Characteristics of drug use on sheep farms in Ontario, Canada

This study examined characteristics of the use of drugs, especially antimicrobials, on Ontario sheep farms. Forty-nine sheep farms participated in a 12-month prospective study. Producers documented treatment events during the study period and drug use data from the records were summarized. The most frequently used drugs of the 15 drug categories used by producers belonged to the following categories: antimicrobial (40.7%, n=2710), vitamin/mineral (12.0%), and biological (11.1%). Short-acting penicillin (27.2%, n=1103), long-acting oxytetracycline (22.9%), and long-acting penicillin (21.9%) were the most frequently used antimicrobials. The drugs that were used most frequently on sheep farms were antimicrobials, of which 93% of treatments were extra-label. Extensive extra-label drug use may be the result of the limited number of drugs that are approved in Canada for use in sheep.     

Effect of tannin extracts on protein degradation during ensiling of ryegrass or lucerne

Eleven laboratory‐scale trials were undertaken in different years where ryegrass (Lolium perenne L.) or lucerne (Medicago sativa L.) were ensiled with different concentrations of tannin extracts (quebracho, Schinopsis balansae Engl., mimosa, Acacia mearnsii DE WILD.), and the effects on protein degradation were assessed. The dry‐matter (DM) content in grass silages ranged between 186 and 469 g/kg and in lucerne silages between 187 and 503 g/kg. Tannin extract, either quebracho or mimosa, was applied at 0–30 g/kg forage DM. Commercial additives such as Lactobacillus plantarum, formic acid or hexamine + NaNO₂ were applied in two of the grass trials and in six of the lucerne trials. Eight of the trials incorporated a maximum ensiling duration of 90 or 180 days in addition to replicates which were opened and evaluated at earlier stages. All trials included silages which were assessed after at least 49 days of anaerobic storage. The crude protein (CP) fraction A (non‐protein nitrogen, NPN) as proportion of total CP, served as the main indicator for proteolysis. In ryegrass, in general, the level of proteolysis was lower than in lucerne. A correlation of DM content in silages and degree of proteolysis was only evident for ryegrass. In both forages, the degradation of true protein slowed considerably after 24 days of ensiling. True protein was conserved most with the highest level of tannin extract addition. However, in lucerne, the combination of formate with lactobacilli was equally effective up to 330 g DM/kg, and deamination was further inhibited by formic acid compared to tannin extracts.     

Genetic variation in resistance to infectious pancreatic necrosis in rainbow trout (Oncorhynchus mykiss) after a challenge test

In this study, we wanted to evaluate genetic variation in resistance to infectious pancreatic necrosis (IPN) in a breeding population of rainbow trout. Two hundred families were challenged at a commercial test station, using methods that were previously developed for testing resistance to IPN in Atlantic salmon. Thirty‐five days after the challenge the accumulated mortality was 26%. The results show that resistance to IPN is moderately heritable in the tested population (h²=0.30). The genetic correlation between IPN resistance and body weight was found to be low and non‐significant. The significant additive genetic variation found in IPN resistance after a controlled challenge test gives promise for successful breeding for increased resistance to IPN in rainbow trout.     

Pelagic–littoral resource polymorphism in Hovsgol grayling Thymallus nigrescens from Lake Hovsgol,Mongolia

Resource polymorphism is a widespread phenomenon in post‐glacial fishes where multiple morphotypes of a species occur sympatrically and exhibit distinct resource use. Availability of open niches and high levels of within and among species competition are thought to drive differences in morphology and may provide insights into early stages of speciation. Hovsgol grayling (Thymallus nigrescens) are endemic to Lake Hovsgol, a lake colonised by fish following the Pleistocene, and are threatened with habitat loss due to climate change and illegal harvest. Previous analysis of Hovsgol grayling diet inferred through C and N stable isotopes suggested the presence of littoral and pelagic foraging groups. We hypothesised that morphology of the two foraging groups would reflect predictions of functional morphology, indicating the presence of resource polymorphism. To test this hypothesis, we evaluated evidence from C and N stable isotopes, stomach contents, fish ages, capture location and morphology. Two foraging groups of Hovsgol grayling were identified through stomach content and C and N stable isotope analysis. Individuals with greater zooplankton consumption were more frequently captured in the pelagic zone, exhibited higher gill raker counts, larger orbit (eye) sizes, longer paired fins, narrower head width, larger maxilla and smaller size at age than the group with greater reliance on benthic invertebrate prey. These differences were generally consistent with those described in other fish species exhibiting littoral–pelagic resource polymorphism. Our study provides the first example of littoral–pelagic resource polymorphism in the salmonid subfamily Thymallinae and highlights the potential influence of competition on fish evolution.     

Earthworms as seedling predators: Importance of seeds and seedlings for earthworm nutrition

Anecic earthworms have been shown to collect, concentrate and bury seeds in their burrows. Moreover, recent studies suggest that earthworms function as granivores and seedling herbivores thereby directly impacting plant community assembly. However, this has not been proven unequivocally. Further, it remains unclear if earthworms benefit from seed ingestion, i.e., if they assimilate seed carbon. We set up a series of three laboratory experiments in order to test the following hypotheses: (1) anecic earthworms (Lumbricus terrestris L.) not only ingest seeds but also seedlings, (2) ingestion of seedlings is lower than that of seeds due to a ‘size refuge’ of seedlings (i.e., they are too big to be swallowed), and (3) seeds and seedlings contribute to earthworm nutrition. L. terrestris readily consumed legume seedlings in the radicle stage, whereas legume seeds and seedlings in the cotyledon stage, and grass seeds and seedlings in the radicle and cotyledon stage were ingested in similar but lower amounts. Importantly, ingestion of seedlings, in contrast to seeds, was lethal for all plant species. Moreover, earthworm weight change varied with the functional identity and vitality of seeds and natural ¹⁵N signatures in earthworm body tissue underlined the importance of seedlings for earthworm nutrition. The results indicate that the anecic earthworm L. terrestris indeed functions as a granivore and seedling herbivore. The selectivity in seedling ingestion points at the potential of direct earthworm effects on plant community assembly. Further, seeds and seedlings most likely contribute significantly to earthworm nutrition potentially explaining the collection and concentration of seeds by L. terrestris in its middens and burrows; however, the present results call for experiments under more natural conditions.     

Comment on "Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification"

Meredith et al. (Reports, 28 October 2011, p. 521) question three findings of our delayed-rise hypothesis for present-day mammals made with reference to the Cretaceous-Paleogene (KPg) boundary, based on their new time tree of the group. We show that their own data do not support their objections and that the macroevolutionary patterns from the respective phylogenies are not statistically different.