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POULTRY
Pages 109-134

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From page 109...
... A crucial factor that appears to govern the TNZ and responses to hot or cold is acclimation (Harrison and Biellier, 1969; Shannon and Brown, 1969; van Kampen, 1974; Waring and Brown, 19671. POULTRY ENVIRONMENT The use of shelter to shield poultry from the macroenvironment is an approach to enhance productivity and thus justify such expenditures.
From page 110...
... A shift toward a higher environmental temperature reduces energy expenditure of poultry (O'Neill et al, 1970; Romijn and Vreugdenhil, 1969; van Kampen, 1974~. Thus, where higher ambient temperatures are available birds expend less of their metabolizable energy for maintaining a constant body temperature and appear to have the option of shifting this savings of energy to production or improving feed efficiency.
From page 111...
... However, when the data are plotted on the basis of lysine intake versus body weight gain, note that one response line can describe the relationship despite the two environments (Figure 19~. Thus, environmental effect on growth was not from a change in nutrient requirements for growth, but instead was a consequence of an environmental effect to reduce feed intake and thus lower the daily intake of lysine (and other nutrients)
From page 112...
... and maintenance energy, the latter at an estimated 4 percent with each 1°C rise above thermoneutrality (Leeson et al., 19731. For example, White Leghorn and Rhode Island Red hens at 33-34°C have a heat loss which is 58 and 51 percent, respectively, of the values at 18.3°C (Ota and McNally, 1961)
From page 113...
... Metabolizable energy values of foodstuffs do not appear to be different for laying hens when in cold, warm, or hot environments (Brown et al., 1967; Davis et al., 19721. Thus, the digestive, absorptive, and excretion processes leading to retention of energy from the diet were not affected in hens held at ambient temperatures ranging from 7 to 35°C for as long as 6 weeks.
From page 114...
... 80 90 100 110 120 130 140 150 60% egg production 50 21.8 19.4 17.5 15.9 14.6 13.4 12.5 11.6 55 24.0 21.4 19.2 17.5 16.0 14.8 13.7 12.8 60 26.2 23.3 21.0 19.1 17.5 16.1 15.0 14.0 65 28.4 25.2 22.7 20.7 18.9 17.5 16.2 15.1 05~/o eve Production ~7 ~ 50 23.7 21.0 18.9 17.2 15.8 14.6 13.5 12.6 55 26.0 23.1 20.8 18.9 17.4 16.0 14.9 13.9 60 28.4 25.2 22.7 20.7 18.9 17.5 16.2 15.1 65 30.8 27.3 24.6 22.4 20.5 18.9 17.6 16.4 70% egg production 50 25.5 22.7 20.4 18.5 17.0 15.7 14.6 13.6 55 28.0 24.9 22.4 20.4 18.7 17.2 16.0 14.9 60 30.6 27.2 24.5 22.2 20.4 18.8 17.5 16.3 65 33.1 29.4 26.4 24.1 22.1 20.4 18.9 17.7 75~c egg production 50 27.3 24.3 21.8 19.9 18.2 16.8 15.6 14.6 55 30.0 26.7 24.0 21.8 20.0 18.5 17.2 16.0 60 32.8 29.1 26.2 23.8 21.8 20.2 18.7 17.5 65 35.5 31.5 28.4 25.8 23.7 21.8 20.3 18.9 they continued to lay at a high rate at the expense of body tissue stores. The energy retention (metabolizable energy)
From page 115...
... Therefore, the improved energetic efficiency of egg production at 35°C, originally calculated as 34.4 percent, was only 26.7 percent when the hen's bodily stores were included in the accounting. This example illustrates two factors: (1)
From page 116...
... This conclusion is arrived at by calculating the efficiency values of 29.6 and 40.6 percent at environmental temperatures of 7 to 10°C and 35°C, respectively (Table 37~. In this experiment, body weight declined 235 g, with 9 percent, or 21.2 g, attributed to a loss of protein (Davis et al., 19721.
From page 117...
... Relationship between dietary ME, feed intake, and ambient temperature for broiler-type chicks 6-10 weeks of age (adapted from Adams et al., 1962)
From page 118...
... 118 ce JO cd ¢' o An cd ED In o cat :' cd so au Em ct On ·_.
From page 119...
... where T = ambient temperature (°C) , Y = percentage change of feed intake from controls in the thermoneutral zone.
From page 120...
... 20 FIGURE 22. Relationship between dietary protein level and daily egg mass from White Leghorn hens at 5.5, 24.4, and 30°C (adapted from Bray and Gesell, 1961)
From page 121...
... Temperatures in the lethal range, especially those in tropical climates,-are tolerated so that egg production is maintained, but only if cooler temperatures occur at the lower range of the daily fluctuations (Squibb, 19591. However, chickens in heated chambers lay smaller eggs with thinner shells (Clark and Amin, 19651.
From page 122...
... in hot ambient temperatures. Where chickens are restricted in their intake at cool cyclic temperatures ranging from 13 to 24°C, daily, to the amount consumed by birds at the hot temperatures (cyclic 26.5~0.5°C)
From page 123...
... Their ME intake per day increased, and this improved their energy balance, considering both egg production and body weight gain. On the other hand, Sell (1979)
From page 124...
... 124 4 - ~ .~ .o ._
From page 125...
... Despite the shell-less eggs and poor shell quality of hens in hot environments, bone mineralization remained at normal levels throughout. ESTIMATING ME REQUIREMENT FOR LAYING HENS Many equations are available to estimate the ME requirements of laying hens exposed to different temperatures (for review, see McDonald, 1978~.
From page 126...
... 126 ca ~ so ~ 2 an o Cal _ ~ ° a., at o au C)
From page 127...
... Their estimate indicates that maintenance energy increases about 9 percent for each unit increase of a score denoting loss of feathers; a score ranging from one to SiX. By assuming a correction of 1.5 percent per °C, compounded for maintenance energy, an efficiency of 80 percent for energy to be converted into weight gain or eggs, and calorigenic values of 4.4 kcal per gram of tissue (derived in the previous section)
From page 129...
... Such water intake is 2-fold and 2/2-fold at 32°C and 37°C, respectively, above that at 21°C. Increasing ambient temperatures appear to cause body temperature to rise slightly until ambient temperatures attain 38-39°C; then higher air temperatures cause a marked rise in body temperature (Figure 24)
From page 130...
... In addition, less feed is consumed as ambient temperatures rise, and this also reduces net energy for production. As the burden of heat stress becomes greater, the evaporative route (use of water)
From page 131...
... Thus, the water serves as a coolant for external evaporation or to absorb heat from the head during drinking positions. In corroboration of these observations, hens were noted to withstand high ambient temperatures when allowed unlimited access to water, as compared to those given equivalent amounts by syringe directly into the crop (Lee et al., 1945~.
From page 132...
... Nutrient requirement was considered to be altered when such adjustments to give equal nutrient intake at different environmental conditions did not yield comparable productive outputs and/or efficiency. Research with poultry reveals that environmental temperatures over the range of 4 to 31°C do not affect nutrient requirement for protein, lysine, or vitamin A, as measured by growth or egg production.
From page 133...
... Carcass composition will change during shifts in environmental temperatures, and much of the change is related to the effect on feed intake and, thus, nutrient intake. As ambient temperatures rise, poultry consume increasing amounts of water.


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