Effect of post-insemination progesterone supplementation on pregnancy rate in dairy cows

Progesterone plays an important role in maintenance of pregnancy. It is hypothesized that insufficient progesterone early in pregnancy may result in embryonic loss, and that supplemental progesterone would decrease pregnancy loss in dairy cows. In Experiment 1, 84 cows and 16 heifers from a single dairy operation were selected randomly. Within each age category, controlled internal drug release (CIDR) devices were inserted into the vagina of every other female on Day 4 post-insemination and removed on Day 18 post-insemination. Transrectal ultrasonography was performed to determine pregnancy at 4 time periods [days 30 to 37 (week 5), days 44 to 51 (week 7), days 58 to 65 (week 9), and days 86 to 93 (week 13)]. Progesterone supplementation had no effect on pregnancy rate. In Experiment 2, there were no differences in progesterone concentrations between cows that did and did not receive a CIDR. Further, cows receiving CIDR devices did not have an increase in circulating progesterone concentrations 30 min or 1 h after CIDR insertion. It appears that progesterone supplementation does not increase circulating levels of progesterone in the early pregnant lactating dairy cow. Alterative methods to influence progesterone concentrations and/or early embryonic loss need to be investigated.     

Remote Sensing of Spatial and Temporal Vegetation Patterns in Two Grazing Systems

One constraint that range scientists must face in grazing studies is the lack of accurate and repeatable techniques for discriminating grazing effects from both temporal variability and spatial heterogeneity of vegetation. Both forms of variability contribute to inconsistent grazing system effects on vegetation response and forage production in semiarid ecosystems. Remote sensing may be an efficient tool for detecting differences in spatial and temporal patterns of grazing impact on vegetation. The purpose of this study was to evaluate the spectral data derived from satellite images as a tool for comparing grazing system impacts on spatial and temporal vegetation patterns. We evaluated the effect of two grazing systems, “Continuous” (C) and “Two-Paddocks Rest-Rotation” (TPRR), on vegetation cover from 1996 to 2006 in a semiarid ecosystem of Argentina. We compared grazing effects on vegetation cover using two indices derived from the Normalized Difference of Vegetation Index (NDVI) data from Landsat Thematic Mapper images. We observed a slight advantage in NDVI improvement for the TPRR over the C. Even though, in both grazing systems, an upward vegetation trend occurred only in areas located far from the watering points, TPRR showed higher relative vegetation cover near the watering point than C. We consider this methodology an important step for monitoring vegetation changes and making management decisions in livestock systems of semiarid regions because grazing system impacts may be compared for both spatial and temporal vegetation patterns. However, we think that the key next step is to develop procedures that discriminate between forage and nonforage components.     

The Ossification of the Pelvic Girdle and Leg Skeleton of the Quail (Coturnix coturnix japonica)

The onset of ossification centres of the pelvic girdle and leg skeleton of the quail in embryos and juvenile birds were studied. Specimens, which were cleared and were stained with Alcian Blue and Alizarin Red S, were examined at the stereomicroscope. The ilium and the pubis began to ossify at the 8th day (E8), whereas the ischium at E9. Perichondral ossification was observed at E6 in the femur, tibia and fibula. A secondary ossification centre was detected in the proximal epiphysis of the tibiotarsus at the 15th post‐hatching day (P15). The patella began to ossify at P30. Regarding the tarsal bones tibiale, pre‐tibiale and fibulare, ossification was observed at the E15, E12 and E16, respectively. The metatarsals II, III, IV ossified at E7, whereas the metatarsal I at E11. The centres of ossification of the 1st phalanges of all digits were observed at E9. At the same day, the ossification centres of the 2nd phalanx of digits II and III as well as the 3rd phalanx of digit III appeared. At E10, ossification was observed in the 2nd phalanx of digit I, in the 3rd phalanx of digit II and in the 2nd and 3rd phalanx of digit IV. In the 4th phalanx of digit III and in the terminal phalanges of digit IV, ossification was observed at E11. The data presented here provide useful baseline information on the normal sequential pattern of ossification in the pelvic girdle and leg skeleton in this species.     

Macroscopic Anatomy of the Lower Respiratory System in Mole rats (Spalax leucodon)

The morphologic and morphometric features of the lower respiratory system in mole rats were examined. It was seen that the low respiratory system of this species leading a special life under highly hypoxic/hypercapnic conditions underground is structurally similar to other mammals living on land in terms of the parts examined; trachea was formed by 29.5 ± 4 oval‐formed cartilaginous tracheals arranged backwards and became gradually more stenotic diameter from cranial to the caudal of the neck. The trachea was separated in two principal bronchus at the fourth thoracal intercostal spatium level. The angle between the two main principal bronchi was 60.5 ± 2.35°. The lung constituted 1.29 ± 0.03% of the body weight and the right lung was heavier than the left lung. Fissura inter‐lobaris was deep and separated the lung lobes wholly, and the right lung was separated in four lobes, whereas the left lung was not separated into the lobes. Also, the medial lobe of the left lung was the lightest lobe.     

Use of stem cells in equine musculoskeletal disorders

Stem cell therapies for musculoskeletal disorders are becoming commonplace in the horse. In order to decipher the many options available for stem cell therapy and interpret results of accumulating experimental and clinical data, practitioners should have a basic understanding of stem cells.     

Ketamine as a part of anaesthetic management in a dog with twiddler's syndrome

An 11‐year‐old male German shepherd dog was referred for possible pacemaker implantation. A routine 6‐lead electrocardiogram revealed a third‐degree atrio‐ventricular block with a heart rate of 40 to 45 beats/minute. A transvenous pacemaker implantation procedure was scheduled. The dog was premedicated with 10 µg/kg acepromazine and 5 mg/kg pethidine. A dose of 5 mg/kg ketamine and 0·2 mg/kg diazepam were used for induction and isoflurane in O₂ and a constant rate infusion of ketamine (20 to 30 µg/kg/minute) were administered for maintenance of general anaesthesia. Due to a twiddler's syndrome, the pacemaker had to be repositioned. For the second procedure, the same protocol was employed except for a lower dose of ketamine both for induction (3 mg/kg) and constant rate infusion (10 to 15 µg/kg/minute). Ketamine appeared to be useful for both management of anaesthesia and cardiac pacemaker implantation in the absence of a temporary pacemaker.     

Sudden cardiac death in a dog during Holter recording—R on T phenomenon

A 6-year-old castrated male Golden Retriever was diagnosed with severe subaortic stenosis with severe left atrial enlargement and high heart rate due to atrial fibrillation. Treatment with digoxin and diltiazem to control ventricular response rate was initiated. Ambulatory electrocardiographic monitoring (Holter monitoring) was performed at the beginning of treatment and was repeated to evaluate the patient's response to drug therapy. Drug dose adjustments were made based on response to therapy as assessed by Holter monitoring. The dog experienced sudden death at home 19 days after beginning treatment while wearing the Holter monitor. Analysis of the Holter recording revealed marked increase in number and complexity of ventricular arrhythmias. A ventricular premature complex occurring on a T wave (R on T) was noted preceding the polymorphic ventricular tachycardia. This arrhythmia immediately degenerated into ventricular fibrillation followed by asystole. This case report describes the arrhythmia that preceded cardiac arrest and reviews the risk factors that could have potentiated the fatal arrhythmia in this dog.     

IN THIS ISSUE – May 2009

Australian poultry industries and highly pathogenic avian influenza  ▪  Diagnosis of canine splenic disorders  ▪  Dermatoses caused by immature Ixodes spp.  ▪  Seizures during medetomidine sedation and local anaesthesia  ▪  Inherited diseases of Holstein-Friesian cattle  ▪  Oral and topical triclabendazole  ▪  Double-outlet right ventricle in a filly