Like humans, a small amount of stress in an animal’s life can provide coping mechanisms for better chance of survival later on in life but more severe forms of stress can cause distress which may lead to serious emotional and physical problems. In non-human animals used in food production, this can also produce negative effects in productivity. Dairy cows, particularly in intensive farming, are susceptible to a number of stressors including poor housing conditions, procedures such as dehorning, transportation, rough handling, human interaction, heat, weather conditions and the separation between calves and their mothers shortly after birth (Wells et al., 1998).
In the interest of productivity, it is beneficial to keep stress to a minimum in dairy cows. When faced with a stressful situation, hormones such as cortisol and adrenalin are released causing metabolic changes as part of a cow’s natural response to possible threats to survival. If a cow experiences stress during milking time, the release of adrenalin can cause a reduced milk yield, which can then lead to residual milk and incomplete milk let-down. Prolonged stress, caused by poor environmental conditions such as heat stress or inadequate ventilation, regular rough handling and struggling to access sufficient food and water, can cause serious long-term problems. The production of cortisol can seriously affect the immune and reproductive systems, making these cows prone to infections (AHDB, n.d).
Separation
Cow-calf separation is a procedure that has the potential to cause a great deal of stress to both the calf and mother. The effects of cow-calf separation are of interest to farmers in terms of productivity and also to the public regarding concern for the welfare of dairy cows and their offspring (Ventura et al., 2013). In nature, weaning is gradual, allowing the calf to adapt to social and dietary independence over a few weeks, although calves usually continue to receive some milk up to six to nine months of age (Weary et al., 2008). In farming, the separation of calves from their mothers commonly takes place less than 24 hours after birth. Calves are fed either milk or a milk substitute, usually much less than the amount of milk they would naturally consume from their mother. The majority of the cow’s milk will end up on supermarket shelves for human consumption.
Research has shown that the less time a calf spends with its mother creates the least amount of stress at the time of separation as a strong bond has not been established between mother and child. Many studies have shown that separation occurring within 24 hours of birth causes less stress than when a separation occurs three days after birth and even more so after seven days (Flower and Weary, 2001; Weary and Chua, 2000). One of the main stressors has been found to be inadequate quantities of milk given to the calf and distress could be caused by hunger. Calves fed with double the normal level of colostrum provided to calves displayed little distress response to separation (Thomas et al., 2001).
Effects of Stress
After separation, it has been found that cows and calves are much more vocal, indicating they are stressed. Separation anxiety is more prevalent in cows and calves that were separated after 14 days compared to those that were separated after just one day. This was particularly high in cows immediately after removal of the calf and also 18 hours after separation which is just before morning milking so this vocalization could be due to udder discomfort due to lack of suckling of milking (Weary et al., 2008). Studies where separation occurred at varying times did not show this apparent second peak. Furthermore, visual or auditory contact after separation appears to cause more vocalisation than without any contact (Stěhulová et al., 2008).
Evidence has shown a difference in social behaviour of calves that were separated within 24 hours after birth and calves that spent an extended period of time with their mothers. Flower and Weary (2001) carried out a social behaviour test where six-week-old calves were placed in a new pen with an unfamiliar conspecific and researchers recorded the interaction. The study found that calves that had been separated at a later stage were more interactive with other calves than those that had been separated shortly after birth. It is believed that maternal presence during the first few days and weeks of life improves social learning and makes them less likely to be nervous around others (Krohn et al., 1999).
Studies have shown that the more time a calf spends with its mother, the more weight is gained. Calves separated shortly after birth take longer to gain weight. Most likely due to having plenty of milk to consume, rather than being fed by bucket or bottle twice per day. This weight difference between calves separated at different ages was maintained until four weeks of age. Weight gain can also improve dominance in a herd later on in life, preventing bullying and having difficulties gaining access to food and water (AHDB, n.d.).
Conclusion
It is clear that dairy cows and their calves possess the capacity to suffer from stressful situations and that stress can cause emotional and physical effects as well as a reduction in productivity. Separation between a calf and its mother is a potentially very stressful procedure and there are a few factors that can affect the amount of stress on the calf. The immediate stress displayed by calves separated within 24 hours is less than that of calves that have spent more time with their mother. On the other hand, calves allowed to remain with their mother for a longer period of time exhibit better general health, weight gain and future productivity as well as sociality, reduction in anxiety and good future maternal behaviour. The positive effects of more time spent with the mother could outweigh the short-term effects of separation. Most research on the effects of cow-calf separation focuses on the days and weeks after separation but further research should focus on the scale and duration of the long-term benefits of extended cow–calf contact.
References
AHDB. (n.d.). Stress - health and productivity. [online] Available at: https://dairy.ahdb.org.uk/technical-information/animal-health-welfare/mastitis/symptoms-of-mastitis/stress-health-and-productivity/#.WoGhEZPFLLY [Accessed 12 Feb. 2018].
Flower, F. and Weary, D. (2001). Effects of early separation on the dairy cow and calf:. Applied Animal Behaviour Science, 70(4), pp.275-284.
Munksgaard, L. and Løvendahl, P. (1993). Effects of social and physical stressors on growth hormone levels in dairy cows. Canadian Journal of Animal Science, 73(4), pp.847-853.
Stěhulová, I., Lidfors, L. and Špinka, M. (2008). Response of dairy cows and calves to early separation: Effect of calf age and visual and auditory contact after separation. Applied Animal Behaviour Science, 110(1-2), pp.144-165.
Ventura, B., von Keyserlingk, M., Schuppli, C. and Weary, D. (2013). Views on contentious practices in dairy farming: The case of early cow-calf separation. Journal of Dairy Science, 96(9), pp.6105-6116.
Weary, D. and Chua, B. (2000). Effects of early separation on the dairy cow and calf. Applied Animal Behaviour Science, 69(3), pp.177-188.
Weary, D., Jasper, J. and Hötzel, M. (2008). Understanding weaning distress. Applied Animal Behaviour Science, 110(1-2), pp.24-41.
Wells, S., Ott, S. and Hillberg Seitzinger, A. (1998). Key Health Issues for Dairy Cattle—New and Old. Journal of Dairy Science, 81(11), pp.3029-3035.
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