Is frequent handling with reinforcement effective in improving management practices for feedlot heifers?

Introduction

The human-animal relationship can be facilitated when we select more docile animals, since they are easier to handle and less stressed than animals with a worse temperament. Another way to minimize animals' reactivity to management is through learning methods such as habituation and operant conditioning with positive reinforcement (Rueda et al., 2015Rueda PM, Sant’Anna AC, Valente TS, da Costa MJP, 2015. Impact of the temperament of Nellore cows on the quality of handling and pregnancy rates in fixed-time artificial insemination. Livest Sci 177: 189-195. https://doi.org/10.1016/j.livsci.2015.04.021
).

Animals that habituate more easily to management are those that show less agitated behavior throughout handling and weighing, have lower carcass losses due to a reduced incidence of bruises, as well as higher weight gains (Tulloh, 1961Tulloh NM, 1961. Behavior of cattle in yards. II. A study of temperament. Anim Behav 9(1-2): 25-30. https://doi.org/10.1016/0003-3472(61)90046-X
; Voisinet et al., 1997Voisinet BD, Grandin T, O’Connor SF, Tatum JD, Deesing MJ, 1997. Bos Indicus-cross feedlot cattle with excitable temperaments have tougher meat and a higher incidence of borderline dark cutters. Meat Sci 46(4): 361-377. https://doi.org/10.1016/S0309-1740(97)00031-4
; King et al., 2006King DA, Pfeiffer CS, Randel RD, Welsh Jr TH, Oliphint RA, Baird BE, Curley Jr KO, Vann RC, Hale DS, Savell JW, 2006. Influence of animal temperament and stress responsiveness on the carcass quality and beef tenderness of feedlot cattle. Meat Sci 74(3): 546-556. https://doi.org/10.1016/j.meatsci.2006.05.004
; Soares-Gellatly, 2015Soares-Gellatly DR, Cyrillo JNSG, Sant'anna, Valente, Schwartzkpf-Genswein K, Paranhos-Da-Costa MJR, 2020. Flight speed as an indicator of Zebu cattle growth performance and suitability to the feedlot environment. Anim Produc Sci 60(4): 560-566. https://doi.org/10.1071/AN18785
).

Conditioning is a learning process in which an animal's behavior is influenced by an environmental stimulus. Operant conditioning does not rely on previous stimuli; rather, it depends on the consequences of the behaviour (Skinner, 1938Skinner BF, 1938. The behavior of Organisms: An Experimental Analysis. Appleton-Century, New York. 460 pp.
). Operant conditioning is a two-way process in which the behavior affects the environment, and the environment shapes the behaviour (Gottlieb, 2009Gottlieb G, 2009. Individual development and evolution: The genesis of novel behavior. Taylor & Francis, UK. 248 pp. https://doi.org/10.4324/9781410604422
). Positive reinforcement is an effective way to shape it (Akpan, 2020Akpan B, 2020. Classical and Operant Conditioning-Ivan Pavlov; Burrhus Skinner. In: Science education in theory and practice: an introductory guide to learning theory; Akpan B, Kennedy TJ (eds.). pp: 71-84. Springer, Champaing.
).

The farming environment may present several potentially stress-inducing factors that can influence animal reactivity (Bourguet et al., 2010Bourguet C, Deiss V, Gobert M, Durand D, Boissy A, Terlouw EMC, 2010. Characterising the emotional reactivity of cows to understand and predict their stress reactions to the slaughter procedure. Appl Anim Behav Sci 125: 9-21. https://doi.org/10.1016/j.applanim.2010.03.008
). The use of frequently handling with positive reinforcement has been described in the literature as efficient in reducing reactivity, lowering blood cortisol concentrations, and greater sexual precocity and pregnancy rate in heifers (Cooke et al., 2009aCooke RF, Arthington JD, Araujo DB, Lamb GC, 2009a Effects of acclimation to human interaction on performance, temperament, physiological responses, and pregnancy rates of Brahman-crossbred cows. J Anim Sci 87: 4125-4132. https://doi.org/10.2527/jas.2009-2021
; Cooke et al., 2009bCooke RF, Arthington JD, Austin BR, Yelich JV, 2009b. Effects of acclimation to handling on performance, reproductive, and physiological responses of Brahman-crossbred heifers. J Anim Sci 87: 3403-3412. https://doi.org/10.2527/jas.2009-1910
; Rueda et al., 2015Rueda PM, Sant’Anna AC, Valente TS, da Costa MJP, 2015. Impact of the temperament of Nellore cows on the quality of handling and pregnancy rates in fixed-time artificial insemination. Livest Sci 177: 189-195. https://doi.org/10.1016/j.livsci.2015.04.021
). Positive stimuli can cause a reduction in the surface temperature of regions such as the nose of humans and muzzle of animals, therefore being an indicator of the emotional state of animals (Proctor & Carder, 2016Proctor H, Carder G, 2016. Can changes in nasal temperature be used as an indicator of emotional state in cows? Appl Anim Behav Sci 184:1-6. https://doi.org/10.1016/j.applanim.2016.07.013
; Cruz-Albarran et al., 2017Cruz-Albarran IA, Benitez-Rangel JP, Osornio-Rios RA, Morales-Hernandez LA, 2017. Human emotions detection based on a smart-thermal system of thermographic images. Infrared Phys Techn 81:250-61. https://doi.org/10.1016/j.infrared.2017.01.002
).

The emotional state is associated with changes in skin blood flow in the facial region; thus, facial temperature can increase or decrease under the control of the autonomic nervous system (Chotard et al., 2018Chotard H, Ioannou S, Davila-Ross M, 2018. Infrared thermal imaging: Positive and negative emotions modify the skin temperatures of monkey and ape faces. Amer J Primatol 80(5): e22863. http://doi.org/10.1002/ajp.22863
), which are closely related to emotion-based behavioral responses (Travain & Valsecchi, 2021Travain T, Valsecchi P, 2021. Infrared thermography in the study of animals’ emotional responses: A critical review. Animals 11(9): 2510. https://doi.org/10.3390/ani11092510
). There are already results about changes in nasal temperature in cows, related to positive emotional states (Proctor & Carder, 2014Proctor HS, Carder G, 2014. Nasal temperatures in dairy cows are influenced by positive emotional state. Physiol Behav 138:340-4. http://doi.org/10.1016/j.physbeh.2014.11.011
). However, few studies have been conducted on surface temperature changes in beef cattle (Stewart et al., 2008Stewart M, Schaefer A, Haley D, Colyn J, Cook N, Stafford K, Webster J, 2008. Infrared thermography as a non-invasive method for detecting fear-related responses of cattle to handling procedures. Anim Welf 17(4): 387-393. http://doi.org/10.1017/S0962728600027895
; Lees et al., 2018Lees A, Lea J, Salvin H, Café L, Colditz I, Lee C, 2018. Relationship between rectal temperature and vaginal temperature in grazing Bos taurus heifers. Animals 8(9): 156. https://doi.org/10.3390/ani8090156
; Leeset al., 2020Lees AM, Salvin HE, Colditz I, Lee C, 2020. The influence of temperament on body temperature response to handling in Angus cattle. Animals 10(1): 172. https://doi.org/10.3390/ani10010172
), mainly related to animal handling and facial surface changes related to handling stress, and not as a result of anticipation of positive reinforcement. Thus, this study aimed to evaluate the frequent handling with positive reinforcement as a way to minimize the stress caused to animals by handling and human-animal contact, with the possibility of a decrease in conduction time during routine handling, with evaluation of emotions by infrared thermography.

Material and methods

Local and facilities

 ⌅

The experiment was conducted at the Laboratório de Biometeorologia e Etologia (LABE) of the Faculdade de Zootecnia e Engenharia de Alimentos, University of São Paulo, Fernando Costa Campus, located in the city of Pirassununga, São Paulo, at 21º57'13" south latitude and 47º27'07" west longitude, with an altitude of 606 m. This study was approved by the Ethics Committee on Animal Use (CEUA/FZEA; number 210718052).

The experimental confinement area was composed of 10 paddocks, with an area of 800 m² each, with access to artificial shade, with 80% protection from solar radiation, at 6 m² per animal, 16 linear meters of concrete trough, with 1.3 to 1.4 m of trough per animal, avoiding excessive trough disputes and with a drinking fountain with easy access, activated by automatic float.

The handling facility had a 5m curved chute, with closed walls, a squeeze chute, a scale and a wide and long corridor after the exit (Figure 1).

Figure 1.  Handling facility for beef cattle used in the study. Not in scale.

Animals and handling

 ⌅

The study utilised 90 confined heifers from commercial crossbreeding of Nellore heifers and Angus bulls, with an average age of 10 months. The animals were randomly divided into 8 initial lots, 6 lots with 11 animals each, and 2 lots with 12 animals, with an initial average weight of 261.2 ± 18.46 Kg. The animals were then divided into two treatment groups composed of four lots each: the frequent handling group and the control group.

Animals were reared in a pasture system with mineral protein supplementation at the farm of origin. The animals remained in an adaptation period for 15 d, to become used to the diet, where only corn silage and water were provided ad libitum, and the facilities, including handlers and the feedlot. After the adaptation period, the animals were fed an initial diet comprising corn silage and concentrate (40/60).

After the adaptation period to the diet and the facilities, the frequent handling animals were moved on foot to the handling facility every 10 days for a period of 16 weeks. The average distance walked by the animals was 220 m, with four lots, two from each treatment, walking a distance of 180 m, and four lots, two from each treatment, walking 260 m (Figure 2). The animals were driven in a calm manner, one lot at a time, using a mounted horse as a pointer/leader, and with previously trained people moving them at a steady pace. Once in the handling facility, the animals were moved one by one in line, by group through the chute, squeeze chute and scale, without restraint, and at the exit to the management corridor, where they received the reinforcement. Access to the corn meal reward was offered for 15 min in plastic troughs, with a minimum distance of 3 m between one trough and another, and with linear space that allowed all animals to eat at the same time without dispute. The lots were arranged in such a way that the average distance walked was the same between treatments.

Figure 2.  Description of the path taken by animals during the conditioning process. Adapted from Google Earth.

Measurements

 ⌅

To evaluate the effectiveness of the frequent handling of the animals to improve daily management, we used the distance to be walked by the animals during the trajectory from the feedlot pen to the handling facility, and the time, determined by a digital stopwatch, in which each lot took to cover the predetermined distance.

Every month, during a four-month experimental period, animals were weighted and data was collected. When the animals reached the handling facility, they entered a chute of 5 m with closed sidewalls, where the respiratory rate was measured. After a sliding door, they entered the squeeze chute and were immobilized for less than 120 s to evaluate rectal temperature and thermographic images. When released from the squeeze chute, they walked through the scale and stayed less than 30 s to assign their reactivity score. The door from the scale provides access to a 2 m wide corridor, 15 m long, where the troughs with corn meal were placed.

The respiration rate was measured in the chute by a previously trained observer before the animals were restrained in squeeze chute by counting the respiratory movements per minute. Afterwards, the animal was contained in the squeeze chute and its rectal temperature was measured using a digital clinical thermometer (Incoterm, precision 0.1°C) placed against the rectal wall.

To capture thermographic images, the infrared camera (875-2, Testo, Germany) was kept at the level of the anatomical region being evaluated, with a lateral image to capture the ocular region and a frontal image to capture the entire forehead of the animal. The emissivity adopted was 0.98 (Hoffmann et al. 2013Hoffmann G, Schmidt M, Ammon C, Rose-Meierhofer R, Burfeind O, Heuwieser W, Berg W, 2013. Monitoring the body temperature of cows and calves using video recordings from an infrared thermography camera. Vet Res Commun 37: 91-99. https://doi.org/10.1007/s11259-012-9549-3
). The camera was positioned at 90° and with a standardized distance of 0.5 m from the face. The average temperature of the forehead was determined by polygonal demarcation, whereas the muzzle and ears were matched to the anatomical region. The surface temperature of the eyeball was analysed by circular tracing over the orbital region, including the eyeball and approximately 1 cm from the eye cavity, to cover the lacrimal gland (Figure 3). These images were analysed using the camera's own program (IrSoft).

Figure 3.  Thermography images of Angus × Nellore heifer. (a) Lateral thermography image with demarcation of the orbital region. (b) Referenced thermal scale. (c) Thermography image of the frontal region with demarcation of the forehead (AV1), muzzle (AV2), left ear (AV3), and right ear (AV4).

To evaluate the reactivity during weighing, we used the reactivity composite score, adapted by Titto (2010)Titto EAL, Titto CG, Gatto EG, Noronha CMS, Mourão GB, Nogueira Filho JCM, Pereira AMF, 2010. Reactivity of Nellore steers in two feedlot housing systems and its relationship with plasmatic cortisol. Livest Sci 129(1-3): 146-150. https://doi.org/10.1016/j.livsci.2010.01.017
. The same trained observer assigned an individual composite score from 1 to 4 as follows: score 1, non-reactive animal: relaxed and without sudden movements; score 2-slightly reactive animal: slightly restless, alert; score 3-reactive animal: vigorous movements, alert, tries to escape; score 4-very reactive animal: very tense, panting, jumping, and struggling. These may present with visible sclerotic membranes and muscle tremors.

The exit velocity test was adapted from Burrow et al. (1988)Burrow HM, Seifeirt GW, Cobert NJ, 1988. A new technique for measuring temperament in cattle. Proc Aust Soc Anim Prod 17: 154-158. http://www.livestocklibrary.com.au/handle/1234/7836
. This evaluation method consists of measuring the speed at which the animal leaves the weighing scale. The stopwatch was started as soon as the animal left the scale and closed when it exceeded 2 m of distance. The speed (m/s) was calculated from the time the animal travelled the distance.

All data was written down on paper worksheets at the time they were collected.

Results

There was a reduction in the time spent driving the heifers of the frequent handling treatment between the paddock and the handling facility, both one-way and return (P<0.05) (Table 1), observed 40 days after the beginning of the process, in the fifth handling event.

There was an effect of month and an interaction of month and treatment (P<0.05) on the driving time of the heifers from the feeding pen to the handling facility for weighing (Table 2). The time reduced over the months for both treatments, but with greater reduction in animals of the frequent handling treatment.

There was an effect of month, and a month x treatment interaction (P<0.05) on the management time for driving heifers from the weighing pen back to the feeding pen (Table 3). In heifers in the control treatment, there was no reduction in time (P>0.05), which was similar to the frequent handling treatment in the first month (P>0.05). In contrast, in animals of the frequent handling treatment, there was a reduction in the time of return driving from the second month (P<0.05), remaining stable until the end of the experiment (P>0.05).

Exit velocity values decreased over time, with higher values at month 1 (Management 1 of data collection) and gradually dropping until month 4 (Management 4 of data collection). This indicated that there was an effect of the interaction treatment x time, and time (P<0.05). But on the other hand, no statistical differences were found in the comparison between frequent handling and control animals, indicating that there was no effect of treatment (P>0.05) (Table 4).

Physiological variables, such as rectal temperature and respiration rate, showed that there was no effect of treatment x month (P>0.05) but treatment and month were significant when evaluated as an isolated effect (Tables 5 and 6). Analyzing only the treatment, it was observed that there was a significant difference (P<0.05) in both rectal temperature and respiration rate, with frequent handling of animals showing lower mean values for both variables (Tables 5 and 6). The values behaved differently in relation to each month (P<0.05) but did not gradually decrease over time.

For reactivity, there was no effect of interaction treatment x month (P = 0.1309), but an effect of treatment, with an average of 1.28 ± 0.081 for the groups of frequent handled heifers and 2.38 ± 0.079 for the group of control heifers. There was also an effect of month (P=0.001), explained by a decrease in reactivity over time, but with and slight increase in the last month (Table 7).

Infrared thermography image analyses showed treatment effects for the muzzle and ocular temperature, with higher means for the control animals (P<0.05; Table 8). The other variables, such as frontal temperature and left and right ear temperatures, were not affected by frequent handling (P>0.001).

Discussion

Reactivity is a behavioral response linked to temperament, which is inherent to an individual with a permanent character (Grandin et al., 1995Grandin T, Deesing MJ, Struthers JJ, Swinker AM, 1995. Cattle with hair whorl patterns above the eyes are more behaviourally agitated during restraint. Appl Anim Behav Sci 46(1-2): 117-123. https://doi.org/10.1016/0168-1591(95)00638-9
). In this study, frequent handling with positive reinforcement did not reduce the animals' reactivity, but the exit velocity showed that there was a reduction in reactivity over time. This corroborates the results of Titto et al. (2010)Titto EAL, Titto CG, Gatto EG, Noronha CMS, Mourão GB, Nogueira Filho JCM, Pereira AMF, 2010. Reactivity of Nellore steers in two feedlot housing systems and its relationship with plasmatic cortisol. Livest Sci 129(1-3): 146-150. https://doi.org/10.1016/j.livsci.2010.01.017
, who observed a significant reduction in reactivity over the time of evaluation and management, suggesting that the animals became accustomed to the management used, classified by the author as gentle. This demonstrates that even in the absence of reinforcement, habituation of animals occurs to the presence of humans and to the environment, with a decrease in reactivity (Ceballos et al., 2016Ceballos MC, Góis KCR, Sant’Anna AC, da Costa, MJ, 2016. Frequent handling of grazing beef cattle maintained under the rotational stocking method improves temperament over time. Anim Prod Sci 58(2): 307-313. http://doi.org/10.1071/AN16025
).

Frequent handling positively influenced reactivity. The animals in the frequent handling group already knew the route to the management corral as well as the route and people involved. This familiarity contributed to a reduction in the time spent driving the animals in the frequent handling group compared to that in the control group, although the time spent on the route to the management corral decreased for both groups over time. Handling also affected the physiological responses of animals during handling in the corral.

The analysis of physiological variables showed that frequent handling was beneficial to the animals, as indicated by a decrease in rectal temperature and respiratory rate. These probably occurred because the animals already knew the route to the management pen and were anticipating a positive stimulus. A study by Waiblinger et al. (2004)Waiblinger S, Menke C, Korf J, 2004. Previous handling and gentle interactions affect behaviour and heart rate of dairy cows during a veterinary procedure. Appl Anim Behav Sci 85(1-2): 31-42. https://doi.org/10.1016/j.applanim.2003.07.002
also observed benefits for the animals and routine management, it was found that previous management and positive interactions between handler and cow (such as feeding and tactile stimulation) reduced heart rate and less movement during rectal palpation or insemination. On the other hand, the animals in the control group that had less frequent trips to the management pen and had no offered reward (positive reinforcement) showed higher respiratory rate and rectal temperature, probably due to the lack of familiarity with the management site (Bourguet et al., 2010Bourguet C, Deiss V, Gobert M, Durand D, Boissy A, Terlouw EMC, 2010. Characterising the emotional reactivity of cows to understand and predict their stress reactions to the slaughter procedure. Appl Anim Behav Sci 125: 9-21. https://doi.org/10.1016/j.applanim.2010.03.008
), route to the pen, and the presence of people making this situation more stressful for the control group.

Stressful situations cause the activation of the hypothalamic-pituitary-adrenal axis, and a cascade of changes occurs in the animal with the increase in the release of catecholamines and glucocorticoids, which can cause an increase in internal temperature (Proctor & Carder, 2014Proctor HS, Carder G, 2014. Nasal temperatures in dairy cows are influenced by positive emotional state. Physiol Behav 138:340-4. http://doi.org/10.1016/j.physbeh.2014.11.011
), as was seen in the females in the present experiment. The increase in rectal temperature may have influenced eye temperature, because eye temperature is sensitive to changes in internal temperature. Therefore, it correlates best with rectal temperature (Barros et al., 2016Barros DV, Silva LKX, Kahwage, PR, Lourenço Júnior JB, Sousa JS, Silva AGM, Franco IM, Martorano LG, Garcia AR, 2016. Assessment of surface temperatures of buffalo bulls (Bubalus bubalis) raised under tropical conditions using infrared thermography. Arq Bras Med Vet Zoot 68(2): 422-430. https://doi.org/10.1590/1678-4162-8327
; McCafferty, 2007McCafferty DJ, 2007. The value of infrared thermography for research on mammals: previous applications and future directions. Mamm Rev 37: 207-223. https://doi.org/10.1111/j.1365-2907.2007.00111.x
). Thus, an increase in body temperature due to stress exposure may increase ocular temperature through ocular vasodilation to eliminate the heat generated by stress. The average muzzle temperature was also higher in animals in the control group than in frequent handling animals. According to Lowe et al. (2019)Lowe G, Sutherland M, Waas J, Schaefer A, Cox N, Stewart M, 2019. Infrared thermography-A non-invasive method of measuring respiration rate in calves. Animals 9(8): 535. https://doi.org/10.3390/ani9080535
, during inspiration, fresh air passes through the nostrils, and during expiration, warm air is eliminated; thus, a higher respiratory rate due to the animal's nervousness would enable more chances of higher temperature readings, besides the nostrils being a form of heat dissipation when the animals are under thermal stress. Furthermore, frequent handling animals showed lower nasal surface temperature, probably as a result of anticipation of a positive reward causing peripheral vasoconstriction in this region (Proctor & Carder, 2014; Chotard et al., 2018Chotard H, Ioannou S, Davila-Ross M, 2018. Infrared thermal imaging: Positive and negative emotions modify the skin temperatures of monkey and ape faces. Amer J Primatol 80(5): e22863. http://doi.org/10.1002/ajp.22863
).

Similar results were found by Mincu et al. (2023)Mincu M, Nicolae I, Gavojdian D, 2023. Infrared thermography as a non-invasive method for evaluating stress in lactating dairy cows during isolation challenges. Frontiers Vet Sci 10: 1236668. https://doi.org/10.3389/fvets.2023.1236668
in dairy cows; after stress by isolation challenge, they showed an increase in orbital and nasal temperatures. Therefore, changes in blood flow (sympathetic capillary activity) can reflect how the central nervous system reacts to different stress conditions; therefore, it can be used as a tool to measure the emotional state of cattle.

It was concluded that the use of frequent handling with positive reinforcement was effective in decreasing animal temperament indicators, such as exit velocity, reactivity score and respiratory rate. It was also effective in decreasing the time the animals spent walking to the pen-chute and back to the paddocks, showing that the management was carried out in a gentle manner and that the animals may have become accustomed to the management and more frequent human contact.

Ethical approval

This study was approved by the Ethics Committee on Animal Use (Comissão de Ética no Uso de Animais da Faculdade de Zootecnia e Engenharia de Alimentos, CEUA/FZEA; number 210718052).

Competing interests

The authors have declared that no competing interests exist.

Statement about use of generative AI

The author(s) employed deepl.com in order to translate to Spanish the title, abstract and key words while preparing this work. Following their use, the author(s) assumed full responsibility for the publication's content and reviewed and edited it as necessary.

Authors’ contributions

Vitor Ramos Pacor: Funding acquisition, Investigation, Project administration, Visualization, Writing - original draft. Messy Hannear de Andrade Pantoja: Writing - original draft, Writing - review & editing. Douglas Henrique Silva de Almeida: Investigation. Isabela Martins Dias Batista: Investigation. Milena Schempp Consorti: Investigation. Cihan Çakmakçı: Formal analysis. Cristiane Gonçalves Titto: Conceptualization, Formal analysis, Funding acquisition, Methodology, Project administration, Supervision, Writing - original draft, Writing - review & editing.

References