Effect of Environment on Nutrient Requirements of Domestic Animals (1981) / Chapter Skim
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ENVIRONMENT-NUTRITION INTERACTIONS
ENVIRONMENT-NUTRITION INTERACTIONS
Pages 13-21
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From page 13... ...
Of the many stresses affecting rate and efficiency of animal productivity, more is known of the consequences of the thermal environment and associated factors of humidity, radiation, and air movement than factors such as altitude, sound, animal density, confinement, chemical or biological contamination, etc. Individual stressors may independently reduce animal performance, or may interact with other factors creating complex stressful situations whose origin may be at times difficult to assess.
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From page 14... ...
.a Heat increments of voluntary activity, fermentation, digestion, absorption, and nutrient metabolism for maintenance and productive functions contribute to body heat and in cold environments aid in maintenance of body temperature. However, in hot conditions these heat increments may be a liability to the thermal balance of the animal.
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From page 15... ...
voluntary activity and obtaining nutrients including the muscular activity of seeking and obtaining food, the processes of digestion, absorption, conversion of food into metabolizable forms, and the formation and excretion of waste products, and (3) combating of external stressors related to an immediate and direct imposition of stress or stresses on the animal.
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From page 16... ...
DIGESTIBILITY AND METABOLIZABILITY Digestibility and metabolizability are biological measures of energy or nutrient value assigned to feeds and depend not only on the physical and chemical nature of the feed itself but also on the animal ingesting the feed, the physiological state of the animal, and the amount of feed ingested (NRC, 1981~. Recognized differences, particularly in digestive processes, among species to which ingested feeds have different nutrient values have led to the development of somewhat independent feeding systems, including lists of feed composition tables for various species.
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From page 17... ...
Thus, caution needs to be exercised when interpreting feed digestibility estimates made during periods where there have been changes in the thermal environment or during constant heat or cold stress. Although possibly related to appetite changes occurring with exposure to hot or cold environments (see page 27)
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From page 18... ...
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From page 19... ...
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From page 20... ...
That warm temperatures decrease thyroid activity and cold temperatures increase thyroid activity in animals is documented for several species (de Andrade et al., 1977; Gale, 1973; Johnson, 1976~. This suggests that the shift in thyroid activity in animals because of exposure to different ambient temperatures may be associated with both a change in gut motility and rate of digesta passage.
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From page 21... ...
Swain and Farrell (1975) observed an increase in metabolizable energy value of diets when chickens were exposed to warmer temperatures, while other researchers (Matterson, 1970; Olson et al., 1972)
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