Low-tannin white sorghum contains more digestible and metabolisable energy than high-tannin red sorghum if fed to growing pigs

The present study was conducted to determine and compare the digestible (DE) and metabolisable energy (ME) and the apparent total tract digestibility (ATTD) of gross energy (GE) in yellow-dent corn, three low-tannin white sorghum cultivars and three high-tannin red sorghum cultivars when fed to growing pigs. Forty-two barrows (34.8 ± 3.1 kg bodyweight) were housed in metabolic crates and allotted to one of seven diets with six pigs per diet in a completely randomised design. The seven diets were formulated to contain 969 g/kg of corn or one of the six sorghum cultivars as well as 31 g/kg vitamin and minerals. Faeces and urine were collected for 5 days following a 7-day adaptation period. The DE and ME were lower (P < 0.05) for red sorghum than for corn while the values for corn were lower (P < 0.05) than those obtained for white sorghum. The ATTD of GE for pigs fed corn was higher (P < 0.05) than for pigs fed red sorghum but was lower (P < 0.05) than the ATTD of GE for pigs fed white sorghum. Tannin had a high negative correlation with DE and ME (both, r = –0.99; P < 0.01) and the ATTD of GE (r = –0.92; P < 0.01). The DE, ME and ATTD of GE were positively correlated with CP (P < 0.05), and negatively with kafirin/CP and phenols (P < 0.05). However, tannin was negatively correlated with CP (r = –0.85; P < 0.05), or positively with kafirin/CP (r = 0.88; P < 0.01) and phenols (r = 0.77; P < 0.05). Therefore, tannin content in sorghum may be the main anti-nutritional factor. The overall results of this study indicate that low-tannin white sorghum varieties are superior to high-tannin red sorghum varieties for use as an energy source in diets fed to growing pigs, and high-tannin red sorghum varieties should be incorporated into pig diets to ease the demand pressure on corn only if favourably priced in terms of their DE and ME values.