Bunching behaviour: Signals stress in dairy herd

T. K. S. Rao¹, Archita Singh², H. P. Thakor³, Shashipal⁴ Rajesh Kumar⁵ Hemant Kumar⁶

College of Veterinary and Animal Sciences, Kishanganj

Bihar Animal Sciences University, Patna

Bunching behaviour in cattle is natural cow instinct also known as protective grouping, is a common behaviour where cattle form stable permanent groups in response to stressors or threats or discomfort for shared interests (Chopra et al., 2024). Cattle group together even though; the bunching may be in less comfortable place of the barn which further worsen the situation. Efforts to disperse the assemblage are likely fail that may cause additional stress to animals and also the attendants.  Stressors for same include heat stress (Erbez et al., 2012), biting flies, lack of fresh air (poor ventilation) or even the presence of strange person. Cow bunching or herding together also associated with social dynamics of herd. Cow housed indoor moving away from side wall and congregating at centre at middle of barn. It is also considered as fresh air seeking behaviour.  This behaviour Common north south as compared to east-west oriented barn.   

Expression of bunching behaviour in cows in a slightly darker area of the barn with slow air flow during hot conditions. Bunching signal heat stress (high temperature humidity index THI), biting flies or insects, lack of fresh air and escaping of light. Cows congregate together in barn with ample free space remain unutilized. It is often difficult to determine the cause of bunching in barn.  Drinking water reduce heat load of body through cooling of the digestive system, respiration and sweating. Cow consume about 50% of daily water intake within an hour of milking, therefore offering fresh water at the exit of milking parlour is a very scientific approach.

Bunching behaviour offers social interactions among the member of the herd. It is actually response of cow to stress in order to share interest in resources such as feeding and watering areas also. It occurs at higher ambient temperature in order to share fly load or to seek shade and protection from direct sun light and heat stress.

Bunching behaviour estimated by spatial measures such as mean herd intercow distance (ICD) and mean herd nearest neighbour distance (NND). If ambient temperature is above 20^oC, herd expressed higher bunching behaviour with reduced ICD and NND.

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^1,4,5 Associate Professor COVAS Kishanganj, ⁶Assistant Professor COVAS Kishanganj ²Assistant Professor BUAT Banda, ³Veterinary Officer KU Gujarat

Herd showing bunching behaviour in cows

Cows always need space: Cows always need space and is always essential, however, bunching behaviourcreate unused space and thus create stress to the animals and herd.  

Cows walk and stand with their head down and they need space for their head to move up and down freely. This also allow them to find safe foot placement, enables them to avoid dominant cow and give them room to respond to pain if animal self-isolate themselves. If heads of cows are up in barn it might be due to lack of sufficient space or they are too tightly packed.

Negative impacts of bunching behaviours in cattle: Negative effect of bunching behaviour in cows include

1. Reduced feed intake and rumination: Feeding pattern deviated from normal due to bunching, moreover, cow spent more time in cud chewing.
2. Increased incidence of limping/ lameness: While expressing the bunching behaviour decreaseslying timewhich further intensify the lameness situation.   
3. Reduced milk production: Bunching behaviour additionally decrease feed intake and its proper utilization which further worsen the production status of animals.
4. Increased heat load: Cows in bunch or close group are likely to experience the heat stress. Therefore, while resting cow during summer maintains a distance between the individual cows while in winter they maintain close sitting between the bunching members.
5. Muddy areas: Bunching on pasture can create muddy areas, increases risk of mastitis to cows and superficial loss of soil layer while mud formation.  
6. Hygienic issues: Bunching behaviour sometimes splash manure on udders, potentially may infect udder to create mastitis.
7. Compromised welfare status: Bunching behaviour symbolize a stress and discomfort, potentially impacting overall wellbeing of the animals.

Management planning against the bunching behaviour in cattle:

1. Heat abatement: Using shades, fans and soakers which help cow to cool down during stress hours.
2. Fly control: Sting of insect cause grouping of cattle i.e., bunching behaviour (Ashmawy et al., 2019). Mosquito net, smoke can be utilized to control insects in barn facilities. Observing the behaviour of cattle help to determine which type of flies may create a problem i.e., stable or face fly. Face fly congregate around eyes and house fly concentrated around nostril and mouths. Cleaning of spilled feed, facilities and reducing breeding area for fly such as wet areas. Fly repellent spray, fly tags may be used along with regular removal of manure promptly reduce heat load and fly population in barn.
3. Ventilation & cooling system: Provision of cross ventilation and fresh air may reduce stress and expression of bunching behaviour. Mechanically ventilated barn is also a very good management option.
4. Water and feed access: Access to plenty of fresh water is essentialregardless of production system, as water cools the body after entry into digestive and respiratory system and finally inform of sweating. Moreover, feed is essential for offering energy to the  
5. Direct sunlight exposure: Direct exposure of sunlight needs to avoided to control bunching behaviour in cattle. Shed cloth may be used from lit side to control light entry.
6. Addressing stray voltage/ mild electric current: Stary voltage is one of the potential stressors that can trigger this behaviour. Actually, stray voltage creates discomfort and some times pain leading cow to seek out areas where they perceive less electrical stimulus. This low intensity of electric current not perceive by human being; cows are comparatively more sensitive and can feel it clearly. Behavioural changes with respect to stary voltage include hesitation to enter the place, rapid exit from place, restlessness or nervousness, avoidance to water and feed source also.  
7. Increased lying time: While bunching cows spend less time lying down to rest and ruminate and more time in standing which is detrimental to health and welfare of cattle. Prolong standing time due to expression of bunching behaviour increased incidence of limping (Blackie et al., 2011) reduced feed intake and ultimately reduced milk production.  Management practice to increase lying time include reducing heat stress, fly problems and improving ventilation.
8. Managing social dynamics: Bunching behaviour affects social dynamics within the herd. Younger or recessive animals may bunch together for protection against dominant individuals. Cows may bunch to facilitate social interaction like grooming or simply to be closed to familiar herd. Moreover, regularly observing social interactions can help identify and address intimidation or aggressive behaviour. 
9. Ensuring sufficient space per cow: Pen design size and layout may be modified to allow more space per cow.
10. Monitoring cow behaviour: Regular visit through the barn particularly during afternoon hours to identify area of expression of bunching behaviour.

Heat stress: Results in expression of both hormonal and behavioural changes-

1. Hormonal changes: It include rise in concentration of GnRH, ACTH, Glucocorticoids and progesterone & decrease in prolactin, oxytocin, TSH, estrogen, T3, T4 etc.
2. Behavioural changes: It covers an increase in visit of water trough, no. of steps or speed, agonistic behaviour, difficult breathing, however, there is decrease in feed intake and resting/lying time.

Important signals expression in cow: Bunching behaviour also known as clustering with their head towards the centre and tail outwards i.e., head to centre and tail to outside. Increased proximity. Increased restlessness, movement towards shelter. Increased standing time, reduced inter-cow distance, seeking shade or ventilation, increased activity near water bodies

Concluding notes:

Cow bunching behaviour is a complex natural behaviour response to stress that affect welfare and management of cattle can be intervened by addressing issues creating stress to the cattle like rise in standing time, manure splashing and stress hormone release. This result in risk of lameness, reduced feed intake, rumination and reduction in milk production. Understanding behaviour is crucial to observe stress and bunching. Microclimate, electromagnetic waves also trigger the behaviour. Other factors include pests, feed, water also some time affect expression of bunching behaviour.   

Heat abatement strategies, plenty of fresh air, water (8 linear metre water/100 cows), control of fly insects along with reduction in variation of light.

Raised head: Lack of sufficient space or tight pack situation in herd- Bunching behaviour

References:

1. Ashmawy, W. R. E., Williams, D. R., Gerry, A. C., Champagne, J. D., Lehenbauer, et al. 2019. Risk factors affecting dairy cattle protective grouping behaviour, commonly known as bunching against Stomoxys calcitrans on California dairies. PLOS ONE 14 (11):e0224987.doi:10.1371/journal.pone.0224987.
2. Blackie, N., Amory, J., Bleach, E. et al. 2011. The effect of lameness on lying behaviour of zero grazed Holstein dairy cattle. Applied Animal Behaviour Science, 134: 85-91.
3. Chopra, K., Hofges, H. R., Barker, Z. E., Thurman, A., Bartlett, D. et al. 2024. Bunching behaviour in housed dairy cows at higher ambient temperature. Journal of Dairy Science, 107 (4): 2406-2425.
4. Chopra, K., Hodges, H. R., Barker, Z. E. et al. 2020. Proximity interactions in a permanently housed dairy herd: Network structure, consistency and individual differences. Frontier Veterinary Science, 7: 583715.
5. Erbez, M., Boe, K. E., Falta, D. et al. 2012. Crowding of dairy cows in a cubicle barn during the hot summer months. Arch. Tierzucht, 55: 325-331.