Massey research update

MASSEY UNIVERSITY RESEARCH UPDATE

Just a squeeze might do it

Sophia Holdsworth, a PhD candidate in Massey University’s Animal Welfare Science and Bioethics Centre, tests a treatment for ailing newborn animals.

BACKGROUND

Some newborn farm animals who are apparently healthy do not behave normally after birth. They have no desire to be near the dams, they lack coordination or cannot stand without help, and their sucking reflex is often absent, preventing their drinking any colostrum or milk. Without intensive veterinary intervention, these newborns often die.

The ‘thoracic squeeze’ is gaining popularity as a therapeutic approach (Toth et al., 2012; Aleman et al., 2017). It involves looping a soft rope three times around a newborn’s chest and tightening it firmly to produce sustained pressure across the thorax. This causes the animal to enter an apparent nonresponsive state, characterised by loss of posture, eye closure and no movement for as long as the squeeze is maintained. Once the squeeze is released they recover immediately, with normal healthy behaviours (Aleman et al., 2013; Stilwell et al., 2019).

The same response to the thoracic squeeze has been demonstrated in healthy newborn foals (Toth et al., 2012). However, previous studies have not provided detailed information on behavioural responses to the squeeze, and there are no reports on responses to the thoracic squeeze in other healthy newborn mammals.

This study aimed to provide a detailed characterisation of behavioural responses to the thoracic squeeze in healthy newborn farm mammals. It recognised

that to apply the squeeze as a therapy it must first be demonstrated as safe – and studies on this would also provide insights into the potential mechanisms underlying the behavioural responses to the squeeze. However, regardless of mechanisms, this technique may have significant practical benefits for the animal production industry.

METHOD

We applied a 10-minute thoracic squeeze to 17 piglets and 16 calves aged between 12 and 36 hours. All animals were assessed to ensure they were healthy and vigorous before being included in the study. Their physiology was monitored throughout the study to evaluate their health.

Behavioural responses to the squeeze were evaluated, and classified as: » successful induction: characterised by posture loss, eye closure and no head or limb movements » low-intensity arousal: characterised by open eyes and movements of the head and limbs that lasted less than 10 seconds before the non-responsive state was resumed » high-intensity arousal: characterised by persistent struggling lasting longer than 10 seconds, with righting onto all four feet that prompted an immediate discontinuation of the squeeze.

RESULTS

All piglets were successfully induced into a non-responsive state after a thoracic squeeze, and this state was maintained for the full 10 minutes in over half of them. All piglets showed either reduced or absent reflexes during the squeeze.

Piglets for whom the squeeze was discontinued before the full 10 minutes appeared to take longer to induce than piglets who remained in the nonresponsive state. They also displayed more low-intensity arousals during the observation period.

In contrast, 81% of the calves were induced into a lower responsive state, characterised by lateral recumbency and no head or limb movements. Half of all calves squeezed maintained this state SOPHIA HOLDSWORTH

for the full observation period. Neural reflexes remained present in nearly all of the calves.

Calves for whom the squeeze was discontinued before the 10 minutes took less time to be induced than calves for whom the squeeze was maintained. These same calves also showed higher rates of low-intensity arousal immediately after the squeeze than did calves who were maintained for the full 10 minutes.

Based on evidence from this and previous studies, it is highly unlikely that the observed response was due to the animals fainting. No significant changes in venous pH, breathing rate, heart rate, oxygen saturation or blood pressure have been reported during the application of the squeeze.

WHERE TO FROM HERE

This pilot study demonstrated a generalised effect of a thoracic squeeze on newborn farm mammals and characterised their behavioural responses.

However, the mechanisms underlying behavioural responses to the thoracic squeeze are unknown, and the animals’ neurological state during the squeeze’s application is unclear. One theory proposes that the squeeze mimics the compressive actions of the birth canal during the birth process (Mellor, 2017). This compression is thought to facilitate the transition from unconsciousness before birth to consciousness after birth. By replicating this compression in the thoracic squeeze, it is thought that the brain transition can be repeated, enabling the newborn to display healthy behaviours after the squeeze (Mellor, 2017). However, this hypothesis has yet to be investigated.

The absence of or reduction in neural reflexes observed in our study suggests that the piglets and calves were in a state similar to sedation. As such, there would be benefits to exploring the pain responses of newborns during the thoracic squeeze to determine whether the apparent sedation is accompanied by analgesia. This information could be useful for developing a low-stress, analgesic method of restraint for painful husbandry procedures such as tail docking and castration.

REFERENCES:

Aleman M, Weich KM, Madigan JE. Survey of veterinarians using a novel physical compression squeeze procedure in the management of neonatal maladjustment syndrome in foals. Animals 7, 69–81, 2017

Aleman MR, Pickles K, Conley AJ, Standley S,

Haggett E, Toth B, Madigan JE. Abnormal plasma neuroactive progestagen derivatives in ill, neonatal foals presented to the neonatal intensive care unit. Equine Veterinary Journal 45, 3, 2013

Mellor DJ. Transitions in neuroinhibition and neuroactivation in neurologically mature young at birth, including the potential role of thoracic compression during labour. In: Aleman M, Weich KM, Madigan JE. Survey of veterinarians using a novel physical compression squeeze procedure in the management of neonatal maladjustment syndrome in foals. Animals 7, 69–81, 2017

Stilwell G, Mellor DJ, Holdsworth SE. Potential benefit of a thoracic squeeze technique in two newborn calves delivered by caesarean section. New Zealand Veterinary Journal 68, 1–4, 2019

Toth B, Aleman M, Brosnan RJ, Dickinson PJ, Conley AJ, Stanley SD, Nogradi N, Williams

CD, Madigan JE. Evaluation of squeeze-induced somnolence in neonatal foals. American Journal of Veterinary Research 73, 1881–9, 2012

PhD candidate Natalie King compiles research projects underway at Massey University.