This assignment is based on a research done by Paul McGreevy and Christine Nicol, Department of Clinical Veterinary Science University of Bristol.

“Physiological and behavioural consequences associated with short-term prevention of crib-biting in horses” published in Physiology & Behavior, Vol. 65, No. 1, pp. 15–23, 1998

reviewed by Anne Tjoenneland

 

Kingdom  Animalia

Phylum Chordata 

Subphylum Vertebrata 

Class Mammalia

Order Perissodactyla

Family Equidae

Genus Equus 

Introduction:

Crib-biting also called wind sucking with the scientific name ”aerophagia” is when the horse holds on to a fixed object such as the rack containing its food and pulls back while engulfing air. During this process the horse may not swallow the air. This is said to be an oral behaviour involving activity of the teeth and lips as well as distension of the oesophagus. It may lead to excessive teeth wear and in worse cases the top front incisors may be worn making it difficult for the horse to graze efficiently on shorter pasture which makes it hard for the owner to put on weight on his or her horse. Some say the cause to crib-biting is due to different factors like;

Paul McGreevy and Christine Nicol wanted to see if the crib-biting resulted in physiological or behavioural changes that favoured either stress coping or digestive regulation hypothesis. By doing so they had 3 aim of determination.

1. Determine baseline plasma levels of cortisol and β-endorphin in normal and stereotypic horses. ( It has been reported that crib-biters have lower β-endorphin levels than normal)
2. Examine the physiological and behavioural response that occurs when horses are subjected to short-term prevention of crib-biting.
3. Examine the physiological and behavioural responses that occur when horses are subjected to short-term prevention of a non-stereotypic behaviour (e.g eating hay).

Six stereotypic (crib-biters) and six normal thoroughbred geldings were used in the research. They were all racehorses. The experiment was conducted over 10 consecutive days.

Paul Mcgeevy and Christine Nicole collected blood samples to determine the β-endorphin and cortisol levels in the blood. In this way they could see if there were a significant difference between the cortisol and β-endorphin levels in the stereotypic horses and normal thoroughbred geldings. They scan sampled each horses behaviour between each episode of blood sampling. It is said that the crib-biting gives the horse a satisfactory feeling because of the β-endorphin “natural happy chemical” that are released into the blood when the air is sucked into the stomach.

Β-endorphin

 is a hormone secreted by the CNS, hypothalamus and gastrointestinal tract. They are the highest concentration in the blood during exercise. It is used as an analgesic in the body to num or dull pains.

Cortisol

is a hormone from the adrenal cortex the principal glucocorticoid. It is the so called stress hormone.

Results:

Β-endorphin in blood

There were no significant differences between the baseline levels of β-endorphins in crib-biters and normal horses. However it was reported that levels of β-endorphin in crib-biters were less than half of those in normal horses. The greatest variations in β-endorphin levels were seen in the responses of crib-biters.

Cortisol levels

The plasma cortisol levels were significantly higher in crib-biters than in normal horses. Crib-biters may be genetically more stress-susceptible animals that adapt to elevated cortisol levels at the time when the stereotypy is developing. But all in all no significant rise in cortisol levels took place at the crib-biters when crib-biting was prevented.

Behaviour

There was significantly more eating in crib-biters than normal horses. The oro-caecal (pertaining to the caecum) motility that occurred in crib-biters suggested that normal gut function in these animals is affected by oral activity and that eating in crib-biting may be partial substitutes for each other.

Afterword:

Dr. McGreevy and Dr. Nicol research into crib-biting by horses has been recognised by the Prince Laurent Foundation of Belgium in 2002 with a research prize that is grated every two years by HRH Prince Laurent. The discoveries leave the way open for further research into dietary treatments behaviour occurring, and for greater understanding of horses already affected.

The research is precise and well founded, but the number of hoses used for this research seems to be somewhat limited. They used only 12 horses whereof six stereotypic and six normal. In order to decrease the uncertainty the number could have been doubled.

Some also say that there is a connection between ulcer and cribbing. They could have checked if the stereotypic horses had ulcer before they started the research. What I mean is that horses with ulcer tend to crib and cribbing dulls the pain because of the raise of β-endorphin.

They could have checked if the cribbers were in some way over stimulated or bored during the procedure since some mean that crib biting can be prevented if you are aware of this.

A very good thing is that they measure the levels of hormones in the stereotypic and normal horses in this way they get a good insight if the level of hormones play a big role in crib-biting or not. This is a very difficult case and no one can say for sure what makes a horse crib and how you can prevent it (short or long term). This is a stereotypic behaviour that is still under research and yet more to be discovered.

http://www.gundogsupply.com/vicebreaker-articles-and-education-cribbing-windsucking.html

http://www3.vet.upenn.edu/labs/equinebehavior//hvnwkshp/hv02/mills.htm

http://vein.library.usyd.edu.au/links/Essays/2003/dampney.html

http://horse.free.fr/dentistry/photosdigital/cribbiting.jpg

http://www.tingler.ie/WindSuck1.jpg

Saunders Comprehensive Veterinary Dictionary by D. C. Blood and V. P. Studdert