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Biomedical subjects

D R Ames

Publications and source records attributed to D R Ames.

8 recordsLinked to original sources
PubMed1988

Adjusting rations for climate.

Cold conditions resulting from a combination of temperature, wind, and wetness result in increased energy required for maintenance. Constant levels of intake reduce energy available for production. Direct effects of cold include reduced rate and efficiency of growth and milk production. Indirect effects on measures of reproductive efficiency are well documented. Impacts on health and longevity are perhaps less obvious but are no doubt affected. Energy supplementation is an obvious need for cold-stressed animals. For maximum effectiveness, efforts should incorporate a systems approach and integrate the expertise of many disciplines into a logical decision-making process. The entire spectrum of animal response, not just short-term acute response, must be included in environmental management.

Animal Feed↗
PubMed1986

Heat production of cattle acclimated to cold, thermoneutrality and heat when exposed to thermoneutrality and heat stress.

Four Hereford X Red Angus yearling steers were acclimated to each of the following environments; cold (3 C), thermoneutrality (TNZ; 20 C) and heat (35 C). Intake was equalized for all treatments at 4.9 X kg X head-1 X d-1 (2.9 Mcal metabolizable energy/kg). Heat production, respiration rate and rectal temperature were determined after 3- and (21-h later) 24-h exposures to thermoneutral and heat stress test-temperatures: 25, 30, 32.5, 35, 37.5 and 40 C. Thermoneutral heat production (kcal X kg-.75 X d-1), after 3- and 24-h exposures, was greater (P less than .05) for the cold-acclimated cattle (139.6 +/- 5.0 and 153.0 +/- 5.8) as compared with the TNZ-acclimated cattle (117.7 +/- 5.0 and 121.6 +/- 5.8). Heat production of the heat-acclimated cattle after 3- and 24-h exposures to thermoneutrality was 121.0 +/- 5.1 and 123.5 +/- 3.2 and was not different from the TNZ-acclimated cattle. Heat production of steers acclimated to different temperatures was variable during the 3- and 24-h exposures to test-temperatures ranging from 25 to 40 C. Heat production increased linearly in the TNZ-acclimated cattle (24-h exposure) and in the heat-acclimated cattle (3-h exposure) at the rate of 1.3 and 2.3 kcal X kg-75 X d-1 X C-1 increase in test-temperature, respectively. In the other four comparisons, analysis by regression indicated no significant change in heat production. Rectal temperature and respiration rate increased significantly in either a linear or quadratic manner in all treatment groups exposed to test-temperatures from 25 to 40 C.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗