Variation in Piglet Weights: Development of Within-Litter Variation Over a 5-Week Lactation and Effect of Farrowing Crate Design

Piglets from 51 litters were weighed weekly over a 5-wk lactation in an experiment that studied the effects of farrowing crate design and other factors on variation in piglet weight. Of two farrowing crates used, one had low horizontal bars that tended to impede access to the upper row of teats, while the other had angled vertical bars which permitted freer access. Fourteen-day weights were more uniform in the vertical-bar crates than in the horizontal-bar crates (P \u3c 0.025), but the difference waned by day 35 (P \u3e 0.05). There were no significant differences in mean body weight owing to crate type (P \u3c 0.05) for any of the weekly measurements but, by day 14, there was a significant linear trend (P \u3c 0.05) at decreasing main body weight with increasing litter size. The interaction between crate type and litter size was significant at the later ages (P \u3c 0.01 at day 35) because the linear trend was more pronounced for horizontal-bar crates than for vertical. Litters differed greatly in the uniformity of their body weights. Much of the variation became established in the first and, to a lesser extent, the second week after birth. In those weeks, weight gains were highly variable and were not closely related to weight at the beginning of the week. Thereafter, the established differences tended to be perpetuated to 35 d, because weight gains were largely proportional to body weight. Within-litter competition appeared to influence weight gain considerably

Variation in Piglet Weights: Weight Gains in the First Days After Birth and Their Relationship with Later Performance

Piglets from 42 litters of Yorkshire sows were weighed 0, 1, 2, 3, 4, 5, 7, 10, and 14 d after farrowing in order to explore the highly variable weight gains during the first 2 wk after birth. All litters were adjusted to 10-12 piglets by fostering. Litters differed greatly in average gain per piglet during the first 3 d after farrowing, with litter means ranging from 5 to 227 g d‒1 per piglet for the 3-d period. Gains during days 0-3 tended to be somewhat lower if the sow had a high body temperature during these days, but the correlation was not high (r = ‒0.35; P \u3c 0.05). Compared to litters with high average gains during days 0-3, litters with low gains during this period continued to have lower average gains during days 3-14 (P \u3c 0.05) and had higher within-litter variation in gain (P \u3c 0.01). On a within-litter basis, weight gain during the first days after farrowing was only weakly correlated with the day 14 weight of individual piglets. Low average gain by a litter in the first 3 d after birth is probably due to low initial milk yield by the sow, and likely indicates a poor start to the sow\u27s lactation. Early identification of litters with low initial gains might allow remedial action to reduce the problems of high mortality and low, variable gains later in lactation

Carrier dynamics in ion-implanted GaAs studied by simulation and observation of terahertz emission

We have studied terahertz (THz) emission from arsenic-ion implanted GaAs both experimentally and using a three-dimensional carrier dynamics simulation. A uniform density of vacancies was formed over the optical absorption depth of bulk GaAs samples by performing multi-energy implantations of arsenic ions (1 and 2.4MeV) and subsequent thermal annealing. In a series of THz emission experiments the frequency of peak THz power was found to increase significantly from 1.4 to 2.2THz when the ion implantation dose was increased from 10^13 to 10^16 cm-3. We used a semi-classical Monte-Carlo simulation of ultra-fast carrier dynamics to reproduce and explain these results. The effect of the ion-induced damage was included in the simulation by considering carrier scattering at neutral and charged impurities, as well as carrier trapping at defect sites. Higher vacancy concentrations and shorter carrier trapping times both contributed to shorter simulated THz pulses, the latter being more important over experimentally realistic parameter ranges.Comment: 6 pages, 7 figure

Aquatic Feeding by Moose: Seasonal Variation in Relation to Plant Chemical Composition and Use of Mineral Licks

Activity of moose (Alces alces) was studied at aquatic feeding areas and at natural, sodium-rich licks during four periods covering late May to early September. Aquatic feeding increased from period 1 (late May and early June) to period 2 (late June and early July) and had declined by late July. Major activity at mineral licks occurred earlier in the season than aquatic feeding, especially for males. Chemical composition of aquatic plants showed no seasonal changes corresponding to the peak of aquatic feeding in period 2, although the sodium content of some species declined in period 3. We suggest that moose in the study area are attracted to sodium sources from late May to mid-July, that aquatic feeding replaces use of licks in June as the most sodium-rich aquatic plants become abundant, and that both activities decrease in midsummer because of declining attraction to sodium

Effect of floor type on the performance, physiological and behavioural responses of finishing beef steers

peer-reviewedBackground:The study objective was to investigate the effect of bare concrete slats (Control), two types of mats [(Easyfix mats (mat 1) and Irish Custom Extruder mats (mat 2)] fitted on top of concrete slats, and wood-chip to simulate deep bedding (wood-chip placed on top of a plastic membrane overlying the concrete slats) on performance, physiological and behavioral responses of finishing beef steers. One-hundred and forty-four finishing steers (503 kg; standard deviation 51.8 kg) were randomly assigned according to their breed (124 Continental cross and 20 Holstein–Friesian) and body weight to one of four treatments for 148 days. All steers were subjected to the same weighing, blood sampling (jugular venipuncture), dirt and hoof scoring pre study (day 0) and on days 23, 45, 65, 86, 107, 128 and 148 of the study. Cameras were fitted over each pen for 72 h recording over five periods and subsequent 10 min sampling scans were analysed. Results: Live weight gain and carcass characteristics were similar among treatments. The number of lesions on the hooves of the animals was greater (P < 0.05) on mats 1 and 2 and wood-chip treatments compared with the animals on the slats. Dirt scores were similar for the mat and slat treatments while the wood-chip treatment had greater dirt scores. Animals housed on either slats or wood-chip had similar lying times. The percent of animals lying was greater for animals housed on mat 1 and mat 2 compared with those housed on concrete slats and wood chips. Physiological variables showed no significant difference among treatments. Conclusions: In this exploratory study, the performance or welfare of steers was not adversely affected by slats, differing mat types or wood-chip as underfoot material

Floor Temperature Preference of Sows at Farrowing

A preference testing apparatus was used to provide sows with continuous access to three identical farrowing crates, each with a different floor temperature. The concrete floor under each crate contained copper pipe through which temperature-controlled water was circulated to achieve unoccupied floor temperatures of 22°C (± 3.5), 29°C (± 1) and 35°C (± 1). Eighteen sows were tested in the apparatus. Video recording was used to determine sow position from 7 days before farrowing (Days ‒7 to ‒1) to 14 days after (Days 1 to 14). On Days ‒7 to ‒1, sows showed no significant preference among the three temperatures when selecting a resting area. Once farrowing had begun, there was a significant increase (P \u3c 0.01) in the use of the 35°C floor and it became the most preferred resting area for Days 1 to 3. After this interval, use of the 35°C floor declined significantly (P \u3c 0.01), and use of the cooler floors increased, resulting in no significant thermal preference during Days 4 to 6. There was a further decline in the use of the 35°C floor after Days 4 to 6 (P \u3c 0.01) to the extent that the coolest floor (22°C) became the most preferred from Days 7 to 14. In summary, sows showed a pronounced increase in preference for a warm floor during the 3 days after the start of farrowing. This change in preference may explain how free-living sows select a suitable thermal environment for their young, and why sows try to avoid metal flooring at the time of farrowing

Polarisation-sensitive terahertz detection by multicontact photoconductive receivers

We have developed a terahertz radiation detector that measures both the amplitude and polarization of the electric field as a function of time. The device is a three-contact photoconductive receiver designed so that two orthogonal electric-field components of an arbitrary polarized electromagnetic wave may be detected simultaneously. The detector was fabricated on Fe+ ion-implanted InP. Polarization-sensitive detection is demonstrated with an extinction ratio better than 100:1. This type of device will have immediate application in studies of birefringent and optically active materials in the far-infrared region of the spectrum.Comment: 3 pages, 3 figure