1. AbstractThe objective of this case report was to present an abnormal socio-nutri-psychologicalbehaviorortail-biting/chewinginweaned Holstein heifers. Dairy heifers raised under commercial systems are separated from their dams and moved to individual or group housing systems which are different from their natural environment. Cross-suckling and non-nutritive behaviors are common in heifersrearedartificiallyunderintensivesystems,especiallythose with restricted milk feeding programs. The behavior observed herein was different from suckling behavior. In this case, in a groupof60headsHolsteinheifers,therewereatleasttwoorthree heifers that exhibited craving to bite and chew other heifers’ tail. Bloodytail wasthe firstsignthatled searchingaboutitsetiology. Factors including nutritional deficiencies, feed ingredients quality, and other management factors such as stocking density and feedbunkspacewereallchecked.Allnutritionalroutineswereapparentlynormal. High stocking density and inadequate feed bunk spaceseemedtobemajortriggeringfactors.Thisphenomenonhad not been seen before on these herds. This might represent an abnormalmulti-factorialsocial-nutritionalandpsychologicalbehavior in Holstein heifers.

2. CasePresentationandDiscussion Tail-biting occurs relatively more frequently in pigs but is rather rareincattle[1,2].Intwolargedairyfarms(>1000milkingdairy cows) in Tehran (Iran), these cases of tail biting associated with bloodyand woundedtails wereobserved.Inthe firstfarm,two 3- month-oldHolsteinheifersweredetected withbleedingatthe tipof their tails. On the next day, three other new cases with similar signs(woundedbloodytail)wereobserved.Heiferswereseparated andcheckedforanyotherabnormalities.Theappetitewasnormal and the body temperature was within normal range (38-39˚C), as well.Theinjuredtailwasbandagedusinggauzeafterdisinfection byiodinesolution.Afterremovingtheaffectedheifers,thehealthy pen mates were monitored for rooting the problem. Surprisingly, weobservedsomeheifersthatbiteandchewothers’tailstiptothe extent that bleeding occurs. In the second large dairy herd (over 1000 milking dairy cows), a similar scenario was detected, while inthiscase,thebloody-tailheiferswereat6-8monthsofage.Tail injuries and hair loss resulting from biting and chewing of biters are presented in Figure 1. Micronutrientdeficiency(suchaszinc,phosphorous,andiron)has beenproposed as a cause of pica [2, 3]. Pica isdefined as craving for consumption of non-nutritive materials such as ice, clay, hair and other materials. In our case, the herd routine nutritional program was checked out but the ration did not have any profound changesregardingmicronutrientstatus.Asaresult,othermanagementfactorsweremonitored.Nonetheless,nutritionaldeficiencies forindividualheifersmaynotberuledoutasacauseoftheabnor- mal tail biting. Investigating the stocking density and feed bunk space of calves revealed that feed bunk space was not adequate and some calve were not able to feed freely beside other pen mates. None of the invadingheifers wereeatingfeed.Instead,theywere walkingand standing behind the bitten heifers, biting and chewing the other heifers’tails(Please see the video). After movingsome heifers to anotherpen,thestockingdensitywasdecreasedandthisbehavior disappeared. It has been demonstrated that short-term increasesinstockingdensityresultedindecreasedlyingbehaviorandin creasedaggressivesocialbehaviorsatfeedbunkinlactatingdairy cows [4]. Additionally, it can be hypothesized that lower bunk spaceitselfcanlimitnutrientsintakebysomeheifersandmight cause nutrient deficiency. It is important to note that since such behaviors are rarely observed and reported on commercial farms, moreresearchis neededto mechanisticallydescribethisrare phe

3. ConclusionTail-biting/chewingwasobservedinfewweanedHolsteinheifers intwocommerciallargedairyherdsinTehran,Iran.Highstocking density and possibly nutrient deficiency may cause some aggressive social and psychological behaviors in commercial Holstein heifers. It is not clear that such a behavior is specified to one or two heifers or can occur in any heifers during special conditions. Future studies are needed to determine and identify physiological and psychological mechanisms of such a rare phenomenon.

References 1. Rabhi M, et al. Association Between Tail-Biting and Intestinal Microbiota Composition in Pigs. Front. Vet. Sci. 2020; 7: 563762.

2. Millar M, Kenward P. Tail biting in calves. The Vet. Rec. 2015;177(16): 422-423.

3. MiaoD,YoungSL,GoldenCD.Ameta-analysisofpicaandmicronutrient status. Am J Hum Biol. 2015; 27: 84-93.

4. Krawczel PD, Klaiber LB, Butzler RE, Klaiber LM, Dann HM,MooneyCS,etal.Shorttermincreasesinstockingdensityaffectthelyingandsocialbehavior,but notproductivity,oflactatingHolsteindairy cows. J Dairy Sci. 2011; 95: 4298-308

NikkhahA . Tail-BitingandTail-ChewinginWeanedHolsteinHeifers. Annals of Clinical and Medical Case Reports 2022