31 research outputs found
Magnetic Field Generation in Stars
Enormous progress has been made on observing stellar magnetism in stars from
the main sequence through to compact objects. Recent data have thrown into
sharper relief the vexed question of the origin of stellar magnetic fields,
which remains one of the main unanswered questions in astrophysics. In this
chapter we review recent work in this area of research. In particular, we look
at the fossil field hypothesis which links magnetism in compact stars to
magnetism in main sequence and pre-main sequence stars and we consider why its
feasibility has now been questioned particularly in the context of highly
magnetic white dwarfs. We also review the fossil versus dynamo debate in the
context of neutron stars and the roles played by key physical processes such as
buoyancy, helicity, and superfluid turbulence,in the generation and stability
of neutron star fields.
Independent information on the internal magnetic field of neutron stars will
come from future gravitational wave detections. Thus we maybe at the dawn of a
new era of exciting discoveries in compact star magnetism driven by the opening
of a new, non-electromagnetic observational window.
We also review recent advances in the theory and computation of
magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo
theory. These advances offer insight into the action of stellar dynamos as well
as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field
generation in stars to appear in Space Science Reviews, Springe
Assessment of completeness of reporting in intervention studies using livestock: an example from pain mitigation interventions in neonatal piglets
Simulação técnico-econômica da inclusão de ractopamina em dietas de suÃnos em terminação
Metabolic and behavioral effects of ractopamine at continuous low levels in rats under stress
Preliminary evaluation of the potential efficacy of Cranial Electrotherapy Stimulation for the control of anxiety in the horse
Modification of piglet behavior and welfare by dietary antibiotic alternatives
Society is demanding a decrease in prophylactic use of antibiotics in animal production. This could impact animal welfare unless alternatives can be found that confer similar benefits without risk of AMR. The objectives of these studies were to determine whether two alternatives – a probiotic and an amino acid supplement – would impact piglet behaviour and welfare post-weaning. In Experiment 1, 240 weaned piglets were assigned to 3 diets for a 2-wk period post-transport: A – an antibiotic diet including Chlortetracycline + Tiamulin, NA – a control diet, and GLN – a diet including L-glutamine. After the 2-week period, all piglets were fed the same control diet. At weaning, piglets were transported for 12 hours. Tear staining and skin lesions were recorded pre- and post-transport. Novel object tests were done in groups in the pigs’ home pen 4 times post-weaning. In Experiment 2, 36 female piglets were assigned to 2 supplement treatments from 24-h to 28 d of age: SYN – a synbioticcontaining Lactobacillus, fructo-oligosaccharide and β-glucan in chocolate milk, and CTL – chocolate milk only. Piglets were subject to episodic-like (Object Recognition), working (Barrier Solving) and long-term (T-maze) memory tests. In Expt 1, NA pigs had larger tear stains than A and GLN pigs. NA pigs had more skin lesions post-mixing than A and GLN pigs. In the first novel object test, A pigs avoided the object more than NA pigs. In later tests, NA pigs spent less time exploring the object and took longer to interact with the object than GLN and A pigs. In Expt 2, in the object recognition test, SYN piglets interacted more quickly with the novel object. In the barrier solving test, SYN piglets had shorter distances to finish the test. In the T-maze test, SYN piglets were quicker to learn the task. Overall, the results demonstrate that short-term feeding strategy can have both short- and long-term effects on behaviour and welfare. Supplementation with L-glutamine appears to confer similar benefits to dietary antibiotics and the synbiotic supplement improved piglet cognitive performance
Effects of floor cooling on behavior and physiology of lactating sows during acute heat stress
Much U.S. swine production is in Köppen climate types classified as ‘hot-summer humid continental’ and ‘humid subtropical’. As a result, farrowing sows are often exposed to temperatures above their upper critical temperature. This heat stress (HS) can affect sow welfare and productivity and have a negative economic impact. The study objective was to evaluate the impact of a cooling pad on sows’ behavioral and heart rate responses to acute HS. Treatments were randomly allotted to 10 multiparous sows to receive a constant cool water flow of 0.00 (CONTROL, n=4), 0.25 (LOW, n=2), 0.55 (MEDIUM, n=2) or 0.85 (HIGH, n=2) L/min for 100 min and replicated eight times, switching treatments so that each sow was exposed to each treatment. The cooling was initiated 1 hour after the room reached 35°C for 100 min. Eating, drinking and nursing behaviors, postures and heart rate were recorded before heating (Period 1), prior to cooling (Period 2), and during cooling (Period 3). There were no differences between LOW, MEDIUM and HIGH flow rates for any periods on all behavioral and heart rate traits, so data were pooled (COOLED). There were no differences in any of the measures during Periods 1 and 2, except for the ratio of short term to long term heart rate variability (SD1:SD2) with higher values for CONTROL than COOLED sows in Period 2. During Period 3, CONTROL sows changed postures more frequently (11.5±1.6 vs 5.1±1.6 changes per hour), spent more time drinker-pressing/drinking (4.4±0.5 vs 1.4±0.4% of time), standing (6.6±1.7 vs 3.8±1.6% of time), sitting (10.0±1.2 vs 4.0±1.1), less time lying (83.0±1.8 vs 92.0±1.7% of time), especially lying laterally (62.0±5.6 vs 75.0±5.3% of time), than sows in all three cooling treatments (all P < 0.001). Heart rate during Period 3 was lower for COOLED sows compared to the CONTROL sows (100.2±3.4 vs 119.0±4.0 beat per min, P<0.001). Sows response to increased thermal load can be effectively reduced using water-cooled cooling pads, thereby improving sow comfort and welfare. The beneficial effects on behavior are noticeable from the lowest flow rate
Effects of stall or small group gestation housing on the production, health and behaviour of gilts
The effects of housing gestating gilts in groups of four (G, n = 8) or individual stalls (S, n = 14) on production, health and behavioural time budget were evaluated. Gilts were allocated to a gestation treatment by d 7 after breeding. They were housed in a single room, floors were fully slatted with no bedding, and all conditions except for housing type were identical. Gilts were weighed and their backfat measured at wk 1 (just after moving to gestation housing), 5, 9 and 13 of pregnancy. After farrowing, litter size, sex ratio, piglet weights and mortality percentages were recorded. Skin lesions were scored using a 6-point scale every 2 wk. Gait was scored using a 6-point scale at the end of gestation. Heart rate was assessed at wk 14 to 15 after breeding. Behaviour was videotaped to collect data on body postures and ingestive behaviour for 24 h at wk 4, 6, 9 and 13 of gestation. Apart from at wk 5, when S gilts had higher backfat than G (P < 0.05), G and S gilts did not differ in body weight or backfat during the study. Reproductive performance did not differ. While skin lesion scores did not differ at wk 1, by wk 13 lesion scores for several regions of the head, face, body, feet and legs were higher in G than S animals (P < 0.05). There were no differences in heart rate, but gait scores at the end of pregnancy tended to be poorer in G than S gilts (P < 0.1). As gestation progressed gilts spent less time standing (P < 0.0001) and more time lying (P < 0.05), but behavioural time budgets (percentages of time spent standing, lying, sitting, eating and drinking) of animals housed in G and S did not differ. In conclusion, there were few differences detected between gilts housed for one pregnancy in groups of four or stalls. Stalls in this study were relatively spacious, while group pens were relatively small and barren. Effects of gestation housing on sows' welfare may be cumulative, taking several parities to emerge, and care must be taken in the design and management of group housing systems to ensure that they achieve their objective of improved welfare for all group members