Quackgrass (Elytrigia repens) managed as a cover crop in herbicide-resistant silage corn

The groundcover levels after corn ( Zea mays L.) silage harvest are rarely adequate to prevent soil erosion, but most corn-growers do not plant cover crops due to time and cost limitations. Herbicide-resistant corn hybrids provide opportunities to control weeds and to utilize cover crops in previously unexplored combinations. Field studies were conducted in 1999 and 2000 at Dryden and Valatie, New York, USA, to determine the potential for managing existing quackgrass ( Elytrigia repens [L.] Nevski) as a cover crop in herbicide-resistant silage corn. Three isolines of the corn hybrid, DKC493, were treated with glyphosate, glufosinate, primisulfuron, nicosulfuron or sethoxydim. Averaged over all site–years, the corn silage yields with glufosinate were similar to those with glyphosate. Glufosinate also resulted in a quackgrass ground cover greater than the 30% threshold for preventing soil erosion. Quackgrass could be managed as a perennial cover crop in silage corn–perennial forage dairy rotations in north-eastern USA.     

有机配体、竞争阳离子和pH对土壤中Zn分解的影响

A series of experiments were conducted to examine the interactive effects of an organic ligand, a competing cation, and pH on the dissolution of zinc （Zn） from three California soils, Maymen sandy loam, Merced clay, and Yolo clay loam. The concentrations of soluble Zn of the three soils were low in a background solution of Ca（NO3）2. Citric acid, a common organic ligand found in the rhizosphere, was effective in mobilizing Zn in these soils; its presence enhanced the concentration of Zn in soil solution by citrate forming a complex with Zn. The ability of Zn to form a complex with citric acid in the soil solution was dependent on the concentration of citric acid, pH, and the concentration of the competing cation Ca^2＋. The pH of the soil solution determined the extent of desorption of Zn in solid phase in the presence of citric acid. The amounts of Zn released from the solid phase were proportional to the concentration of citric acid and inversely proportional to the concentration of Ca（NO3）2 background solution, which supplied the competing cation Ca^2＋ for the formation of a complex with citrate. When the soil suspension was spiked with Zn, the adsorption of Zn by the soils was retarded by citric acid via the formation of the soluble Zn-citrate complex. The dissolution of Zn in the presence of citric acid was pH dependent in both adsorption and desorption processes.     

Effect of Tamoxifen Citrate on Canine Immobilization (Disuse) Osteoporosis

The effect of tamoxifen citrate on bone mass in immobilization osteoporosis was studied in 11 growing dogs. Immobilization osteoporosis was induced by fiberglass cast immobilization of the right hindlimb for 28 days, while the left hindlimb served as a nonimmobilized control. Six dogs received tamoxifen citrate (1.5 mg/kg per os) once daily for 28 days; five dogs received no treatment. All dogs were euthanatized on day 28 and bone samples were collected. Bone mineral content of the distal tibial metaphysis of casted and uncasted limbs was measured by single photon absorptiometry. Immobilization resulted in a significant reduction in bone mass in the casted limb of untreated and tamoxifen-treated dogs. However, tamoxifen-treated dogs had less severe immobilization osteoporosis than untreated dogs. The calculated bone mass sparing effect of tamoxifen was 24.4%. Because of the complexity of pathologic bone remodeling, use of a single therapeutic agent may not be the optimal means of preventing bone loss associated with immobilization.     

Subtropical goats ovulate in response to the male effect after a prolonged treatment of artificial long days to stimulate their milk yield

The objectives of this study were to determine (i) if in subtropical goats that gave birth during mid‐December, the exposition to an artificial long‐day photoperiod consisting in only 14 hr of light per day can increase the milk yield and (ii) to test whether these females can respond to the male effect at the end of the prolonged photoperiodic treatment. In experiment 1, 17 lactating goats were maintained under natural short days (control group), while another 22 goats were maintained under artificial long days (treated group) consisting in 14 hr light and 10 hr darkness starting at day 10 of lactation. The continuous exposition to an artificial long‐day photoperiod produced an increase in the milk yield level during the first 110 days of lactation (time × treatment interaction; p = .01), while none of the milk components were modified due to the photoperiodic treatment (p > .05). In experiment 2, all control and treated anovulatory goats were submitted to the male effect using photostimulated males. All females showed oestrous behaviour within the first 10 days that were in contact with males (100% in both groups; p > .05). Thus, the latency to onset of oestrus did not differ between females from control (58.2 ± 3.0 hr) and treated (62 ± 4.6 hr) groups. Male exposition provoked ovulation independently if females were previously under long days or natural photoperiod (96 vs 100%, respectively; p = .79). It was concluded that exposure to 14 hr of light per day in subtropical goats that gave birth in late autumn stimulates milk yield without preventing the ovulation in response to the male effect at the end of the prolonged photoperiodic treatment.     

Detection of Toxoplasma gondii DNA in Fresh and Frozen Semen from Rams in Brazil

The aim of this study was to estimate the prevalence of genomic DNA of Toxoplasma gondii in semen samples from commercial rams in artificial insemination centres in Brazil, as well as in fresh semen from rams in the northeast of Brazil. In total, 108 semen samples were obtained from artificial insemination centres, and genomic DNA of T. gondii was detected in 24 of 108 (22.2%). The prevalence of antibodies anti‐Toxoplasma gondii among sheep on rural properties was 9.2% (10/109), and 100% of the semen samples of these animals were positive in the PCR for T. gondii DNA. The molecular identity was confirmed through sequencing, which indicated 99.9% similarity with the T. gondii DNA sequences stored in the GenBank. This study reports the first occurrence of T. gondii DNA in the semen of rams, which came from artificial insemination centres in Brazil, as well as the occurrence of T. gondii DNA in the fresh semen of naturally infected rams in the northeast of Brazil.     

Short‐term outcome of equine emergency admissions at a university referral hospital

Reasons for performing study: Obtaining data on emergency admission survival rates is important to provide clients with an estimate of prognosis and to identify areas in which improvements in case management can be achieved. Objective: To determine the short‐term outcome of equine emergency admissions to a university referral hospital during a 12 month period. Methods: Short‐term outcome was defined as survival to discharge or died/euthanasia during hospitalisation. The overall death (euthanasia) rate was calculated; and rate for horses with different categories of: age; admission month, day and time; presenting complaint (PC); duration of clinical signs prior to presentation; clinical pathology abnormalities; and therapy/therapeutic‐related procedures performed was recorded. Results: There were 918 admissions. The overall death rate was 24%. Foals (34%) and geriatric (40%) subjects had a death rate that was higher than that for mature horses (21%, referent). The death rate was highest in March (37%). Horses with a PC categorised as neurological (46%) or neonatal (41%) had the highest and as ophthalmological (5%) or trauma/skin (13%) the lowest death rates. There was no difference in death rate between different admission days or times or the duration of clinical signs prior to presentation. The death rates for horses with abnormal peritoneal fluid (71%), coagulopathy (63%), acid‐base abnormalities (52%), hypoproteinaemia (47%), dehydration (43%), hypoxia/hypercapnia (48%), leucopenia (44%), electrolyte abnormalities (39%), hyperlactataemia (39%) or azotaemia (35%) were high. The death rate for horses treated with intranasal oxygen (57%), plasma (34%) or polymixin B (35%) was high and for horses undergoing laceration repair/joint (0%) or synovial cavity lavage (4%) was low. Conclusions: Age and critical illness were important contributing factors to a higher death rate. Potential relevance: Improving the understanding of disease processes in and developing treatment strategies for neonatal and geriatric patients as well as critically ill patients is required.