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D B Stephens

Publications and source records attributed to D B Stephens.

59 records · Page 4Linked to original sources
PubMed1970

The relation between body size and maximum and minimum metabolic rates in the new-born pig.

1. Measurements of rates of oxygen consumption were made on a total of sixty-two Large White pigs aged between 1 hr and 6 days, with a range of body weight from 0.75 to 2.40 kg.2. The maximum rate was determined from the continuous estimation of oxygen consumption as the environmental temperature fell past the point at which the maximum occurred.3. The minimum rate was determined both as the environmental temperature rose through the zone of thermal neutrality, and from measurements at thermal neutrality.4. In animals aged 1-6 days the mean maximum rate was 49.0 ml. O(2)/kg.min, and the mean minimum was 15.3 ml. O(2)/kg.min. Both rates were proportional to body weight and not to surface area.5. Pigs less than 1 day old exhibited lower maximum and minimum rates than the older pigs.

Age Factors↗
PubMedDate not supplied

Behaviour of groups of weaner pigs in three different housing systems.

Behavioural observations were made on 150 3-week weaned pigs housed in pens with fully perforated floors, or a solid-floored lying area with or without straw. Observations were made during a period of high ambient temperatures and during cool weather. At high ambient temperatures pigs with part-solid floors defaecated and urinated in the lying area and showed a higher (P less than 0.01) incidence of rooting behaviour associated with wallowing. Pigs on fully perforated floors showed reduced levels of activity in hot conditions (P less than 0.01). Pigs given straw were more active (P less than 0.01) and spent 25% of active behaviour in straw directed behaviour. There was a higher incidence (P less than 0.01) of oral behaviour directed at penmates and pen fittings amongst pigs housed on fully perforated floors.

Animals↗
PubMedDate not supplied

Maximal horizontal flight performance of hummingbirds: effects of body mass and molt.

Hovering and fast forward flapping represent two strenuous types of flight that differ in aerodynamic power requirement. Maximal capabilities of ruby-throated hummingbirds (Archilochus colubris) in hovering and forward flight were compared under varying body mass and wing area. The capability to hover in low-density gas mixtures was adversely affected by body mass, whereas the capability to fly in a wind tunnel did not show any adverse mass effect. Molting birds that lost primary flight feathers and reduced wing area also displayed mass loss and loss of aerodynamic power and flight speed. This suggests that maximal flight speed is insensitive to short-term perturbations of body mass but that molting is stressful and reduces the birds' speed and capacity for chase and escape. Hummingbirds' flight behavior in confined space was also investigated. Birds reduced their speeds flying through a narrow tube to approximately one-fifth of that in the wind tunnel and did not display differences under varying body mass and wing area. Hence, performance in the flight tube was submaximal and did not correlate with performance variation in the wind tunnel. For ruby-throated hummingbirds, both maximal mass-specific aerodynamic power derived from hovering performance in low-density air media and maximal flight velocity measured in the wind tunnel were invariant with body mass.

Animals↗