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Houpt, K. A., Eggleston, A., Kunkle, K., & Houpt, T. R. (2000). Effect of water restriction on equine behaviour and physiology. Equine Vet J, 32(4), 341–344.
Abstract: Six pregnant mares were used to determine what level of water restriction causes physiological and/or behavioural changes indicative of stress. Nonlegume hay was fed ad libitum. During the first week of restriction, 5 l water/100 kg bwt was available, during the second week 4 l/100 kg bwt and, during the third week, 3 l/100 kg bwt. Ad libitum water intake was 6.9 l/100 kg bwt; at 3 l/100 kg bwt water intake was 42% of this. Daily hay intake fell significantly with increasing water restriction from 12.9 +/- 0.75 kg to 8.3 +/- 0.54 kg; bodyweight fell significantly for a total loss of 48.5 +/- 8.3 kg in 3 weeks. Daily blood samples were analysed; osmolality rose significantly with increasing water restriction from 282 +/- 0.7 mosmols/kg to 293.3 +/- 0.8 mosmols/kg bwt, but plasma protein and PCV did not change significantly. Cortisol concentrations fell from 8.1 ng/ml to 6.4 ng/ml over the 3 week period. Aldosterone fell from 211.3 +/- 74.2 pg/ml to 92.5 +/- 27.5 pg/ml at the end of the first week. The behaviour of 4 of the 6 mares was recorded 24 h/day for the duration of the study. The only significant difference was in time spent eating, which decreased with increasing water restriction from 46 +/- 3% to 30 +/- 3%. It is concluded that water restriction to 4 l/100 kg bwt dehydrates pregnant mares and may diminish their welfare, but is not life- or pregnancy-threatening.
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McGreevy, P. D., Richardson, J. D., Nicol, C. J., & Lane, J. G. (1995). Radiographic and endoscopic study of horses performing an oral based stereotypy. Equine Vet J, 27(2), 92–95.
Abstract: There is confusion in the veterinary literature concerning the definition of oral based stereotypies in the horse. This study reports the use of fluoroscopy and endoscopy during cribbiting/wind-sucking in afflicted horses. This permitted observations of movements of the pharyngeal and oesophageal tissues and of the air column within during the stereotypic behaviour. The findings reported show that the sequence of events during crib-biting/wind-sucking is not related to deglutition and that air is not swallowed to the stomach. Transient dilation of the upper oesophagus was recorded and the characteristic noise of wind-sucking coincided with the in-rush of air through the cricopharynx. The oesophageal distension was relieved when the air returned to the pharynx although small quantities passed caudally. It is proposed that the role of contraction of the strap muscles of the neck is to create a pressure gradient in the soft tissues surrounding the oesophagus which provokes movement of air from the pharynx into the oesophagus. The findings suggest that the definitions currently used in the sale of horses are in need of revision.
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Dallmeyer, M. D., Turner, R. M., McDonnell, S. M., Sertich, P. L., Dolente, B. A., Parente, E. J., et al. (2006). Theriogenology question of the month. Behavior problems in a stallion caused by a nephrolith. J Am Vet Med Assoc, 229(4), 511–513.
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