The new legislative situation raises once again the question which alternatives exist in order to avoid boar taint exist, if piglet castration would be forbidden and fattening of boars would be a common practise. The aim this study was to contrast approaches from the large number of new and elder literatures with the subjects of reducing and eliminating boar taint and to assess the effectiveness of these methods to avoid boar taint. For the first time, these findings were presented in a summarised and concentrated form. After reviewing 857 titles out of the year 1911 up to 2015, 664 sources of literature were chosen from all fields of pig breeding, housing and feeding, application of drugs, meat processing and the answer of consumers give a comprehensive understanding on the term of boar taint and the alternatives of piglet castration. There is no single strategy against boar taint being exposed after this work. There are some approaches possible: the immunocastration that gained acceptance in Australia and Belgium is an animal welfare friendly and in practice feasibly method. But it needs an inspection for boar taint at the slaughter line. The fattening of young boars, supported by Switzerland, could be improved by an optimised housing and feeding strategy, as well as the use of breeding lines for low boar taint. The processing of boar meat to premium products is possible. However, the amount of tainted boar meat coming into processing is still not clarified. It remains to be seen, how Germany will solve the problem of piglet castration.

The new legislative situation raises once again the question which alternatives exist in order to avoid boar taint exist, if piglet castration would be forbidden and fattening of boars would be a common practise. The aim this study was to contrast approaches from the large number of new and elder literatures with the subjects of reducing and eliminating boar taint and to assess the effectiveness of these methods to avoid boar taint. For the first time, these findings were presented in a summarised and concentrated form. After reviewing 857 titles out of the year 1911 up to 2015, 664 sources of literature were chosen from all fields of pig breeding, housing and feeding, application of drugs, meat processing and the answer of consumers give a comprehensive understanding on the term of boar taint and the alternatives of piglet castration. There is no single strategy against boar taint being exposed after this work. There are some approaches possible: the immunocastration that gained acceptance in Australia and Belgium is an animal welfare friendly and in practice feasibly method. But it needs an inspection for boar taint at the slaughter line. The fattening of young boars, supported by Switzerland, could be improved by an optimised housing and feeding strategy, as well as the use of breeding lines for low boar taint. The processing of boar meat to premium products is possible. However, the amount of tainted boar meat coming into processing is still not clarified. It remains to be seen, how Germany will solve the problem of piglet castration.:Table of contents II Abbreviations and Definitions V 1 Introduction 1 2 Alternatives for boar taint reduction or elimination 3 2.1 Breed and genetics 3 2.1.1 Literature review 3 2.1.2 Breeding efforts 6 2.1.2.1 Differences in breeds 6 Breeding differences with view to boar taint perception and androstenone 6 Breeding differences on chromosomal and enzymatic level 9 Breeding differences with view to skatole and indole 10 Breeding differences with view to boar taint compounds 11 2.1.2.2 Heritability 13 Heritability for boar taint in general 13 Heritability for androstenone 14 Heritability for skatole and indole 15 2.1.2.3 Breeding selection 16 Breeding selection for boar taint 16 Breeding selection for androstenone 18 Breeding selection for skatole and indole 19 Using selection against boar taint in breeding programs 19 2.1.3 Genetic selection 20 2.1.3.1 Genetics of enzymes 20 Enzymes and QTL for androstenone 21 Enzymes and QTL for skatole and indole 25 2.1.3.2 Genetics on the chromosomal level 27 Genetic features for lowering androstenone and boar taint levels 29 Genetic features for lowering skatole and indole levels 35 2.2 Sperm-sexing 37 2.3 Killing of newborn male piglets 39 2.4 Fattening of boars 39 2.4.1 Feeding of boars – literature review 39 2.4.2 Feeding strategies 42 2.4.2.1 Energy/nutrient-density/protein diet 42 2.4.2.2 Ad libitum/restrictive feeding/fasting 43 2.4.2.3 Wet feeding/whey/lactose 48 2.4.2.4 RPS - raw potato starch 51 2.4.2.5 FOS - fructooligosaccarides 56 2.4.2.6 NSP- non starch polysaccharides/readily digestible raw fibre/alternative energy – pectin 64 2.4.2.7 Raw protein 68 2.4.2.8 Corn/cereals/plants with cellulose, a NSP 72 2.4.2.9 Garlic 76 2.4.2.10 Bicarbonate/organic acids 76 2.4.2.11 Enzyme/vitamins/trace elements 76 2.4.2.12 Other feedstuffs 76 2.4.2.13 Activated carbon/Tween-60: polyoxyethylene sorbitan monostearate 76 2.4.3 Housing conditions of boars – literature review 80 2.4.4 Housing conditions to avoid boar taint 81 2.4.4.1 Hygiene/fully slatted floor 81 2.4.4.2 Space/employment 84 2.4.4.3 Photoperiod/season/temperature 87 2.4.4.4 Sex composition of pig groups/mixed or single sex group 94 2.4.4.5 Social hierarchy/split marketing/farrow-to-finish system 102 2.4.5 Age and weight of boars 111 2.5 Application of drugs 112 2.5.1 Literature review 112 2.5.2 Down–regulation of the hypothalamic-pituitary-gonadal axis by exogenous hormonal drugs 112 2.5.2.1 Foragynol 113 2.5.2.2 Stilbene/DES 113 2.5.2.3 Estrogens 114 2.5.2.4 Progesterone 114 2.5.2.5 Testosterone and Trenbolone together with Estrogens 114 2.5.2.6 Testosterone 115 2.5.2.7 Gestagens/inhibitors: NTÖ, CMA, CPA, 19-NTA 115 2.5.2.8 GnRH 117 2.5.2.9 pST 118 2.5.3 Inhibitors of metabolism pathways 118 2.5.3.1 3β-HSD 118 2.5.3.2 Progesterone/5α-pregnane-3,20-dione 119 2.5.3.3 5α- reductase and CYP 17 119 2.5.4 Antibiotics 119 2.5.5 Immunocastration 121 2.6 Consumer evaluation 122 2.7 Processing of tainted boar meat 127 2.7.1 Literature review 127 2.7.2 Hanging/chilling 129 2.7.3 Mix/dilution 130 2.7.4 Heating/cold consumption 130 2.7.5 Masking 132 2.7.5.1 Masking (spices, starter cultures, liver tissue) 132 2.7.5.2 Smoking 133 2.7.6 Curing 134 2.7.7 Varieties of processed meat 135 2.7.7.1 Ham 135 2.7.7.2 Bacon 137 2.7.7.3 Salami sausages 137 2.7.7.4 Sausages 138 2.7.8 Other processing methods 139 3 Discussion 140 3.1 Breed and genetics 140 3.1.1 Breed difference 140 3.1.2 Heritability 141 3.1.3 Breeding selection 141 3.1.4 Genetics of enzymes 142 3.1.5 Genetics on chromosomal level 143 3.2 Fattening of boars 144 3.2.1 Feeding 144 3.2.2 Housing 147 3.3 Application of drugs 149 3.4 Processing of boar meat 151 4 Conclusion 154 4.1 Breed and genetics 154 4.2 Fattening of boars 155 4.2.1 Feeding 155 4.2.2 Housing 155 4.3 Application of drugs 156 4.4 Processing of boar meat 156 5 Summary 157 6 Zusammenfassung 159 7 Annexe 161 8 List of tables 225 9 List of figures 226 10 References 227 Acknowledgment 272