Does cribbing behavior in horses vary with dietary taste or direct gastric stimuli?

https://doi.org/10.1016/j.applanim.2017.01.015Get rights and content

Highlights

  • Effects of sweet-tasting diets on cribbing were assessed in cribbing horses.

  • Cribbing was assessed after diets were tasted or delivered via nasogastric tube.

  • Concentrated feed is the strongest trigger of cribbing behaviors.

  • Taste appears to be primary stimulation for cribbing.

  • Other gastric and post-gastric process may be involved in cribbing.

Abstract

Concentrated feed diets have been shown to drastically increase the rate of the cribbing, an oral stereotypy in horses, but the specific component causing the rise has not been identified. Furthermore, the mechanism through which feed affects cribbing has not been explored. In the first experiment of this study, we quantified the latency to crib and number of cribs in 15 min after the horses tasted various grain, sugar, and artificial sweetener solutions. Undiluted grain stimulated the most cribs (P < 0.01) compared with all other solutions, and shortest latency to crib, although this was significantly higher only when compared with diluted grain (P = 0.03). In Experiment 2, latency to crib and number of cribs in 15 min after the grain and sugar solutions were administered via nasograstric tube were also evaluated. There were no statistical differences among cribbing responses to grain, fructose, and water administered directly to the stomach although grain stimulated cribbing behavior more quickly than 10% fructose (P = 0.03) and 100% tap water (P = 0.04). These results confirm that highly palatable diets, possibly mediated through the opioid and dopaminergic systems, are one of the most potent inducers of cribbing behavior. The highly palatable taste remains the probable “cribogenic” factor of concentrated diet, although gastric and post-gastric effects cannot be excluded.

Introduction

Stereotypies are abnormal repetitive, invariant, and seemingly functionless behaviors, and these behaviors are associated with suboptimal environmental conditions, although the exact causal factors remain unknown (Mason, 1991). Cribbing, or crib-biting, is an equine oral stereotypy characterized by a horse placing its upper incisors on a horizontal surface and drawing air into the esophagus while flexing the ventral neck muscles (McGreevy et al., 1995). The prevalence of the behavior has been estimated to be around 2–10%, with some breeds demonstrating a predisposition for cribbing (Albright et al., 2010, Bachmann et al., 2003, Luescher et al., 1998, Vecchiotti and Galanti, 1986). Management practices related to social contact, pasture time, and high-concentrate diet have also been linked to the performance of cribbing (reviewed by Wickens and Heleski, 2010).

Provision of concentrated feed to young horses at weaning is a particularly strong risk-factor for the development of cribbing (Waters et al., 2002). Sweet feed is also known to increase the rate of cribbing immediately post-ingestion in established cribbing horses (Kusunose, 1992). Consuming roughage (Gillham et al., 1994) and plain oats (Whisher et al., 2011) does not have the same crib-inducing effect. Some hypothesize that highly palatable diets induce the release of endogenous opioids and, in turn, cribbing through a complex interplay of the opioid, dopaminergic, and glutaminergic neural systems (Dodman et al., 1987, Gillham et al., 1994).

The goal of this study was to characterize further the relationship between sweet-tasting substances and cribbing. The first objective was to compare the effects of sugars, artificial sweetener, and sweet feed ingested by mouth on cribbing behavior. We measured the number of cribs and latency to crib as indicators of the strength of motivation to crib. We hypothesized that the taste of food influenced cribbing rate and predicted the commercial sweet feed would be the strongest stimulator of cribbing, followed by sucrose and fructose solutions. The second objective was to compare cribbing after delivery of a single-sugar or grain solution directly to the stomach via nasogastric tube. We hypothesized that some aspect of taste, such as neurophysiologic mechanisms associated with the activation of sweet taste receptors and reward neural circuitry, is the critical factor in palatable diet-initiated stereotypies; therefore, we predicted that bypassing these receptors would not result in a difference in the post-delivery cribbing rate and latency to crib among the various solutions.

Section snippets

Animals and husbandry

All procedures were approved by the Cornell University Institutional Care and Use Committee. Six client-owned horses (two mares, four geldings; four thoroughbreds, one warmblood, and one horse of undetermined breed), ranging in ages between 4 and 25 years old, were lent to Cornell University for this project. The horses were all otherwise healthy established cribbers, although the exact age at onset of cribbing behavior was unknown. The horses were housed in 3.3 × 3.3 m stalls with a combination

Effect of consuming various oral solutions on the number of cribs and latency to crib

There was no significant difference in the number of cribs or latency to crib between the two concentrations of diluted grain (12% and 25%) (P = 0.94 number of cribs; P = 0.99 latency), saccharin (0.1% and 0.2%; P = 0.28, 0.99), or sucrose (5% and 10%; P = 0.99, 1.00); therefore, the results were combined into one variable per sugar, sweetener, or diluted grain for this experiment. Horses cribbed a significantly greater number of times after consuming 100% grain compared with the same period after

Discussion

Concentrated feed and, to a lesser extent, sugar solutions were the most robust inducers of cribbing behavior after tasting or ingesting by mouth. As with other cribbing studies, number of cribs was used as the primary indicator of a diet’s potency to activate cribbing (Kusunose, 1992, Bachmann et al., 2003, Whisher et al., 2011), and we predicted latency to crib would inversely correlate with this number. However, this relationship is only significant with very strong responses, such as those

Conclusion

The results of this study confirm that concentrated feed is one of the most potent triggers of cribbing behavior. The palatable taste seems to be the major responsible component, but high-concentrated sugar solutions alone were either not palatable to horses, or not sufficient to induce the same effect. Gastric or post-gastric effects, perhaps mediated through pathways such as the parasympathetic nervous system, could not be ruled out as underlying mechanisms as well. Future studies should be

Conflict of interest

The authors have no conflicts of interest to report.

Acknowledgments

The authors thank Heather Edington, Katherine Anguish, and Scott Baxendell for assistance with data collection, and the owners who lent equine subjects for this study.

References (28)

  • S.S. Schiffman et al.

    Bitterness of sweeteners as a function of concentration

    Brain Res. Bull.

    (1995)
  • D.J. Shide et al.

    Opioid mediation of odor preferences induced by sugar and fat in 6-day-old rats

    Phys. Behav.

    (1991)
  • L. Whisher et al.

    Effects of environmental factors on cribbing activity by horses

    Appl. Anim. Behav. Sci.

    (2011)
  • C.L. Wickens et al.

    Crib-biting in horses: a review

    Appl. Anim. Behav. Sci.

    (2010)
  • Cited by (5)

    • Discovering the relationship between dietary nutrients and cortisol and ghrelin hormones in horses exhibiting oral stereotypic behaviors: A review

      2020, Journal of Veterinary Behavior
      Citation Excerpt :

      Practically, it is highly understandable that animal experimentation using the horse model is limited in terms of financial resources, especially involving a large sample size and the availability of the subject interest, such as crib-biting. Even so, a study conducted by Albright et al. (2017), using only six horses of different breeds and ages, provided an interesting insight into the effect of palatability on the crib-biting behavior. If more similar studies were to be conducted by different facilities, it is likely that these would yield comparable findings supporting the palatability hypothesis in relation to the crib-biting behavior.

    • Behavior and training for optimal welfare in therapy settings

      2021, The Welfare of Animals in Animal-Assisted Interventions: Foundations and Best Practice Methods
    • Equine behavioral medicine

      2019, Equine Behavioral Medicine

    This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

    View full text