Effects of 3 levels of distillers grains (DG) and 3 ratios of steam-flaked corn (SFC) to ground corn (GC) were used to evaluate IVDMD, in vitro gas production kinetics, and in vitro H 2 S produc
The effects of wet distillers grains with solubles (WDG) on in vitro rate of gas production, IVDMD, H(2)S production, and VFA were evaluated. Five substrate treatments that were balanced for ether extract content were arranged in a 2 x 2 + 1 factorial. Factors were concentration (15 or 30%; DM basis) and source of WDG (corn or sorghum WDG; CDG and SDG, respectively) plus a 0% WDG control in substrates with steam-flaked corn as the basal grain. Control substrates had greater (P < 0.01) IVDMD and total gas production per gram of substrate DM than WDG-based substrates, and IVDMD was greater (P = 0.03) for CDG than for SDG substrates. Increasing WDG inclusion from 15 to 30% decreased IVDMD and total gas production (P < 0.05), but H(2)S production (micromol/g of fermentable DM) increased (P = 0.01) as inclusion of WDG increased. There were no differences (P > or = 0.10) among treatments in proportions of major VFA, acetate:propionate ratio, and total VFA concentration. These results suggest that including WDG in the substrate decreased IVDMD and gas production, which was particularly evident as WDG increased from 15 to 30% of substrate DM. In addition, CDG seemed to be more digestible than SDG. Hydrogen sulfide production increased with increasing WDG in the substrate, reflecting greater S concentrations in WDG, but in vitro VFA profiles were not affected by WDG concentration or source.
Abstract. 1. Species that undertake regular two‐way migration may be expected, through population connectivity, to exhibit some level of genetic similarity over broad spatial scales. Although seldom following two‐way migration, highly mobile insect species tend to exhibit either low haplotype diversity and no phylogeographic structuring, or relatively high haplotype diversity and pronounced phylogeographic structuring. 2. This study reveals the first wide‐scale genetic characterisation of a migratory dragonfly, the common green darner Anax junius Drury. Unusually for insects, north‐south two‐way migration is common in this species, although not obligatory. In at least part of its range, some individuals follow an extended developmental period and overwinter in a state of diapause. 3. Mitochondrial sequence data were obtained from 92 A. junius individuals collected from 35 sites across Canada, U.S.A., and Mexico. These revealed 38 haplotypes, some of which were extremely widespread, although the majority (27 haplotypes) was found in only one individual. In contrast to previous studies on mobile insects, the overall pattern was of relatively high haplotype diversity in the absence of phylogeographic structuring. 4. Migrants and non‐migrants, which sometimes shared haplotypes, were distributed across multiple genetic lineages. This suggests that, contrary to some earlier assertions, developmental pathways in this species may be plastic. Such plasticity would allow highly mobile species to adapt to a range of environmental conditions, and may be key to the widespread distribution of multiple haplotypes.
The ultrasound-induced negative phonotactic response of tethered, flying Australian field crickets habituates to repeated stimuli. Using the magnitude of the metathoracic leg's swing during a series of ultrasonic stimuli as a measure of habituation, we show that: (1) the response declines exponentially; (2) the response recovers spontaneously; (3) repeated trials produce more rapid and stronger habituation; (4) successive stimuli presented more rapidly produce more rapid and stronger habituation; (5) a weaker stimulus intensity produces more rapid and stronger habituation; (6) the habituation shows stimulus generalization (i.e. the response is similar for different ultrasonic frequencies); (7) a novel stimulus produces dishabituation; and (8) the effect of the dishabituating stimulus habituates after repeated trials. These findings place habituation of cricket negative phonotaxis in the context described for habituation in mammals.
Most Odonata probably exert some control over their body temperature. Such behaviour is favored by the high, variable temperature of their terrestrial habitat and by the fact that dragonflies are relatively large insects and thus exchange heat with the environment comparatively slowly. Different species may thermoregulate behaviorally by controlling the external heat load or physiologically by altering the amount of heat generated by or dissipated from the thoracic muscles. The former method is characteristic of perchers, which are usually in a situation that permits considerable modulation of intercepted solar radiation, mostly by postural adjustments. There is also evidence that some species may perch more frequently in the shade when ambient temperature is high. Fliers, by contrast, have little opportunity to control intercepted solar radiation but continually generate large amounts of heat during flight. They may alter their rate of heat loss by controlling haemolymph flow from the thorax or their rate of heat gain by changing the proportion of gliding vs. flapping flight. Some species combine behavioral and physiological modes of regulation. Adaptive geographic, seasonal, and inter-habitat variation occurs in the responses of dragonflies to temperature. Voluntary avoidance of high temperature seems most closely adapted to the thermal environment. Temperature responses and thermoregulatory ability also vary with age and sex. The effects of temperature on the activity patterns of Odonata and the adaptive significance of thermoregulation have yet to be rigorously demonstrated in most cases.
Two experiments were conducted to evaluate the effects of BeefPro (C&E Agri Products, Baldwin, ND), a microencapsulated direct-fed microbial containing lactate-producing bacteria and digestive enzymes, on performance and carcass characteristics of feedlot cattle and on in vitro fermentation of high-concentrate substrates. In the performance study, 96 steers (average BW = 321 kg) were allotted randomly to 2 treatments: (1) control or (2) 200 mg/d per steer of BeefPro. Final BW did not differ between treatments (P = 0.19); however, steers fed BeefPro tended (P = 0.10) to have a greater carcass-adjusted final BW. Steers fed BeefPro tended (P < 0.07) to have a greater live-weight-basis ADG for the overall feeding period, and carcass-adjusted ADG was greater (P = 0.037) for cattle fed BeefPro. Dry matter intake was greater by steers fed BeefPro (P = 0.04), but G:F (P > 0.55) did not differ between treatments on a live-weight or carcass-adjusted basis. In the in vitro study, the same treatments as in the performance study were used in high-concentrate substrates to determine IVDMD and gas production kinetics. Neither gas production kinetics nor IVDMD was altered by BeefPro at 21.2 mg/kg of DM compared with control (P ≥ 0.10). Although in vitro data did not provide evidence of alterations in ruminal fermentation by including BeefPro in substrates, feedlot performance data suggest that BeefPro, when fed daily at a dose of 200 mg per steer, can have positive effects on DMI and ADG of finishing beef cattle.
