Emergence of four weed species in response to rainfall and temperature

The key to achieving effective weed control is to target them when they are young. Understanding their temperature and moisture requirements for emergence will help growers to develop timely control strategies. This study examined the emergence requirements of four key species: Conyza bonariensis, Sonchus oleraceus, Echinochloa colona and Chloris virgata. Two experiments were conducted in a growth room with temperatures of 25/15 and 30/20°C day/night with a photoperiod of 12 h. The first experiment examined emergence under single rainfall events of 0, 2, 5, 10, 20, 30 and 50 mm. The second experiment examined emergence under accumulated rainfall events of 0 mm, 5 mm × 2 (consecutive) days, 5 mm × 4 days, 5 mm × 6 days, 10 mm × 1 day, 10 mm × 2 days and 10 mm × 3 days. The temperature was not significant on emergence in both experiments. In the first experiment, at least 10 mm of rainfall was required for the emergence of all the species, with significantly higher germination rates at rainfall amounts of >20 mm. In the second experiment, the species had higher emergence rates with accumulated rainfall over consecutive days, rather than single rainfall events of the same amount. The length of time that the soil surface remained above the permanent wilting point, allowing the imbibition of water, was also an important factor. This study has provided information on the drivers for emergence of these species and will assist growers in determining what rainfall events are likely to trigger emergence in the field and make timely weed management decisions.     

Ecosystem services: Classification for valuation

This letter is in response to an article by Ken Wallace titled “Classifications of ecosystem services: problems and solutions” (Biological Conservation 139, 2007). This letter discusses the points we see as problematic with Wallace’s framework and sets out our conceptualization of linking ecosystem services with human welfare. In this letter we suggest that utilizing the terms intermediate services, final services and benefits should go a long way to clearing up much of the ambiguity in ecosystem services typologies, especially for economic valuation purposes. As Wallace points out, clearly defining and organizing the concept of ecosystem services is not just a semantic decision, but it is integral to operationalizing something that can clearly illuminate tradeoffs in natural resource management.     

Vaccination of cows with clostridial antigens and passive transfer of clostridial antibodies from bovine colostrum to lambs

Two Friesian cows were used to attempt to produce colostrum containing a high concentration of clostridial antibodies which could be fed to newborn lambs in order to passively transfer immunity to diseases caused by clostridia. One cow was given a commercial multicomponent clostridial sheep vaccine in two successive pregnancies and the second cow in one pregnancy. The first cow produced a low concentration of epsilon antitoxin (Clostridium perfringens, type D) in its blood and colostrum after the first course of three injections of vaccine. A higher concentration was produced by cow 2 after a course of six injections and by cow 1 after a further course of four injections in its next pregnancy. Two hundred ml of colostrum from cow 1 (after the second course of vaccine) was given to 12 newborn colostrum-deprived lambs. All showed a high concentration of antitoxin 48 hours later. The lambs were actively immunised by injections of the same clostridial vaccine at three and nine weeks or six and 12 weeks old and all produced sufficient antitoxin to protect up to slaughter at 24 weeks. It is concluded that colostrum from cows vaccinated with sheep clostridial antigens can be fed to protect lambs passively.     

Heritability of body length and measures of body density and their relationship to backfat thickness and loin muscle area in swine

The objective of this study was to estimate heritability for body length (LEN) at the end of performance testing and to estimate genetic correlations with backfat (BF) thickness and loin muscle area (LMA) in Landrace, Yorkshire, Duroc, and Hampshire breeds of swine. Also examined were two measures of body density involving body length and weight and their relationships to backfat and loin muscle area. Data consisted of performance test records collected in a commercial swine operation from 1992 to 1999. Boars from 60% of the litters were culled at weaning based on a maternal breeding value of the dam. Remaining boars and all females were grown to 100 d of age (15,594, 55,497, 12,267, and 9,782 Landrace, Yorkshire, Duroc, and Hampshire pigs, respectively). At this time, all pigs were weighed (WT100) and selected for performance testing based on a combination of maternal and performance indexes, which differed by breed. All pigs were weighed at the end of the 77 d performance test (WT177) when BF, LMA, and LEN were measured. Two measures of body density involving length were calculated: Body mass index (BMI) = WT177/LEN2 and body density (DENSITY) = WT177/LEN. For each breed, genetic parameters were estimated using an animal model with random litter effects and multiple-trait REML procedures. A series of three-trait models including WT100 and combinations of two other traits in each analysis was conducted. Fixed effects included contemporary group and age as a covariate. Average estimates of heritability were 0.16 to 0.32 for LEN (unadjusted for WT177), 0.12 to 0.26 for LEN (adjusted for WT177), 0.23 to 0.33 for DENSITY, and 0.16 to 0.25 for BMI. Genetic correlations between LEN and LMA were low. Genetic correlations between LEN (unadjusted for WT177) and BF were 0.10 to 0.41. Adjusting LEN for WT177 gave correlations of 0.11 for Landrace and Hampshire and negative correlations (-0.06 and -0.19, respectively) for Yorkshire and Duroc. Genetic correlations between LMA and DENSITY and between LMA and BMI were comparable and ranged from 0.44 to 0.54. Genetic correlations between BF and DENSITY were slightly higher (0.53 to 0.68) than those between BF and BMI (0.37 to 0.67). In these data, not much relationship between BF and body length at a constant weight and age was found. There was a negative relationship between LMA and LEN at a constant weight and age, implying that longer pigs had smaller LMA.     

Teaching the principles of health management to first year veterinary students

A course called Health Management 1 was created as part of a new DVM curriculum at the Ontario Veterinary College. This full year course was designed to introduce students to basic concepts of health management, integrating the disciplines of epidemiology, ethology, and public health in the context of selected animal industries. The course was comprised of 60 lecture hours and four two-hour laboratories. A common definition of health management, incorporating five principles, was used throughout the course, in order to reinforce the concepts and to maintain continuity between lecture blocks. Unlike in the years prior to the introduction of the new curriculum, epidemiology was presented as a tool of health management rather than as a separate discipline. To supplement the lecture and laboratory material, a Web-based resource was created and the students were required to review the appropriate section prior to each lecture block. Small quizzes, consisting of 10 questions each within WebCT, were used to stimulate self-directed learning. Overall, the course was well received by the students. The Web resources combined with the WebCT quizzes proved to be an effective method of stimulating students to prepare for lecture.     

Effect of dietary oils and alpha-tocopheryl acetate supplementation on lipid (TBARS) and cholesterol oxidation in cooked pork

The effect of n-3 fatty acid-enriched diets (in the form of 0.5% linseed oil with either 1.5% sunflower oil or 1.5% olive oil) and alpha-tocopheryl acetate supplementation (200 mg/kg feed) on lipid oxidation (thiobarbituric acid-reactive substances, TBARS) and cholesterol oxide products (COPS) in cooked pork was investigated. Longissimus muscle was studied. Meat from pigs fed 0.5% linseed oil-enriched diets had a higher proportion of n-3 fatty acid than meat from pigs in other dietary groups in neutral (P < 0.0001) and polar lipids (P < 0.0001), and a 20% reduction in the n-6:n-3 ratio was observed. Alpha-tocopheryl acetate supplementation increased (P < 0.05) monounsaturated fatty acids in polar lipids and increased (P = 0.0001) alpha-tocopherol levels in muscle. Alpha-tocopherol concentration in muscle was affected by dietary fat (P < 0.05). Groups receiving diets enriched with sunflower oil had significantly higher alpha-tocopherol levels (P < 0.05) in muscle than those groups receiving olive oil-enriched diets. Numbers of TBARS were significantly (P < 0.05) lower in the group fed supplemental olive oil than in those fed sunflower oil. Dietary linseed oil increased (P < 0.05) lipid oxidation principally at the initial period of storage in cooked pork. Overall, dietary alpha-tocopheryl acetate supplementation significantly increased (P < 0.001) lipid stability and decreased (P < 0.05) total COP production across the dietary groups. Alpha-tocopherol was a more effective antioxidant for decreasing TBARS values in cooked meat when adding sunflower oil to the diets instead of olive oil.     

Pharmacology of narcotic analgesics in the horse: selective blockade of narcotic-induced locomotor activity

The locomotor responses of horses given morphine and fentanyl were blocked or lessened by administration of naloxone or acepromazine. Naloxone given at the dosage of 0.015 mg/kg completely blocked the locomotor activity induced in horses given fentanyl (0.020 mg/kg of body weight). The locomotor stimulation produced by morphine given at the dosage of 2.4 mg/kg was reduced by 75% of naloxone (0.020 mg/kg). Acepromazine partially blocked the locomotor responses to fentanyl and morphine. This blockade activity reached its peak about 30 minutes after acepromazine was given (IV) and lasted more than 6 hours. Simultaneous administration of acepromazine and morphine was associated with substantial respiratory depression for more than 4 hours after administration of both drugs. In other experiments, fentanyl did not add to the partial locomotor response observed after large doses of pentazocine were given--this being consistent with the concept that pentazocine possesses both antagonist and agonist actions at the narcotic receptor. Furosemide and phenylbutazone, given at usually used clinical doses, had no effect on the locomotor response to fentanyl, indicating that the usual clinical dosages of neither drug exerted stimulant or depressant actions.     

Ovarian follicular cysts in dairy cows: an abnormality in folliculogenesis

Ovarian follicular cysts are a major reproductive problem in lactating dairy cows. The primary physiological defect leading to the formation of ovarian follicular cysts is a failure of the hypothalamus to trigger the preovulatory surge of luteinizing hormone (LH) in response to estradiol. The factor responsible for this hypothalamic defect may be progesterone. Intermediate levels of progesterone have been shown to prevent ovulation and promote persistence of dominant follicles in normal cycling cows. Recently, we found that 66% of cows with ovarian follicular cysts had progesterone concentrations in an unusual, intermediate range (0.1-1.0 ng/mL) at the time of their detection. A majority of new follicles (76%) that develop in the presence of these intermediate progesterone concentrations became cysts. Only 10% ovulated. Based on these observations, a novel model for the formation and turnover of ovarian follicular cysts is proposed.     

Feline diabetes mellitus in the UK: the prevalence within an insured cat population and a questionnaire-based putative risk factor analysis

Prevalence and risk factors for the development of diabetes mellitus (DM) in cats in the United Kingdom have not previously been reported. The prevalence of DM was evaluated in a large insured population and was found to be 1 in 230 cats. In this insured cat population Burmese cats were 3.7 times more likely to develop DM than non-pedigree cats. A convenience-sampling questionnaire-based study was used in order to identify putative risk factors for the development of DM. The univariate risk factor analysis identified being male, neutered, inactive, weighing >or=5 kg and having a history of corticosteroid treatment as significant risk factors for the development of DM in these cats. In addition, male cats treated with megestrol acetate had a significantly increased risk of developing DM compared to females. In contrast, there was no difference in DM occurrence between male and female Burmese cats. A multivariate classification tree-based model on the questionnaire data looking for interactions between risk factors, identified gender as the most important overall risk factor for the development of DM with low physical activity being the next most important risk factor for female cats and breed the next most important for male cats.