Phages - a more attractive alternative to antibiotics

Saturday, October 3, 2015

These natural viral organisms can identify and destroy harmful bacteria. Phages are specific in their action, thus avoiding the blanket kill of some antibiotic solutions and also discouraging development of bacterial resistance to antibiotics

by NORMAN DUNN

Acocktail of bacteriophages is being prepared to control salmonella strains that are causing infections on British hog farms. The yellow press, those publications that thrive on eye-catching headlines, have already dubbed these bacteriophages "killer viruses" because they can home in on specific bacteria, attach themselves to the cells and effectively cause the host bacterium to explode. While this sounds extremely satisfying, the real value of introducing phages into veterinary medicine is that their specific action avoids the development of bacterial resistance, the greatest present-day problem with antibiotics.

In fact, intensive work featuring phages is already being done on controlling one of the most notorious antibiotic resistant strains in humans: Clostridium difficile. A pioneer in this work at the University of Leicester's Department of Microbiology and Immunology is Prof. Martha Clokie. Clokie now also works with the British Pig Executive (BPEX) in developing phages to help tackle salmonella and other bacterial diseases in swine production.

In a first stage of developing specific phage treatments, the Leicester University researchers are visiting eastern English hog farms, collecting and identifying salmonella types from various herds.

The next step, says the professor, is identifying suitable phages for effective destruction of the Salmonella strains identified. Then, targeted treatments can be set up for individual farms using the phage mix that is most effective in each case.

Speaking at this year's BPEX Innovation Conference, Clokie admits that applying phages to defeat specific pathogens in human medicine is really nothing new, having been recognized as effective since at least the early 1900s. The trouble was that when the new "wonder antibiotic drugs" — e.g. penicillin — appeared on the scene, the phage approach was sidelined in western countries. In lands such as the former Soviet Union, however, the treatment was continued as a cheaper alternative to antibiotic drugs in both clinical and veterinary medicine.

Professor Clokie feels that phages now have an increasingly important role to play in effectively overcoming bacterial resistances.

Poor health: the real root of profit erosion
Paul de Smet can prove that top health in swine production can save over 70 kilograms of feed per slaughter hog. Where health standards are mediocre, you can be shovelling in over three kilograms of feed for every kilogram of meat produced, points out this nutritionist. But where health and sanitary management is first class, you can get the same weight gain from two kilograms of feed.

Paul de Smet owns the Belgian swine nutrition firm Bivit Nutritional Engineering and can prove just how effective herd health can be for feeding efficiency and thus overall profitability. He surveyed results from a wide range of herds with differing health status. Naturally, it is sometimes hard to pinpoint where a system is failing in health management.  But this expert suggests that maybe stress is an important common denominator. Stress, he reckons, leads to poor performance not only directly but also indirectly by making hogs more susceptible to disease.

He told over 400 swine experts attending the latest European Pig Producers (EPP) Congress in Belgium that errors in housing standards, hygiene, air quality or stocking density all cause stress that, in turn, leads to lower disease resistance, drops in feed consumption and digestion efficiency. The direct effect of stress is also a performance stealer, increasing breathing rate and heartbeat, adrenaline and cortisol production, with associated higher metabolic rate and thus energy demand.

Paul de Smet demonstrated the difference that health status can make in a closed herd performance. His survey results show that average feed conversion ratios for specific pathogen free (SPF) herds were between 2.2 and 2.4 kilograms for one kilogram liveweight gain. For these high-health herds it took an average 207 kilograms of feed to slaughterweight. The respective average figures from farms in this survey classified as "problem herds" were 3.0 to 3.2 kilograms and 279 kilograms of feed. In other words, excellent health was worth, on average, 72 kilograms of feed!

A 500-sow Danish hog farm pays for eight government workers
Just how far the influence of a hog farming enterprise stretches is ably demonstrated by Danish swine expert Klaus Jorgensen from the breeding firm DanAvl.

He cites a typical Danish farm with 500 sows. According to the latest performance figures, such herds can be expected to produce 11,000 slaughter hogs plus a further 4,000 offspring leaving the farm earlier as weaners. The Danish weaner trade, incidentally, mostly features sales to German feeding farms, which often offer higher prices than anywhere else in northern Europe.

But back to the typical Danish production unit. Jorgensen says this would employ eight workers, with another 15 people normally involved in the associated slaughter, butchery, processing and packing of the pork produced.

The swine unit turnover, based on 2014 figures, would be around the equivalent of C$2.15 million. For the slaughterhouse and the associated processing industries, the pork produced would probably bring in a turnover of around $3.6 million.

Then there's the tax creamed off these revenues by the Danish state. When this is considered, there's enough money produced by the 500-sow business to pay the salaries of eight civil servants, Jorgensen maintains.

The real costs of catering to European consumer demand
At an-eye watering 34 Canadian cents per kilogram of carcass weight, Swedish hog farmers not only have the highest European labour costs in hog production, they also top the league for total costs per kilogram of pork produced. The management data network InterPIG puts this figure at C$3.54 for 2014 compared with $3.44 for Italy, the country with the next highest costs in this field, or $2.55 for the United States and even lower in Brazil at $1.92.

Naturally, labour is much cheaper in most of these lands compared with Sweden, traditionally a very high wage country. And, to be fair, poor harvests meant Swedish hog feeders paid a premium for feed on last year's markets, which didn't help their input costs either.

But the biggest expense in the longer term for hog producers is this country's comprehensive animal welfare legislation. Since the end of the 1980s, Swedish hog producers have had to provide 50 per cent more space per animal in their barns compared with demands from the European Union (EU). Straw bedding on all swine lying areas has been mandatory, with slats allowed on a maximum half of any flooring area.

These, and other perceived welfare introductions in hog farming, have slashed production margins to the extent that the number of swine producers in Sweden has dropped by 90 per cent — from over 14,000 in 1990 to some 1,400 this year. Back then, Sweden was 110 per cent self-sufficient in pork and its products. Now, the country has to import 40 per cent of its requirements.

Has this led to more caution when introducing welfare rulings in the rest of Europe? Not a bit of it.  Politicians — and their advisors — believe that consumers want increasingly high welfare for farm animals. EU legislation maybe hasn't yet caught up with Sweden, but it's not far behind nowadays. For instance, just this year, scientists advising the German Ministry of Agriculture (BMEF) delivered a 400-page paper warning that current hog production methods — and those for other farm animals — were not sustainable and were unacceptable to consumers. For hog production, the paper calls for the following changes:

• Animal access to different temperature zones within housing and, ideally, the opportunity for outdoor access;
• More space in swine production and feeding barns. Currently, 30-50 kilogram liveweight hogs must have at least 0.5 square metres of floor space, rising to a minimum 0.75 square metres for 85-110 kilogram liveweight;  
• Complete bans on any non-curative operations, e.g. castration or tail docking;
• More training for all stockpersons.

Other northern EU countries are heading in the same direction, a route leading directly to higher costs and less chance of survival for smaller family farms. Always affected by such changes is domestic production and pork processing employment. In Europe, you won't find anyone actually opposing the welfare suggestions — they represent really hot potatoes politically. But there's growing support for an alternative route towards this goal, one involving directly-paid welfare incentives instead of rigid legislation. This would mean, say supporters, that smaller farms could stay in business with support for perceived welfare improvements available to everyone.

Tail biting? Give 'em grass!
Yes, here we go again! Another tail biting cure. But this one really seems to work. And these results from the University of Giessen in Germany are all the more important because they come at a time when there's increasing pressure from animal welfare organizations in Europe to stop tail docking altogether.

This time, the silver bullet features grass pellets formed from permanent pasture and therefore potentially not too expensive. In a trial involving 400 mixed-sex growers (week 7 - 14), half were on standard rations and the rest with five per cent of feed value supplied by grass pellets. The Giessen scientists calculate that tail-biting injuries were cut by over 40 per cent where the growing hogs had grass pellets added to their diet.

On top of this, cases of diarrhea were 75 per cent fewer with the grass pellet group. A strong link was found between diarrhea and tail biting. In both groups, the hogs with acute diarrhea all had tail injuries. Amongst those with no reported diarrhea and fed grass pellets, there was zero tail biting.

The diet with grass pellets in the standard rations meant crude protein content was reduced from 17.7 to 17.5 per cent and energy from 13.5 to 13.1 MJ ME per kilogram whilst crude fibre was up from 4.4 to 5.2 per cent. The piglets in the trial were from an organically-managed farm with weaning at six weeks.  

Is the extra fibre a key to the significant reduction in tail biting here?

The researchers are still analyzing the results to come up with more answers. While welfare advantages seem clear enough, any economic gains naturally depend on the availability and price of grass pellets. BP