Gossypol
Cottonseed hulls do not contain significant amounts of free gossypol: reported values are lower than 0.1% DM (Mujahid et al., 2000b; Noftsger et al., 2000), about ten times less than in the seed (see the Cotton seeds datasheet). Consequently, feeding animals with cottonseed hulls is less likely to result in negative effects due to gossypol. However, there have been several reports on the risk of feeding cottonseed hulls to livestock. When cottonseed hulls were fed to fattening lambs for a long period (8 months), it was found that gossypol accumulated in the testis, liver, kidney, spleen and muscle (in order of decreasing content) (Tuerxhun et al., 2010). Meat inspection of 1004 Karakul sheep, slaughtered in Uzbekistan in the late 1980s, revealed hepatosis in 41%, cirrhosis in 11% and multiple abscesses of the liver in 4% of the cases. In a trial on 30 sheep fed 2 kg/d of cottonseed hulls, liver disease developed within 2 months and values for blood albumin and glucose were low (Norbaev, 1989). In Russia, several poisoning incidents in pigs (mortality up to 30%) have been reported following the feeding of cottonseed meal and cottonseed hulls (Tishkov et al., 1988).
Tannins
Cottonseed hulls contain condensed tannins (3-7% DM), mainly bound to protein and fibre (Yu et al., 1996). However, it seems that the condensed tannins of cottonseed hulls do not significantly reduce the rumen protein solubility (Yu et al., 1995a; Yu et al., 1995b).