Oxford Sandy & Black Pigs As a Method of Weed Control

Oxford Sandy & Black pigs as a method of weed control.

When do they stop being an asset and start becoming a problem?

A dissertation submitted as part of a BSc (Hons) Forestry

By David Benjamins

At Riseholme, School of Agriculture

De Montfort University, Lincoln

April, 2002

Table of contents

ACKNOWLEDGEMENTS......

ABSTRACT......

Chapter 1: INTRODUCTION......

1. History of Silvopastoral systems involving pigs in the UK......

1.1 The Early Days......

1.2 Denbera......

1.3 Pannage......

1.4 The decline in the practice......

1.5 Revival?......

1.5.1 Burnham Beeches.

1.5.2 Rahoy Hills Reserve......

1.5.3 The Shenmore Estate (Herefordshire)......

1.5.4 The Cranborne Estate......

1.5.5 Hill Holt wood......

2. Advantages of Silvopastoral Agroforestry systems involving pig......

2.1 A tool to enhance Species richness......

2.2 An alternative to methods that put the environment at risk......

2.3 Advantages to the animals......

2.3.1 Welfare and health benefits......

2.3.2 The benefit of being in a forest Environment......

2.4 Economical advantages......

2.5 A managerial tool......

3 Disadvantages of Silvopastoral Agroforestry Systems involving pigs......

3.1 Tree damage......

3.1.1 Stem damage......

3.1.2 Root damage and disturbance......

3.1.3 Foliage......

3.1.4A solution?......

3.2 Environmental disadvantages......

3.3 Economical disadvantages......

3.3.1 Low productivity......

3.3.2 Managerial difficulties......

3.3.3 Fencing and other equipment may be expensive......

3.4 Uncertainty......

4 The need for more research......

Chapter 2: METHODS......

1 Study Area......

2 Design of the experiment......

Chapter 3: RESULTS......

Chapter 4: DISCUSSION & CONCLUSION......

1 Analysis of results......

2 Recommendations......

3 Further work......

4 Conclusion......

References......

Appendix 3: Notes taken during trial......

Appendix 4: Pictures taken during the experiment......

1

“…The feather from the raven’s breast

Falls on the stubble lea,

The acorns near the old crow’s nest

Drop pattering down the tree

The grunting pigs, that wait for all,

Scramble and hurry where they fall…”

John Clare in Autumn (19th century poet)

ACKNOWLEDGEMENTS

Firstly, I would like to thank Nigel and Karen Lowthrop for being so kind to me, and allowing this project to come through. Without them, nothing could have been possible.

Much respect to Tony Cowell, my supervisor, who showed me the way but without trying to take control.

Thank you, Jon Watson for making me doubt at the beginning of this project. You should always put yourself in question when striving to do your best.

To Sam, Abe, Mick, Stewart and all the lads at Hill Holt who helped me with the establishment of the fences and the “rugby tackling” of the pigs I would like to give my thanks.

Thank you Swan for your precious moral help throughout the whole experience and for leading me on the right track.

Thank you very much, Brenda Mayle, Alan Sibald, Helen Read and Helen Armstrong for finding some time to help me, despite their busy lives. Thanks to Adrian, Bruce and Tom for trying to open my eyes to the world of statistics. Finally I would like to dedicate this thesis to Boris, his sows and all his piglets without whom no weed would have been controlled at all…

Thank you all deeply…

Merci beaucoup.

1

ABSTRACT

Damage to trees has been the main factor that has made foresters reticent to the reintroduction of pigs in forests. An experiment involving Oxford Sandy & Black pigs was set up in a deciduous woodland, in the British midlands. The rate of damage to the trees caused by the pigs was monitored over a period of 369 hours. This rate of damage was also compared with 3 different feeding regimes (high, medium and low). It was found that tree numbers decreased over time in all species as a result of the presence of the pigs (e.g. ANOVA between birch and time for plot 1: P value of 0.00677 or ANOVA between oak and time for plot 1: P value 0.000176).

It was also found that the pig feeding regimes had an effect on the pig damage of trees. High feeding levels are believed to lead to a lesser oak seedling mortality than on less well-fed plots (The percentage of oak seedlings destroyed at 148 hours for the better fed pigs is 25 % whereas the less well-fed pigs at the same time had destroyed about 69.2 % of them).

Most weeds had disappeared after about 90 hours of pig presence while tree seedlings were still numerous even though the speed at which the pigs clear the land of weeds might depend on the density of brambles.

The results are discussed in relation to strategies of managing pigs in forest and indeed the use of pigs as a silvicultural tool has been shown to be possible and the added benefit of using a rare breed, such as Oxford Sandy & Black pigs, adds to the positive points of the venture.

Chapter 1: INTRODUCTION

This dissertation will investigate the rate of tree damage by pigs, with regards to weed control in a silvopastoral agroforestry system, in “Hill Holt Wood”, a local woodland near Newark. Silvopastoral agroforestry systems, involving pigs, have been known for generations but very little modern research has been done on the subject. Use of pigs in nature conservation is very understudied (Tolhurst & Oates, 2001).

Examples of land use systems integrating domestic pigs or wild boars with trees can be observed throughout the world, where underlying motivations include opportunistic resource use, tradition, product orientation and service functions. Although there is considerable interest in such agroforestry systems in the UK, this is yet to be reflected in widespread practical application, and there is little research available on their biology and performance (Brownlow, 1994).

The owner of Hill Holt wood originally brought in the pigs to replicate the effect of wild boar in ancient forests, however he observed that the pigs preferred to feed first on the weeds before attacking the trees (Pers com: Nigel Lowthrop, 2001). Furthermore another woodland pig breeder, called Ray Harris, has observed that the pigs will feed through the undergrowth but leave tree and saplings to continue to grow (Broomhead, 2001). Pigs have been used as a weed control method for several years in parts of Austria (Brownlow, 1994). The forest manager needs more information concerning the feasibility of the operation before being able to use the animals as a weed control method as he is aware that tree damage can be the main drawback with silvopastoral systems. The advantages gained by the animal ground preparation can easily be outweighed by the destruction of natural regeneration by the pigs.

The Oxford Sandy and Black pig was the breed used for this experiment. It originates from Oxfordshire and was sometimes known as the “Oxford Forest Pig” (Sheppy, 1986) therefore appearing to be an appropriate breed for this agroforestry experiment.

The pigs were kept in a mixed broadleaf, community forest in Nottinghamshire at the border of Nottinghamshire. The woodland is called “Hill Holt wood” and covers approximately fourteen hectares on the side of a very busy road of roman origin. It is composed of species such as oak (Quercus robur), ash (Fraxinus excelsior) or birch (Betula pendula) and is a typical British deciduous woodland. The history of the woodland is worth introducing:

Previous owners felled several hundreds of the highest quality oak trees, partly clear felled and partly under the selective system. The clear fell area was very badly replanted and apart from that no other replanting had taken place. The ground flora had disappeared under a carpet of bramble (Rubus fruticosus) and invasive alien rhododendron (Rhododendron ponticam)had spread through to the middle of the wood. This plant shades out all the ground cover, is poisonous and puts out a growth inhibitor from the roots, preventing other plant from establishing for a number of years after its removal. Furthermore a comprehensive ditch system of unknown but possibly ancient origin had been significantly damaged during timber extraction with a large crawler, leaving much of the wood waterlogged. This combined with endemic honey fungus (Armillaria mellea) has caused considerable dieback and death in the remaining trees. Very old coppice stools could be found but they had not been managed since World War 2 and were in terminal decline (Pers com: Nigel Lowthrop). Despite all these negative points the owner turned it into a successful social forest where local communities are invited to contribute to the planning of the forest and its management. Many problems had to be faced and not one of the easiest one to solve was the clearing up of the ground floor…

A study was carried out on the timing of damage to the tree seedlings. To understand more about the pigs feeding pattern would allow the forest manager to rotate efficiently the location of his pigs throughout his woodland, maximise his production through effective weed control and minimise the damage to the tree seedlings caused by the animals.

One of the aims of this research was to investigate the grazing behaviour of Oxford sandy & Black pigs in a woodland enclosure and to look into the relation between the animals and the forest in which they are kept. I have more particularly tried to answer the question as to how long can pigs be used as a method of weed control. How long does it take for the pigs to stop being an asset for the forester and start becoming a problem? When do they start damaging the trees? Providing useful managerial information to the forest manager is the ultimate aim of this dissertation.

To achieve these aims, a literature review has been carried out on silvopastoral systems involving pigs in the UK. A historical background was provided and the medieval practices of denbera (Old-English word meaning “swine pasture”) and pannage (Norman word succeeding to denbera, which relates maybe more to woodlands) was introduced (Brownlow, 1992). The medieval model was looked at with the possibility of its modern application. Indeed, the practice of grazing pigs in traditional woodlands is not a new idea, but when a thousand years ago pigs were essentially reared in the forest for basic commodities such as food, nowadays there is a more environmental and ecological base to the venture (Broomhead, 2001).

A discussion was then presented where the advantages and the disadvantages of silvopastoral systems will be examined and where the value of pigs as a silvicultural tool will be looked at.

To find out the rate of attrition to the tree element in this silvopastoral experiment, piglets have been kept in fenced enclosures while damage to trees was recorded at regular intervals to assess grazing habits.

It was then possible to understand more about the grazing patterns of the concerned pigs. Statistical tests were used to find out relationships and trends within the silvopastoral system. Damage to trees was plotted against time and quantity of added food in order to find out useful information concerning the timing of animal removal from the forestland and the quantity of added food necessary to minimise damage to the trees.

1. History of Silvopastoral systems involving pigs in the UK.

Historically, the pig has been a scavenger, living and foraging in the forests, woods and orchards. According to the legend in Britain, the keeping of large herds of pigs out of doors can be traced back to the middle of the ninth century BC (Thornton, 1990).

1.1 The Early Days

Agroforestry involving pigs has been used for a long time in the UK. Neolithic man probably kept swine in the profuse forest surrounding early human settlements (Brownlow, 1992). In fact at that period there would have been much similarities between this domesticated pig and wild boar, and they would have fed from nuts, acorns and browse from the forest most of the time (Seebohm, 1976). The importance of pigs to the human population was beyond doubt. In fact in the UK, during the early Iron Age, it is documented that the, much valued, and domesticated, pigs were fed in the great forests of the Weald and guarded by fierce dogs (Seebohm, 1976).

For the early Celts it became customary to send them to the woods for mast and acorns from the feast of St. John until January 15th, between which dates were preserved for their use (Seebohm, 1976).

1.2 Denbera

During the Saxon period, it was reported that domesticated pigs were often turned out in public forests after having been bred in farms (Seebohm, 1976). A man was often designated to drive the whole village’s herd into the woods (Trow-Smith, 1951).

As the manorial system developed the lords of the manor seem to have annexed the woods as their property, and in the season of acorns and beechmast, between the feast of St. John and the New Year, only allowed the villagers to run their pigs there on payment of a certain proportion of the herd. The customary payment was known as denbera (Seebohm, 1976). “Den” is derived directly from the old-English word and is a village suffix from the original denbera, meaning a large clearing in the forest or a swine pasture ( A careful eye was kept on the benefit the pigs derived from their feeding in the woods and the contribution regulated accordingly: of those which had acquired three fingers thickness of fat one-third were taken at the end of the season, of two fingers fate one-quarter and of one thumb thickness one-fifth.

During most months of the year, in the medieval period, pigs ranged the woods for roots, wild pears, wild plums, crab apples, sloes, haws, beech mast, and acorns; the pigsties were usually built in the woods (Ernle, 1961).

A detailed record of woodland just after the Anglo-Saxon period comes from the Domesday Book statistics of 1086. The numerous records of woods in relation to swine numbers refer to the practice of pannage, or the taking of tame pigs into the woods to fatten them with acorns (Rackham, 1986). In fact denbera is nothing but the way the Saxon called the right of pannage.

1.3 Pannage

A good definition of pannage has been given by Rackham (1980): Pannage is often referred to as the seasonal practice of taking domestic pigs into the woods in autumn to fatten on acorns or beechnuts, before being slaughtered and salted down. However it properly means a payment by the pigs’ owners to the owner of the wood; it was extended to the activity itself and later other activities of pigs.

In the Domesday Book the right of pannage, or running of pigs in the manorial woods, was a valuable privilege. Pigs fed on acorns, beech mast, bracken, ferns, roots, fruits and seeds from a wide range of vegetation (Thornton, 1990).

During the Norman day in the UK the pigs were daily collected and driven to grasslands or to woods according to the season and the villains paid certain dues for their feeding. A very usual payment for pannage was one pig in ten and at Belchamp on the St. Paul’s estates all the pigs were fed in the woods were driven to the hall of the manor to be taxed.

To the king pannage was only a minor bonus whenever there was an acorn crop. At this period, lack of pannage implied that there were no oaks big enough to produce acorns on which pigs might be sufficiently fattened (Rackham, 1986). That was the pig problem with pannage: The acorn crop varied enormously and unpredictably from year to year. In fact surveys valued pannage cum acciderit, “when it happens” (Rackham, 1980).

It is important to differentiate the records of pannage in parks, fields, stubble and even gardens from the regular pannage in woods. The last record of regular pannage in Eastern England appears to be in Hatfield forest in 1446 but the practice still survives in the New forest and possibly the Forest of Dean (Rackham, 1980).

1.4 The decline in the practice

A decline in the practice has been observed in the UK. Under the Norman’s, the period during which the pigs were fed in the woods seems to have been about 6 to 8 weeks in October and in November, the pigs being killed in December. Under the Saxon’s the period stretched from August 29th to the New Year and under the Celts, it extended to January the 15th (Seebohm, 1976).

Rackham (1990) found that Hayley wood, Cambridgeshire, was used for feeding pigs but that this practice had disappeared by 1251 and belonged to the wood’s history.

Some sort of pannage endured in the sixteenth century as it is mentioned that pigs were still brought in the woods for the mast but the period only lasted 6 weeks (Seebohm, 1976). During the seventeenth century, as the woodlands decreased, less was heard of driving the swine out to mast in autumn.

In the eighteenth century Berkshires pigs became very popular. They were said to have the quality of eating “noxious weeds” (Seebohm, 1976).

Pig production changed dramatically in the eighteenth century, with the enclosure of land and the first major increase in human population (Thornton, 1990). In fact the decline is linked to a diminishing woodland resource, progressive land-use intensification and unacceptable damage to trees by the animals (Brownlow, 1992).