Effects of feed on plasma leptin and ghrelin concentrations in crib-biting horses.

The reason why some horses begin an oral stereotypy such as crib-biting is not known. The aim of this study was to measure ghrelin and leptin concentrations in plasma concentrations to determine whether there is a link to crib-biting in horses. Plasma samples (n=3) were collected for plasma leptin and ghrelin assay before and during the morning first feeding in the usual environments of 15 horses with stereotypic crib-biting and 15 matched controls. The crib-biting intensity was scored in three 5-min phases, and a subgroup of verified crib-biters (n=8) was defined as horses that were seen to crib-bite during this study. Plasma leptin concentration (mean and 95% confidence interval [CI]) was lower in horses observed to crib-bite before and after feeding of concentrates (1.2, CI 0.8-1.7 ng/mL and 1.0, CI 0.6-1.7) than in non-crib-biters (2.3, CI 1.6-3.4 and 2.3, CI 1.6-3.4 ng/mL, respectively) and correlated negatively with crib-biting intensity. Crib-biting intensity was significantly higher shortly after feeding than before or 30 min later. Plasma ghrelin concentration was significantly higher before feeding concentrate than before hay feeding or after the concentrate, but did not differ between groups. There was a significant negative correlation between body composition score and plasma ghrelin concentration. These findings suggest that leptin concentrations may be associated with crib-biting behaviour in horses.

Hemmann KE ，Koho NM ，Vainio OM ，Raekallio MR ... -  《-》

Circadian variation in ghrelin and certain stress hormones in crib-biting horses.

Crib-biting is classified as an oral stereotypy, which may be initiated by stress susceptibility, management factors, genetic factors and gastrointestinal irritation. Ghrelin has been identified in the gastric mucosa and is involved in the control of food intake and reward, but its relationship to crib-biting is not yet known. The aim of this study was to examine the concentration and circadian variation of plasma ghrelin, cortisol, adrenocorticotropic hormone (ACTH) and β-endorphin in crib-biting horses and non-crib-biting controls. Plasma samples were collected every second hour for 24h in the daily environment of eight horses with stereotypic crib-biting and eight non-crib-biting controls. The crib-biting horses had significantly higher mean plasma ghrelin concentrations than the control horses. The circadian rhythm of cortisol was evident, indicating that the sampling protocol did not inhibit the circadian regulation in these horses. Crib-biting had no statistically significant effect on cortisol, ACTH or β-endorphin concentrations. The inter-individual variations in β-endorphin and ACTH were higher than the intra-individual differences, which made inter-individual comparisons difficult and complicated the interpretation of results. Further research is therefore needed to determine the relationship between crib-biting and ghrelin concentration.

Hemmann K ，Raekallio M ，Kanerva K ，Hänninen L ，Pastell M ，Palviainen M ，Vainio O ... -  《-》

Exploration of known stereotypic behaviour-related candidate genes in equine crib-biting.

Hemmann K ，Ahonen S ，Raekallio M ，Vainio O ，Lohi H ... -  《-》

Physiological and behavioral consequences associated with short-term prevention of crib-biting in horses.

McGreevy P ，Nicol C 《PHYSIOLOGY & BEHAVIOR》

Efficacy and effects of various anti-crib devices on behaviour and physiology of crib-biting horses.

Crib-biting is a common oral stereotypy. Although most treatments involve prevention, the efficacy of various anti-crib devices, including surgically implanted gingival rings, has thus far not been empirically tested. Demonstrate the effect that 2 anti-crib collars, muzzle and gingival rings have on crib-biting, other maintenance behaviours, and cortisol levels in established crib-biting horses. Randomised, crossover clinical trial. In Experiment I, 2 anti-crib collars and a muzzle were used on 8 established crib-biting horses; horses wore each of 3 devices for 7 days, with a 7-day device-free period between treatments. Horses were video recorded for 24 h at least 3 times each week prior to any device placement, and always the day after a device was removed. In Experiment II, gingival rings were used in 6 established crib-biting horses; horses were video recorded for 3 days prior to ring implantation and the day after surgery until the rings became ineffective. Plasma cortisol levels were assessed every day during Experiment II and on Days 1, 3 and 5 of each week during Experiment I. All devices significantly reduced crib-biting compared with control periods. There was no significant difference in crib-bite reduction amongst devices in Experiment I, or between pre-device periods and the first day the device was removed. The only increase in plasma cortisol occurred on the day of surgery in Experiment II. Common anti-crib devices are effective in reducing crib-biting and significant distress was not evident from our findings. We did not find a post inhibitory rebound effect. Surgical rings were successful only temporarily and implantation was probably painful to the horses. Because stereotypies involve suboptimal environmental conditions, efforts should be made to improve husbandry factors previously shown to contribute to crib-biting, and research into decreasing horses' motivation to crib-bite should continue.

Albright JD ，Witte TH ，Rohrbach BW ，Reed A ，Houpt KA ... -  《-》