How The Use Of Analgesia Affects Behavior In Newborn Calves

The welfare of farmed animals is under increasing scrutiny from consumers as well as governmental and industry bodies and plays an important part in the sustainability of farming for the future. Millions of dairy calves are born worldwide every year, and although birth is a necessity experienced by all calves, research into the potential for birth to be a painful event and the effects of birth on calf welfare is lacking.

Behavioral studies have been used to assess animal welfare in a number of species since behavior is a sensitive indicator of animal welfare. Pain is considered to be an adverse welfare state, and in environments where other factors affecting welfare are controlled, animals experiencing pain are considered to be in a poorer welfare state than those that are not experiencing pain. Cattle are a prey species and as such, often do not show signs of pain that are obvious to humans, which can make the assessment of pain difficult. Although behavioral responses to stimuli are complex and multifactorial, it is thought that some behaviors such as play are associated with positive welfare states. This is because play behavior in young animals is considered to be a “luxury” behavior (i.e. not directly needed for survival) and is therefore displayed by choice.

It has been demonstrated that play behavior is exhibited at higher frequencies in animals that are experiencing positive welfare, therefore the proportion of time spent engaged in play behavior can be used as an indicator of the welfare state experienced by the animal. In young calves, lying positions are also considered to be an indicator of pain or ill health. Newborn calves spend approximately 80% of their time lying down (1) and typically adopt a sternal lying position (i.e. on their front). Calves that are in ill health or in pain typically adopt a lateral lying position (on their side), which is considered to be an abnormal lying position in calves (2).

Studies into the use of pain relief in calves experiencing surgical interventions have demonstrated that the use of analgesia improves calf welfare, but the potential welfare benefits of administering analgesia after birth has not previously been studied. Most calves are born without the need for human assistance; however, a substantial minority will be born via assisted birth each year. The rate of assistance has been reported to be up to 50% by some authors (3), which in the UK dairy industry alone equates to up to 900,000 calves every year. It is unknown whether assistance at birth is painful for calves, although there is evidence that calves born to assisted parturition have subsequently poorer health than their counterparts born without human intervention (4).

We designed a study to assess the effect of birth status (assisted or unassisted) on the behavior of calves and whether administration of analgesia to newborn calves alters behavior in a way that might suggest a reduction in pain experience (5). As pain is considered to be detrimental to welfare, experiencing pain during and after birth can be considered to adversely affect the welfare of calves. Consequently, this aspect of calf welfare can potentially be improved through the implementation of strategies to provide analgesia during the neonatal period. Calves were all recruited from a single dairy farm and management of all calves was the same, therefore other factors affecting calf welfare (for example housing, socialization, feeding) were uniform for all calves in all groups. Calves born via either assisted or unassisted birth were randomly assigned to either a treatment group (administered analgesia within 3 hours of birth) or a placebo group (administered a saline placebo within the same time frame).

The calves were filmed using CCTV cameras positioned above the calf pens for the first 48 hours of life. Detailed behavioral observations were obtained using a method called instantaneous scan sampling. This method of behavioral analysis is performed by recording the behavior shown by the subject at set time intervals and combining the data to produce a time budget for the time period of interest. Primary behaviors were mutually exclusive behaviors that the calf had to be engaging in and comprised of lying behaviors (including both body and head posture) or active behaviors (walking, standing, attempting to stand, and play behaviors); these behaviors were recorded in all time points that each calf was visible. In addition, other behaviours that were displayed at the same time as primary behaviors (feeding, drinking, grooming and social behaviors) were recorded and termed “secondary behaviors.”

Behavioral data from seventy-five calves was included in the final analysis. Consistent with previous research, calves in all groups spent more than 80% of the time budget lying down and lying in sternal recumbency was the most common lying position observed. Both assistance status and treatment status affected some behaviors:

  • Calves born to assisted parturition in both the treatment and the saline groups spent more time lying in lateral recumbency, more time with their head in a lowered position, and less time engaged in play behaviors than those born to unassisted parturition.
  • Calves born to both assisted and unassisted parturition that received analgesia after birth showed a tendency to spend less time in lateral recumbency and spent more time engaged in play behaviors than those that received a saline placebo after birth.

Some behaviors were also affected by the interaction between treatment and assistance status:

  • Calves that were born to assisted parturition and received analgesia engaged in walking behavior more than other calves.
  • Calves that were born to unassisted parturition that received analgesia laid in lateral recumbency less than other calves.
  • There was no treatment/assistance interaction effect on overall time engaged in play behavior; however, the proportion of active time spent engaged in play behavior tended to be higher in calves born to unassisted parturition that were treated with analgesia than other calves.

The behavioral data obtained from our study provides some interesting insights into the behavior of very young calves. Behavioral differences observed between calves exposed to different birth experiences suggest that assisted parturition does adversely affect the welfare of calves. Additionally, differences observed in calves that received analgesia compared to those that received a placebo suggests that this effect on welfare is due in part to pain and therefore analgesia can contribute to improved welfare of neonatal calves. Interestingly, calves born to unassisted parturition who received analgesia showed behaviors consistent with an enhanced welfare state as well as calves born to assisted parturition – this is suggestive that birth in general is possibly painful to calves, not just birth that requires assistance.

This is a novel study and, although the results are exciting, the small number of calves recruited means that cautious interpretation is required, especially for non-lying behaviors that did not occupy a large proportion of the time budget. Despite the limitations, the results of our study have gone some way to address a knowledge gap and do indicate that providing analgesia to all newborn calves has the potential to improve their welfare. This is useful information for farmers and veterinary surgeons who might be considering whether to administer analgesia to calves after birth, in particular, if the birth required assistance. Research in this area is ongoing, and we will be further studying behaviors of interest, especially play behavior, to further our understanding of the role that analgesia may have to play in the improvement of neonatal calf welfare.