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Almost two-thirds of all livestock in North America are raised in regions where the mean January temperature is below 0 C. The effects of cold conditions on productivity and efficiency of feed conversion by swine, dairy and beef cattle are reviewed. Swine are rather cold-susceptible and are therefore usually kept in heated housing when raised in colder(More)
The ability of an animal to cope with new environments arises from its capacity to respond to environmental variables and maintain body equilibrium (homeostasis). Each compensating mechanism depends on, and is a part of, a physiological feedback process. The severity (intensity and duration) of an environmental change relative to the animal's capacity to(More)
Fifty-four Large White gilts were used to determine the effect of body composition at selection (145 d of age) on the onset of puberty and subsequent reproductive development until 202 d of age. Gilts were assigned to one of three groups based on their backfat depth at selection: 10 to 12 mm (L), 13 to 15 mm (M), and 16 to 18 mm (F). All of the F gilts, 92%(More)
Swine exposed to cold air have elevated serum values of total triiodothyronine (TT3) and free T3 (FT3). To characterize the mechanism of these increases, we measured in vivo kinetic parameters after a bolus intravenous injection of 125I-labeled T3 by use of both multicompartmental (MC) and noncompartmental (NC) methods and in vitro hepatic type I(More)
A review is presented of biological issues and practical consequences of the effects of cold stress on ruminant animals. When animals are subjected to extreme cold stress, substantial dietary energy may be diverted from productive functions to the generation of body heat. Failure to produce sufficient heat can result in death. More often, however, cold(More)
OBJECTIVE To investigate the extent of heat load problems, caused by the combination of excessive temperature and humidity, in Holstein-Friesian cows in Australia. Also, to outline how milk production losses and consequent costs from this can be estimated and minimised. PROCEDURES Long-term meteorological data for Australia were analysed to determine the(More)
Metabolic heat production and rectal temperature were measured in 19 newborn calves (41.8 +/- 3.7 kg) during hypothermia and recovery when four different means of assistance were provided. Hypothermia of 30 degrees C rectal temperature was induced by immersion in 18 degrees C water. Calves were rewarmed in a 20 to 25 degree C air environment where thermal(More)
Distribution of cardiac output was measured in 0- and 12-hour-old piglets using 103Ruthenium-labelled microspheres, 15 +/- 3 micrometer in diameter. The 12-hour-old piglets had remained with the sow and had suckled. Coronary and bronchial fractions of cardiac output were high in piglets at birth. The coronary fraction remained high at 12 h but the bronchial(More)