Dissipation of bacterially derived C and N through the meso- and macrofauna of a grassland soil

Feeding relationships between organisms may be determined by observations of behaviour in manipulative experiments or, as in more recent times, by the use of stable isotope labelling to trace the passage of ¹³C and ¹⁵N through food webs. Here we introduce living bacteria, labelled with both ¹³C and ¹⁵N into intact soil cores to understand further the movement of bacterially sourced C and N into the meso- and macrofauna of a grassland soil. We found that these groups showed a range of isotope levels which relate to their feeding strategies. Some had no label (e.g. dipterous larvae), whilst others were highly labelled which may indicate a preference for the added bacteria. This latter group included Collembola, generally perceived as being predominantly fungal feeders. This work describes a novel technique which has the potential to provide critical information about the dissipation of bacterially derived C and N through the soil food web.     

Seedbank persistence,germination and early growth of glyphosate‐resistant Kochia scoparia

This study describes the seedbank persistence of glyphosate‐resistant (GR) Kochia scoparia at two sites in western Canada and examines if GRK. scoparia from western Canada and mid‐western United States (USA) differ from their susceptible counterparts in seed germination and early growth characteristics at low‐temperature regimes. Site or depth of seed burial (surface, 2.5 cm, 10 cm) did not affect seed viability over time and time to 50% and 90% loss of viability averaged 210 and 232 days respectively. Glyphosate‐resistant K. scoparia generally germinated later and had lower cumulative germination than glyphosate‐susceptible (GS) K. scoparia from Saskatchewan, Canada; and Kansas, USA; but not Colorado, USA. Similarly, time to 10% first leaf of GSK. scoparia from Saskatchewan and Kansas tended to be sooner than that of GRK. scoparia, with a greater percentage of GS vs. GR seedlings of populations from all regions having attained first leaf by the end of the experiment. The short seedbank longevity and delayed and reduced germination and time to first leaf of GRK. scoparia may potentially be exploited to maximise management efficacy through delayed preseeding weed control or alternatively by early seeding date to enhance crop competitiveness.     

Impact of ferulic acid esterase‐producing lactobacilli and fibrolytic enzymes on ensiling and digestion kinetics of mixed small‐grain silage

This study evaluated the effects of a ferulic acid esterase (FAE) and a non‐FAE‐producing inoculant applied alone or in combination with exogenous fibrolytic enzymes (EFE) on the fermentation and nutritive value of mixed grain (barley, oats and spring triticale) silage. The mixed crop was ensiled in laboratory mini‐silos either untreated (CON), or treated with a FAE inoculant (FAE), a non‐FAE inoculant (NFAE) or NFAE + EFE. Inoculated silages were lower (P < 0·01) in water‐soluble carbohydrate, whereas NFAE and NFAE + EFE silages had higher (P < 0·001) DM loss than other silages. FAE and NFAE silage had higher neutral detergent fibre (NDF), but were lower in NFAE + EFE than other silages (P < 0·001). Copy numbers of 16S rRNA associated with Lactobacillus buchneri were higher (P < 0·001) in NFAE and NFAE + EFE silages than in others, resulting in higher (P < 0·001) acetic acid in these silages. NFAE + EFE silage had lower (P < 0·001) in vitro gas production and NDF digestibility (NDFD) than other silages. FAE silage had higher (P < 0·01) in situNDFD than CON and NFAE + EFE silages. Inoculation of mixed small‐grain silage with NFAE‐producing inoculants combining EFE reduced NDFD.     

麦秸覆盖与除草剂相结合对免耕玉米田杂草的控制效果研究

1997～2001年,采用大田试验与室内生物测定相结合的方法,就麦秸覆盖与苗后除草剂减量施用相配合对免耕玉米田杂草的控制作用及机理进行了研究.结果表明玉米播种后田间采用麦秸覆盖可在一定程度上控制杂草的发生.当麦秸覆盖量为4 500～7 500 kg/hm2时,玉米田杂草密度比不覆盖的处理降低49.1%～96.1%,在这样的小区除草剂采用定向喷雾,即使苗后茎叶处理除草剂玉农乐和阿特拉津的用量比常规用药量减少1/4时,小区内除草效果仍可以达到91.8%～94.3%.     

Some factors influencing the economics of pesticide use in grassland

The point at which benefits from pest control exceed costs will vary because of fluctuations in prices. This is particularly true for grassland pests where the value of grass is measured indirectly as animal protein. Successful pest control in grass will result in an increased margin/ha for the farm. Simple models are presented to illustrate differences in cost/benefit ratios resulting from different strategies for the utilization of the increased resources made available by pest control. It is concluded that the point where pest control costs equals benefits in grass is never constant but is unique to a farm, a season and a management strategy.     

THE EFFECT OF PEN DESIGN AND THE TRANQUILISING DRUG, AZAPERONE, ON THE GROWTH AND BEHAVIOUR OF WEANED PIGS

SUMMARY Two experiments were carried out in a 55-sow, specific pathogen free commercial unit, to assess the effects of the tranquilising drug, azaperone, on pigs mixed at weaning. The drug is claimed to inhibit aggression in pigs mixed at weaning, and also to increase the average weight gain in groups of growing pigs. The first experiment used a single test and control group, and the second experiment was a 2 times 2 factorial design, the variables being the presence or absence of the drug, and the presence or absence of a box used to modify the weaner pen environment. In both experiments there were no significant differences in rates of agonistic interactions between treated and untreated groups, although the drug delayed the first agonistic encounters for about 8 hours. Nor was there any difference in the relative growth rate between treated and untreated groups in either experiment.     

EFFECT OF FEEDING REGIMEN ON GASTRIC ULCERATION OF THE PARS OESOPHAGEA OF INTENSIVELY RAISED PIGS

Three groups of pigs (total 23 pigs) were fed ad libitum from weaning until market weight and these were compared with three groups of pigs (total 26 pigs) fed ad libitum until 12 weeks of age, and then fed on a restricted regimen (twice per day) until marketed.
There was a significant difference in degree of ulceration between the two feeding regimens; those pigs fed ad libitum had the most severe gastric ulcers.
The pigs fed ad libitum , had significantly less agonistic interactions per minute than did the restricted fed pigs. Growth rates of the pigs from weaning to market weight did not differ significantly in the two regimens, although the average pig on ad libitum feeding consumed 182.9 kg, and the restricted fed pigs ate 148.2 kg per pig.     

The effect of air movement on the activity, lying position and huddling behaviour of weaned piglets

An experiment was carried out in a 55-sow, specific pathogen-free commercial unit, to observe the behavioural adaptation of newly weaned pigs (7 to 10 kg) to air movement in a typical weaner pen. Direct air currents were generated by a fan placed at 4 positions around the pen. Observations were made of activity, lying position, huddling and orientation. Increased activity was observed when the wind was directed on to the preferred lying area of the pigs. The pigs usually moved out of the region of greatest air movement and indirect currents appeared to be more favourable. Wind inhibited huddling in the pigs when it was directed over the lying area but orientation was unaffected. Social factors were important in the choice of lying position. The percentage of pigs huddling gave a behavioural indication of the suitability of the husbandry environment for production and welfare.