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J APPL POULT RES 2007. 16:206-218
© 2007 Poultry Science Association
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Research Reports

Apparent Metabolizable Energy Needs of Broilers from Two to Four Kilograms as Influenced by Ambient Temperature1

W. A. Dozier, III*,2, J. L. Purswell*, M. T. Kidd{dagger}, A. Corzo{dagger} and S. L. Branton*

* Poultry Research Unit, Agricultural Research Service, USDA, Mississippi State 39762; and {dagger} Department of Poultry Science, Mississippi State University, Mississippi State 39762

Correspondence: 2 Corresponding author: bdozier{at}msa-msstate.ars.usda.gov


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
During winter production, the optimum temperature set points for heavy broilers (>3.4 kg) approaching market weight are subject to debate in commercial practice. Apparent ME needed to optimize nutrient utilization may be influenced by ambient temperature. This experiment examined potential interactive effects of AME x ambient temperature from 36 to 60 d of age. A 4 x 2 factorial arrangement of treatments was used. Dietary treatments were diets formulated to 3,175, 3,220, 3,265, and 3,310 kcal of AME/kg. Two temperature regimens were provided consisting of variable temperature regimen (VTR) or constant temperature regimen (CTR) set points. The VRT was 21.1°C from 36 to 38 d of age, 20.2°C from 39 to 42 d of age, 18.9°C from 43 to 46 d of age, 17.8°C from 47 to 50 d of age, 15.6°C from 51 to 54 d of age, and 12.8°C from 55 to 60 d of age. The CTR was 21.1°C from 36 to 60 d of age. Significant AME x temperature interactions were observed for cumulative BW, BW gain, feed consumption, feed conversion, and mortality. In the CTR, increasing AME led to increased BW gain but not in the VTR. As dietary AME increased, the improvement in feed conversion was more pronounced in the CTR than the VTR. With the VTR, decreasing AME increased feed consumption. The experimental treatments did not influence abdominal fat percentage or total breast meat yield. These data provide evidence that broilers exposed to CTR respond to increased AME.

Key Words: broiler • metabolizable energy • temperature


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The influence of ambient temperature on broiler chicken productivity has been reviewed [1, 2]. May and Lott [3] determined the temperature need as 16 and 12°C, respectively, for feed conversion and BW gain from 21 to 49 d of age. These authors reported a 4% increase in feed consumption as temperature was decreased from 20 to 12°C. If temperature is lowered too aggressively before broilers reach 3.0 kg, then feed conversion may be adversely affected. This has resulted in broiler companies being conservative in lowering temperatures with broilers grown to heavy weights (3.3 to 4.0 kg) during winter production periods. Conversely, if temperature is not reduced, performance will be limited. Therefore, discrepancy among broiler companies exists with minimum temperature set points as heavy broilers approach marketing during winter growouts.

Dietary energy needs for maintenance (kcal consumed/g of two-thirds of BW) are increased when broiler chickens are subjected to environmental temperature above their thermal neutral zone [4]. Broilers subjected to temperatures beyond their thermal neutral zone lose metabolic heat through heat of evaporation via panting [5]. Panting requires energy to remove metabolic heat that would otherwise be available for growth, thus increasing AME need. Recently, Dozier et al. [6] reported the feed conversion response to AME from 30 to 59 d of age was more acute with broilers exposed to 25°C as compared with 18°C. It was suggested that AME should be increased by 20 kcal/kg (3,240 vs. 3,220 kcal/kg) in the withdrawal periods during the summer compared with winter production.

Genetic potential of the modern broiler when grown to heavy weights may be obtained if the temperature is reduced during the latter weeks of the growout. Delineating AME needs of broilers approaching 4.0 kg subjected to lower temperatures (13°C) is warranted. This study examined the potential interactive effects of AME and ambient temperatures on growth and meat yield of broilers from 2.0 to 4.0 kg.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Bird Husbandry
Two identical trials were conducted from September 2005 through February 2006. In each trial, 2,500 Ross male [7] x Hubbard Ultra Yield females [8] chicks were purchased from a commercial hatchery and placed in a common environment until 35 d of age. Chicks received vaccinations at the hatchery [9] for Marek’s disease, Newcastle disease, and infectious bronchitis and Gumboro at 12 d of age. Temperature set points and lighting schedules used from 1 to 35 d of age were according to the recommendations of Hubbard [10]. At 36 d of age, 1,920 broilers were randomly distributed to 32 floor pens (30 males and 30 females per pen; 0.09 m2/bird) of an open-sided facility. Bird BW on a pen basis was equalized within blocks (1 diet treatment of each block). Each pen had 2 tube feeders, a drinker line having 15 nipples, and fresh pine shavings. Light intensity was 2.5 lx with a 16L:8D period from 36 to 49 d and continuous lighting after 49 d of age, which was based on the recommendations of Hubbard [10].

Experimental Treatments
Treatment structure was a 4 x 2 factorial arrangement. Four dietary treatments were formulated to contain 3,175, 3,220, 3,265, and 3,310 kcal of AME/kg (Tables 1Go and 2Go). Dietary TSAA, Lys, Thr, mineral, and vitamin concentrations were increased 1% for each 45 kcal/kg addition of AME. Nutrient density was increased to account for a 4% reduction in feed consumption with increments of AME (3,175 to 3,310 kcal/kg) based on calculations from previous research [6].


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  		Table 1. Ingredient and nutrient composition of experimental diets provided to male and female Ross x Hubbard Ultra Yield broilers from 36 to 47 d of age
 

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  		Table 2. Ingredient and nutrient composition of experimental diets provided to male and female Ross x Hubbard Ultra Yield broilers from 48 to 60 d of age
 
The experimental facility consisted of 32 identical pens that were separated with 2 solid doors in the middle of the building, thus creating 2 identical rooms with each room having 16 floor pens. In one end, the temperature regimen was characterized as variable with temperature being set at 21.1°C on d 36 and reduced as birds progressed with age (Table 3Go). The constant temperature regimen (CTR) had a set point of 21.1°C from 36 to 60 d of age (Table 3Go).


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  		Table 3. Temperature set points and actual temperatures provided to Ross x Hubbard Ultra Yield broilers from 36 to 60 d of age
 
Measurements
Birds by pen and feed were weighed at 36, 48, and 60 d of age to determine BW gain, feed consumption, and feed conversion. Mortality was recorded daily. In addition, birds were weighed by pen on d 41 and 55. The 5 weigh days were used to estimate the days to reach a target BW of 3.82 kg. The target BW of 3.82 kg was selected, because this is in the range (3.74 to 3.86 kg of BW) of broilers raised to heavy weights within some of the "big bird" complexes in Mississippi during winter production. In addition, 3.82 kg was the average BW of broilers subjected to the constant temperature regimen.

Air temperature was measured 30 cm from the floor in 4 locations in each room using 30 k{Omega} thermistors [11]. Thermistors were calibrated against a National Institute of Standards and Technology-traceable thermometer [12] in a waterbath. Readings were recorded every 10 min with a datalogger [13].

At 60 d of age, 12 birds from each pen (6 males and 6 females) were selected for processing. Feed was removed 12 h before processing. At 61 d of age, birds were weighed, placed in coops, and transported to the processing plant. Birds were electrically stunned, bled (severing the jugular vein with a knife), scalded, de-feathered, and manually eviscerated. Carcasses (without abdominal fat pad) and abdominal fat pad were weighed. Carcasses were split into front and back halves. The front halves were placed in ice for 18 h, and the pectoralis major and pectoralis minor muscles were deboned and weighed. Carcass, abdominal fat pad, and total breast meat (sum of pectoralis major and pectoralis minor muscles) yields were based on 61-d BW of birds that were selected for processing. Diet samples were used to assess pellet quality using standard procedures [14] and for CP and crude fat determination [15].

Statistics
Data from the 2 trials were merged for statistical analysis. Design structure was a split plot with temperature as the main plot and AME being the subplot. Apparent ME effect was conducted as a randomized complete block. Apparent ME x temperature had 8 replicate pens; main effect of diet was represented by 16 replicate pens and temperature effect by 2 replicate rooms. Treatment structure was a 4 x 2 factorial arrangement consisting of 4 diets differing in AME and 2 temperature regimens. Five analyses were conducted: 1) ANOVA followed by least significance difference comparison evaluating treatment means, 2) ANOVA using a linear trend to explain potential AME effects, 3) a quadratic trend to explain potential AME effects, and 4) trend analysis evaluating AME x temperature interaction. Intercept and slope were estimated for AME effects within each temperature regimen. This comparison was tested to determine if the slopes due to AME were different between the 2 temperatures. In the fifth analysis, diet was a linear trend, and day was a quadratic trend resulting in a response surface for each temperature. Response surface was used to estimate the number of days to reach a target BW based on treatment effects. Analyses were performed with PROC MIXED [16]. Statistical significance was considered at P ≤ 0.05.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Although dietary treatments are described in terms of AME, these diets did vary in nutrient density to avoid confounding effects due to amino acid, mineral, and vitamin consumption with diets differing in AME due to the associated decrease in feed consumption. Analyzed values of crude fat increased with increments of AME in experiment 1 and 2 (Tables 1Go and 2Go), indicating diets were in agreement with fat supplementation to increase AME content. Actual temperatures for the CTR were approximately 1.4°C higher than the temperature set points, whereas variable temperature was similar to its set points with the exception from 55 to 60 d (Table 3Go). The increase in actual temperature compared with set points of the variable temperature regimen (VTR) from 55 to 60 d may have occurred due to high dew points during this period that exceeded the capabilities of the facility. However, it is important to note that relative differences were apparent from 47 to 60 d with the VTR vs. CTR.

Increasing AME from 3,175 to 3,310 kcal/kg decreased pellet durability index by 21 and 15%, respectively, in the withdrawal 1(WD1; 36 to 47 d) and withdrawal 2 (WD2; 48 to 60 d) periods (Figure 1Go). Increments of AME decreased (P ≤ 0.001) feed consumption and feed conversion linearly from 36 to 47 d of age independent of temperature regimen but not BW, BW gain, and mortality (Table 4Go). With broilers subjected to VTR, providing broilers AME of 3,265 kcal/kg decreased (P ≤ 0.05) BW and BW gain compared with birds fed the 2 lower AME diets. Feed consumption was significantly higher (P ≤ 0.05) with broilers fed diets of 3,175 or 3,220 kcal of AME/kg compared with 3,265 or 3,310 kcal of AME/kg and broilers fed the 3,175 kcal of AME consumed more (P ≤ 0.05) feed than the other dietary treatments. Feed conversion was only adversely affected (P ≤ 0.05) when AME was decreased from 3,310 to 3,175 kcal of AME/kg. When exposed to CTR, broiler BW and BW gain was lower (P ≤ 0.05) when provided the diet containing 3,265 kcal of AME/kg compared with broilers fed the 3 other diets. Feed consumption increased (P ≤ 0.05) with broilers fed AME of 3,175 and 3,220 kcal/kg compared with birds given diets formulated to contain 3,265 or 3,310 kcal of AME/kg. When a diet of 3,310 kcal of AME/kg was fed, feed conversion was decreased (P ≤ 0.05) compared with broilers fed the 3 lower AME diets, but poor feed conversion was observed (P ≤ 0.05) when the 3,175 kcal of AME/kg was fed with comparison to the 3 higher AME diets. Broilers subjected to the CTR had decreased (P ≤ 0.04) feed consumption (2.42 vs. 2.45 kg) compared with birds exposed to VTR. No AME x ambient temperature interactions were observed for live performance.


Figure 1
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  		Figure 1. Influence of AME on pellet durability index (PDI) percentage with diets fed during the withdrawal 1 (WD1) and withdrawal (WD2) periods (36 to 47 d and 48 to 60 d, respectively). Apparent ME linear effects were P ≤ 0.001 for the WD1 and WD2 periods.

 

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  		Table 4. Influence of ambient temperature on live performance responses of Ross x Hubbard Ultra Yield broilers provided diets varying in AME from 36 to 47 d of age1
 
Apparent ME x ambient temperature linear interactions occurred (P ≤ 0.04) for all live performance measurements from 36 to 60 d of age (Table 5Go). With the VTR, BW was decreased (P ≤ 0.05) as AME increased from 3,175 to 3,265 kcal/kg. Conversely, BW was lower (P ≤ 0.05) of broilers fed 3,175 kcal of AME/kg compared with birds provided the 3 higher AME diets in CTR. Body weight gain increased (P ≤ 0.05) as AME increased from 3,175 to 3,220 and 3,310 kcal/kg with broilers exposed to CTR, but AME did not affect growth rate of broilers grown under VTR. As AME decreased, broilers fed diets formulated to contain 3,175 or 3,220 kcal/kg consumed (P ≤ 0.05) more feed than birds provided AME of 3,265 and 3,310 kcal/kg when subjected to both temperature regimens. With the VTR, broilers fed a diet containing 3,175 kcal of AME/kg had higher (P ≤ 0.05) feed consumption than birds given a diet of 3,220 kcal of AME/kg. Conversely, no difference in feed consumption was noted between broilers fed diets formulated to 3,175 and 3,220 kcal/kg subjected to CTR. Increasing AME to 3,310 kcal/kg improved (P ≤ 0.05) feed conversion in both temperature regimens. Feed conversion was lower (P ≤ 0.05) with broilers given a diet containing 3,310 kcal of AME/kg compared with birds fed the diet having 3,175 kcal of AME/kg within each temperature regimen, but no differences in feed conversion occurred among broilers fed diets containing 3,175, 3,220, and 3,265 kcal of AME/kg within VTR. In contrast, broilers provided diet formulated to 3,175 kcal of AME/kg had poorer (P ≤ 0.05) feed conversion than birds fed diets formulated to 3,220 or 3,265 kcal of AME/kg with CTR. Increasing AME did not influence mortality with VTR, whereas broilers exposed to CTR had an increase (P ≤ 0.05) in mortality when a AME concentration of 3,175 kcal/kg was fed compared with birds given a diet containing 3,265 kcal of AME/kg. Increasing AME decreased (P ≤ 0.001) feed consumption and feed conversion linearly, regardless of temperature regimen. Broilers subjected to VTR regimen had advantages in BW (4.07 vs. 3.82 kg), BW gain (2.11 vs. 1.87 kg), feed consumption (4.90 vs. 4.58 kg), and feed conversion (2.31 vs. 2.45) that approached significance (P ≤ 0.10) and significantly decreased mortality (2.94 vs. 7.20%; P ≤ 0.02).


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  		Table 5. Influence of ambient temperature on live performance responses of Ross x Hubbard Ultra Yield broilers provided diets varying in AME from 36 to 60 d of age1
 
Apparent ME influenced the days to reach 3.82 kg with the CTR but not with VTR (Figure 2Go, panels A and B). With the CTR, broilers were predicted to reach 3.82 kg at varying ages as influenced by AME (Table 6Go). The prediction equation used to estimate the number of days to reach 3.82 kg was ln(predicted BW) = –0.7377 + 0.0159 x AME + 0.0391 x d + –2.7E-4 x d2 + –7.3E-3 x AME x d + 7.5E-6 x AME d2. Broilers subjected to the VTR were predicted to reach 3.82 kg of BW at approximately 4.75 d sooner than CTR, but AME did not affect days to achieve 3.82 kg of BW (Table 6Go). The equation used to estimate days to 3.82 kg for the VTR was ln(predicted BW) = –0.913 + 0.0362 x AME + 0.0479 x d + –3.9E-4 x d2 + –1.8E-3 x AME x d + 2.0E-5 x AME x d2. These equations can be used by inserting AME kcal/kg for AME and days for broiler age to predict BW. These equations are only valid for data collected during this experiment.


Figure 2
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  		Figure 2. Panel A: response surface analysis to estimate the number of days to reach 3.82 kg as influenced by AME for broilers subjected to the constant temperature regimen. Prediction equation is as follows: ln(predicted BW) = –0.7377 + 0.0159 x AME + 0.0391 x d + –2.7E-4 x d2 + –7.3E-3 x AME x d + 7.5E-6 x AME x d2. Panel B: response surface analysis to estimate the number of days to reach 3.82 kg as influenced by AME for broilers subjected to the variable temperature regimen. Prediction equation is as follows: ln(predicted BW) = –0.913 + 0.0362 x AME + 0.0479 x d + –3.9E-4 x d2 + –1.8E-3 x AME x d + 2.0E-5 x AME x d2.

 

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  		Table 6. Predicted days to reach 3.82 kg as influenced by AME for broilers subjected to diverse temperature regimens1
 
Apparent ME and ambient temperature did not interact to influence abdominal fat and meat yield (Table 7Go). Carcass weight and yield, breast meat weight and yield, and abdominal fat percentage were not affected by additions of AME within VTR and CTR. Broilers fed the diet containing 3,265 kcal of AME/kg had lower (P ≤ 0.05) abdominal fat weight than birds provided the diet having 3,310 kcal of AME/kg when subjected to CTR. Broilers subjected to the CTR had higher (74.2 vs. 73.7%; P ≤ 0.002) carcass yield than birds exposed to the VTR, but temperature regimen did not influence carcass weight.


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  		Table 7. Influence of ambient temperature on carcass traits of Ross x Hubbard Ultra Yield broilers provided diets varying in AME from 36 to 60 d of age1
 
Significant AME x ambient temperature linear interactions were observed for energy intake (P ≤ 0.001) and energy intake per gram of BW gain (P ≤ 0.03), whereas caloric intake per gram of breast meat was approaching statistical significance (P = 0.07; Table 8Go). As AME decreased to 3,175 kcal of AME/kg, broilers consumed more energy (P ≤ 0.05) than broilers fed the 3 higher AME diets within VTR, but energy intake was similar among AME treatments with CTR. Decreasing AME to 3,175 kcal of AME/kg adversely affected (P ≤ 0.05) energy intake per gram of BW gain compared with the 3 higher AME treatments in CTR, but differences did not occur due to AME in VTR. Conversely, broilers fed the diet containing 3,175 kcal of AME/kg had poorer energy intake per gram of breast meat than broilers given the 3,265 kcal of AME/kg diet when exposed to VTR, whereas energy intake per gram of breast meat was similar among AME treatments when broilers were subjected to CTR. Additions of AME, regardless of ambient temperature, improved (P ≤ 0.001) energy intake per gram of BW gain linearly. Nonsignificant (P ≤ 0.10) trends of energy consumption (15,878 vs. 14,854 kcal) and energy intake per gram of BW gain (7.50 vs.7.93 kcal/g) occurred with the VTR over the CTR.


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  		Table 8. Influence of ambient temperature on caloric efficiency of Ross x Hubbard Ultra Yield broilers provided diets varying in AME from 36 to 60 d of age1
 
With the trend analysis, AME x ambient temperature linear interactions were apparent for BW, BW gain, feed consumption, feed conversion, energy intake, and energy intake:BW gain, indicating that slopes within CTR were significantly different (P ≤ 0.03) from VTR (Table 9Go). As AME increased, BW and BW gain had positive slopes when broilers were subjected to the CTR, and slopes were different (P ≤ 0.001) from zero. Conversely, negative slope values were observed with broilers fed increasing AME when exposed to VTR, with slopes not being statistically different from zero for BW (P = 0.10) and BW gain (P = 0.14). Negative slopes were observed for feed consumption and feed conversion, and slopes were statistically different (P = 0.001) from zero with VTR and CTR. Apparent ME x ambient temperature linear interaction for mortality occurred that approached significance (P = 0.06), but slopes were statistically similar to zero for VTR (P = 0.27) and CTR (P = 0.10). Slope of energy intake was negative and was significantly different (P = 0.001) from zero within VTR but not (P = 0.15) in the CTR. Both slopes for energy intake:BW gain had negative slopes, with the slope within CTR being different (P = 0.001) from zero, whereas the slope for VTR was not (P = 0.32).


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  		Table 9. Trend analysis of responses of Ross x Hubbard Ultra Yield broilers provided diets varying in AME from 36 to 60 d of age1
 
Apparent ME may need to be increased to optimize feed conversion when heavy broilers are subjected to temperatures simulating summer vs. winter production [6]. Energy needs for maintenance have been shown to be affected by ambient temperature [4]. Dozier et al. [6] determined that the slope for feed conversion from 36 to 59 d was more pronounced with increasing AME with broilers subjected to 25°C vs. 18°C. Conversely, Veldkamp et al. [17] reported with turkeys that feed conversion was more pronounced with increasing AME at 18°C than 28°C.

In the present research, AME x ambient temperature interactions were observed for live production parameters. Slope for feed conversion was greater with broilers fed diets providing increasing AME when subjected to CTR vs. VTR. As AME increased with each 45 kcal/kg unit, feed conversion decreased by 7 and 4 points, respectively, for CTR and VTR. This is in agreement with Dozier et al. [6], who reported 8- and 4-point improvements in feed conversion with each 45 kcal/kg (3,175 to 3,310 kcal/kg) increase.

Increasing AME decreases feed consumption and improves feed conversion of broiler chickens [6, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]. In the current research, significant linear AME effects were apparent for both feed consumption and feed conversion, but linear differences were not observed for breast meat yield or abdominal fat percentage. Dietary amino acids, minerals, and vitamins were increased by 1% with each 45 kcal of AME/kg increase to compensate for reduced feed intake based on feed consumption differences previously reported [6] to minimize adverse affects on breast meat yield.

In the research reported herein, broilers subjected to the VTR reached 3.82 kg approximately 4.75 d sooner than birds exposed to the constant regimen. This would have large economic ramifications to a broiler complex during a winter production period. With broilers subjected to the CTR, days estimated to reach 3.82 kg decreases as AME increases. Apparent ME had minimal effects on days to achieve 3.82 kg with birds exposed to the VTR. This difference in response to AME as influenced by ambient temperature is in agreement with previous research [6] suggesting the maintenance need is increased [4] when birds are subjected to higher temperatures.

Ambient temperature effects on broiler performance have been well documented [1, 2, 3, 30]. In the present research, advantages were found with BW, BW gain, feed consumption, and feed conversion at P ≤ 0.10 that approached significance and significant reduction in mortality with broilers exposed to VTR compared with CTR. Benefits in BW, BW gain, feed consumption, and feed conversion are in agreement with previous research of broilers grown to heavy BW [3]. The CTR used in the present research should not have resulted in a high incidence of mortality due to heat stress conditions, because this temperature is in the range for a set point used in commercial practice during winter production. It is hypothesized that the higher mortality may have occurred due to reduced movement of the broilers subjected to the CTR, in turn leading to a higher incidence of leg abnormalities. Broilers that are exposed to temperatures higher than their thermoneutral zone tend to rest in the litter, as observed with previous research from this laboratory [31, 32]. The incidence of mortality was not categorized in this research; however, it was noted that some of the birds that died had associated leg problems.

Energy efficiency has been shown to be adversely affected in broilers provided increasing concentrations of AME during 63-d production periods [20, 21]. In contrast, Dozier et al. [6] reported improved caloric intake per gram of BW gain with increasing AME from 36 to 59 d, but caloric intake per gram of breast meat weight and caloric intake were unaffected. Broilers have been shown to adjust feed intake when fed diets varying in AME [6, 22]. In the present research, broilers were able to adjust to a constant caloric intake as AME increased. In addition, AME x ambient temperature interactions were observed for energy intake and energy intake per gram of BW gain. This indicates as AME was increased to 3,310 kcal/kg with broilers exposed to the CTR that increasing growth was more efficient, but increasing AME had no effect on broiler growth when subjected to VTR. This difference in response to AME may indicate the increased need for AME is due to more energy being partitioned toward maintenance via panting when ambient temperature increases. The inconsistent AME response reported among Saleh et al. [20, 21], Dozier et al. [6], and the present research may have occurred because previous work by Saleh et al. [20, 21] evaluated AME responses from 1 to 63 d, whereas Dozier et al. [6] and current research were conducted from 5 to 9 wk of age.


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. From 36 to 60 d of age, feed conversion decreased markedly as AME increased when broilers were subjected to CTR, but the feed conversion response to AME was less pronounced when broilers were exposed to VTR. This may indicate that latent heat removal necessitates a greater need for AME.
  2. Broilers subjected to the VTR achieved 3.82 kg of BW approximately 4.75 d earlier than the CTR based upon prediction equations. The days to reach 3.82 kg of BW were influenced by AME in the CTR but not the VTR.
  3. Apparent ME should not only be formulated based on company history and shadow prices but also for temperature set points during winter production.


   FOOTNOTES
 
1 Mention of trade names or commercial products in this publication is solely to provide specific information and does not imply recommendation or endorsement by the USDA. Back


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

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