Comparative performance of broiler chickens offered nutritionally equivalent diets based on six diverse, ‘tannin-free’ sorghum varieties with quantified concentrations of phenolic compounds, kafirin, and phytate

Abstract

Abstract. Starch is the main source of energy in sorghum-based diets but starch/energy utilisation by broiler chickens offered these diets may be substandard. Both in vitro and in vivo data indicate that the digestibility of sorghum starch is inferior to that of other feed grains, especially maize. Three 'starch-extrinsic' factors in grain sorghum, namely 'non-tannin' phenolic compounds, kafirin and phytate may negatively influence starch/energy utilisation in sorghum-based broiler diets. To test this hypothesis, concentrations of polyphenols, free, bound and conjugated phenolic acids, kafirin and phytate were quantified in six diverse 'tannin-free' (Type I) grain sorghum varieties. These sorghums were incorporated into nutritionally equivalent diets at 620 g/kg and offered to male broiler chickens from 7 to 28 days post-hatch. Growth performance, nutrient utilisation (AME, ME : GE ratios, N retention, AMEn) and starch and protein (N) digestibility coefficients and disappearance rates in four small intestinal segments were determined. Numerous relationships that were either significant (P < 0.05), or approached significance (P < 0.10), were detected that indicated various 'non-tannin' phenolic compounds, kafirin and phytate in sorghums negatively influenced nutrient utilisation parameters in broiler chickens. ME : GE ratios are sensitive indicators of efficiency of energy utilisation and were most negatively influenced by flavan-4-ols (r = -0.919; P < 0.015), which are polyphenolic compounds. Moreover, flavan-4-ols in tandem with conjugated vanillic acid negatively influenced (r = -0.993; P < 0.005) ME : GE ratios on the basis of a valid multiple linear regression. Similarly, conjugated vanillic and bound ferulic acids in tandem negatively influenced AME (r = -0.990; P < 0.005). N retention was most negatively influenced by kafirin (r = -0.887; P < 0.025). Thus, it appears that both phenolic compounds and kafirin may have deleterious effects on nutrient utilisation of sorghum-based broiler diets and recommendations are made that should enhance the quality of sorghum as a feedstuff for chicken-meat production based on these findings.

The potential of rapid visco-analysis starch pasting profiles to gauge the quality of sorghum as a feed grain for chicken-meat production

“…The consensus is that kafirin impedes starch utilisation ( Taylor, 2005 , Taylor and Emmambux, 2010 ) although dissenting opinions have been expressed ( Gidley et al., 2011 ). However, 3 of our studies ( Truong et al., 2015b , Truong et al., 2016b , Liu et al., 2016 ) strongly indicate that kafirin does indeed impede starch energy utilisation in sorghum-based poultry diets although the underlying biophysical and biochemical interactions have not been defined precisely. The depressive impacts of kafirin on RVA starch viscosities reported herein are entirely consistent with the proposition that kafirin has a deleterious influence on the efficiency of energy utilisation of broiler chickens offered sorghum-based diets.…”

“…Pearson correlations between sorghum RVA starch pasting profiles and parameters of nutrient utilisation in broiler chickens offered corresponding sorghum-based diets are shown in Table 6 . The analysed data was derived from 5 experiments ( Khoddami et al., 2015 , Selle et al., 2016b , Truong et al., 2015a , Truong et al., 2015b , Truong et al., 2016a , Truong et al., 2016b , Truong et al., 2016c ) involving 9 sorghum varieties (LvP 3, LvP 5, FW, Tiger, Block I, HP, Liberty, MP, JM). Three results for Tiger, and 2 results from both Block I and HP provided a total of 13 sets of observations.…”

“… 1 Data derived from Khoddami et al., 2015 , Selle et al., 2016b , Truong et al., 2015a , Truong et al., 2015b , Truong et al., 2016a , Truong et al., 2016b , Truong et al., 2016c ). P is the significance of probability value and r is the correlation coefficient.…”

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Fig. 2 Linear relationships between (A) peak ( r = 0.810; P < 0.001) and (B) final ( r = 0.764; P < 0.0025) rapid visco-analysis (RVA) viscosities and ME:GE ratios in broilers offered diets based on 9 sorghum varieties in 5 feeding studies [adapted from Khoddami et al., 2015 , Selle et al., 2016b , Truong et al., 2015a , Truong et al., 2015b , Truong et al., 2016a , Truong et al., 2016b , Truong et al., 2016c )].

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“…(2016) used sorghums Block I, HP and Liberty to formulate 10 nutritionally equivalent broiler diets that were compared in an ‘equilateral triangle’ response surface design. Truong et al. (2016b) compared sorghums Block I, HP, Liberty, Tiger, MP and JM directly and in another study sorghums HP and Tiger were again assessed Truong et al.…”