{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T21:57:42Z","timestamp":1787695062886,"version":"build-2784847793"},"reference-count":51,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2022,8,24]],"date-time":"2022-08-24T00:00:00Z","timestamp":1661299200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004329","name":"Slovenian Research Agency","doi-asserted-by":"publisher","award":["L4-5521"],"award-info":[{"award-number":["L4-5521"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Slovenian Research Agency","doi-asserted-by":"publisher","award":["P4-0133"],"award-info":[{"award-number":["P4-0133"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Slovenian Research Agency","doi-asserted-by":"publisher","award":["P4-0053"],"award-info":[{"award-number":["P4-0053"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Slovenian Research Agency","doi-asserted-by":"publisher","award":["P2-0041"],"award-info":[{"award-number":["P2-0041"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Ministry of Agriculture and the Environment of the Republic of Slovenia","award":["L4-5521"],"award-info":[{"award-number":["L4-5521"]}]},{"name":"Ministry of Agriculture and the Environment of the Republic of Slovenia","award":["P4-0133"],"award-info":[{"award-number":["P4-0133"]}]},{"name":"Ministry of Agriculture and the Environment of the Republic of Slovenia","award":["P4-0053"],"award-info":[{"award-number":["P4-0053"]}]},{"name":"Ministry of Agriculture and the Environment of the Republic of Slovenia","award":["P2-0041"],"award-info":[{"award-number":["P2-0041"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>The ingestion of hydrolysable tannins as a potential nutrient to reduce boar odor in entire males results in the significant enlargement of parotid glands (parotidomegaly). The objective of this study was to characterize the effects of different levels of hydrolysable tannins in the diet of fattening boars (n = 24) on salivary gland morphology and proline-rich protein (PRP) expression at the histological level. Four treatment groups of pigs (n = 6 per group) were fed either a control (T0) or experimental diet, where the T0 diet was supplemented with 1% (T1), 2% (T2), or 3% (T3) of the hydrolysable tannin-rich extract Farmatan\u00ae. After slaughter, the parotid and mandibular glands of the experimental pigs were harvested and dissected for staining using Goldner\u2019s Trichrome method, and immunohistochemical studies with antibodies against PRPs. Morphometric analysis was performed on microtome sections of both salivary glands, to measure the acinar area, the lobular area, the area of the secretory ductal cells, and the sizes of glandular cells and their nuclei. Histological assessment revealed that significant parotidomegaly was only present in the T3 group, based on the presence of larger glandular lobules, acinar areas, and their higher nucleus to cytoplasm ratio. The immunohistochemical method, supported by color intensity measurements, indicated significant increases in basic PRPs (PRB2) in the T3 and acidic PRPs (PRH1\/2) in the T1 groups. Tannin supplementation did not affect the histo-morphological properties of the mandibular gland. This study confirms that pigs can adapt to a tannin-rich diet by making structural changes in their parotid salivary gland, indicating its higher functional activity.<\/jats:p>","DOI":"10.3390\/ani12172171","type":"journal-article","created":{"date-parts":[[2022,8,24]],"date-time":"2022-08-24T21:03:51Z","timestamp":1661375031000},"page":"2171","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Salivary Gland Adaptation to Dietary Inclusion of Hydrolysable Tannins in Boars"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7560-5341","authenticated-orcid":false,"given":"Ma\u0161a","family":"Mavri","sequence":"first","affiliation":[{"name":"Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0231-126X","authenticated-orcid":false,"given":"Marjeta","family":"\u010candek-Potokar","sequence":"additional","affiliation":[{"name":"Animal Production Department, Agricultural Institute of Slovenia, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gregor","family":"Fazarinc","sequence":"additional","affiliation":[{"name":"Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8252-8022","authenticated-orcid":false,"given":"Martin","family":"\u0160krlep","sequence":"additional","affiliation":[{"name":"Animal Production Department, Agricultural Institute of Slovenia, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2009-4898","authenticated-orcid":false,"given":"Catrin S.","family":"Rutland","sequence":"additional","affiliation":[{"name":"School of Veterinary Medicine and Science, Faculty of Medicine and Health Science, University of Nottingham, Leicestershire LE12 5RD, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5140-3358","authenticated-orcid":false,"given":"Bo\u017eidar","family":"Poto\u010dnik","sequence":"additional","affiliation":[{"name":"Institute of Computer Science, Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7198-8728","authenticated-orcid":false,"given":"Nina","family":"Batorek-Luka\u010d","sequence":"additional","affiliation":[{"name":"Animal Production Department, Agricultural Institute of Slovenia, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Valentina","family":"Kubale","sequence":"additional","affiliation":[{"name":"Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,8,24]]},"reference":[{"key":"ref_1","first-page":"1261","article-title":"Dose-Response Relationship between Dietary Polyphenols from Acorns and Parotid Gland Hypertrophy in Pigs","volume":"3","author":"Cappai","year":"2012","journal-title":"Food Nutr. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1149","DOI":"10.1007\/s10886-006-9077-0","article-title":"Salivary proteins as a defense against dietary tannins","volume":"32","author":"Shimada","year":"2006","journal-title":"J. Chem. Ecol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2010","DOI":"10.1002\/jsfa.2577","article-title":"Unravelling the conundrum of tannins in animal nutrition and health","volume":"86","year":"2006","journal-title":"J. Sci. Food Agric."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"539","DOI":"10.22358\/jafs\/66319\/2010","article-title":"The effect of grain polyphenols and the addition of vitamin E to diets enriched with \u03b1-linolenic acid on the antioxidant status of pigs","volume":"19","author":"Flis","year":"2010","journal-title":"J. Anim. Feed Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1080\/1828051X.2018.1503043","article-title":"The effect of polyphenols on the performance and antioxidant status of sows and piglets","volume":"18","author":"Antoszkiewicz","year":"2019","journal-title":"Ital. J. Anim. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1016\/j.aninu.2015.11.002","article-title":"Effects of catechins on litter size, reproductive performance and antioxidative status in gestating sows","volume":"1","author":"Fan","year":"2015","journal-title":"Anim. Nutr."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.tox.2006.10.001","article-title":"The effect of plant phenols on the expression and activity of phorbol ester-induced PKC in mouse epidermis","volume":"230","author":"Szaefer","year":"2007","journal-title":"Toxicology"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/S1383-5718(98)00130-2","article-title":"Antimutagenicity of hydrolyzable tannins from Terminalia chebula in Salmonella typhimurium","volume":"419","author":"Kaur","year":"1998","journal-title":"Mutat. Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0278-6915(99)00114-3","article-title":"Mutagenicity and antimutagenicity studies of tannic acid and its related compounds","volume":"38","author":"Chen","year":"2000","journal-title":"Food Chem. Toxicol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1007\/BF02877259","article-title":"Two types of antimutagenic effects of gallic and tannic acids towards N-nitroso-compounds-induced mutagenicity in the Ames Salmonella assay","volume":"32","author":"Gichner","year":"1987","journal-title":"Folia Microbiol."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Youness, A.R., Kamel, R., Elkasabgy, A.N., Shao, P., and Farag, A.M. (2021). Recent Advances in Tannic Acid (Gallotannin) Anticancer Activities and Drug Delivery Systems for Efficacy Improvement; A Comprehensive Review. Molecules, 26.","DOI":"10.3390\/molecules26051486"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1007\/s40495-020-00211-y","article-title":"Tannic Acid: Specific Form of Tannins in Cancer Chemoprevention and Therapy-Old and New Applications","volume":"6","author":"Szaefer","year":"2020","journal-title":"Curr. Pharmacol. Rep."},{"key":"ref_13","first-page":"87","article-title":"Tannic acid prevents post-weaning diarrhea by improving intestinal barrier integrity and function in weaned piglets","volume":"11","author":"Yu","year":"2020","journal-title":"J. Anim. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1017\/S1751731119002143","article-title":"Invited review: Tannins as a potential alternative to antibiotics to prevent coliform diarrhea in weaned pigs","volume":"14","author":"Girard","year":"2020","journal-title":"Animal"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0378-8741(01)00277-X","article-title":"Gastric antiulcer effect of Rhizophora mangle L.","volume":"77","author":"Perera","year":"2001","journal-title":"J. Ethnopharmacol"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1007\/s10787-019-00637-x","article-title":"In vivo antiulcer activity, phytochemical exploration, and molecular modelling of the polyphenolic-rich fraction of Crepis sancta extract","volume":"28","author":"Ebada","year":"2020","journal-title":"Inflammopharmacology"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"152970","DOI":"10.1016\/j.phymed.2019.152970","article-title":"Antiulcer activity of Cyperus alternifolius in relation to its UPLC-MS metabolite fingerprint: A mechanistic study","volume":"62","author":"Farrag","year":"2019","journal-title":"Phytomedicine"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"432","DOI":"10.1080\/15569543.2019.1662813","article-title":"Health effects, sources, utilization and safety of tannins: A critical review","volume":"40","author":"Sharma","year":"2021","journal-title":"Toxin Rev."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1571","DOI":"10.5713\/ajas.2014.14204","article-title":"Assessment of Anti-nutritive Activity of Tannins in Tea By-products Based on In vitro Rumen Fermentation","volume":"27","author":"Kondo","year":"2014","journal-title":"Asian-Australas. J. Anim. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"287","DOI":"10.1016\/j.freeradbiomed.2004.04.034","article-title":"Potential toxicity of flavonoids and other dietary phenolics: Significance for their chemopreventive and anticancer properties","volume":"37","author":"Galati","year":"2004","journal-title":"Free Radic. Biol. Med."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"168","DOI":"10.1016\/S0924-2244(98)00028-4","article-title":"Are tannins a double-edged sword in biology and health?","volume":"9","author":"Chung","year":"1998","journal-title":"Trends Food Sci. Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"100064","DOI":"10.1016\/j.animal.2020.100064","article-title":"Review: Chestnut and quebracho tannins in pig nutrition: The effects on performance and intestinal health","volume":"15","author":"Caprarulo","year":"2021","journal-title":"Animal"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1016\/j.livsci.2010.05.019","article-title":"Feed conversion rate and estimated energy balance of free grazing Iberian pigs","volume":"132","year":"2010","journal-title":"Livest. Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"335","DOI":"10.1086\/284065","article-title":"Tannins: Does Structure Determine Function? An Ecological Perspective","volume":"121","author":"Zucker","year":"1983","journal-title":"Am. Nat."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1063","DOI":"10.1016\/S0278-6915(01)00054-0","article-title":"Subchronic toxicity study of gallic acid by oral administration in F344 rats","volume":"39","author":"Niho","year":"2001","journal-title":"Food Chem. Toxicol."},{"key":"ref_26","first-page":"1215","article-title":"Acorn poisoning in a cow and a sheep","volume":"147","author":"Fowler","year":"1965","journal-title":"J. Am. Vet. Med. Assoc."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"430","DOI":"10.1016\/j.pbi.2005.05.009","article-title":"Plant secondary metabolites and vertebrate herbivores\u2014From physiological regulation to ecosystem function","volume":"8","author":"Foley","year":"2005","journal-title":"Curr. Opin. Plant Biol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"184","DOI":"10.1177\/154411130201300208","article-title":"Interaction of plant polyphenols with salivary proteins","volume":"13","author":"Bennick","year":"2002","journal-title":"Crit. Rev. Oral Biol. Med."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3423","DOI":"10.1046\/j.1432-1327.2001.02241.x","article-title":"Proteolytic processing of a human salivary proline-rich protein precursor by proprotein convertases","volume":"268","author":"Chan","year":"2001","journal-title":"Eur. J. Biochem."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"838","DOI":"10.1021\/jf990820z","article-title":"Binding affinity of hydrolyzable tannins to parotid saliva and to proline-rich proteins derived from it","volume":"48","author":"Bacon","year":"2000","journal-title":"J. Agric. Food Chem."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1042\/bj2630497","article-title":"Primary structure and possible origin of the non-glycosylated basic proline-rich protein of human submandibular\/sublingual saliva","volume":"263","author":"Robinson","year":"1989","journal-title":"Biochem. J."},{"key":"ref_32","unstructured":"Pinna, W., Cappai, M.G., Moniello, G., and Nieddu, G. (2007, January 1\u20133). Tannins concentration and ultrastructural peculiarities of starch granules in acorns of Quercus ilex L.; Quercus Pubescens Willd. and Quercus suber L.. Proceedings of the 11th Congress of the European Society of Veterinary and Comparative Nutrition, Leipzig, Germany."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1016\/j.livsci.2010.06.136","article-title":"Effect of whole acorns (Quercus pubescens) shred based diet on parotid gland in growing pigs in relation to tannins","volume":"134","author":"Cappai","year":"2010","journal-title":"Livest. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1007\/s00114-005-0040-7","article-title":"Interaction of gut microflora with tannins in feeds","volume":"92","author":"Goel","year":"2005","journal-title":"Naturwissenschaften"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1080\/17450390903461584","article-title":"Effect of tannins on growth performance and intestinal ecosystem in weaned piglets","volume":"64","author":"Biagia","year":"2010","journal-title":"Arch. Anim. Nutr."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1016\/j.tvjl.2015.02.012","article-title":"Hydrolysable tannin fed to entire male pigs affects intestinal production, tissue deposition and hepatic clearance of skatole","volume":"204","author":"Zamaratskaia","year":"2015","journal-title":"Vet. J."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"378","DOI":"10.1080\/1745039X.2016.1206735","article-title":"Effect of hydrolysable tannins on intestinal morphology, proliferation and apoptosis in entire male pigs","volume":"70","author":"Kubale","year":"2016","journal-title":"Arch. Anim. Nutr."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1617","DOI":"10.1017\/S1751731116002597","article-title":"Hydrolysable tannin-based diet rich in gallotannins has a minimal impact on pig performance but significantly reduces salivary and bulbourethral gland size","volume":"11","author":"Bee","year":"2017","journal-title":"Animal"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1016\/j.meatsci.2017.06.012","article-title":"Supplementing entire male pig diet with hydrolysable tannins: Effect on carcass traits, meat quality and oxidative stability","volume":"133","author":"Rezar","year":"2017","journal-title":"Meat Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"447","DOI":"10.1002\/aja.1001520402","article-title":"Histology and ultrastructure of the pig parotid gland","volume":"152","author":"Boshell","year":"1978","journal-title":"Am. J. Anat."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1016\/j.livsci.2014.06.011","article-title":"The bilateral parotidomegaly (hypertrophy) induced by acorn consumption in pigs is dependent on individual\u2019s age but not on intake duration","volume":"167","author":"Cappai","year":"2014","journal-title":"Livest. Sci."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"376","DOI":"10.1007\/s10886-007-9413-z","article-title":"Salivary amylase induction by tannin-enriched diets as a possible countermeasure against tannins","volume":"34","author":"Lamy","year":"2008","journal-title":"J. Chem. Ecol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1016","DOI":"10.1177\/0192623313512429","article-title":"Adaptive parotid gland hypertrophy induced by dietary treatment of GSE in rats","volume":"42","author":"Inoue","year":"2014","journal-title":"Toxicol. Pathol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"105077","DOI":"10.1016\/j.archoralbio.2021.105077","article-title":"Structure of the parotid gland in natural infection by Leishmania infantum in Canis familiaris","volume":"124","author":"Fonseca","year":"2021","journal-title":"Arch. Oral Biol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"316","DOI":"10.1016\/j.livsci.2013.05.003","article-title":"Pigs use endogenous proline to cope with acorn (Quercus pubescens Willd.) combined diets high in hydrolysable tannins","volume":"155","author":"Cappai","year":"2013","journal-title":"Livest. Sci."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1146\/annurev.nu.07.070187.002231","article-title":"Dietary tannins and salivary proline-rich proteins: Interactions, induction, and defense mechanisms","volume":"7","author":"Mehansho","year":"1987","journal-title":"Annu. Rev. Nutr."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1007\/BF02033455","article-title":"Salivary proline-rich proteins in mammals: Roles in oral homeostasis and counteracting dietary tannin","volume":"21","author":"McArthur","year":"1995","journal-title":"J. Chem. Ecol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1016\/j.legalmed.2014.12.011","article-title":"Detection of proline-rich proteins for the identification of saliva by enzyme-linked immunosorbent assay","volume":"17","author":"Igoh","year":"2015","journal-title":"Leg. Med."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"495","DOI":"10.1177\/10454411930040033401","article-title":"Salivary proline-rich proteins: Biochemistry, molecular biology, and regulation of expression","volume":"4","author":"Carlson","year":"1993","journal-title":"Crit. Rev. Oral Biol. Med."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"4418","DOI":"10.1016\/S0021-9258(18)89281-X","article-title":"Induction of proline-rich glycoprotein synthesis in mouse salivary glands by isoproterenol and by tannins","volume":"260","author":"Mehansho","year":"1985","journal-title":"J. Biol. Chem."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"899","DOI":"10.1016\/S0021-9258(19)75871-2","article-title":"Induction of tissue-specific proline-rich protein multigene families in rat and mouse parotid glands by isoproterenol. Unusual strain differences of proline-rich protein mRNAs","volume":"262","author":"Ann","year":"1987","journal-title":"J. Biol. Chem."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/12\/17\/2171\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:14:39Z","timestamp":1760141679000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/12\/17\/2171"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,8,24]]},"references-count":51,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2022,9]]}},"alternative-id":["ani12172171"],"URL":"https:\/\/doi.org\/10.3390\/ani12172171","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,8,24]]}}}