Grass Yields Under Clipping and Watering Explain Varied Efficacy of Management Intensive Grazing on Rangelands

Management intensive grazing (MIG) may not maximize plant productivity on rangelands because of morphophysiological traits of grassland vegetation. We examined defoliation and moisture effects on the biomass yield of rhizomatous and caespitose grass pairs that were either phylogenetically similar or of similar agroclimatic adaptation, including two agronomic grasses. From relatively low to high moisture regime adaptation, species pairs included western wheatgrass (Pascopyrum smithii [Rydb.] A. Love) and needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkw.), northern wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.]) and western porcupine grass (H. curtiseta [Hitchc.] Barkw.), plains and foothills rough fescue (Festuca hallii [Vasey] and F. campestris Rydb.), and smooth and meadow brome (Bromus inermis Leyss. and B. riparius Rehm). Response variables were shoot yield, root-shoot ratio, and water-use efficiency. We hypothesized that caespitose grasses, regardless of their origin or adaptation to agroclimate regime, would respond more determinately in biomass accumulation. Defoliation effects on shoot biomass were more pronounced under high moisture. Low intensity ? high frequency defoliation yielded similarly to deferred controls in all grasses, and the same was true for high-intensity ? low-frequency (HILF) defoliation in 1 rhizomatous grass. Three of the 4 rhizomatous grasses and 1 caespitose grass yielded greater under HILF defoliation compared with high-intensity ? high-frequency defoliation. Caespitose grasses allocated more biomass to roots under low moisture conditions. Water-use efficiency decreased under high moisture conditions and more intense and/or frequent defoliation and peaked in agronomic grasses. Overall, our results suggested that growth patterns corresponded more with phylogenetic similarity as opposed to growth form. A conceptual model from these results showed that across all species, only the introduced bromes generated greater biomass under HILF defoliation, and this may explain why past research consistently concludes that MIG does not enhance plant productivity on rangelands.     

Effects of exercise-induced stress and dexamethasone on plasma hormone and glucose concentrations and sedation in dogs treated with dexmedetomidine

OBJECTIVE: To compare the effects of pretreatment with dexamethasone, physical stress (exercise), or both on sedation and plasma hormone and glucose concentrations in dogs treated with dexmedetomidine (DEX). ANIMALS: 6 healthy purpose-bred Beagles. PROCEDURE: Dogs received 4 treatments each in a randomized order prior to i.v. administration of DEX (5 fLg/kg). Pretreatments were as follows: (1) i.v. administration of saline (0.9% NaCI) solution and no exercise (control group); (2) IV administration of dexamethasone (0.05 mg/kg) and no exercise (DM group); (3) i.v. administration of saline solution and exercise (EX group; 15 minutes of trotting on a treadmill at a speed of 2 m/s); and (4) i.v. administration of dexamethasone and exercise (DM+EX group). RESULTS: Following DEX administration, all dogs had similar times to recumbency and sedation index values, irrespective of pretreatment with values, irrespective of pretreatment with dexam-d ethasone or exercise. Plasma catecholamine concentrations decreased after DEX administration. Compared with control group dogs, plasma cortisol concentrations were higher in EX-group dogs prior to DEX administration and lower in DM- and DM+EX-group dogs following DEX administration. Administration of DEX decreased plasma cortisol concentration in EX-group dogs only. Plasma glucose concentration was not influenced by exercise or dexamethasone administration was lower than baseline concentrations at 30 minutes after DEX administration and returned to baseline values by 90 minutes. Heart and respiratory rates and rectal temperature increased during exercise. After DEX administration, these values decreased below baseline values. The decrease in heart rate was of shorter duration in dogs that underwent pretreatment with dexamethasone, exercise, or both than in control group dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Pretreatment with dexamethasone, moderate physical stress (exercise), or both did not influence sedation or cause adverse effects in healthy dogs treated with DEX.     

The detection and characterisation of Dichelobacter nodosus from cases of ovine footrot in England and Wales

Footrot, caused by the strictly anaerobic bacterium Dichelobacter nodosus, is the most common cause of lameness in sheep in Great Britain but problems exist in association with its diagnosis and control. The fastidious nature of D. nodosus means that complex media and several weeks are required for characterisation. An alternative method to simplify and enhance the detection of D. nodosus in clinical samples is therefore highly desirable. In terms of control, anecdotal evidence from the farming community suggests that the commercially available vaccine, based on Australian isolates of D. nodosus, is not widely employed in this country due to its perceived inefficacy. Seven hundred and six isolates, collected from outbreaks in England and Wales, were therefore used to investigate these issues. A 16S rRNA PCR was adapted to detect D. nodosus in clinical material within 1 day of sampling; a 15% increase in detection compared with culture and less than 1% false negatives were achieved. This represents a major advance in the rapid diagnosis of footrot and will be of great value to practitioners and diagnostic laboratories. Bacterial virulence was tested using protease thermostability and zymogram assays, whilst serogrouping was performed by slide agglutination. All isolates demonstrated virulence patterns previously recorded in Australia and all nine serogroups of D. nodosus (A-I) were represented. Serogroup H was predominant. There was, therefore, no evidence for the presence of novel strains of D. nodosus compared with Australia suggesting the need for further investigation into farmers' views on the use of the commercial vaccine in Great Britain.     

Acute post-parturient haemoglobinuria in dairy cows and phosphorus status

During the conduct of an experiment designed to examine the nutritional management of dairy cows in late pregnancy, four cows out of 72 suffered from acute haemoglobinuria two to four weeks after calving. Thirty-six thin and 36 fat cows were individually fed one of three diets based on a total mixed ration with different energy or protein concentrations during the last 3 to 4 weeks before expected calving date. After calving, cows grazed pasture and were offered 6 kg dry matter of pelleted concentrates daily. The P concentrations of the feeds offered suggested that the cows' diets were marginally deficient in P relative to requirements. Plasma P concentrations were significantly (P < 0.05) lower in fat cows than in thin cows during the first 6 weeks of lactation (0.87 versus 1.12 mmol/L), but precalving diet had no effect (P > 0.05). Concentrations of plasma inorganic P of the four fat cows that developed acute haemoglobinuria were less than 0.3 mmol/L. However, plasma P concentrations in another 12 cows, none of which displayed overt symptoms, declined to similar levels. It appeared that inadequate dietary P may have predisposed cows to acute haemoglobinuria, but the precipitating cause was not readily obvious.     

The Effects of the Periodical Use of In-feed Chlortetracycline on the Reproductive Performance of Gilts and Sows of a Commercial Pig Farm with a History of Clinical and Subclinical Viral and Bacterial Infections

The objective of this study was to assess the effects of in‐feed chlortetracycline (CTC) as a measure of preventing or minimizing infectious problems of reproductive failure in gilts and sows. In a farm of 400 Large White × Landrace gilts and sows with a clinical history of porcine respiratory and reproductive syndrome (PRRS) virus, the animals were treated with CTC. Treatment consisted of 10 g CTC sow/day for 15 days every 3 months. It improved the health status of sows by decreasing post‐farrowing clinical mastitis and vaginal discharges, abortions, return‐to‐oestrus and irregular return‐to‐oestrus rates. These beneficial effects had a positive impact on the performance of the litter. More piglets were born live and weaned. These positive effects improved with repeated use of CTC. The serological evidence of PRRS virus, Leptospira spp. and Chlamydia spp. and the subsequent beneficial use of the antimicrobial agent indicate that reproductive failure, possibly resulting from the bacterial agents can be controlled with in‐feed use of broad spectrum antimicrobials.     

Temporomandibular dysplasia in American Cocker Spaniels

Temporomandibular dysplasia was found in six American Cocker Spaniels related to each other. Clinical signs and diagnosis are described.     

Aortic interruption in a dog.

A 3-month-old English Bulldog was found to have a discontinuity between the ascending and descending aorta. There were no signs of illness associated with the interruption. The descending aorta was supplied with blood by collateral circulation. An aortic graft of woven synthetic material was surgically implanted to connect the ascending and descending aorta. Without any restrictions on the dog's activity, the dog has lived for over 1 year and continues to do well.     

Suspected chlorpyrifos toxicosis in a llama, and plasma pseudocholinesterase activity in llamas given chlorpyrifos

Five days after treatment with chlorpyrifos, a 1.5-year-old male llama was unable to stand, had saliva flowing from its mouth, and had constricted pupils, hyperglycemia, a metabolic acidosis, and a plasma pseudocholinesterase activity of 111 IU/L. Mean (+/- 1 SD) plasma pseudocholinesterase activity of 29 healthy llamas was 233.76 +/- 51.55 IU/L. Five to 8 days after topical application of chlorpyrifos (25 mg/kg of body weight) to 3 healthy llamas, the pseudocholinesterase activity decreased to 38% to 62% of pretreatment (base-line) activity and returned to within 90% of base-line activity by the 36th to 48th day after treatment.     

Conjunctivitis, tracheitis, and pneumonia associated with herpesvirus infection in green sea turtles

Fourteen juvenile (15- to 20-month-old) green sea turtles (Chelonia mydas), representative of a group of sea turtles with clinical signs of respiratory tract disease, were euthanatized and submitted for necropsy. Macroscopically, lesions included periglottal necrosis, tracheitis with intraluminal caseous and laminated necrotic debris, and severe pneumonia. Several turtles had caseous conjunctival exudate covering the eyes. Microscopically, the turtles had fibrinonecrotic inflammation around the glottal opening, tracheitis, and severe bronchopneumonia and interstitial pneumonia. In multifocal areas, periglottal and tracheal epithelial cells adjacent to areas of necrosis had hypertrophic nuclei with amphophilic intranuclear inclusions. A mixed population of primarily gram-negative microorganisms was isolated from the tracheal and glottal lesions. Attempts at viral isolation in cultures of green sea turtle kidney cells resulted in the development of cytopathic effects characterized by giant cell formation and development of intranuclear inclusions. Using electron microscopy, intranuclear viral particles (88 to 99 nm in diameter) were seen in inclusion-containing tracheal and glottal epithelial cells and infected green sea turtle kidney cells; particles were consistently seen enveloping from nuclear membranes, and mature particles (132 to 147 nm) were found in the cytoplasm. On the basis of size, conformation, location, and presence of an envelope, the particles most closely resembled those of herpes-viruses.