Final Report Wa0321

FINAL REPORT WA0321

A review and workshop

to agree advice on

reduced nutrient pig diets

A report for Defra compiled by:

University of Newcastle:

Professor Sandra Edwards

Dr Helen Edge

Dr Philip Cain

Dr Jonathan Guy

Premier Nutrition:

Mr Mick Hazzledine

MLC:

Dr Pinder Gill

School of Agriculture Food and Rural Development

King George VI Building

University of Newcastle

Newcastle upon Tyne NE1 7RU

November 2002

Contents

1. Introduction1

1. Review of literature4
2. Legislation

2.2Strategies for reducing nutrient excretion:

(1) Better agreement between supply and demand12

2.2.1 Formulating to digestible nutrient constraints12

2.2.2 Better knowledge of animal requirements14

2.2.3 Single sex feeding15

2.2.4 Phase feeding16

2.3Strategies for reducing nutrient excretion:

(2) Improving nutrient digestibility20

2.3.1 Raw material selection20

2.3.2 Inclusion of dietary enzymes21

2.3.3 Diet manufacture and processing conditions30

2.3.4 The use of digestive enhancers and growth promoting agents32

2.4Strategies for reducing nutrient excretion:

(3) Changing diet formulation to reduce crude protein37

2.4.1 Defining ideal protein37

2.4.2 The use of synthetic amino acids in diet formulation44

2.4.3 Environmental benefits of reduced protein diets53

2.4.4 Areas of concern in the use of low protein diets55

1. Formulation of low pollution diets57
2. Formulation criteria57
3. Formulation exercise60
4. Protein levels in commercial feeds69
5. Sensitivity to assumptions on ideal protein composition70
6. Implications of formulations for raw material use70

1. Physical and Financial Modelling72
2. Phase Feeding72
3. Potential reductions in whole herd pollution from reformulated diets74
4. Further reductions in dietary protein76
5. Overestimation of growth potential79
6. Enterprise costings79

1. Industry Consultation92
2. Organisation of workshop92
3. Programme and attendance92
4. Feedback and wider consultation92

1. Conclusions98

1. Bibliography100

1. Appendices115

Executive Summary

Introduction (section 1)

1. Pig production has the potential to make a significant contribution to environmental pollution as a result of excreted nutrients (particularly Nitrogen, Phosphorus and Heavy Metals). These arise from both metabolic inefficiencies and the formulation of diets containing a surplus of nutrients relative to animal requirement.

1. The large quantities of slurry and manure that are produced can be considered as a valuable fertiliser if used responsibly, but can also provide cause for concern when their disposal is not regulated in an environmentally sensitive manner.

1. In recent years there has been an increasing amount of legislation regarding the spreading of such products onto land and, in consequence, more importance will be placed on minimising the level of nutrients in manure/slurry.

1. The objectives of this project were to:

i)Review the scientific literature to assess how pig diets may be modified to reduce environmental pollution. The review was carried out in relation to the current and pending legislation which may impact on commercial practice. In addition, the literature review also sought to highlight areas where gaps in knowledge indicate a need for further research.

ii)Investigate the feasibility and cost of formulating diets for pigs of UK genotypes, which would reduce nutrient excretion without compromising performance.

iii)Investigate the influence of diets and feeding strategies designed to reduce pollution on physical and financial performance of the pig enterprise.

iv)Facilitate a period of industry consultation, including a Workshop to discuss the subject of reduced nutrient pig diets.

Review of Literature (section 2)

1. A review of literature was carried out using searches of computerised databases (Web of Science, CAB Abstracts), technical leaflets from industry and direct discussion with key industry representatives, and communication with scientists working in the subject area in the UK and overseas. The review identified three main strategies for improving the utilisation of nutrients by the pig sector.

1. Utilising diets and feeding programmes which more closely match supply to animal requirements (section 2.2).

This category of approaches included formulating diets to digestible nutrient and net energy constraints, applying specific knowledge and modelling of the animals requirements at any given stage of growth, and changing feeding practices at the farm level to incorporate single sex and phase feeding strategies.

i)Conventionally, UK diets have been formulated to digestible energy, total amino acid and total phosphorus constraints. This is still the case for many smaller compounders and home-mixers. These measures do not give accurate prediction of the value of a feedstuff and are misleading in terms of nutrient capture. Data now exist to allow diets to be formulated to standardised ileal digestible amino acids, digestible phosphorus and net energy, and these criteria should be integrated into best practice.

ii)Although published tables of nutrient requirements for pigs exist, they are in general unsuitable for modern UK pig genotypes. Existing published UK tables are out of date and commercial diet specifications bear little resemblance to such recommendations. Standards published overseas are based on pigs of different genotypes and/or on castrates as opposed to entire males. A variety of pig growth models exist which can predict pig nutrient requirements, provided that accurate input data are known. However, these models are expensive to purchase, require specialist expertise to operate, and are used by only major feed compounders and specialist consultants. A major limitation of these models is that they work at the level of the individual animal, whereas rationing is currently applied to a potentially diverse population.

iii)Single sex and phase feeding both offer opportunities to significantly reduce nutrient excretion by the provision of a diet or series of diets that more accurately match nutrient demand of a specific group of animals at a given point in time. Some larger units are already implementing these approaches, which give more cost effective pigmeat production as well as reduced nutrient excretion. However, on smaller units it is logistically more difficult to form matched groups of animals and provide a greater number of diets.

1. Improving diet digestibility (section 2.3).

This category of approaches included selection of raw materials with higher digestibility value, increasing digestibility by inclusion of dietary enzymes or feed processing techniques, and the use of digestive enhancers and growth promoters.

i)Exclusion of raw materials with a low digestibility value, whilst reducing nutrient excretion, can be economically undesirable since such products are often also those by-products which are sold at low cost. Furthermore, feedstuffs with a low digestibility value consequent on higher fibre content may contribute to animal welfare. This includes enhancing satiety in restrict-fed animals, such as gestating sows, and promoting normal gut function and integrity in pigs of all ages.

ii)The addition of dietary enzymes can enhance nutrient digestibility. This has been most comprehensively researched in the case of microbial phytase, which can reliably increase digestibility of phosphorus from plant sources and permit reduction in total dietary phosphorus. The major limitation on phytase use is the issue of heat stability, with inactivation occurring at temperatures commonly used in large scale diet processing. Other enzymes with potential to make some contribution to improved nutrient digestibility include the -glucanases, arabinoxylanases and proteases. Their contribution is currently less well researched and predictable, and is an area for future development.

iii)The heavy metals, copper and zinc, are currently included at high levels in many diets for weaned and growing pigs to promote growth and prevent digestive illness. Similarly, antimicrobial growth promoters are widely used and of proven benefit in enhancing growth and nutrient capture. The withdrawal of these substances from pig diets is likely to be required in the near future, but has the potential to seriously compromise pig welfare, increase use of therapeutic antibiotics and increase nutrient excretion. These adverse effects will be much more serious on farms which are experiencing chronic health problems, and acceptable alternatives which reliably deliver the same benefits as heavy metals and AGPs are urgently needed.

1. Changing diet formulation to reduce crude protein (section 2.4).

Pigs do not have a requirement for nitrogen per se but rather a requirement for the correct supply and balance of individual amino acids. Total dietary protein can be reduced by supplementation with synthetic amino acids. Three synthetic amino acids are currently widely used in pig diets and a fourth is available.

i)The strategy requires a precise knowledge of the correct balance of amino acids for each stage of production (the ‘ideal’ protein). Whilst there is relative agreement about requirements for the most commonly limiting amino acids, recommendations regarding some of the less commonly limiting amino acids show great variation. This is a potential problem in achieving diets with marked reductions in crude protein, where use of the currently available synthetic amino acids results in these ‘lesser’ amino acids becoming limiting, and requires further research.

ii)There is a vast amount of literature relating to the use of reduced protein diets supplemented with synthetic amino acids. Most studies relate to the growing/finishing pig, but there are also studies on weaned pigs and breeding sows. Such diets can give equivalent performance to higher protein diets, but only when correctly formulated to all limiting digestible amino acids and net energy and results have not always been positive. Whilst the ability of such diets to substantially reduce nitrogen excretion is beyond doubt, there is still real concern that they can increase fatness and impair carcass grading. There are also questions about the requirement for specific amino acids to optimise imune function which require further research.

1. From the review of literature there is clearly a significant potential to reduce nutrient excretion through the modification of pig diets. However, many of the trials reported in the literature have been carried out using castrated boars and pigs of genotypes dissimilar to those in the UK. As such, the results should be treated with caution, particularly with relation to the diet specifications used, although the strategies themselves are certainly applicable in the UK.

Formulation of low pollution diets (section 3)

1. A formulation exercise was conducted, using September 2002 costs, to determine the feasibility of reducing the crude protein and phosphorus content of pig feeds in the UK. All feeds were formulated to current industry standards, but using 10 standardised ileal digestible amino acids, net energy and pig digestible phosphorus criteria.

1. Least cost formulations for September were some 1.5-2.0% points lower in crude protein than current levels in compound feeds (i.e. this reduction in crude protein reduces raw material cost). A further reduction in crude protein could be achieved of about 0.8% points but this resulted in an increase in feed cost. Feeds were infeasible below this level either due to valine, leucine or isoleucine constraints.

1. Providing that feeds are accurately formulated, no differences in physical performance are thought likely. However, assumptions made about the composition of the ideal protein can have a major impact on the result of the formulation, emphasising the need for better information on this subject. This exercise suggests that a 15-20% reduction in pig nitrogen excretion can be achieved at the same time as reducing feed costs. However, there would be consequences for raw material supply, including increased use of cereals and synthetic amino acids and displacement of home grown protein sources by imported soya.

1. Phytase was cost-effective in all feeds saving up to £1/t. Total phosphorus in the feed was reduced by about 0.1% points (15-20%). Monocalcium phosphate reduced both costs and total phosphorus in comparison to dicalcium phosphate, which has a lower phosphorus digestibility.

Physical/Financial Modelling (section 4).

1. To further investigate the financial implications of changes to dietary specification or feeding practices designed to reduce nutrient excretion from pig units, various scenarios were modelled using a combination of pig growth models, nitrogen partitioning calculator spreadsheets and a pig enterprise financial model.

1. Modelling of adoption of phase feeding indicated that a change from one to two feeds between 30 kg and slaughter at 95 kg can reduce feed cost by £1.11 per pig and give a 9% decrease in nitrogen excretion. A change from one to three feeds over this period can reduce feed cost by £2 per pig and give a 30% reduction in nitrogen excretion. However, the model also predicted increases in carcass backfat thickness of 0.3 and 0.6 mm P2, which could impact adversely on grading profile and carcass value in some herds.

1. The impact on whole herd annual nitrogen excretion of the low protein diets from the formulation exercise was modelled using simple spreadsheet calculators. Reductions of 16% in maiden gilts, 22% in sows with litter, 14% in weaned pigs, 12% in growing pigs and 15% in finishing pigs were predicted when compared to commercial control diets.

1. Modelling of the further reductions in dietary crude protein necessary to conform to current proposals for BAT, indicated that liveweight gain, feed conversion efficiency and carcass grading would be impaired. This would reduce net margin per pig by at least 44p in herds with average performance, and by £1.29 per pig in high performing herds.

1. Modelling of enterprise cost implications of changing from conventional to low protein diets developed in the formulation exercise, showed that the slight increase in feed costs was partially offset by reductions in water and slurry handling costs. The net result was an increase of 0.2 p/kg carcass production cost. Slurry volume was reduced by approximately 15%. The reduction in slurry N production and manurial value to the farm was equivalent to 7-9 pence per pig if replacement inorganic fertiliser was required.

1. Removal of zinc oxide from weaner diets was predicted to increase production cost by 0.6 p/kg carcass in a best case scenario, assuming no subsequent detrimental effects on lifetime performance. Removal of antibiotic growth promoters from all growing pig diets was predicted to increase production cost by 2.7 p/kg carcass because of slower growth, reduced feed efficiency and increased veterinary costs.

Industry consultation (section 5)

1. An initial letter, outlining the objectives of the project and seeking opinions, was sent to key industry people and professional organisations at the onset of the study. A number of people responded by letter, phone or meeting to raise issues and opinions. Following the review of literature and the diet formulation and modelling exercises, a workshop was organised at the NAC, Stoneleigh on the 25th September 2002. Direct invitations were issued to 45 members of the allied industries, 247 pig producers and all relevant professional societies. A synopsis of the conclusions to date was circulated in a preliminary briefing document to delegates and others who requested it.

1. The workshop consisted of a series of four presentations, detailing the findings to date of the project, and the formation of break out groups to allow delegates to discuss and evaluate the findings. Break out groups reported back to the workshop via a nominated rapporteur and the comments made are noted in this report. The main causes of concern amongst the delegates were a suspicion as to how future environmental legislation would be implemented and regulated, and who would bear the cost. In addition, it was felt that in certain areas, such as the effect of low protein diets on carcass composition, more research was necessary before there would be industry confidence in implementing such a strategy.

Conclusions (section 6).

1. The results of this study highlight both the potential scope and many strategies that could be used to reduce environmental pollution by modifying pig diets. Although there appears to be a large scope for change, it is important that areas of concern are addressed. Foremost amongst these are the need for up to date tables of requirements for pigs of UK genotypes, not only to maximise production but also for optimal health, and the need to further investigate the effect of low protein diets on carcass composition.

1. From the diet formulation and growth modelling exercises it can be clearly seen that it is possible to reduce nutrient excretion from the UK pig herd, sometimes even at a reduced cost to the producer. However, it is necessary to proceed with caution to ensure that the strategies implemented are suitable for the UK, take account of the variability in animal performance and raw material composition, and do not result in adverse effects on animal health or carcass value.

1

1. Introduction

The objective of this study was to review the practical solutions to reduce environmental pollution by alteration of diets fed to pigs. Agriculture makes a significant contribution to environmental pollution through the excretion of unutilised dietary nutrients, resulting from inefficiencies in metabolic processes and the input of nutrients surplus to metabolic needs. Intensive pig production leads to the production of large quantities of slurry and manure. The disposal of such products, often high in nitrogen and phosphorus, is of environmental concern. It is predicted that more importance will be given to minimising the level of such nutrients in manure as environmental legislation restricts application to land.

Current feeding practices (both dietary formulation and on-farm feeding strategies) result in nutrient excretions into slurry that are consistently higher than the minimum that could be achieved. The cause of this is twofold; economic considerations in selection of raw materials according to least cost formulations and management considerations in achieving simplicity of feeding under practical farm conditions.The scope to reduce environmental pollution by modifying the diets fed to pigs is great. Of the total dietary nitrogen fed to pigs, only around 33% is retained (Dourmad et al. 1997). The situation with respect to phosphorus utilisation is similar, with retention in the growing pig being around 30-35% (Jongbloed and Lenis 1992).

Improved efficiency of utilisation of dietary ingredients by the pig sector can be achieved in many ways. The possible strategies that could be adopted can be broadly grouped under one of three headings:

i)Producing diets and feeding programmes which match nutrient supply and demand more closely.

• Formulation of the diet on the basis of digestible rather than total nutrients, and hence better matching of diet formulation criteria to nutrient utilisation by the animal.
• Better matching of diet specification to the needs of the animal at each stage of production by more precise knowledge of the requirements of the animal in a given situation.
• Better matching of diet specification to the needs of the animal at each production stage by using a greater number of diets on the farm.

ii)Improving diet digestibility.