of notifiable diseases such as Bovine Spongieform Encephalitis (BSE).  This research "has the potential to produce a cheaper, high value biomedical commodity out of a traditionally low value material currently used for fertiliser or disposed of into the environment" (Mucalo & Worth, 2008).

Section of cow femur & prepared bone specimens.

To prepare bone for a xenograft, cubes of bone are cut from the knee end of a cow femur (thigh bone). The cubes are then boiled and treated chemically to remove blood and fat, before soaking them in an oxidising agent such as hydrogen peroxide to remove collagen. This leaves a chalky cube of carbonated hydroxyapatite, which can be cut to a suitable shape before being used as an implant. The material can also be produced as a powder, which could then be sprayed onto artificial joint surfaces, improving bonding between the artificial joint and new bone growth.

Do the xenografts work?  In 2007 the research team reported their use in a labrador with a bone lesion in its right foreleg (Worth et al., 2007). The usual treatment for such bone damage involves draining the cavity & removing the damaged tissue (leaving a cavity), with or without use of a bone graft. (In really severe cases the leg would be amputated.)

In the case of the labrador, the dog's owner gave permission for the surgical team at Massey University's Veterinary School to use the Waikato xenografts as part of their treatment. The xenograft was cut to fit the cleaned-out cavity in the dog's foreleg, and any gaps between it and the undamaged bone were packed with healthy bone from the dog itself.

Two months after the operation, X-rays showed that new bone was forming in the cavity and integrating with the graft. And after 10 months the bone had completely healed.

M.R. Mucalo & A.J. Worth (2008) Biomedicals from bone. Chemistry in New Zealand January 2008: 13-18

A.J. Worth, K.G. Thompson, M.C. Owen, M.R. Mucalo & E.C. Firth (2007) Combined xeno/auto-grafting of a benign osteolytic lesion in a dog, using a novel bovine cancellous bone biomaterial. NZ Veterinary Journal 55(3): 143-148.

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Pasture probes & farm management

Pasture probes are tools used by farmers to measure the proportion of dry matter in grass. The farmer takes the device out to a paddock where he’s growing hay. Over time he can develop an idea of how much hay the paddock would yield – that is, he can picture yield against time, and will harvest at the optimum time (when the graph begins to flatten out).

Pasture probes were developed in the 1950s, and used a capacitance method to measure the amount of water in plant tissues. The modern version, the GrassMaster, is an electronic probe that uses an electromagnetic field to make these measurements. And not only is it a useful piece of equipment on the farm, it's also a valuable research tool. There is a great deal of research going on into new grass species and into pastoral management. The probe can help here by giving a quick quantitative measurement of drymatter weight per hectare. By predicting average grass growth rates, the farmer can identify excesses or deficits in available grass coming up over the next few weeks, and make management decisions accordingly.

Engineering student Steven McCabe spent last summer working on the GrassMaster, looking at ways to improve its performance. Under the guidance of electronic engineering professor Jonathan Scott, Steven was able to improve the probe's accuracy and quadruple the sample area that the probe can measure. Steven did the work while on a work placement with electronic product development company Novel Ways, as part of his BSc(Tech) degree. "I thought we might find it was too difficult to improve the existing probe," says Novel Ways' Graham Lynch, "but we got some results very quickly thanks to Steven and Jonathan's input." The plan now is to incorporate the developments into a new version of the probe.

Steven McCabe (foreground) and Graham Lynch measuring dry matter
in a paddock, using the GrassMaster.

(Thanks to Angie Knox and Graham Lynch for some of the material used in this item.)

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