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An alternative in an attempt to minimize the effects triggered by intravenous (IV) bolus administration of α-2 adrenergic receptor agonists are continuous rate infusions (CRI). The requirement for sedation protocols in sheep for procedures to be performed without physical restraint and with reduced adverse effects, commonly observed with bolus use, justifies the study of CRI. The aim of study was to compare the cardiopulmonary and sedative effects of IV bolus injection and CRI of dexmedetomidine (DEX) in sheep. Six adult male sheep (38.3 ± 7.6 kg) received DEX as a bolus (5 µg kg−1, DEXbolus treatment) or CRI (5 µg kg−1 h−1 for 1 h, DEXCRI treatment). We recorded heartrate (HR), respiratory rate, systemic arterial blood pressure, pulse oximetry, hemodynamic parameters, blood gases and sedation scores over 120 min. HR was significantly lower in DEXbolus at 5 and 15 min than in DEXCRI, with HR reduction observed for 30 min in DEXbolus. Hypoxemia was noted in DEXbolus at 10 and 30 min. Pulmonary vascular resistance index increased at 5 min, and cardiac index (CI) decreased at all timepoints compared with baseline in DEXbolus. In DEXCRI, CI decreased only at 45 min. Sedation scores were higher in DEXbolus at 15 and 30 min. DEX CRI administration resulted in fewer cardiorespiratory and hemodynamic changes compared with bolus injection and lower sedation scores (<4/10), which would not allow animal handling without a reaction. The load dose used in CRI was a limitation to constant infusion. [ABSTRACT FROM AUTHOR]

A longitudinal study was conducted to identify the morphological development of eyes and head of Jersey cattle at different ages. A total of 48 healthy Jersey cattle, 1 to 58 months of age, were included in the study. Ophthalmologic examinations were performed to identify healthy cattle to form the age groups: GI (1‐ to 11‐month‐old), GII (16‐ to 24‐month‐old) and GIII (25‐ to 58‐month‐old). The animals were physically restrained and examined by transcorneal ultrasound of both eyes; the axial length (AxL), corneal thickness (CO), lenticular thickness (L), depth of the anterior (AC) and vitreous (VC) chambers were evaluated. The cranial measurements obtained included the total, cranial, and nasal lengths and widths. Subsequently, the cephalic index (CI) was calculated. The AxL (GI: 2.83 cm; GII: 3.16 cm; GIII: 3.24 cm), AC (GI: 0.44 cm; GII: 0.53 cm; GIII: 0.53 cm), L (GI: 0.88 cm; GII: 1.01 cm; GIII: 1.04 cm) and VC (GI: 1.44 cm; GII: 1.55 cm; GIII: 1.59 cm) increased (p ≤.001) according to age, but the CO (GI: 0.07 cm; GII: 0.08 cm; GIII: 0.08 cm) (p >.05) did not. The total length (GI: 30.83 cm; GII: 43.29 cm; GIII: 44.15 cm), cranial length (GI: 18.11 cm; GII: 23.82 cm; GIII: 22.69 cm), nasal length (GI: 12.72 cm; GII: 19.47 cm; GIII: 21.46 cm) and nasal width (GI: 26.22 cm; GII: 33.82 cm; GIII: 34.00 cm) increased (p <.001), and the CI (GI: 85.66 cm; GII: 78.15 cm; GIII: 77.02 cm) decreased (p <.001). The AxL correlated positively (p <.001) with the cranial length and width and negatively with the CI (p >.05). The ocular biometry of Jersey cattle correlates with their cranial measurements at different ages. With increasing age, the eyes and the head grow, establishing growth curves similar to those of other mammals. [ABSTRACT FROM AUTHOR]

The use of sheep in experiments is widespread and is increasing worldwide, and so is the need to develop species-specific anaesthetic techniques to ensure animal safety. Previous studies have mentioned several protocols involving the administration of alpha-2 adrenergic agonists in sheep; however, assessment of the efficacy and safety of these infusion techniques is still relatively new. Thus, the aim of the present study is to assess the effectiveness of detomidine constant rate infusion (CRI) in sheep by measuring the cardiovascular and respiratory parameters, blood gas variables and sedation scores. Eight adult female Santa Inês sheep received 20 µg/kg of detomidine hydrochloride intravenously as a bolus loading dose, followed by an infusion rate of 60 µg/kg/h. The heart rates and respiratory rates changed continuously during the CRI period. No arrhythmias were observed. The reduction in arterial partial pressure of oxygen (PaO2) was not significant, but one animal showed signs of hypoxaemia (minimum PaO2 of 66.9 mmHg). The arterial partial pressure of carbon dioxide (PaCO2) increased, but the animals did not become hypercapnic. The bicarbonate (HCO3−), pH and base excess (BE) tended towards metabolic alkalosis. The cardiac output (CO), stroke volume (SV), cardiac index (CI) and ejection fraction (EF%) showed no significant changes. The fractional shortening (FS%) decreased slightly, starting at T45min. Sedation scores varied between 3 (0/10) after sedation and during recovery and 7 (0/10) during CRI. We concluded that administering detomidine at an infusion rate of 60 µg/kg/h in Santa Inês sheep is a simple technique that produces satisfactory sedation for minimally invasive procedures. [ABSTRACT FROM AUTHOR]