Effect of Environment on Nutrient Requirements of Domestic Animals (1981) / Chapter Skim
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FEED INTAKE
FEED INTAKE
Pages 27-34
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From page 27... ...
Those who consider the direct effects of heat or cold stress on feed intake and performance important for farm feeding should also be aware of the influence of summer temperatures on changes in forage quality. DAIRY COWS When lactating dairy cows are fed free choice a diet consisting of 60 65 percent Inequality roughage and 35~0 percent concentrates and exposed to constant temperature conditions, feed intake will increase approximately 35 percent at-20°C over the level at 1~20°C (Figure 5~.
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From page 28... ...
But, when daily maximum temperature is in the range of 8-22°C, the performance of grazing cows receiving concentrate supplement at the rate of 1:2 will be nearly equal to that for cows on the 60:40 diet (Van Soest, 1981~. When maximum daily temperature exceeds 25°C, the rate of dry matter intake from grazing may decline rapidly due in part to the direct effects of thermal stress on the cow causing suppression of activity and the indirect decline due to the quality of the forage.
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From page 29... ...
found that during 7day periods of above-average ambient temperatures in Puerto Rico average daily gain declined by 50 percent, but gains following high-temperature periods were 50 to 70 percent greater even though average daily maximum temperature was only 0.5°C lower. Similar behavior has been observed in hot controlled environment rooms.
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From page 30... ...
FIGURE 6. Estimated changes in dry matter intake of feedlot cattle on a ration with 70 percent apparent digestibility or at temperatures above 27°C, 75 percent apparent digestibility.
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From page 31... ...
The marked reduction in daily gain indicates both intake and efficiency of utilization of ME for gain are lowered. From 10°C to approximately 25°C there was little change in feed consumption; however, on a 70 percent digestibility diet daily intake declined rapidly when the cattle were exposed to more than 6 h per day of temperature above 30°C (Figure 6~.
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From page 32... ...
SWINE The estimated relationship of feed intake to ambient temperature for pigs of two weight ranges are shown in Figure 7. The associations of temperature with feed intake were developed largely from studies under controlled temperature conditions.
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From page 33... ...
When the hens were shifted from 18 to 7°C, their ME intake was lowered for approximately 1 week due to behavioral adaptation before feed intake returned to a level of about 102 percent of the amount consumed before the shift. The estimated changes in feed intake for laying hens acclimated to the environmental temperature and fed a diet of 3.17 kcal ME/g DM iS shown in Figure 9.
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From page 34... ...
low as 0°C. Similar to other species, level of intake at low temperatures is erratic due to behavior changes to alleviate rapid heat loss; hence, the intake curve is represented by a broken line below 5°C and represents an extrapolation of needs for thermal equilibrium.
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