Table 1 – Empirical values of constants A – D used in Wiseman equation to predict the apparent metabolizable energy
(AME) values of poultry at different ages
Young broilers (< 21 days)a
Old broilers (> 21 days)a
38.112 ± 1.418
-0.009 ± 0.002
39.025 ± 0.557
-0.006 ± 0.001
-15.337 ± 2.636
-0.506 ± 1.186
-8.505 ± 0.746
-0.403 ± 0.088
a Empirical values of constants A – D were categorized into two groups, young broilers (aged < 21 days) and old broilers (aged > 21 days). All
young broilers (aged < 21 days) followed the same empirical values for constants A – D, likewise for old broilers (aged > 21 days).
Predicted Apparent Metabolizable Energy (AME) values for all samples
Using GC-FID and acid-base titration, all samples were analyzed for their lipid composition and FFA content
(Table 2). Descriptive analysis of eight different oil types were presented in Table 3. AME of young broilers
(aged < 21 days) and old broilers (aged > 21 days) were studied in this paper. Based on the GC-FID analyses, it was
determined that the U:S for crude palm oil was lowest amongst all samples analyzed while the U:S for soybean oil was the
highest, with relatively low FFA content of 1.01% oleic acid recorded (Table 3). When the data was further extrapolated
using Equation 1, it was found that the highest predicted mean AME values were from soybean oil, at 8362 kcal/kg
(young broilers) and 8672 kcal/kg (old broilers). On the other hand, the lowest predicted mean AME values were from
crude palm oil with the predicted AME values at 6617 kcal/kg (young broilers) and 7669 kcal/kg (old broilers) (Table 3).
It was apparent that the predicted AME values were inconsistent across all oil samples. In particular, a large spread
of AME for fish oil samples for different age groups of broilers was observed. The energy gaps for young (< 21 days old)
and old broilers (> 21 days old) were 2295 kcal/kg and 1417 kcal/kg, with a relative variation of 36% and 19%
respectively (Table 3). The AME gap for crude palm oil for young (< 21 days old) and old broilers (> 21 days old) were
found to be 1057 kcal/kg and 540 kcal/kg with relative variations of 17% and 7% (Table 3). Comparatively, refined palm
oil also showed a smaller AME spread relative to crude palm oil, with 506 kcal/kg for young broilers (8% variation) and
250 kcal/kg for old broilers (3% variation) (Table 3). As the three major oil groups (e.g. tallow, rice bran oil, and fish oil)
accounted for 63% of the total oil and fat samples collected and represented the majority of the oil and fat products
(Table 2), the data for these groups were further analyzed (Table 4).
Large AME discrepancy of 2670 kcal/kg for young broilers with relative variation of 49% and 1565 kcal/kg for old
broilers with a relative variation of 23% were observed (Table 3). Out of 163 samples, 85% of the samples were received
from five different sources originating from South Korea (Table 4). Majority of the samples were from the same source,
supplier 1, where it accounted for approximately 78% of the tallow samples received from South Korea. Large spread of
AME was observed for supplier 1, at 1248 kcal/kg with a relative variation of 20% for young broilers and 626 kcal/kg
with a relative variation of 8% for old broilers (Figure 1). As such, supplier 1 from South Korea was singled out with
samples collected in eight batches over a span of five years, from year 2012 to 2016. The AME values observed were
inconsistent even within batches where the energy spread was in the range of 230 kcal/kg to 1063 kcal/kg with relative
variation of 3% to 17% (Table 5). Likewise, AME values for tallow samples from supplier 3 were inconsistent as well, with
energy spread at 1362 kcal/kg for young broilers (aged < 21 days) and 740 kcal/kg for old broilers (aged > 21 days)
(Figure 1). This translated to relative variations of 20% for young broilers (aged < 21 days) and 10% for old broilers (aged
> 21 days).
Rice bran oil
All rice bran oil samples received were from Thailand since 2012. From 2012 to 2014, the predicted ME values
were highly variable as shown in Figure 2. However, from 2015 onwards, the predicted AME values were calculated to be
more consistent where the energy values ranged from 7500 kcal/kg to 8000 kcal/kg (relative variation of 7%) with only
seven outlier samples. High FFA content of 12.50% oleic acid was observed (Table 3).
Majority of the fish-based oil samples were from Indonesia and Thailand (63% of fish oil samples). Figure 3 showed
that fish oils from Thailand consisted of large energy gaps of 2295 kcal/kg (young broilers) and 1417 kcal/kg
(old broilers). Similarly, when the AME for different batches of fish oils from the same supplier (supplier A) in Thailand
were determined, it was found that the AME ranged from 6442 kcal/kg to 8738 kcal/kg with relative variation of 36% in
young broilers (Table 4). Likewise, a difference of 1926 kcal/kg in terms of AME variation (30%) was observed between
fish oil samples from Indonesia (Table 4).
To cite this paper: Thng A, Ting JX, Tay HR, Soh CY, Ong HC and Tey D (2020). The use of predicted apparent metabolizable energy values to understand the oil and fat
variability in broilers. Online J. Anim. Feed Res., 10 (4): 150-157.