AMEn determination
In Experiment 1, the determined AME
n for grain sorghum at 3-weeks of age presented in
Table 4 were 3,524±122.03 (red/bronze), 3,252±122.03 (white/tan), and 3,039±123.44 (U.S. No. 2 grain sorghum) kcal/kg. Red/bronze had the highest AME
n compared to dextrose-control, white/tan, and U.S. No. 2 (p<0.0001). At 6-weeks of age, the determined AME
n, shown in
Table 4, were 3,373±297.35 (red/bronze), 3,279±297.35 (white/tan), and 2,966±298.64 (U.S. No. 2) kcal/kg. The highest determined AME
n was the red/bronze grain sorghum, while white tan was intermediate when compared to U.S. No. 2 (p = 0.0322), but not significantly different from red/bronze. No significant differences were observed in the 72-h FI at 3 and 6-weeks of age (p>0.05). No differences were observed in mortality (p>0.05) with an overall mean of 5.5%.
AME
n values determined in Experiment 1 for meat-type quail were not affected by age from 3 to 6-weeks of age (p = 0.5147) or when age and treatment interaction were anlayzed (p = 0.8746). This indicates no effect of age on AME
n value and that a single-phase feeding program is an adequate recommendation for quail as was provided as a starter/grower diet. In a previous study by Moritz et al [
11] determining the AME
n of grain sorghum for broilers, values varied by feed phase; mean AME
n values of modern grain sorghum varieties for broilers in the grower diet-phase were determined as 3,336 (red/bronze), 4,000 (white/tan), and 3,341 (U.S. No. 2 grain sorghum) kcal/kg (as-fed), respectively. In the finisher diet-phase, average AME
n values were determined as 3,001 (red/bronze), 3,599 (white/tan), and 3,705 (U.S. No. 2 grain sorghum) kcal/kg (as-fed), respectively. Other studies in comparison, show AME
n values of 2,790 and 2,651 kcal/kg (DM) for tannin-free, white and red sorghum varieties, respectively, in broiler chickens from 7 to 28 days of age [
12]. Additional variations in feed intake, excreta measurements, and AME
n methodology can also influence AME
n values [
13].
Species, age, and sex of birds are a few variables known to cause variability in energy metabolism [
14]. Feed intake in Experiment 1 was not affected by AME
n, suggesting no influence of treatment when 20% of the GE of corn is substituted by grain sorghum even though there were varying AME
n values across treatments at 3 and 6-weeks of age. Muniz et al [
15] and Wilson et al [
16] reported a negative correlation between FI and AME
n of which, birds consume more feed of lower AME
n and less feed of higher AME
n. However, this finding was not in agreement with the lack of difference in feed intake of Experiment 1. This may also suggest that quail do not respond as similarly to energy levels as would broilers to adjust their feed consumption to meet their energy requirement [
16]. The lower AME
n observed in Experiment 1 in the U.S. No. 2 grain sorghum may be a result of a lower GE value compared to the other GE analyses for grain sorghum varieties (
Table 1); therefore, the energy available and used by the bird was numerically lowest for the U.S. No. 2 treatment. Previous studies by Moritz et al [
11] and Khalil et al [
17] observed lower AME
n values for tannin-free and low-tannin grain sorghum, respectively with increasing age attributed by increased FI and as a result, increased rate of passage and digestion. In addition, starch digestibility has been reported to have a negative correlation with increasing FI and reduce AME
n [Svihus]. Similiarly, in this present study, nutrient analyses (
Table 1) show U.S. No. 2 grain sorghum with the highest crude fiber content which may be a result of lower AME
n values compared to other treatments. Furthermore, additional variations in the nutrient composition of an ingredient can be a result of its region, environment, and season in which it is grown, and such variability can influence the energy density of a feed; thus, diet formulation [
18,
19].
Growth performance and carcass traits
In Experiment 2, growth performance in
Table 6 showed the greatest BW observed in the U.S. No. 2 grain sorghum treatment compared to corn, red/bronze, and white/tan treatments (p = 0.0031). No significant differences were observed among treatments for FI and FCR (p>0.05).
Although performance data for quail fed tannin-free grain sorghum is limited, results are in agreement with previous studies evaluating performance of quail fed tannin-free red and white grain sorghum varieties with no effect of treatment or performance [
20]. Compared to broilers, Hulan and others demonstrated that low tannin grain sorghum can replace corn by 45% to 58% inclusion without detrimental effects on weight gain, feed conversion, CY, and feed intake [
21]. Higher tannin grain sorghum varieties resulted in decreased bodyweight, feed intake and poorer feed conversion in broilers [
17]. Dykes and Rooney [
22] indicated that birds can consume both tannin and non-tannin sorghum varieties, but it has been observed that birds will eat low-tannin white sorghum before they will low-tannin red grain sorghum. They also noted that varieties containing tannins do result in adverse effects on performance and efficiency. It is widely known by researchers, nutritionists, and grain producers that previous varieties of grain sorghum are associated with tannins and have suboptimal effects on digestibility and growth performance in broilers [
22]. Nevertheless, in Experiment 1 and 2, tannin-free grain sorghum varieties were acquired in the U.S. and analyzed as tannin-free (Figures 1 and 2).
The high mortality observed in Experiment 2 (
Table 6), primarily in the first week of grow-out, was thought to be explained by high fumonisin mycotoxin levels detected in white/tan, red/bronze and U.S. No. 2 grain sorghum. However, based on mycotoxin analyses, the average fumonisin level detected for grain sorghum varieties was 0.463 mg/kg compared to <0.005 mg/kg of aflatoxin (B1, B2, G1, G2,), ochratoxin A, T-2 toxin, HT-2 toxin, vomitoxin, and zearalenone. No adverse effects on performance were evident in Experiment 2. According to Awad and others [
23], poultry have a high tolerance specifically to
Fusarium species like fumonisin mycotoxin which have been shown to have immunotoxic effects on gut/immune function and feed consumption when
Fusarium toxin is >5 mg/kg. It has been shown that long-term exposure to dietary mycotoxins have previously presented adverse effects on bird performance including decreased BW and efficiency [
24]. However, in a study by Swamy et al [
24] growth parameters were not impacted in the finisher diet-phase when evaluating
Fusarium mycotoxins in broilers suggesting that birds potentially adapt to mycotoxins over time. Although the high mortality observed in this current study was thought to be a result of a similar immunotoxic effect in early grow-out, the
Fusarium toxin level was not >5 mg/kg. Therefore, the observed high, first-week mortality may have been due to poor chick quality and on-farm management practices. In a study by Yerpes et al [
25], risk factors influencing high rates of first-week mortality in broiler chicks were identified and included internal factors such as chick quality dependent on hatchery management, and external factors dependent on house management and environmental factors.
While mycotoxins were analyzed and may have been one of many contributing factors to high mortality in Experiment 2, it should be noted that lower AME
n values for U.S. No.2 grain sorghum in Experiment 1, (
Table 4) could also be due to potential mycotoxin contamination. Previous research by Nelson et al [
26], found that contaminated corn with mycotoxins significantly reduced nutrient digestibility and energy utilization. Additionally, reduced grain quality can also have a significant effect on mycotoxin production [
25]. As mentioned previously, grain quality and its variations in nutrient composition can exist depending on the region or environment the feedstuff is grown and sourced from which can influence energy values [
19].
Carcass traits in
Table 7 show LBW (p = 0.0409) and HCW (p = 0.0234) were greatest in U.S. No. 2 compared to all other treatments; however, CY (p<0.0001) was lowest in the U.S. No. 2 treatment. No significant differences were observed among treatment for BrW and BY (p>0.05).
Carcass traits are essential parameters when processing meat for retail markets [
27]. Quail in the U.S. No. 2 treatment had heavier LBW and HCW, but had the lowest CY compared to other treatments. Lower CY may be due to early onset of egg laying/sexual maturity for quail in the U.S. No. 2 treatment. A previous study by Yang et al [
28] compared the level of adipose tissue and its physiological changes in onset laying and pre-laying quail. Results showed that onset laying quail had heavier BWs, increased body fat and increased liver weight than pre-laying quail [
28]. In this current study, the heavier weight in the U.S. No. 2 treatment may have been contributed by the higher body fat and liver weight for sexually mature quail at 39 days of age than for muscle deposition on the carcass for CY results. Not to mention, the ingredient composition and nutrient analysis for the U.S. No. 2 diet (
Table 5) had a higher fat inclusion and crude fat analysis which may have influenced the observed results. Nonetheless, compared to published data, CY and BrY are consistent with what has been previously reported by Santhi and Kalaikannan in which optimal CY is between 64% to 65% and breast yield is 33% [
2] at 42 days of age. Effect of sex (male or female) can influence yield [
29]; however, when statistically analyzed, there was no significant effect of sex in sample birds.