Antler development was inhibited or stimulated by cryosurgery to periosteum or skin in a central antlerogenic region respectively.

Antler development is triggered by interactions between antler stem cells resident in the antlerogenic periosteum (AP) and the niche cells in the upper portion of overlying skin mediated by diffusible molecules. These interactive cell populations are interposed by the lower portion of the skin and the subcutaneous loose connective tissue (SLCT). It is known that mechanical deletion of just the central AP (having an area equivalent to the size of a pedicle base) by cutting through the skin and SLCT effectively stimulates the marginal AP to initiate antler development. This study was designed to investigate whether the SLCT layer plays a role in antler development by acting as a physical barrier. The results showed that the marginal AP failed to give rise to an antler after the central AP was cryosurgically destroyed with the preservation of the collagen structure of the SLCT. Furthermore, antler development was significantly advanced when the collagen structures of the skin and SLCT layers were substantially attenuated by repeated sprays with liquid nitrogen while keeping the central AP intact. Therefore, we conclude that the interposing SLCT layer acts as a physical barrier between antler stem cells and the niche cell types, and that timing of antler development is primarily controlled by the permeability of the SLCT layer to the putative interactive diffusible molecules.

Development and design of a novel loading device for the investigation of bone adaptation around immediately loaded dental implants using the reindeer antler as implant bed.

The assessment of the behavior of immediately loaded dental implants using biomechanical methods is of particular importance. The primary goal of this investigation is to optimize the function of the implants to serve for immediate loading. Animal experiments on reindeer antlers as a novel animal model will serve for investigation of the bone remodeling processes in the implant bed. The main interest is directed towards the time and loading-dependant behavior of the antler tissue around the implants. The aim and scope of this work was to design an autonomous loading device that has the ability to load an inserted implant in the antler with predefined occlusal forces for predetermined time protocols. The mechanical part of the device can be attached to the antler and is capable of cyclically loading the implant with forces of up to 100 N. For the calibration and testing of the loading device a biomechanical measuring system has been used. The calibration curve shows a logarithmic relationship between force and motor current and is used to control the force on the implant. A first test on a cast reindeer antler was performed successfully.

Assessment of the production of analgesia induced by application of a rubber ring or local anaesthetic to the antler pedicle of yearling stags.

AIMS: To compare two methods of applying rubber rings to the pedicles of yearling stags to induce analgesia in the antler prior to removal. To compare the application of a rubber ring with that of a lignocaine ring block of the antler pedicle on the efficacy and time course of the analgesia produced in yearling stags. METHODS: Rubber rings were applied to the pedicles of 36 yearling stags that required velvet antler removal. The standard method, a doubled-over ring expanded and lowered down from the distal end of the antler and released midway down the pedicle, was compared with a cable-tie method on the other pedicle, where a ring was pulled around the pedicle by an electrical cable tie threaded through the ring. Brief electrical stimulation (train-of-four mode) was applied proximal and distal to the ring before, and at regular intervals for 1 hour after, application of the ring to a level that produced an auriculopalpebral reflex response. In a second experiment, each pair of antlers per yearling stag (n=36) was allocated to one of three pairs of treatments, viz no treatment (control) and the cable-tie method as described above, control and local anaesthesia (a ring block of 2 ml 2% lignocaine per cm pedicle circumference), or the cable-tie method and local anaesthesia. Electrical stimulation (tetanic mode) was applied to each antler approximately 25 mm distal to the pedicle/antler junction before, and at intervals up to 1 hour after, application of treatments at a level required to produce a head/neck avoidance behavioural response. In a third experiment, the two electrical stimulation protocols used above were directly compared by measuring the response of stags (n=8) to one protocol on each pedicle/antler prior to, and at intervals for 1 hour after, application of a rubber ring. At the end of each treatment in all three experiments, analgesia of the antler was established as a nil behavioural response of the stag to a saw cut to the antler (the 'nick test'). RESULTS: For both methods of application of a ring the minimum electrical stimulation required distal to the ring to elicit a reflex response increased from around 16 to 55 mA by 60 minutes. In contrast, the electrical stimulation required proximal to the ring remained low (approximately 17.0 mA) throughout. No stag subjected to either of the methods of application responded to the nick test 60 minutes after application of the ring. The electrical stimulation required to produce a behavioural response increased very rapidly in stags treated with local anaesthetic and at a slower rate in those treated with the cable-tie method but showed no significant increase in control stags. After 4 and 30 minutes, for local anaesthesia and the cable-tie method, respectively, 95% of stags were not responding to 80 mA. A significantly greater proportion of stags with antlers treated with local anaesthetic and the cable-tie method did not respond to the nick test than controls, and there was no significant difference in the frequency of the response between stags with treated antlers. The minimum current required to produce a response proximal to a rubber ring was slightly higher on average for train-of-four electrical stimulus (mean 18.1 (SD 2.6) mA) than for the tetanic mode (mean 11.9 (SD 2.5) mA). The increase in minimum current required to produce the respective response to stimulation distal to the ring was similar for both methods, although the maximum predicted value (67.4 mA) was lower for train-of-four than for the tetanic mode (84.5 mA). No stag responded to the nick test > or = 60 minutes after application of the ring. CONCLUSIONS: The cable-tie method was no different from the standard method as a procedure for producing analgesia in the antlers of yearling stags and should be accepted as an appropriate procedure for applying analgesic rings to yearling stags. The analgesia produced in the antlers of yearling stags by rubber rings applied by the cable-tie method to the pedicle was similar to that of a lignocaine ring block, but the time course for the development of analgesia was markedly different. Given that a lignocaine ring block is accepted as an adequate method of pain relief for antler removal, the application of rubber rings followed by a period of > or = 30 minutes after application can be advocated as a viable alternative for pain relief.

Role of heterotypic tissue interactions in deer pedicle and first antler formation-revealed via a membrane insertion approach.

Heterotypic tissue interactions play an indispensable role in organ generation and regeneration. In contrast to the classic examples of tissue interactions prevailing in the formation of tetrapod limbs or pectoral fins that can only take place when the interactive tissues are in intimate contacts, the interactions in deer antler formation are novel in that the inducer and the responder are separated by a distance of 1-2 mm. This feature offers a unique opportunity to explore the mechanism underlying tissue interactions by permitting membrane insertion between the two interactive tissues. Four experiments were conducted in this study. The results showed that the impermeable membranes inhibited antler formation. In contrast, the permeable membrane (0.45 microm in pore size) substantially slowed pedicle growth and antler initiation but did not stop them. Interestingly, the impermeable membrane/sheath only slightly retarded antler elongation. Overall, our results demonstrate that interactions between the two interactive tissues, antlerogenic tissue and the overlying skin, are indispensable for first antler initiation and are achieved through diffusible molecules rather than direct physical contact. As the heterotypic tissue interactions are only required during antler initiation but not elongation, they must be transient in nature, and thus differ from those operating in limb/fin formation that can only be sustained by continuous interactions. A system in which organ development is achieved only through transient tissue interactions must be novel, if not completely unique. Understanding this system will undoubtedly enrich the knowledge in the field of tissue interactions and organogenesis.

Comparison of analgesic techniques for antler removal in halothane-anaesthetized red deer (Cervus elaphus): electroencephalographic responses.

OBJECTIVE: To provide evidence for an analgesic effect of antler pedicle compression or lidocaine 'ring block' by comparing changes in median and spectral edge frequencies and total electroencephalographic (EEG) power during the application of each technique followed by antler removal. ANIMALS: Twenty-nine 2-year-old red deer (Cervus elaphus) stags weighing 106-131 kg each were used in this study. Stags were carrying immature growing antler suitable for commercial harvest. MATERIALS AND METHODS: Anaesthesia was induced using propofol (8.25 +/- 1.28 mg kg(-1)) and ketamine (2.18 +/- 0.15 mg kg(-1)) and maintained with halothane in oxygen. End-tidal halothane (Fe'HAL), expired CO(2) tension (Pe'CO(2)), SpO(2), EEG, ECG, and direct arterial blood pressures were recorded continuously. Respiratory rate and somatic responses were recorded at specific time points. After stabilization of anaesthesia (Fe'HAL was approximately 0.8%) baseline data were recorded. Stags were randomly allocated to one of three treatment groups; control, local anaesthesia, or compression band. One antler was removed 4 minutes after the application of treatment. Electroencephalographic responses to application of treatment and antler removal were analysed using area under the curve (AUC) analysis. Mean AUC was compared between groups using anova, and when significant differences were found, groups were compared post hoc with two-tailed t-tests. Significance levels were set at p

Comparison of analgesic techniques for antler removal in halothane-anaesthetized red deer (Cervus elaphus): cardiovascular and somatic responses.

OBJECTIVE: To compare changes in heart rate and arterial pressures resulting from compression of the antler pedicle or lidocaine 'ring block' and during subsequent antler removal during minimal halothane anaesthesia. ANIMALS: Twenty-nine 2-year-old red deer (Cervus elaphus) stags, weighing 106-131 kg and carrying immature growing antler suitable for commercial harvest were studied. MATERIALS AND METHODS: Anaesthesia was induced using intravenous propofol (median dose 8.0 mg kg(-1), range 5.2-11.0) and ketamine (median dose 2.2 mg kg(-1), range 1.9-2.4) and maintained using halothane in oxygen. End-tidal halothane concentration (Fe'HAL) end-tidal CO(2) tension (Pe'CO(2)), SpO(2), EEG, ECG, and direct systolic (SAP) mean (MAP) and diastolic (DAP) arterial pressures were recorded continuously. Respiratory rate and somatic responses were recorded. Baseline data were recorded once anaesthesia (Fe'HAL approximately 0.8%) was stable. Stags were randomly allocated to control, lidocaine 'ring block' or compression band treatment groups. One antler was removed 4 minutes after treatment. Cardiovascular responses to the application of analgesia and antler removal were analysed using a general estimates equation for repeated measures or area under the curve (AUC) analysis. Mean AUC was compared between groups using anova, and when significant differences were found, groups were compared post hoc with two-tailed t-tests. Somatic response data were compared with Fisher's exact chi-square test. A value of p < 0.05 was considered significant. RESULTS: Heart rate fell during observations in all groups with no significant differences between groups. Arterial pressures in the control and lidocaine groups during treatment and removal were not different from baseline values or from each other. Compression group pressures were significantly higher than baseline during both treatment and removal. Compression group DAP and MAP were significantly higher after antler removal than during treatment. In control and lidocaine groups, the AUC for SAP, DAP, and MAP over the combined baseline, treatment, and removal period did not differ. The compression group AUC for DAP and MAP were significantly greater over the experimental period than both the lidocaine group and control groups. Somatic responses occurred in one animal at lidocaine injection and three at compression application. Somatic responses occurred in eight control animals and two in the compression group at antler removal. More animals responded to antler removal in the control group than in the compression (p = 0.015) or lidocaine (p < 0.001) groups. CONCLUSIONS: Compression of the antler pedicle appears to be noxious. Pedicular compression is a less effective analgesic technique for antler removal compared to 'ring blocks' with lidocaine. CLINICAL RELEVANCE: This study suggests that lidocaine 'ring blocks' are the current technique of choice for antler removal in deer.

Comparison of lidocaine and compression for velvet antler analgesia in wapiti.

This research compared ring block lidocaine anesthesia (L) and compression (C) for velvet antler removal in elk. Thirty-two wapiti were given 1 mg/kg body weight of zuclopenthixol acetate. The next day, they were restrained in a hydraulic chute and given either a compression device or a lidocaine ring block on the antler pedicle. Behavioral and physiological responses to treatment application and antler removal were recorded, and blood was collected for cortisol analysis. During application of L and C, increases in mean heart rate and systolic arterial blood pressure were greater in the C treatment group (P < 0.05, and P = 0.05, respectively). When antler was removed, more behavioral responses occurred in the C treatment group (P = 0.02) and its median behavior score was higher (P = 0.03). Mean heart rates increased for both treatment groups when antlers were removed (P < 0.01). It was concluded that application of C may be painful, and that C was not as effective as L for analgesia for velvet antler removal.

Comparison of analgesic techniques for antler removal in wapiti.

The purpose of this research was to compare the effectiveness of ring block anesthesia (LA) and electroanesthesia (A) for antler removal in elk given a long-acting tranquilizer to remove stress from restraint. Thirty-two male wapiti were given 1 mg/kg body weight of zuclopenthixol acetate; the next day, they were restrained in a hydraulic chute, provided with electroanesthesia or a lidocaine ring block, and had their antlers removed. Behavioral response to antler removal was scored. Significantly more (P = 0.032) animals responded to antler removal in the EA group. Heart rates and arterial pressures were measured by a catheter connected to a physiological monitor. Heart rate increased significantly over time with EA, but not with LA. Heart rate increased from baseline significantly more in the EA group immediately prior to antler removal (P = 0.017), immediately post antler removal (P = 0.001), and at 1 min post antler removal (P = 0.037). It was concluded that EA is not as effective a method of anesthesia as is LA for antler removal.

Disbudding of red deer stag calves to prevent antler growth.

Red deer stag calves aged five to seven months were disbudded with a standard cattle disbudding iron as a means of preventing antler growth and development. Two sizes of iron, one 2.2 cm in diameter and one 1.5 cm in diameter, were compared at disbudding in November or January. Disbudding in November and January with the 2.2 cm iron had success rates of 97 per cent and 92 per cent, respectively. Treatment with the 1.5 cm iron was less effective at both times. There was no significant difference between the liveweights of the treated groups and a non-disbudded control group at turnout in the spring or at slaughter in November when the stags were 16 months of age.