Application of the voluntary human approach test on commercial pig fattening farms: a meaningful tool?

Abstract

Background A Voluntary Human Approach Test (VHAT) was performed in pig pens, and relationships between environmental conditions and welfare indicators were investigated. Five variables were measured in 1668 pens in 214 fattening pig herds in Germany: time until the first contact (touching) between a pig and the person in the pen (TUFC), time until the observer was surrounded by pigs within a radius of approximately two meters, percentage of pigs relative to group size [%] surrounding the observer after 1 min (PPSO), percentage of pigs relative to group size [%] that completely avoided contact with the observer during the entire test period, and how the pigs contacted the observer (Score 0 [no touching] - 3 [biting]). Furthermore, variables indicative of the pigs’ environment (e.g., feeding system, ventilation system), management (e.g., number of usable drinkers, number of usable manipulatable materials), and welfare (e.g., tail lesions, ear lesions) were documented. Results Pigs engaging in more forceful means of contact (nibbling, biting) approached the observer faster than those exhibiting more gentle types of contact (touching). A lower TUFC was associated with more manipulatable materials present, a higher number of drinkers, and with the control position of the caretaker located inside the pen. Pigs kept in larger groups showed a lower TUFC than those in smaller groups ( P = 0.0191). However, PPSO was lower in pigs kept in smaller groups (1–12 pigs per pen) with more manipulatable materials available. In groups with low PPSOs, more tail lesions were observed ( P = 0.0296). No relationship between contact type and tail or ear injuries was detected. In younger pigs, PPSO was higher (49.9 ± 23.2%) than for animals in the second half of the fattening period (45.1 ± 19.9%). Conclusions In this on-farm study, the relationships between VHAT behavior and environmental factors revealed that external factors (e.g., management practices, housing conditions) impact animals’ responses to this behavioral test. Therefore, using the VHAT as an animal welfare indicator is valid only if these variables are studied as well.

The Pig as a Translational Animal Model for Biobehavioral and Neurotrauma Research

“…They often involve introducing a subject to an unfamiliar pig in order to observe social interactions between animals, dominance hierarchies, play behavior, and social recognition. A voluntary human approach test was conducted by Wegner et al (2020), which revealed that pigs who approached a motionless human observer more quickly were more likely to engage in forceful means of contact, i.e., biting, when compared to pigs who were more reserved [ 46 ]. Aggression tests assess aggressive behavior and response to social challenges in pigs.…”

The Open Field Test as a Tool for Behaviour Analysis in Pigs: Recommendations for Set-Up Standardization – A Systematic Review

“…Another testing methodology that is often used in combination with the OFT is the human approach test (HAT), in which the pig is free to contact a motionless observer within the arena. The HAT evaluates the human-animal relationship based on the pig's possible fear reactions [ 22 ]. The latency to approach the observer [ 23 ] and the duration of contact are also recorded [ 11 ].…”

“…The latency to approach the observer [ 23 ] and the duration of contact are also recorded [ 11 ]. This test is usually conducted on individual pigs rather than groups of pigs and has the advantage of low inter-observer variation [ 22 ]. Like the OFT and NOT, the HAT is also influenced by several factors.…”

“…Like the OFT and NOT, the HAT is also influenced by several factors. For instance, repeated performance reduces the time until the animal approaches the observer [ 24 ], while pen dimension, group size, handling, or health can also influence the results of the HAT [ 22 ]. Since external factors strongly influence the OFT alone and in combination with the NOT or HAT, this systematic review summarizes the overlap of the set-up, performance, and parameters across studies and provides future recommendations for the standardization of the OFT for pigs.…”