The Spectre of Pollution from Animal Excreta with Special Reference to Pigs

There is much talk across the world, in locations as wide apart and diverse as the UK and New Zealand for example, about food safety and animal welfare.

While these are important areas of concern to the pig producer, the threat of pollution from farm livestock is an ever-increasing one, even if it gets comparatively less media coverage at the present time. This paper by two livestock consultants working at the sharp end of farm advice and based at opposite ends of the world deals with this growing threat to the future of individual pig farms and possibly, in the long-term, to some complete pig industries in their present locations.

Pollution from animal excreta exists in soils, surface waters and the atmosphere. Soil contamination is drawn from excess nitrogen and phosphate as well as heavy metals (usually in trace-element form) and occasionally excessive organic material puddling in soils. Taken to excess this can reduce crop production and even get into the human food chain with largely unknown results.

Pond, lake, canal, river, estuary and coastal pollution result from the same materials (also including pesticides) in the form of runoff from land. This can affect fish and other aquatic life both throughout inland watercourses and on the seashore, and in crop (especially vegetable) production in areas close to rivers where water is abstracted especially in dry weather in order to irrigate crops.

Again, in excessive cases human health can be directly affected by high concentrations of raw sewage and the dangerously high absorption of some pollutants in crops. Atmospheric pollution can be considered in local, topical or distant sources. Localized atmospheric pollution involves a build-up of gases within or among farm buildings which can affect both animal and human health and performance.

Topical pollution in the atmosphere can be described as when farm odours can cause distress to members of the public or hotels and restaurants close to animal production. Finally, distant pollution of the atmosphere is exemplified by acid rain, where nitrites and sulphates not only from agriculture but also from industrial production are taken up in clouds and humid weather strata and transported over hundreds of kilometres to fall as acid rain which can then affect crop production and forestry.


European agriculture and the pollution crisis

Parts of Northwestern Europe have very high concentrations of human population. In addition to the presence of the required amount of livestock needed to feed such a dense urban population, such countries as Holland, Denmark, Brittany/France and parts of the UK also have an animal population ‘overload’ owing to involvement in world exports of various meats.

For example, quite large parts of Denmark have over 30 times the number of pigs needed to feed the local urban population and in Holland (before the recent swine fever crisis) over 50 times the pig numbers needed. Overloads are also present for dairy cows and poultry. In Holland, for example, animal density now vastly exceeds that of human beings (Table 1).


Table 1. Livestock production in excess: density of various livestock in Holland in 1991.


Pauenza, 1991.



UTILISABLE AGRICULTURAL AREA

The acute problem which livestock-intensive Europe has in relation to the rest of the world is shown in Figure 1. Utilisable agricultural area is defined as the amount of crop-generating or fallow land needed to take up pollutants without damaging the growth or yield of the indigenous plant, whether it be grass, cereals, brassicas, root crops or upland vegetation. Pig density in the primary ten EU livestock-producing member-countries is over five times the world average, with poultry and cattle density three times the world average.


The polluting potential of animal waste: biochemical oxygen demand

The pollution crisis is not one of sheer animal numbers, however. The position is made much worse by the fact that most farm livestock waste has far higher biochemical oxygen demand (BOD) than other polluters (Table 2).

The term biochemical oxygen demand is used to measure pollution from organic wastes, and is defined as the amount of oxygen required in a specified period of time to fully decompose organic material at a temperature of 20°C. When compared to raw human domestic sewage, pig slurry BOD is 70 times higher.

This means little to the man-in-the-street, but in general (because pig slurry varies in potency) the BOD produced by one growing pig is at least the equivalent of 2.5 human beings. Thus a farrow-to-finish pig farmer with 500 sows (not an unreasonable size) producing 20 pigs/sow/year has the pollution potential of 25,000 people. A town of that size would certainly demand a sewage treatment plant paid for out of local taxes and the cost spread among the majority of the 25,000 inhabitants it serves.




Figure 1. Index of pig numbers relative to utilisable agricultural area (UAA) in the major regions of the world.



Table 2. Examples of typical biochemical oxygen demand.


MAFF, 1991.


Our 500 sow farrow-to-finish farmer would largely have to cover the cost of such a biochemical treatment plant himself, perhaps receiving up to 25% government grant-in-aid. Even so, the extra cost loading over a (long and generous) 15 year amortisation period would be likely to remove 60% of his net profit on every finished pig sold during that time-scale!

Methane generating systems (which work) cost about 30% more and this extra cost is just about repaid by reduced power bills depending on how cheap power is, so the loss of profit is still there. Many pig farmers in Europe have done the sums in advance and walked away from a farm treatment plant.Afew courageous souls have built their own treatment plants, but all except a very few have come to regret it in financial terms.

Generally speaking, lagoon systems of purification work well in a country with long, hot, dry weather patterns and also where there is the space to place the lagoons away from domestic habitation. Contrary to what farmers are inclined to tell you, the initial lagoons in the chain often do create a smell nuisance! Even so, such facilities are not available to many pig-producing nations where lack of space and a colder climate exist. Until more research, engineering design and governmental financial backing are forthcoming, we must look at other ways of reducing pollution, and biotechnology can assist.


HOW MUCH CAN CROPS ABSORB?

We have seen that the pig is a much heavier polluter (in sewage terms) than the human. If we take cereals as the main ‘pig-recyclable’ crop which is placed to take up nitrogen and phosphorus from pig slurry, and that 150 acres (approx. 61 ha) of cereals provide virtually all the annual energy and 66% of the protein needs of a farrow-to-finish pig farm of 100 sows, then Table 3 gives an indication of the nitrogen and phosphorus overload per year such a modest 100 sow unit generates under cold-temperature climatic conditions.


Table 3. Calculated annual nitrogen and phosphate production and utilisation on a 100 sow, farrow-to-finish farm of 150 acres.*


*150 acres (61 ha) of cereals assumed to supply 85 to 90% of the feed energy needs of such a farm.


Bearing in mind that many pig industries are around one million sows in number, this means that one such industry would be fed 161,000 t of nitrogen and 47,000 t of phosphorus every year via compound feed.

Even if all this one million sow herd were to use solely home-grown grains as a sponge to help mop up the 113,000 t of unused nitrogen and 33,000 t of unused phosphorus appearing in the pig slurry after digestion, this leaves each 100 sow farm having a surplus of 5.1 t nitrogen and 1.8 t phosphorus to apply to its land, or get treated, every year. For a million sow national herd this is 51,000 t surplus nitrogen and 11,800 t phosphorus annually.

The position is made worse parochially because some countries, already small in agricultural acreage (e.g. Holland, Japan, Denmark, Taiwan) nevertheless produce pigs or other livestock in very concentrated areas. For example 37% of Holland’s pigs are produced in or near the Brabant region, which itself contains only 16% of the country’s land area.

It is because of problems of crop nutrient overload (when the nutrient essentially becomes a poison) that more and more countries are beginning to place restrictions on livestock production. The Dutch, with potentially the worst threat, have been actively addressing the problem for 12 years and have been placing ever stricter constraints on the number of livestock that can be carried on a farm depending on the sewage take-up/disposal facilities available.

For example, Holland is committed to reduce phosphate production from the 1993 level of 72,000 t to 55,000 t by 2005, and will shut farms down if it is not achieved by other means.

The current Dutch position with regard to dairy cows at the time this paper was written is given in Table 4 and reveals the reduction in permitted nitrogen and phosphate application to each hectare planned over the next 10 to 15 years. It also reveals a system of ‘fining’ or taxing those dairy farmers exceeding the allowed levels.

Thus for the first time we have a penalty yardstick against which we can measure the cost of any technical proposals. What Table 4 reveals is that a dairy farmer with 100 ha in 1998 will only be allowed to keep up to 250 cows of all types. In 2005 this herd must be reduced to 200 animals. In 1998 if the farmer puts 60 kg phosphates/ha in place of the 40 kg allowed (from any source) he will pay a tax of 300 Dfl (about US$144) per hectare; but in 2005 this same excess will cost him 675 DFl ($326). The polluter pays!


Table 4. Dutch pollution constraints.


*1 animal unit = 1 dairy cow.
†Still to be decided.



Table 5. The latest UK advice on quantities and nitrogen content of pig excreta.


To enlarge the image, click here

MAFF, 1997.
†Liquid feed at 4:1.
*Meal/pellet food



Table 6 gives the equivalent output of phosphate from sows and their progeny to finish, which the Dutch estimate to be about 25 kg/ha/year. If the same financial strictures are applied to our 100 sow pig unit quoted in Tables 3 and 6, this producer, with his 150 acres (61 ha) in a worst scenario situation would have to pay $2,374 a year in 1998 but $8,310 in 2005 even though his arable acreage is fully cropped and all the crops fed back to his pigs!


Table 6. Dutch phosphate pollution constraints (pigs) as of January, 1998. All other species are compared to the term Grootvee Eenheden (gve) which is one dairy cow producing 41 kg P₂O₅/year.


Schuerink (personal communication).



These are the sorts of future cost penalties pig producers will have to start considering now, and against which the cost of some of the countermeasures to reduce pollution at source could be compared.


IS TREATING YOUR OWN FARM EFFLUENTACOST-EFFECTIVE OPTION?

Let us take the analogy a little further. Assuming the Dutch dairy cow ‘overload tax’ is applied to our 100 sow, 150 cereal acreage pig producer (seems likely as it is a tax on the degree of pollution, not on the animal), then he could be faced with a $5,300/year average penalty for the next 7 years, as his pigs will produce this degree of phosphorus overload if the plant physiologists are right.

Best estimates of capital needs for even a modest, part homeinstalled sewage treatment plant for a 2,200 pig turnover/year today approach $200,000. Amortised (with reducing interest) over 15 years this will cost our pig farmer in capital terms alone over $14,000 per year. Deducting his average $5,300 ‘fine’ over the period he is still $8,700 a year adrift, but there is more bad news to come as it will cost at least $2,000 a year to run the treatment facility. He solves his effluent problem, but at an extra cost of $5.35 per pig sold if he sells 20 finishers per sow, or $4.46 per pig sold if he sells 24, which is about top productivity for 1998.

Even at this top productivity level he suffers a savage reduction in gross margin. Again, the polluter pays! Sure, if he could purchase more land, at 2.5 acres (1 ha) per sow, or buy a bigger treatment plant and process some of his neighbour’s slurry as well then his costs would fall; but transporting slurry is an expensive business, and land is extremely costly. So at present, farm treatment plants look to be a rather problematical option. Centralised processing plants could be another solution and the Dutch are working on this.


CAN IT HAPPEN WHERE YOU ARE ?

It is important to have some form of econometric sounding-board against which to judge the viability of reducing pollutants by other means, which is why we have taken the home-treatment option as a case in point.

The Dutch over the past 12 to 15 years have been doing much technological research and thinking up carrot-and-stick economic solutions. Of course not every country has the problems Holland has, but politicians and bureaucrats all over the world, being what they are, will be quick to spot plausible suggestions/possible solutions which are far enough advanced to merit examination under their own conditions and even adopt them quickly if needs be.

So the answer to the question often asked across the world, ‘Will it happen here?’ is much more likely to be ‘Probably’, than ‘We hope not’. It is the time frame which is unknown. Already we are seeing constraints similar to those in Holland in Denmark and Germany. The UK has Nitrogen Vulnerable and Nitrogen Sensitive Zones (NVZs and NSZs) where slurry application constraints are in operation, and the UK Ministry of Agriculture are compiling an accurate inventory of ammonia emissions from UK agriculture.

The EU itself is getting together a proposed set of integrated pollution controls (IPPC) which are very far-ranging; and even in the US with its vast distances, new model environmental legislation for regulating hog farms may be headed for national adoption rather than the piecemeal controls, some lax, some draconian, now imposed by individual states or countries.

The US system under proposal is called The Comprehensive Environment Framework For Pork Production Operations. It consists, as presently proposed under a variety of nationally applied headings (see below), of establishing a permit system to farm hogs. Existing farms will have 5 years after the framework is adopted to comply with most of the recommendations, while new or expanded farms must comply before work begins. Eventually, no permit issued will mean no hogs!

1. Design and Management Standards: All farms must register their manure storage facilities and provide a plan for disposal which must satisfy the national authority. New or expanded farms must locate manure storage facilities based on an analysis model from the Environmental Protection Agency.

2. Land Application Planning: A nutrient utilisation plan or application method for all land must be submitted and biennial soil tests and manure nutrient tests conducted.

3. Nutrient Basis Application: Pork producers must apply manure based on nitrogen concentration unless soil tests suggest phosphate levels are likely to exceed the phosphorus carrying capacity of the soil at which point the phosphorus basis takes over.

4. Protection of Runoff: Limitations are placed on application to highly erodable land during wet weather and to frozen or saturated soils.

5. Odour Control: A restriction based on odour control is also recommended, held back at present by the lack of an accurate measurement method, an area where British (Silsoe) and Dutch (IMAG) engineering research centres are hard at work to produce a legally enforceable test.

6. Emergency Response: All farms must submit an emergency response plan in the event of an unauthorised discharge of manure or wastewater.

7. Operator Certification: All operators of hog farms must be certified as competent in pollution control.

8. Clean-up Surety: An operator cannot sell the farm or go insolvent and abandon a manure storage facility without clearing it up. An adequate financial bond has to be lodged in advance to cover the estimated cost of closure/clean-up.

9. Enforcement: Periodic inspection of all hog farms is included in the framework.


Financial and technical assistance

Government (state and federal) provision is made for producers to be given financial and technical help to meet the framework’s stipulations where this is merited. Thus, with the Dutch experience spearheading the EU proposals and the proposed American framework, two powerful regulating moves are in progress.


Econometric yardsticks needed

Before we deal with the various methods of reducing pollution, we should examine what financial penalties are proposed for exceeding pollution targets and assess how reduced animal stocking rate enforcements per unit of land available are likely to affect output, income and cash flow. We hear much, for example, of the following:

‘Phytase addition (to reduce the phosphates in slurry) is barely costeffective at present.’

Comment: It has already become cost-effective in the scenario described earlier where the cost penalty is likely to be around $5 per pig, or at four pigs/t (world average) $20/t. That pays for a lot of phytase!

‘Forcing down crude protein by a degree of synthetic amino acid replacement is too expensive, even if performance is not impaired.’

Comment: Substantial reductions in nitrogen pollution are possible (see later).

If these allow production to continue at the present level, or remove the threat of punitive financial ‘fines,’ then the extra cost could well be justified.

‘Changing to blend (phase) or multi-phase feeding leading to challenge feeding is too costly in capital requirements.’

Comment: It is certainly costly, but not too costly. These changes have some performance benefits – probably less than computer-modelling suggests – but these systems nearly always significantly reduce pollution levels of nitrogen and phosphorus. Taking the two together, plus some other advantages (better exploitation of on-farm performance caused by differences in disease, for example) they could well be economically important in the light of growing constraints on pollution.

What is needed from research and from the authorities are more data on what agricultural pollution really does cost the community and what the envisaged penalties of over-pollution will therefore be likely to cost the farmer. It is only when we have this basic yardstick (data) that the farmer can assess the least-expensive alternatives available and so prioritise which needs to be researched first as the most cost-effective solutions.

One of us (Gadd) has been attempting to quantify from the rather meagre data available, the costs of what present constraints on nitrogen, phosphate and ammonia (NH₃) gas are likely to inflict on those prominent European pig industries. To meet Dutch pig pollution standards already in place, then by 2000 (Table 6), this will cost between 8 and 11% per pig sold. To meet the IPPC and other British standards either proposed or in place by 2000 will cost at least 4% per pig sold and to meet Danish proposals will cost them around 6% per pig sold.

These cost increases may not sound high in raw percentage terms, but from the 1995–1997 period of quite reasonable profit margins, this in gross margin terms is a 28% reduction in Holland and 16% in Britain and Denmark.

But, in the period of late 1997 when profits were much lower, this would equate to 70% of Dutch profits, over 66% of UK profits and around 60% of Danish profits.


Alternatives and possible action

These worrying penalties can be reduced if one or more alternative solutions are attempted. So what are these alternatives? And what might they cost? The main goal is of course to lower the amounts of the pollutants fed to the animal in the first place. This may be achieved by one or more of the following:


USING SYNTHETIC AMINO ACIDS TO LOWER CRUDE PROTEIN INTAKE

Table 7 demonstrates two hog diets, one formulated from normal protein sources, and one where some of them are judiciously replaced by synthetic amino acids. Done correctly, the pig’s performance does not suffer. However, because the pig has to process less surplus protein to satisfy his amino acid needs, it excretes 27% less nitrogen. This is a large saving of a major pollutant for only a 4.5% increase in dietary cost; often recouped from less requirement for deamination (which uses up and so unbalances energy). Deamination is the process by which the animal excretes surplus amino acid intake as nitrogen.


Cost penalty

In the UK (1997 MLC Yearbook) a 4.5% increase in grower feed cost would cost our 100 sow farrow-to-finish farmer £1.24 ($2.03) per pig or £2,480/year ($4,067). German workers have found an even greater benefit (Table 8). Here nitrogen was reduced by a massive 42% and they had the added important benefit that slurry volume was reduced by one-third, too.


Table 7. Reduction in nitrogen from reducing crude protein.


Benefit = 27% less N excreted



Less deamination required

Lowering the energy needed in such a modified diet (at present under research) would reduce the cost penalty (possibly to a considerable extent as energy is costly) with only a 1.5% cost increase has been postulated.


Verdict

Using synthetics and other methods to more closely match amino acid supply to requirement is worth exploration. Alltech’s product Ultimate Protein 1672 for pigs has a part to play in this reassessment of amino acid/nitrogen/protein needs, as it is a rich source of available amino acids while sparing in non-needed nitrogen.

On post-weaning performance alone it is cost-effective (Table 8) in reducing the check to growth. Such pigs will grow faster to slaughter, consume less food and so excrete fewer pollutants.

There is large pollution reduction but at some cost, which may possibly reduce in future.


Table 8. Results of feeding Ultimate Protein 1672 to strong and healthy weaners 0–7 days post-weaning (7.52 kg).





PHASE/MULTIPHASE FEEDING.

Feed managers and pig producers have been encouraged to reduce the number of feed formulas for their livestock for convenience as well as for economic reasons, such as the extra cost of multi-sourced protein ingredients and extra storage facilities. This simplified feed production system has resulted in the use of a single feed for growing-finishing pigs.

The unavoidable result of this is an excess of protein during the less demanding phases of production, i.e., during the finishing period of growth. Figure 2 shows typical nitrogen intake and excretion from single phase, two phase and multiphase feeding regimes at the later stages of growth – where pollution is worst.


Benefits

Other results examined suggest that the benefits of a ‘simple multiphase’ (three to five diets from 25–30 kg) over a single feed is a reduction in nitrogen of 6% and in phosphorus of 10%. By using a multiphase system (9⁺ diets) a further 5% reduction in nitrogen and 8% in phosphorus has been obtained.


Cost penalty

It costs little more to multiphase feed than to phase-feed three to five diets in the 25–110 kg stages; but to convert a 1,000 head finishing barn to either system using a wet (pipeline) feeder will add between 4 and 5% to the total cost of producing a finisher if capital is amortised over 10 years and the plant properly maintained. Most, if not all, of this extra cost (admittedly rather less than expected) is gained back by improved physical performances (Table 9).




Figure 2. Effect of feeding strategy during the growing-finishing period (25 to 105 kg body weight) on N output. (1) single 17% CP diet from 25 to 105 kg BW, (2) 17% CP diet from 25 to 55 kg BW and 15% CP diet from 55 to 105 kg BW, (3) adaptive feeding strategy from 17 CP at 25 kg BW to 13% CP at 105 kg BW (from Dourmad et al., 1992).



Table 9. Saleable meat per tonne of feed in multifeed versus two stage feeding regimes (pigs 26–90 kg, pipeline fed).


*Value of extra meat/t feed at £1.02/kg = £8.16 ($13.38).



Cost benefit The extra cost of conversion to wet-feeding means an extra 4.5% higher costs on the average. On our 100 sow farrowing-to-finish unit this costs the farmer £2,480/year ($4,067). From Table 8, he feeds 340 t of feed per year and looks to gain back £2,774 in increased meat sales. Therefore his investment is recouped and his critical pollution levels are likely to be reduced by 12 to 18%.


Verdict

Multiphase feeding is also worth exploration. It represents a reasonable reduction in pollution, probably at minimal or no cost.


FEED ENZYMES

The pig industry worldwide is on the threshold of widespread enzyme use.

Specific enzyme supplementation can expect to benefit performance from wheat, rye, barley and oats, and future work will bring maize (corn) into the fold. Similarly there are benefits in diets which include rape seed, field beans or peas and now soya. In future ‘novel’ feedstuffs (silage, brassica tops, fresh grass, banana leaves, etc.) will be useful with appropriate enzyme complements.

Supplementation of the host’s endogenous enzymes in a variety of ways is well documented. In the case of pigs most improvements in feed conversion and daily gain help increase the amount of meat produced per tonne feed (MTF). Generally speaking, converting the present run of trial results, mainly concerning cereals, to an MTF figure shows that MTF increases by a range of from 4 kg to 17 kg/t feed. While added enzymes are not cheap, a return to extra outlay ratio (REO) of between 0.85 to 3.4:1 is the range established so far from the trials studied with only 10% of the trials being economically negative (i.e. REO under 1:1).

Phosphorus is required in large amounts by the pig and its vegetable food sources are low in available phosphorus. The addition of phytase has a major effect on the release of phosphorus from plant phytin (30 to 80%) depending on grain type. This allows a reduction in the amount of inorganic phosphorus needed in the diet by as much as 6 kg/t.

Typical improvements in available phosphorus among common feed ingredients are given in Table 10. The improvements workers were getting in the early 1990s are listed in Table 11. Since then pigs are growing faster and have greater phosphorus accretion needs. Additonally, sows are heavier and have bigger litters.


Table 10. Improvements from phytase addition.


Newman, 1991.



Table 11. The use of microbial phytase in pig diets.


P=phosphorus.



Effect of phytase enzyme on nutrient digestibility

Response in the digestibility of phosphorus varies according to the dietary combination of cereal and protein sources as indicated in Table 12. This variation may reflect intrinsic differences in phytase activity of these materials.

There may also be amyolytic and proteolytic enzyme activities in addition to the phytase activity. Practically, calculation of phosphorus digestibility and meeting phosphorus requirements must therefore involve the combined effect on the whole diet, not just the individual ingredients. Future research trials should be designed on the basal diet and difference method used in this trial.

Research with Allzyme Phytase (Alltech) (Table 13) indicates positive digestibility effects on several nutrients besides phosphorus (Fandrejewski et al., 1997; Barnett et al., 1993; Khan and Cole, 1995) compared to values usually found (INRA, 1984).


Table 12. Digestibility of phosphorus in rapeseed meal and soyabean meal.





Table 13. Nutrient digestibility improvements (%) of rapeseed meal with Allzyme Phytase.*


*1,000 units/kg.
Fandrejewski et al., 1997; Barnett et al., 1993.
†P < 0.05.
‡P < 0.01.



Phytase research and economic response

The research with rapeseed (Fandrejewski et al., 1997) did not present technical performance or energy and amino acid digestibility data. Future work should expand on the nitrogen and ether extract digestibility findings.

Growth performance differences were not noted by Barnett et al. (1993) or by several other workers. In practice, growth improvements with these digestibility effects may not be observed because the diet could already be over-formulated relative to pig requirements.Any improvements observed with phytase could further over-specify the diets if not re-formulated. Taken together, phytase usage decisions and economic benefits can be pragmatically and conservatively made by reducing dietary or increasing raw material nutrient values as appropriate.

This has been a common commercial technique employed by nutritionists when exploiting such positive nutritional effects. Choosing improvements for fat in maize of 5% and 50% in barley, with changes in nitrogen of 5% and in phosphorus of 20%, and extrapolating these data to potential, but conservative energy and amino acid digestibility responses, indicates potential returns (Table 14).

Performance responses to phytase inclusion levels between 250 and 2,000 units/kg have been reported (Cromwell et al., 1995). While not all research reports economically positive responses, data must be analysed as in Table 15 to demonstrate positive effects on REO are achievable.


Table 14. Potential economic improvements with phytase effect on nutrient digestibility.*


*De-Odorase, $7.5/t; Phytase, 1,000 units/kg; Base feed, 28¢/kg.
Gadd, 1998.



Table 15. Responses to varying phytase levels.*


Cromwell et al., 1995.
*Base feed, $0.32/kg, Growth 13.1 to 35.4 kg bodyweight.
†P<0.01.



Pig performance and economics

The author has examined four feed company trials comparing phytase addition with non-supplemented controls.
French work in the 1980s suggests significant improvements in average daily gain (11%) and feed efficiency (9.6%) but in fairness most UK feed company trials (unpublished) have shown much less than this; and until 1995 the UK feed trade felt the extra inclusion cost purely on a performance basis was barely repaid. However, Dutch feed firms with their country’s acute awareness of phosphorus overload, have been enthusiastic users of phytase for 8 years at least.

Once financial penalties for overloading phosphorus start become reality in other countries (as we have seen, potentially around $6,000 net for a 100 sow farrow-to-finish farm in the particular case of Holland, which is nearly $18/t of feed used), phytase inclusion will increase substantially. Again, $18 pays for a lot of phytase.


Verdict

Phytase inclusion in pig diets is certainly on the brink of becoming costeffective if it is not already there. More updating work on the performance benefits is needed. Because the economics are changing rapidly, feed manufacturers should test-model the economic response at least twice yearly, and re-double their own test trials on phytase inclusion using their preferred raw materials.

In the field of general enzyme addition, the use of enzymes to reduce antinutrient factors is an important area in which to save feed costs by increasingly using novel and previously discarded feed ingredients. The same goes for fibre-splitting enzymes in young pigs and their effect on gut flora and energy use. Also soya enzyme complements like Vegpro (Alltech) and UP 1672 can make good proteins more available.

All these aspects provide better pig performance, thus more MTF and thus lower pollution per tonne of meat produced because less food is needed per kg of meat. Establishing a MTF figure helps the producer relate the cost of adding enzymes to the financial benefit he receives from their inclusion, and the authors suggest will speed up their acceptance by the farmer.


Atmospheric pollution: ammonia

Until recently pig farmers and their advisers have under-estimated the damaging effect of ammonia gas on both humans and pig performance. Having escaped death from manure gases by seconds when a student pre-agitated a barn slurry system before pumping, one of your authors (Gadd) is as concerned about the effect of piggery gases on human health as ever he is on the health and performance of the pig! That piggery gases have a serious effect on the stockpeople working inside them is confirmed by Table 16. Also, it is reported that (up to 1990) more Scottish pigmen died of lung diseases than Scottish coal miners!


Table 16. Symptoms regularly experienced by workers in pig confinement units.


Donham and Gustafson, 1982.



The same writer has surveyed as many farm and academic trials using Alltech ‘De-Odorase’ yucca extract-based ammonia reducer as he can find. The results are summarised in Table 17.

These data suggest that when atmospheric ammonia is reduced from a pig performance-sapping, unpleasant-to-breathe 28 ppm to a still recognisable but quite tolerable 16 ppm, some 18 kg of saleable meat/t may be obtained from the ‘growth promotant’ effect of De-Odorase.

This is because the pig living in a cleaner, fresher atmosphere is likely to eat more, so should perform better, all things being in order.


COSTS AND BENEFITS OF REDUCING AMMONIA

Quite apart from the more pleasant working conditions and lower structural damage (ammonia corrodes metal buildings), around £20 ($33)/t of feed is recouped from improved performance. If the cost of supplementation is around £2.50/t (it is cheaper in the USA), the REO is a comfortable 8:1.


Table 17. Average of six farm trials where De-Odorase was incorporated into feed at 120–150 g/t versus controls.





Dutch literature suggests that under practical conditions ammonia levels are always below 10 ppm. Therefore no human or animal should be worried about health, welfare, performance or economic loss – or should they?

An extensive survey of 27 Dutch pig farms (Schuerink, 1995) reported that in summer, 75% of measurements were above 10 ppm and in winter (low ventilation) 90% were above 10 ppm (Table 18). There was an effect of ventilation as expected. Under-floor vacuuming and ceiling ventilation gave the lowest readings (8–12.4 ppm). Inlets on side and roof outlets gave the highest results (19.5–36 ppm). Ad libitum feeding systems led to higher ammonia than limit feeding systems.


Table 18. Seasonal effects on ammonia measurement.


Schuerink, 1995.
* P<0.001



The results of the five Dutch Farms on which effects of De-Odorase where evaluated are reported in Table 19. The Dutch research gave an average economic improvement of £2.70 ($4.37) per fattening pig per year with an REO of 3.7:1. The mortality reduction of 13% is highly significant and is proof that ammonia and other associated gases and conditions promote respiratory problems and disease. In New Zealand this would account for 0.5 pig per sow per year.

In a Danish study pneumonia frequency increased from 76.5 to 90% and number coughing by 25.3 to 70% as ammonia increased from <5 ppm to 50 and 100 ppm when pigs were challenged with Pasturella multocida (Andreason et al., 1994).

Irish research reports a reduction in ammonia of 56% (30.5 ppm down to 19.9 ppm) and an improvement in daily gain of 3.7% (De Molenaar, 1996). Recent French research (Morel, 1997) with De-Odorase (120 g/t) reported a reduction in ammonia of up to 30% with a reduction of 40% in mortality. Medication costs were also reduced significantly. Final evidence (Andreason et al., 1994) for the detrimental and fatal effects of ammonia even for short periods of time (20 min, four times per day) is presented in Table 20.


Table 19. Dutch farm performance responses to De-Odorase.*


Schuerink, 1995.
*Average of five farms.



Without further evidence the effect of ammonia on feed conversion efficiency is assumed to be linear except in the range below 10–15 ppm. As a guide for estimating responses to De-Odorase from this trial, 1 ppm ammonia approximately equals 1 point (0.01) of feed conversion efficiency.

The effect on reducing air pollution levels with De-Odorase is more difficult to quantify due to the plethora of variables affecting any one situation; however, it will be positively linked towards improving air quality and pollution. The writer, in observing farms with ammonia above 15–20 ppm, has seen reductions in the range of 25–50% inside buildings when De-Odorase is used.

Air pollution or complaint frequency is more variable due to the multifactorial cause and effect on piggery and treatment source odour. However, piggery and treatment source odour as an air pollutant or contaminant is often a perceived problem rather than one necessarily endangering health or well being or sustainability of the environment (mainly people).

Tolerance of agricultural odour is also declining. From a consultant, client and regulatory satisfaction point of view, it has proven wise and successful to meet perception with perception. In this writer’s experience, including odour blockers such as De-Odorase as mandatory in diets has allowed necessary consents for operation to be granted and removed local political problems. Odour complaints are commonly minimised, the result of an actual and perceived effect. It is a win/win situation.

The effect on REO for various changes in feed conversion ratio (FCR) based on the Danish trial data is presented in Table 21. In addition, in breeding houses/sections where the roof is low, the ventilation somewhat poor, and the flooring rather dirty (all commonly encountered even in 1998) one of the authors has recorded what seem to be small before-and-after improvements in farrowing rate, empty days, returns to service and days between weaning and service where De-Odorase is used which nevertheless and significantly have all added up to quite worthwhile economic returns (Table 22).

The likely reason for this is that gases may tend to neutralise the effect of stimulatory pheromones and in the majority of rather poorly-managed breeding houses this gives a critical edge to reproductive performance. Research in the US has shown that when the ammonia level reaches 20 ppm puberty is delayed (Malayer et al., 1988). In the study summarised in Table 22 the cost of adding De-Odorase was £3.10 sow/year. The benefits assuming £2.87 per empty day are £6.03 plus £1.96 improved throughput for a total of £7.99 per sow per year. The REO is therefore 2.78:1.


Table 20. Pig performance when exposed to varying ammonia concentrations.


*20 min, four times per day.
Andreason et al., 1994.



Table 21. Potential effect of feed conversion changes on return on extra outlay (REO).





Table 22. Improvements in performance from sows ranging in parity from 2 to 8.*


*11 farms, Client’s records 1991 to 1994.



Verdict

While there are other, sometimes cheaper products used to reduce ammonia pollution, the yucca extract-based De-Odorase is not expensive and generally is more reliable/less variable in effect. With expected REO in the range of 8:1 in finishing pigs and approaching 3:1 with sows, use of such an ammoniareducer should be routine.


Zinc pollution issues and options

Zinc oxide has proven beneficial for 10 years in reducing post-weaning morbidity and mortality around the world when used in diets at 2,500–4,000 ppm (Holm and Poulson, 1996). Zinc oxide has replaced antibiotics in many cases.

The mode of action of zinc oxide is probably mainly in the gut as workers (Wedekind et al., 1994; Vermeire, 1996) have shown zinc oxide to have inferior bioavailability compared to zinc sulphate and organic zinc sources.
In young growing pigs it is shown that apparent digestibility of zinc from zinc oxide is no better than 20% (Poulson and Larsen, in press). Zinc oxide may only be 30% as available as zinc sulphate (Jongbloed, personal communication). Power et al. (1994) showed zinc proteinate (Alltech’s Bioplex Zinc) bioavailability to be 159% of zinc sulphate values in rats. Put together this means zinc from zinc oxide is up to eight times less bioavailable than Bioplex Zinc.

There are concerns about toxicity, feed intake suppression, detrimental mineral interactions, environmental pollution and public health issues with the current levels of zinc oxide being used for any length of time. Toxicity has been shown to develop with pigs when feed contains 2,000 ppm and is fed for 6 weeks or more (Vellanga et al., 1992).

Holland has regulated dietary copper levels to 175 ppm before, and 35 ppm after, 45 kg and zinc to 250 ppm in all diets. Denmark also has a 250 ppm maximum with a veterinary prescription. Sweden allows 2,500 ppm for 2 weeks post-weaning only. In light of environmental considerations and the EC directive 70/524 to limit zinc to 250 ppm, other zinc sources and associated effects must be explored as is happening in Denmark currently (Holm and Poulson, 1996). Alltech are focusing attention on the opportunities for Bioplex Zinc and Copper as viable alternatives to inorganic sources of these minerals.

References

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